9. Eating too much fruit
Due to unwarranted fears of saturated fats, and unwarrant beliefs in the healthfulness of fruit, would-be paleo dieters may replace the agricultural carbohydrates (cereals, legumes, etc.) with fruits. They may take a lead from Katherine Milton, Ph.D., who has proposed that high fruit consumption promoted human brain evolution and thus that fruit formed the main food in human ancestral Paleolithic diets.
This hypothesis has many counts against it, among which is evidence that humans do not have dental enamel well adapted to high consumption of the acids present in fruit. Grobler et al showed that just 6 minutes of exposure to fruit acids in the form of whole fruit caused enamel erosion on human teeth. West et al showed that orange juice erodes dental enamel in humans. Kunzel et al showed a positive correlation between degree of dental erosion and proximity to citrus plantations in Cuban children.
Cordain et al reported that among the Aussie Aborigines fruit appears to have supplied the bulk of energy from plant foods consumed. This supports optimal foraging theory, which indicates that animals including people will seek to get the maximum caloric return for foraging energy expenditures. Fruits are relatively easy to collect compared to digging up underground storage organs (USOs) like roots and tubers so we would predict foragers to prefer collecting fruits to digging up roots.
However, fruit did not supply the bulk of the total energy in their diet. Cordain (Table 1) reports that Aborigines obtained 77% of their total energy from animal food, only 23% from plant foods. About 41% of the plant food energy in Aborigine diets came from fruits, which means only about 9% of total energy in Aborigine diets came from fruit. Assuming a 2000 kcal diet, this would mean about 180 kcal from fruit daily, or about two pieces of modern fruit amounting to ~45 g carbohydrate.
Most of the wild fruits eaten by most hunter-gatherers did not provide the abundance of sugar supplied by modern hybridized fruits. Modern fruits supply large amounts of fructose, which Stanhope and Havel report can cause dyslipidemia, insulin resistance and hyperinsulinemia, which perpetuate a metabolic state dependent on sugars.
So it appears humans do not have a high tolerance or adaptation to diets containing large amounts of fruit. This again indicates that humans adapted to a diet built on fat and protein from hunted animals. A successful modern version of the paleodiet should put fruit in a minor, supporting role.
Wednesday, May 27, 2009
Tuesday, May 26, 2009
Grassroots Health Vitamin D Study Seeks Participants
Before I get on with the other nine problems people have when implementing paleo diet, I wanted to pass along a link to the website of Grassroots Health, an organization that has organized an open study of vitamin D and health under the auspices of leading vitamin D scientists. From the site:
GrassrootsHealth has launched a worldwide public health campaign to solve the vitamin D deficiency epidemic in a year through a focus on testing and education with all individuals spreading the word.I signed up. As a participant, you pay $40 every 6 months to receive a vitamin D lab test delivered to your door, and you agree to fill in some surveys along the way, over a 5 year period. You can't beat the price for the vitamin D test, and your participation will contribute greatly to our understanding of the health protective effects of vitamin D.Everyone is invited to join in this campaign! Join Daction and test two times per year during a 5 year program to demonstrate the public health impact of this nutrient.
$40 and a quick health survey allows everyone to
- get a vitamin D blood spot test kit to be used at home (except in the state of New York)
- have the results sent directly to them
- take action to adjust their own levels to get to the desired ranges with whatever help is needed from their healthcare practitioners.
With only 100 people joining up today, and getting 2 friends to join in 2 weeks (and those 2 friends getting 2 more), by week 42, there could be 400,000,000 people who are vitamin D ‘replete’! (more than the United States population)
Wednesday, May 20, 2009
Top Ten Problems With Applying The Paleolithic Diet Principles: Number 10
When I wrote The Garden of Eating (hereafter GOE), I still had not totally gotten past all the false beliefs I held about dietary fats and the benefits of eating lots of fruits and vegetables. Since publishing The Garden of Eating, I have continued to learn and refine my understanding and practice of Paleolithic diet, and along the way I have discovered a number of ill-founded mistakes I made and that I think others make in applying paleo diet principles to modern life. Rectification of these errors in my own practice have resulted in improvements in my health and body composition. So, in the next 5 to 10 posts I will report and explain the most important errors that create problems for would-be paleodieters, and how to correct them.
10. Eating on an agricultural schedule
In the GOE, we laid out meal plans that suggested three to four meals daily. Like many people, at the time I still believed that research had shown that people need to eat every four to five hours to prevent a decline in metabolism, stabilize blood sugar, and maintain a supply of amino acids to prevent loss of lean mass. Since then, I have learned otherwise. We have no scientific support for frequent eating, especially not in the context of a Paleolithic diet.
When I attempted to eat palediet four meals daily, I frequently found that I simply did not have an appropriate hunger for each meal. Also, I intermittently had bouts with indigestion, abdominal bloating, and constipation triggered by eating foods rich in fat. At times, I literally felt fed up with eating protein and fat, and would gravitate toward eating more tubers and fruits.
So I started questioning. My experience suggested that either people aren’t physiologically adapted to eat a diet high in fat and protein, or that my application of paleodiet principles contained some error. Ethnographic, archaeological, anatomical, and clinical trial evidence all ruled out the former alternative, so I figured the problem lay in my application of the diet.
What did I do wrong? Recent hunter gatherers typically consumed only one or two main meals in a day, often after spending a morning and early afternoon hunting or gathering mostly on an empty stomach. At these meals, H-Gs ate large amounts of animal protein and fat. The human gut has several characteristics indicating adaptation to intermittent feeding on high caloric density foods:
Three meals or more in a day developed only after the rise of agriculture and the adoption of high carbohydrate diets. A constant high meal frequency requires constant presence of stored food, which requires either non-perishable staple foods like grains or a ready refrigerator, neither available to hunter-gatherers.
If you eat a low-fat, high-carbohydrate diet, you will very likely be driven to eat frequently by the insulin response to the high-carbohydrate intake, which locks up your fat stores and drives down your blood sugar, putting you in the constant pincer grip of hunger. Frequent eating and its attendant fluctuations in blood sugar and insulin surges also promote daytime fatigue as energy goes into digestion, activating the parasympathetic—rest and digest—nervous system.
However, if you eat a paleodiet based largely on fat and protein, eating too frequently will not give your liver adequate time to produce sufficient bile for smooth digestion of fats, and you may get the kinds of digestive problems I mentioned above, along with the impression that you don’t or can’t tolerate a high fat diet. It could cause you to question or abandon paleodiet.
Of interest here, eating too frequently could also promote colon cancer by prolonging the colon’s exposure to bile acids. Wei et al did a case-control study (correlation, not causation) found a 50% lower risk of colon cancer among men, but not women, eating fewer than three meals daily. This weakly supports the hypothesis that humans are adapted to eating fewer than 3 meals daily.
Further, if you eat animal protein in Paleolithic quantities, this will by nature reduce your appetite for many hours, which signals that your body is not ready to eat. During this period your liver works intensively converting amino acids to glucose. Naturally, this would tend to reduce your appetite for animal protein.
Finally, a reduced carbohydrate intake reduces your insulin level, and this allows the body to mobilize fat stores so that you can go longer between meals. In other word, if eating paleo, you will have a low normal blood sugar level (due to low carbohydrate intake) and you will run on fat, not sugar, so you won’t have eat to “stabilize your blood sugar.”
We have no evidence that anyone must eat every few hours to avoid a depression of metabolic rate. Studies of fasting have shown that people can go at least 72 hours without food with no decline in metabolic rate, and no loss of lean tissue, and, once the fat starts flowing, no loss of energy. Webber and McDonald even found an increase in metabolic rate after 36 hours of fasting [Br J Nutr. 1994 Mar;71(3):437-47].
We also have no evidence for the claim that you must eat protein several times daily to prevent loss of muscle, or promote gain of muscle. In fact, Stote et al showed that when people ate all their daily caloric requirement in one meal (in a four hour period) daily for eight weeks, they gained muscle and lost fat, whereas when they ate the standard three meals daily they did not experience this body recomposition. The infrequent feeding regimen also reduced cortisol levels, suggesting a reduction in physiological stress.
During a 24 hour fast GH output increases markedly; the frequency of GH pulses increases by 25%, the peak amplitude of GH pulses doubles, and the interpeak serum GH levels quadruple [read this and this]. A study by Norrelund et al indicates that the protein-retaining effects of GH inhibit muscle-protein breakdown during fasting. Fasting-induced increases in GH may therefore account for the increase of lean mass found in the Stote et al study mentioned above.
Since the release of GOE, I have reduced my own meal frequency to not more than thrice daily, most usually eating only twice daily, with both meals consumed in a 6-8 hour window, so that I now fast 16-18 hours daily. This has improved my digestion and elimination, my energy level, my mood, and my body composition (less fat, more muscle). My next book will explain how to adopt this intermittent fasting schedule in a systematic fashion.
Stay tuned for the next installment, we have nine to go.
10. Eating on an agricultural schedule
In the GOE, we laid out meal plans that suggested three to four meals daily. Like many people, at the time I still believed that research had shown that people need to eat every four to five hours to prevent a decline in metabolism, stabilize blood sugar, and maintain a supply of amino acids to prevent loss of lean mass. Since then, I have learned otherwise. We have no scientific support for frequent eating, especially not in the context of a Paleolithic diet.
When I attempted to eat palediet four meals daily, I frequently found that I simply did not have an appropriate hunger for each meal. Also, I intermittently had bouts with indigestion, abdominal bloating, and constipation triggered by eating foods rich in fat. At times, I literally felt fed up with eating protein and fat, and would gravitate toward eating more tubers and fruits.
So I started questioning. My experience suggested that either people aren’t physiologically adapted to eat a diet high in fat and protein, or that my application of paleodiet principles contained some error. Ethnographic, archaeological, anatomical, and clinical trial evidence all ruled out the former alternative, so I figured the problem lay in my application of the diet.
What did I do wrong? Recent hunter gatherers typically consumed only one or two main meals in a day, often after spending a morning and early afternoon hunting or gathering mostly on an empty stomach. At these meals, H-Gs ate large amounts of animal protein and fat. The human gut has several characteristics indicating adaptation to intermittent feeding on high caloric density foods:
- A relatively small stomach (only about 20 percent of total gut volume) despite large energy requirements, indicating adaptation to consuming high energy density, i.e., high fat foods.
- Most (about 65 percent) of gut volume in the small intestine, a characteristic which seems more appropriate for prolonged inter-meal digestion and absorption periods than for frequent feeding.
- A well-developed gall bladder, which stores bile for intermittent use on demand to emulsify fats for enzymatic digestion, and which only empties efficiently with large doses of dietary fat (See Barry Groves’s good discussion of how low-fat diets cause gallstone formation).
Three meals or more in a day developed only after the rise of agriculture and the adoption of high carbohydrate diets. A constant high meal frequency requires constant presence of stored food, which requires either non-perishable staple foods like grains or a ready refrigerator, neither available to hunter-gatherers.
If you eat a low-fat, high-carbohydrate diet, you will very likely be driven to eat frequently by the insulin response to the high-carbohydrate intake, which locks up your fat stores and drives down your blood sugar, putting you in the constant pincer grip of hunger. Frequent eating and its attendant fluctuations in blood sugar and insulin surges also promote daytime fatigue as energy goes into digestion, activating the parasympathetic—rest and digest—nervous system.
However, if you eat a paleodiet based largely on fat and protein, eating too frequently will not give your liver adequate time to produce sufficient bile for smooth digestion of fats, and you may get the kinds of digestive problems I mentioned above, along with the impression that you don’t or can’t tolerate a high fat diet. It could cause you to question or abandon paleodiet.
Of interest here, eating too frequently could also promote colon cancer by prolonging the colon’s exposure to bile acids. Wei et al did a case-control study (correlation, not causation) found a 50% lower risk of colon cancer among men, but not women, eating fewer than three meals daily. This weakly supports the hypothesis that humans are adapted to eating fewer than 3 meals daily.
Further, if you eat animal protein in Paleolithic quantities, this will by nature reduce your appetite for many hours, which signals that your body is not ready to eat. During this period your liver works intensively converting amino acids to glucose. Naturally, this would tend to reduce your appetite for animal protein.
Finally, a reduced carbohydrate intake reduces your insulin level, and this allows the body to mobilize fat stores so that you can go longer between meals. In other word, if eating paleo, you will have a low normal blood sugar level (due to low carbohydrate intake) and you will run on fat, not sugar, so you won’t have eat to “stabilize your blood sugar.”
We have no evidence that anyone must eat every few hours to avoid a depression of metabolic rate. Studies of fasting have shown that people can go at least 72 hours without food with no decline in metabolic rate, and no loss of lean tissue, and, once the fat starts flowing, no loss of energy. Webber and McDonald even found an increase in metabolic rate after 36 hours of fasting [Br J Nutr. 1994 Mar;71(3):437-47].
We also have no evidence for the claim that you must eat protein several times daily to prevent loss of muscle, or promote gain of muscle. In fact, Stote et al showed that when people ate all their daily caloric requirement in one meal (in a four hour period) daily for eight weeks, they gained muscle and lost fat, whereas when they ate the standard three meals daily they did not experience this body recomposition. The infrequent feeding regimen also reduced cortisol levels, suggesting a reduction in physiological stress.
During a 24 hour fast GH output increases markedly; the frequency of GH pulses increases by 25%, the peak amplitude of GH pulses doubles, and the interpeak serum GH levels quadruple [read this and this]. A study by Norrelund et al indicates that the protein-retaining effects of GH inhibit muscle-protein breakdown during fasting. Fasting-induced increases in GH may therefore account for the increase of lean mass found in the Stote et al study mentioned above.
Since the release of GOE, I have reduced my own meal frequency to not more than thrice daily, most usually eating only twice daily, with both meals consumed in a 6-8 hour window, so that I now fast 16-18 hours daily. This has improved my digestion and elimination, my energy level, my mood, and my body composition (less fat, more muscle). My next book will explain how to adopt this intermittent fasting schedule in a systematic fashion.
Stay tuned for the next installment, we have nine to go.
Thursday, May 14, 2009
Perils of Indoor Living: Skin Cancer
Aaron Hicks just sent me a copy of this paper from Medical Hypotheses:
Increased UVA exposures and decreased cutaneous Vitamin D3 levels may be responsible for the increasing incidence of melanoma
This paper may enlighten, or upset, dermatologists mired in the "sunlight causes cancer" myth. It also has the potential to damage the sunscreen industry, also based on the myth that sun exposure causes skin cancer.
The authors, Dianne E. Godar, Robert J. Landry, and Anne D. Lucas propose that intermittent, intense exposure to UVB initiates cutaneous malignant melanoma (CMM), but that promotion of CMM requires increased UVA exposures and inadequately maintained cutaneous levels of vitamin D3.
Some interesting facts cited in support of their hypothesis:
Increased UVA exposures and decreased cutaneous Vitamin D3 levels may be responsible for the increasing incidence of melanoma
This paper may enlighten, or upset, dermatologists mired in the "sunlight causes cancer" myth. It also has the potential to damage the sunscreen industry, also based on the myth that sun exposure causes skin cancer.
The authors, Dianne E. Godar, Robert J. Landry, and Anne D. Lucas propose that intermittent, intense exposure to UVB initiates cutaneous malignant melanoma (CMM), but that promotion of CMM requires increased UVA exposures and inadequately maintained cutaneous levels of vitamin D3.
Some interesting facts cited in support of their hypothesis:
- "Although outdoor workers get much higher outdoor solar UV doses than indoor workers get, only the indoor workers’ incidence of cutaneous malignant melanoma (CMM) has been increasing at a steady exponential rate since before 1940."
- "Outdoor workers have a lower incidence of CMM compared to indoor workers."
- People who use UVB-absorbing sunscreens have a significantly increased risk of melanoma and these sunscreens promote the growth of melanoma in mice.
- People who maintain an all-year-tan have a reduced risk of melanoma, and outdoor workers, who receive three to nine times the erythemally effective UV dose of indoor workers have a significantly lower incidence of melanoma.
- Excluding sunburns, outdoor activities in childhood decrease the incidence of melanoma and research has failed to find a ‘‘critical period,” such as childhood, where intense exposures contribute more towards the induction of melanoma.
- Sunburns throughout life increase the risk of melanoma, while low level solar UV exposures reduce the risk.
- Melanoma patients who receive regular sun exposures live longer than those who do not.
- UVA not only promotes skin tumor growth in mice after initiation by artificial sunlight, but also causes twice as many tumors to form .
- UVA increases melanomas in a mouse model after initiation by UVB.
- People can get considerable UVA exposure from windows, but windows do not allow passage of adequate UVB to stimulate vitamin D production.
- UVA exposure, absent UVB exposure, leads to degradation of vitamin D; and UVA also causes DNA damage.
- "High-rise office buildings, needing many large windowpanes, became increasingly popular around the mid 1910s, about 20 years prior to the first observed increase in the incidence of CMM. The time-line for the industrial revolution fits the CMM observations, unlike the introduction of fluorescent lights in the mid-1940s [80] or any other events that occurred after the mid- 1930s. Thus, the industrial revolution caused many workers to stay indoors during the day reducing their cutaneous vitamin D3 levels and, the UVA entering their offices caused photodegradation of vitamin D3 and mutations to the DNA of their skin cells."
"In the early 20th century, people went against evolution by going indoors during the day to work, which drastically decreased their daily amount of cutaneous vitamin D3 and, along with it, their blood levels. With the addition of larger buildings and sky scrappers, people created an unnatural UV barrier when windows were developed and used in abundance. The UV barrier created by window glass divided UVB from UVA, so that the vitamin D making UVB was excluded from our indoor working environment; only the vitamin D-breaking and DNA-mutating UVA was included. Because this unnatural UV environment existed for decades in buildings and cars, CMM began to steadily increase about 20–30 years later in the mid-1930s."In short, a boat-load of evidence that avoiding the full-spectrum UV light provided by old Sol and hiding inside drives the production of CMM. This paper shows how elegantly the theory of evolutionary adaptation can explain all of the known facts about CMM and provide the basis for uncovering the cause of a degenerative process.
Tuesday, May 12, 2009
Dr. McDougall on B-12: A study in vegan thinking?
In his November 2007 Newsletter, Dr. John McDougall, a tireless advocate of a strict vegetarian (vegan) diet, writes the following:
“Since the usual dietary source of vitamin B12 for omnivores is the flesh of other animals, the obvious conclusion is that those who choose to avoid eating meat are destined to become B12 deficient. There is a grain of truth in this concern, but in reality an otherwise healthy strict vegetarian’s risk of developing a disease from B12 deficiency by following a sensible diet is extremely rare—less than one chance in a million.”
Dr. McDougall apparently has not read the scientific literature on B-12 deficiency in vegans and vegetarians. In 1999, Haddad et al reported a study that included 25 vegan participants. Of these, “2 had macrocytosis (mean red cell volume 398 fL), 3 had circulating concentrations of vitamin B-12<150>376 nmol/L, which is the critical cutoff point that represents
3 SDs above the population mean.” Macrocytosis represents gross vitamin B-12 deficiency, which in this study occurred in 2 of 25 vegan individuals, or 8% -- an 80,000 times greater incidence than “one-in-a-million” (i.e. 0.0001%). Three of 25 or 12% had low VT-B12 concentrations, and 5 of 25 or 20% had elevated methylmalonic acid concentrations, which most experts consider the most sensitive indicator of vitamin B-12 deficiency.
Furthermore, the Haddad et al reported that “Although the average time subjects consumed a vegan diet was 4.2 y in this study, the data showed that 10 of the 25 vegans had at least one indicator of vitamin B-12 deficiency, either macrocytosis, low serum vitamin B-12, or elevated methylmalonic acid concentration (Table 4).” Therefore, this study alone suggested that approximately 40% of vegans may suffer from some degree of vitamin B-12 deficiency. In other words, this study recorded an incidence of B-12 deficiency 400,000 times as high as McDougall claims. Meanwhile, not one of the non-vegetarians had any of the indicators of B-12 deficiency.
Of interest, in table 2 of this paper, Haddad et al report that average intakes of B-12 from both food and supplements did not differ much between the vegans and nonvegetarians. This suggests strongly that B-12 supplements and fortified foods (the only significant sources of B-12 in vegan diets) do not prevent B-12 deficiency in long-term vegans. This could occur because the form used in supplements and fortified foods, cyanocobalamin, differs from the form supplied by animal foods.
This deficiency also affects lacto-vegetarians. In 1999 Hokin and Butler reported a study of 340 Seventh Day Adventist Vegetarians, 245 of which were lactovegetarians or vegans. In the vegetarians, 53% had serum B-12 levels below the laboratory reference range of 171 pmol/L, and 73% had levels below 221 pmol/L, the level identified as normal for an individual with adequate production of the intrinsic factor required for vitamin B-12 absorption. By conducting the Schillings test for intrinsic factor activity, Holin and Butler determined that dietary inadequacy caused the B-12 deficiency in 70% of the vegetarian subjects in this study.
In 2003, Herrmann et al conducted a study of 66 lactovegetarians or lactoovovegetarians
(LV-LOV group), 29 vegans, and 79 omnivores. This team tested three indicators of B-12 deficiency in all subjects: holotranscobalamin II, methylmalonic acid (MMA), and homocysteine levels. Low serum B-12 or holotranscobalamin II, or elevated MMA or homocysteine, indicate B-12 deficiency. They reported:
“Irrespective of vitamin usage, low vitamin B-12 concentrations (<> 271 nmol/L) was found in 5% of the omnivores, 61% of the LV-LOV subjects, and 86% of the vegans.”
Again, the facts dispute McDougall’s claim. In this study, signs of B-12 deficiency appeared not only in up to 90% of vegans, but also in up to 73% of LV-LOVs, and this despite use of vitamin B-12 supplements among the vegetarians.
In table 2 of this study they report the following findings among subjects not using vitamins:
• Normal B-12 status occurred in 78% of omnivores, 11% of LV-LOVs, and only 8% of vegans.
• Stage I or II B-12 deficiency occurred in 10% of omnivores, 21% of LV-LOVs, and 8% of vegans.
• Stage III B-12 deficiency occurred in 3% of omnivores, 60% of LV-LOVs, and a disconcerting 83% of vegans.
McDougall also claims that vegan diets work the best for reduction of homocysteine because of their high levels of folate and low levels of methionine—an amino acid abundant in meat but not plant proteins. But in this study, vegans and LV-LOVs, not omnivores, had the highest homocsteine (tHcy) levels, due to their B-12 deficiency. Herrmann et al wrote:
“We found tHcy concentrations <> 7 nmol/L). In contrast, hyperhomocysteinemia occurred in the LV-LOV subjects and vegans when serum folate was as high as 42.0 nmol/L.”
In other words, high folate and low methionine intakes do not protect against elevated homocysteine. High homocysteine appears linked to heart disease, cancer, osteoporosis, and many other common degenerative conditions, none of which occurred in healthy hunting and gathering groups.
So McDougall doesn’t have his facts correct about the incidence of B-12 deficiency or elevated homocysteine levels in vegetarians. But he goes on from that error to add:
“Take a moment to compare the possible consequences of your dietary decisions. You could choose to eat lots of B12-rich animal foods and avoid the one-in-a-million chance of developing a reversible anemia and/or even less common, damage to your nervous system. However, this decision puts you at a one-in-two chance of dying prematurely from a heart attack or stroke; a one-in-seven chance of breast cancer or a one-in-six chance of prostate cancer. The same thinking results in obesity, diabetes, osteoporosis, constipation, indigestion, and arthritis. All these conditions caused by a B12-sufficient diet are found in the people you live and work with daily. How many vegans have you met with B12 deficiency anemia or nervous system damage? I bet not one! Furthermore, you have never even heard of such a problem unless you have read the attention-seeking headlines of newspapers or medical journals.”
This paragraph contains several fallacies. First of all, he asserts a false dilemma: Either eat no animal foods and court a miniscule risk of B-12 deficiency, or eat “lots of B12-rich animal foods” and incur a high risk of heart attack, stroke, breast cancer, prostate cancer, obesity, diabetes, osteoporosis, constipation, indigestion, and arthritis.” This dilemma is false in several ways:
• He suggests falsely that you have only two choices, either eat no animal foods, or eat an undefined “lots” of them, when in fact a diet can vary from 0% to 100% animal food.
• He has not defined what percent will constitute “lots” of animal food, and though it refers generally to large amounts, by contrasting it with “no” animal food, Dr. he implies without evidence that eating any amount of any kind of animal food will put you at high risk for the listed diseases
• He implies that eating “lots” of animal foods will put anyone or everyone at risk for the listed diseases, and conversely that eating a vegan diet will prevent all these diseases in anyone or everyone.
Traditional Eskimos eat a diet composed of up to 90% animal food, and on their traditional diet, they had a low risk of heart attack and no cancer, no obesity, no diabetes, and no constipation. I do not think the Eskimo diet is ideal, but traditional Eskimo dietary experience certainly disproves McDougall’s implied claim that eating “lots” of animal food causes all the disorders he listed.
Dr. McDougall goes on to cite one study finding that “The human gut also contains B12-synthesizing bacteria, living from the mouth to the anus.” Although apparently true, he fails to mention that in order to produce true vitamin B-12 (cobalamin), these bacteria would need a source of cobalt, since a functional B-12 molecule contains this mineral.
Foods can supply cobalt, either as B-12 or in elemental form. A study by Hokin et al found that in Australia meat and potatoes are the main dietary cobalt sources. Comparing cobalt intakes of 10 omnivores, 10 lacto-ovo-vegetarians, and 10 vegans, Hokin et al found that lacto-ovo-vegetarians had the lowest cobalt intakes, that vegans who ate large amounts of potatoes had cobalt intakes similar to omnivores, and that vegans who did not eat large amounts of potatoes had cobalt intakes similar to lacto-ovo-vegetarians. Hokin et al found no correlation between dietary cobalt intake and serum B-12 concentrations in any of the dietary groups.
Hokin et al reported both vegans and vegetarians had mean serum B-12 levels of 175 pmol/L, compared to 366 pmol/L in omnivores. (As noted above, levels below 221 pmol/L are considered deficient and are associated with macrocytosis and elevated homocysteine in vegetarians.) Hokin et al noted that even the lowest cobalt consumption in the groups studied (6.67 mcg/d) would support the production of 165 mcg of B-12, about 80 times the RDA for B-12 – but that did not happen in the vegans, indicating that human gut flora does not produce significant or adequate amounts of B-12 from dietary cobalt.
Dr. McDougall goes on to discuss the fact that the intestinal flora of ruminant animals (such as cattle, sheep, deer, bison, giraffes, and goats) produce vitamin B-12. These animals ingest cobalt, carbon, hydrogen, phosphorus, and nitrogen by eating grass, a food inedible to humans, and their intestinal flora use that material to produce B-12. They absorb and use some of that B-12, so that the B-12 appears in the meat and milk of these animals, but they also pass much out in their feces.
McDougall goes on to say:
“The [human] colon contains the greatest number of bacteria (4 trillion/cc of feces), and here most of our intestinal B12 is produced. However, because B12 is absorbed in the ileum, which lies upstream of the colon, this plentiful source of B12 is not immediately available for absorption—unless people eat feces (don’t gasp). Feces of cows, chickens, sheep and people contain large amounts of active B12. Until recently most people lived in close contact with their farm animals, and all people consumed B12 left as residues by bacteria living on their un-sanitized vegetable foods.”
Why shouldn’t we gasp? Is he suggesting that it is healthier to eat feces than to eat meat or milk? I venture to say without any scientific reference that people all over the planet feel revulsion at the idea of eating feces, and that no successful culture has failed to recognize the need to take steps to remove fecal matter from foods before consumption.
Moreover, every culture that keeps farm animals does so to have access to meat, milk, and eggs, not so as to have vegetables contaminated with fecal matter. But McDougall writes as if he wants us to believe that in the old days people avoided eating animal products and only kept farm animals so they could have access to vegetables contaminated with fecal matter.
I don’t know of any human group that has a tradition of keeping farm animals just for the purpose of eating unwashed vegetables contaminated with feces. I find his insinuation insulting to the intelligence of the reader and the human race in general. In case the reader or McDougall does not know, consumption of fecal matter can kill by ingestion of deadly coliform bacteria or protozoans. Yet McDougall appears to think it is better to eat vegetables contaminated with fecal matter than to eat animal flesh.
McDougall goes further to say: “Why would a plant-food-based diet, heralded as a preventative and cure for our most common chronic diseases be deficient in any way? Such a diet appears to be the proper, intended, diet for humans, except for this one blemish.”
Okay, one thing at a time. First, here he clearly uses the phrase “plant-food-based diet” to refer only to a vegan diet. But in fact the phrase “plant-based” does not mean plant-only. Any diet that provides more than 50% of its bulk or energy from plant foods can legitimately be called plant-based. What else would you call a diet that provided 75% of its energy from plant foods and 25% from animal foods? I certainly would not call that diet “animal-based.”
A vegan diet is not only plant-based, it is plant-only. Vegans quite commonly apply the concept of dietary base inconsistently. They commonly call the omnivorous diet “animal-based” when in fact the majority of modern omnivores eat plant-based diets, i.e. the bulk of the diet of omnivores comes from plants, not animals. If a diet contains any animal foods at all, vegans call it “animal-based,” but will call a diet “plant-based” only if it is 100% plant food.
Moreover, B-12 deficiency is not the only “blemish” on plant-only diets. Plant-only diets may fail to meet human needs for taurine, DHA, zinc, iron, vitamin B-6, and vitamin A.
Further, what does he mean when he says a plant-only diet is the “proper, intended” diet for humans? Who does he think “intended” for humans to eat a plant-only diet? Does he opine that some supernatural creator “intended” for humans to eat vegan diets? I find this sudden reference to an “intended” diet creepy.
I know many readers may believe in a god, but no one has ever produced any scientific evidence that any of Nature or human physiology occurred as a result of the “intention” of any supernatural entity. In addition, various human tribes have claimed to “know” the existence, will, or intent of many different gods– the Judeo-Christian God, the Islamic Allah, Vishnu, Brahman, Zeus, Poseidon, Buddha, etc. The opinions as to what these entities supposedly “intended” for humans appear quite contradictory. Compare the dietary proscriptions of Islam and Hinduism, or of Seventh Day Adventists and Jews, etc., and you will quickly see that the experts on the gods’ wills for human diets have major disagreements. Even within cults there appears dispute about what the god wants. Some Buddhists claim Buddha prohibits meat-eating, some say not. Some Christians say their God allows meat-eating, some say not.
Discussions of human nutritional requirements require evidence from scientific research, not vague references to the “intended” diet of man without reference to any entity that could have intent (such as humans). Certainly rice did not “intend” for humans to eat its seeds; apple trees did not produce apples for humans; soybean plants do not intend for humans to eat their seeds; and so on.
Nature did not “intend” for humans to eat any diet; rather, humans adapted to eating what Nature provided in the ecological niche humans chose to inhabit. All the scientific evidence indicates not only that humans have always eaten omnivorously, but in fact that prehistoric humans depended primarily on animal-source foods for millions of years during the ice ages.
In fact, humans could not have spread from Africa to inhabit Europe, starting 50, 000 years ago, unless they heavily utilized meat, poultry, fish, and eggs as staple foods. From that time until about 10, 000 years ago, an ice age gripped the planet, and humans moved out of Africa into Central Asia, and from there eventually to Australia, Europe, China, Siberia, and North America. The climate did not allow the earth to produce sufficient quantities of edible plant foods along many of the routes of migration humans followed. So they lived on meat and fish of whatever type they could find.
What every vegan needs to know about B-12: http://www.veganhealth.org/articles/everyvegan/
Another study showing low B-12 levels and elevated homocysteine in vegans and vegetarians:
http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowAbstract&ArtikelNr=12827&Ausgabe=224621&ProduktNr=223977
Notes
Haddad et al, Dietary intake and biochemical, hematologic, and immune status
of vegans compared with nonvegetarians, Am J Clin Nutr 1999;70(suppl):586S–93S.
Hokin and Butler, Cyanocobalamin (vitamin B-12) status in Seventh-day Adventist
ministers in Australia, Am J Clin Nutr 1999;70(suppl):576S–8S.
Herrmann et al, Vitamin B-12 status, particularly holotranscobalamin II and
methylmalonic acid concentrations, and hyperhomocysteinemia
in vegetarians, Am J Clin Nutr 2003;78:131–6.
Albert MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human small intestinal bacteria. Nature. 1980 Feb 21;283(5749):781-2.
Hokin et al, Comparison of the dietary cobalt intake in three different Australian diets, Asia Pac J Clin Nutr 2004;13 (3):289-291.
“Since the usual dietary source of vitamin B12 for omnivores is the flesh of other animals, the obvious conclusion is that those who choose to avoid eating meat are destined to become B12 deficient. There is a grain of truth in this concern, but in reality an otherwise healthy strict vegetarian’s risk of developing a disease from B12 deficiency by following a sensible diet is extremely rare—less than one chance in a million.”
Dr. McDougall apparently has not read the scientific literature on B-12 deficiency in vegans and vegetarians. In 1999, Haddad et al reported a study that included 25 vegan participants. Of these, “2 had macrocytosis (mean red cell volume 398 fL), 3 had circulating concentrations of vitamin B-12<150>376 nmol/L, which is the critical cutoff point that represents
3 SDs above the population mean.” Macrocytosis represents gross vitamin B-12 deficiency, which in this study occurred in 2 of 25 vegan individuals, or 8% -- an 80,000 times greater incidence than “one-in-a-million” (i.e. 0.0001%). Three of 25 or 12% had low VT-B12 concentrations, and 5 of 25 or 20% had elevated methylmalonic acid concentrations, which most experts consider the most sensitive indicator of vitamin B-12 deficiency.
Furthermore, the Haddad et al reported that “Although the average time subjects consumed a vegan diet was 4.2 y in this study, the data showed that 10 of the 25 vegans had at least one indicator of vitamin B-12 deficiency, either macrocytosis, low serum vitamin B-12, or elevated methylmalonic acid concentration (Table 4).” Therefore, this study alone suggested that approximately 40% of vegans may suffer from some degree of vitamin B-12 deficiency. In other words, this study recorded an incidence of B-12 deficiency 400,000 times as high as McDougall claims. Meanwhile, not one of the non-vegetarians had any of the indicators of B-12 deficiency.
Of interest, in table 2 of this paper, Haddad et al report that average intakes of B-12 from both food and supplements did not differ much between the vegans and nonvegetarians. This suggests strongly that B-12 supplements and fortified foods (the only significant sources of B-12 in vegan diets) do not prevent B-12 deficiency in long-term vegans. This could occur because the form used in supplements and fortified foods, cyanocobalamin, differs from the form supplied by animal foods.
This deficiency also affects lacto-vegetarians. In 1999 Hokin and Butler reported a study of 340 Seventh Day Adventist Vegetarians, 245 of which were lactovegetarians or vegans. In the vegetarians, 53% had serum B-12 levels below the laboratory reference range of 171 pmol/L, and 73% had levels below 221 pmol/L, the level identified as normal for an individual with adequate production of the intrinsic factor required for vitamin B-12 absorption. By conducting the Schillings test for intrinsic factor activity, Holin and Butler determined that dietary inadequacy caused the B-12 deficiency in 70% of the vegetarian subjects in this study.
In 2003, Herrmann et al conducted a study of 66 lactovegetarians or lactoovovegetarians
(LV-LOV group), 29 vegans, and 79 omnivores. This team tested three indicators of B-12 deficiency in all subjects: holotranscobalamin II, methylmalonic acid (MMA), and homocysteine levels. Low serum B-12 or holotranscobalamin II, or elevated MMA or homocysteine, indicate B-12 deficiency. They reported:
“Irrespective of vitamin usage, low vitamin B-12 concentrations (<> 271 nmol/L) was found in 5% of the omnivores, 61% of the LV-LOV subjects, and 86% of the vegans.”
Again, the facts dispute McDougall’s claim. In this study, signs of B-12 deficiency appeared not only in up to 90% of vegans, but also in up to 73% of LV-LOVs, and this despite use of vitamin B-12 supplements among the vegetarians.
In table 2 of this study they report the following findings among subjects not using vitamins:
• Normal B-12 status occurred in 78% of omnivores, 11% of LV-LOVs, and only 8% of vegans.
• Stage I or II B-12 deficiency occurred in 10% of omnivores, 21% of LV-LOVs, and 8% of vegans.
• Stage III B-12 deficiency occurred in 3% of omnivores, 60% of LV-LOVs, and a disconcerting 83% of vegans.
McDougall also claims that vegan diets work the best for reduction of homocysteine because of their high levels of folate and low levels of methionine—an amino acid abundant in meat but not plant proteins. But in this study, vegans and LV-LOVs, not omnivores, had the highest homocsteine (tHcy) levels, due to their B-12 deficiency. Herrmann et al wrote:
“We found tHcy concentrations <> 7 nmol/L). In contrast, hyperhomocysteinemia occurred in the LV-LOV subjects and vegans when serum folate was as high as 42.0 nmol/L.”
In other words, high folate and low methionine intakes do not protect against elevated homocysteine. High homocysteine appears linked to heart disease, cancer, osteoporosis, and many other common degenerative conditions, none of which occurred in healthy hunting and gathering groups.
So McDougall doesn’t have his facts correct about the incidence of B-12 deficiency or elevated homocysteine levels in vegetarians. But he goes on from that error to add:
“Take a moment to compare the possible consequences of your dietary decisions. You could choose to eat lots of B12-rich animal foods and avoid the one-in-a-million chance of developing a reversible anemia and/or even less common, damage to your nervous system. However, this decision puts you at a one-in-two chance of dying prematurely from a heart attack or stroke; a one-in-seven chance of breast cancer or a one-in-six chance of prostate cancer. The same thinking results in obesity, diabetes, osteoporosis, constipation, indigestion, and arthritis. All these conditions caused by a B12-sufficient diet are found in the people you live and work with daily. How many vegans have you met with B12 deficiency anemia or nervous system damage? I bet not one! Furthermore, you have never even heard of such a problem unless you have read the attention-seeking headlines of newspapers or medical journals.”
This paragraph contains several fallacies. First of all, he asserts a false dilemma: Either eat no animal foods and court a miniscule risk of B-12 deficiency, or eat “lots of B12-rich animal foods” and incur a high risk of heart attack, stroke, breast cancer, prostate cancer, obesity, diabetes, osteoporosis, constipation, indigestion, and arthritis.” This dilemma is false in several ways:
• He suggests falsely that you have only two choices, either eat no animal foods, or eat an undefined “lots” of them, when in fact a diet can vary from 0% to 100% animal food.
• He has not defined what percent will constitute “lots” of animal food, and though it refers generally to large amounts, by contrasting it with “no” animal food, Dr. he implies without evidence that eating any amount of any kind of animal food will put you at high risk for the listed diseases
• He implies that eating “lots” of animal foods will put anyone or everyone at risk for the listed diseases, and conversely that eating a vegan diet will prevent all these diseases in anyone or everyone.
Traditional Eskimos eat a diet composed of up to 90% animal food, and on their traditional diet, they had a low risk of heart attack and no cancer, no obesity, no diabetes, and no constipation. I do not think the Eskimo diet is ideal, but traditional Eskimo dietary experience certainly disproves McDougall’s implied claim that eating “lots” of animal food causes all the disorders he listed.
Dr. McDougall goes on to cite one study finding that “The human gut also contains B12-synthesizing bacteria, living from the mouth to the anus.” Although apparently true, he fails to mention that in order to produce true vitamin B-12 (cobalamin), these bacteria would need a source of cobalt, since a functional B-12 molecule contains this mineral.
Foods can supply cobalt, either as B-12 or in elemental form. A study by Hokin et al found that in Australia meat and potatoes are the main dietary cobalt sources. Comparing cobalt intakes of 10 omnivores, 10 lacto-ovo-vegetarians, and 10 vegans, Hokin et al found that lacto-ovo-vegetarians had the lowest cobalt intakes, that vegans who ate large amounts of potatoes had cobalt intakes similar to omnivores, and that vegans who did not eat large amounts of potatoes had cobalt intakes similar to lacto-ovo-vegetarians. Hokin et al found no correlation between dietary cobalt intake and serum B-12 concentrations in any of the dietary groups.
Hokin et al reported both vegans and vegetarians had mean serum B-12 levels of 175 pmol/L, compared to 366 pmol/L in omnivores. (As noted above, levels below 221 pmol/L are considered deficient and are associated with macrocytosis and elevated homocysteine in vegetarians.) Hokin et al noted that even the lowest cobalt consumption in the groups studied (6.67 mcg/d) would support the production of 165 mcg of B-12, about 80 times the RDA for B-12 – but that did not happen in the vegans, indicating that human gut flora does not produce significant or adequate amounts of B-12 from dietary cobalt.
Dr. McDougall goes on to discuss the fact that the intestinal flora of ruminant animals (such as cattle, sheep, deer, bison, giraffes, and goats) produce vitamin B-12. These animals ingest cobalt, carbon, hydrogen, phosphorus, and nitrogen by eating grass, a food inedible to humans, and their intestinal flora use that material to produce B-12. They absorb and use some of that B-12, so that the B-12 appears in the meat and milk of these animals, but they also pass much out in their feces.
McDougall goes on to say:
“The [human] colon contains the greatest number of bacteria (4 trillion/cc of feces), and here most of our intestinal B12 is produced. However, because B12 is absorbed in the ileum, which lies upstream of the colon, this plentiful source of B12 is not immediately available for absorption—unless people eat feces (don’t gasp). Feces of cows, chickens, sheep and people contain large amounts of active B12. Until recently most people lived in close contact with their farm animals, and all people consumed B12 left as residues by bacteria living on their un-sanitized vegetable foods.”
Why shouldn’t we gasp? Is he suggesting that it is healthier to eat feces than to eat meat or milk? I venture to say without any scientific reference that people all over the planet feel revulsion at the idea of eating feces, and that no successful culture has failed to recognize the need to take steps to remove fecal matter from foods before consumption.
Moreover, every culture that keeps farm animals does so to have access to meat, milk, and eggs, not so as to have vegetables contaminated with fecal matter. But McDougall writes as if he wants us to believe that in the old days people avoided eating animal products and only kept farm animals so they could have access to vegetables contaminated with fecal matter.
I don’t know of any human group that has a tradition of keeping farm animals just for the purpose of eating unwashed vegetables contaminated with feces. I find his insinuation insulting to the intelligence of the reader and the human race in general. In case the reader or McDougall does not know, consumption of fecal matter can kill by ingestion of deadly coliform bacteria or protozoans. Yet McDougall appears to think it is better to eat vegetables contaminated with fecal matter than to eat animal flesh.
McDougall goes further to say: “Why would a plant-food-based diet, heralded as a preventative and cure for our most common chronic diseases be deficient in any way? Such a diet appears to be the proper, intended, diet for humans, except for this one blemish.”
Okay, one thing at a time. First, here he clearly uses the phrase “plant-food-based diet” to refer only to a vegan diet. But in fact the phrase “plant-based” does not mean plant-only. Any diet that provides more than 50% of its bulk or energy from plant foods can legitimately be called plant-based. What else would you call a diet that provided 75% of its energy from plant foods and 25% from animal foods? I certainly would not call that diet “animal-based.”
A vegan diet is not only plant-based, it is plant-only. Vegans quite commonly apply the concept of dietary base inconsistently. They commonly call the omnivorous diet “animal-based” when in fact the majority of modern omnivores eat plant-based diets, i.e. the bulk of the diet of omnivores comes from plants, not animals. If a diet contains any animal foods at all, vegans call it “animal-based,” but will call a diet “plant-based” only if it is 100% plant food.
Moreover, B-12 deficiency is not the only “blemish” on plant-only diets. Plant-only diets may fail to meet human needs for taurine, DHA, zinc, iron, vitamin B-6, and vitamin A.
Further, what does he mean when he says a plant-only diet is the “proper, intended” diet for humans? Who does he think “intended” for humans to eat a plant-only diet? Does he opine that some supernatural creator “intended” for humans to eat vegan diets? I find this sudden reference to an “intended” diet creepy.
I know many readers may believe in a god, but no one has ever produced any scientific evidence that any of Nature or human physiology occurred as a result of the “intention” of any supernatural entity. In addition, various human tribes have claimed to “know” the existence, will, or intent of many different gods– the Judeo-Christian God, the Islamic Allah, Vishnu, Brahman, Zeus, Poseidon, Buddha, etc. The opinions as to what these entities supposedly “intended” for humans appear quite contradictory. Compare the dietary proscriptions of Islam and Hinduism, or of Seventh Day Adventists and Jews, etc., and you will quickly see that the experts on the gods’ wills for human diets have major disagreements. Even within cults there appears dispute about what the god wants. Some Buddhists claim Buddha prohibits meat-eating, some say not. Some Christians say their God allows meat-eating, some say not.
Discussions of human nutritional requirements require evidence from scientific research, not vague references to the “intended” diet of man without reference to any entity that could have intent (such as humans). Certainly rice did not “intend” for humans to eat its seeds; apple trees did not produce apples for humans; soybean plants do not intend for humans to eat their seeds; and so on.
Nature did not “intend” for humans to eat any diet; rather, humans adapted to eating what Nature provided in the ecological niche humans chose to inhabit. All the scientific evidence indicates not only that humans have always eaten omnivorously, but in fact that prehistoric humans depended primarily on animal-source foods for millions of years during the ice ages.
In fact, humans could not have spread from Africa to inhabit Europe, starting 50, 000 years ago, unless they heavily utilized meat, poultry, fish, and eggs as staple foods. From that time until about 10, 000 years ago, an ice age gripped the planet, and humans moved out of Africa into Central Asia, and from there eventually to Australia, Europe, China, Siberia, and North America. The climate did not allow the earth to produce sufficient quantities of edible plant foods along many of the routes of migration humans followed. So they lived on meat and fish of whatever type they could find.
What every vegan needs to know about B-12: http://www.veganhealth.org/articles/everyvegan/
Another study showing low B-12 levels and elevated homocysteine in vegans and vegetarians:
http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowAbstract&ArtikelNr=12827&Ausgabe=224621&ProduktNr=223977
Notes
Haddad et al, Dietary intake and biochemical, hematologic, and immune status
of vegans compared with nonvegetarians, Am J Clin Nutr 1999;70(suppl):586S–93S.
Hokin and Butler, Cyanocobalamin (vitamin B-12) status in Seventh-day Adventist
ministers in Australia, Am J Clin Nutr 1999;70(suppl):576S–8S.
Herrmann et al, Vitamin B-12 status, particularly holotranscobalamin II and
methylmalonic acid concentrations, and hyperhomocysteinemia
in vegetarians, Am J Clin Nutr 2003;78:131–6.
Albert MJ, Mathan VI, Baker SJ. Vitamin B12 synthesis by human small intestinal bacteria. Nature. 1980 Feb 21;283(5749):781-2.
Hokin et al, Comparison of the dietary cobalt intake in three different Australian diets, Asia Pac J Clin Nutr 2004;13 (3):289-291.
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