More Raw Truth About Raw Vegan Diets

Raw fooders like to point to other primates as evidence that humans should eat a raw plant food diet.  

For example, Steve Pavlina :

“There’s very compelling biological evidence that a high fruit diet is optimal for human beings. I can’t share the volumes of info I’ve read about this, but one of the more convincing points is that the nearest animal species to human beings, including gorillas, chimpanzees, orangutans, and bonobos all naturally favor a high fruit diet, meaning that when fresh fruit is readily available, they’ll get the vast majority of their calories from fruit. How they get the rest of their calories varies (nuts, seeds, insects, or even other animals), but a clear preference for a high fruit diet is something they all have in common.”

Like other raw fooders, Pavlina here confused quantity consumed with preference.  The fact that chimps eat more fruit than any other type of food does not indicate that they prefer fruit to all other types of food, any more than the fact that Chinese eat mostly rice means that they prefer rice to all other foods. In fact, chimps prefer to eat termites over fruit, and always start their foraging looking for insects, only moving on to fruits after they have exhausted their insect supplies. The preference for animal matter occurs in other apes; see "Omnivorous Primate Diets and Human Overconsumption of Meat" by William J Hamilton in Food and Evolution edited by Harris and Ross.

Far from vegan, the wild chimpanzee diet is about 5% animal food in the forms of insects (primarily termites) and hunted monkeys and antelope. 

Like other raw vegans, Pavlina appears either to ignore or not know that humans have different gut anatomy and physiology from the great apes. Milton discusses this in detail in "Primate Diets and Gut Morphology: Implications for Hominid Evolution" also found in Food and Evolution.

Briefly, both of the apes closest to humans by genetic constitution (about 98% identical), chimps and gorillas, are hindgut fermenters.  In chimps and gorillas, the hindgut, or colon, comprises about 52 percent of the total gut volume.  It houses microbes that ferment fiber, converting it to fatty acids that supply up to 65% of the animal’s energy requirements.  In contrast, in humans the hindgut comprises only about 17 percent of total gut volume, and has relatively small microbial population.  At most, microbial fermentation in the hindgut can provide about 10% of human energy requirements. 

Because hindgut fermentation provides the majority of the energy used by a chimp or gorilla, the colon is a vital organ for these animals and they will die if you amputate it.  In contrast, the hindgut is of so little importance to human energy acquisition that humans can live without the colon (as shown by victims of colonectomies).

In the human gut, the small intestine dominates, comprising 67 percent of the total gut volume. 

In great apes, most digestion and absorption occurs in the hindgut, aided by microbes, whereas in humans most digestion and absorption occurs in the sterile small intestine.   Human digestion occurs using enzymes released from the pancreas and small intestine, not microbial action.

Non-human primates have more guts than us.

In short, the largely vegetarian apes are, well, adapted to a largely vegetarian diet composed primarily of cellulose.

OK, let’s say you don’t know all of this and want to eat a raw diet based on the chimpanzee model, but don’t want to lose body weight because you already have a desired body composition.  What would that look like?

I expend about 2500 calories daily, so, using the chimpanzee diet as model, to meet my energy requirements for one day, I would have to eat something like this:

·      2 pints blueberries

·      8 apples (106 g ea., 2.5” diameter)

·      8 bananas (101g ea., 6-7” long)

·      4 large oranges (~3” diameter)

·      4 cups raw bok choy

·      16 cups raw collard greens

·      7 ounces raw antelope or termites (vegans substitute nuts)

This comes to 4778 g, or about 10.5 lbs., of food. 

The typical person consumes only 3-5 pounds of food daily.  Can you imagine downing the volume of food in the menu listed above?  Probably not.  Even raw vegan blogger Steve Pavlina had difficulty getting it down:

“The mental adaptation was more difficult than the physical adjustment. Even during the last week of the trial, I still found it difficult to come to terms with how much food I had to eat each day. For example, on the first day of the trial I ate 8-1/2 pounds of food, and I was 2.8 pounds lighter on the scale the next morning. That really takes some getting used to.”

On this note, Pavlina expressed amazement that he increased his total food and crudely calculated caloric consumption yet lost body mass over a 30 day period of eating only raw food:

“During the 30-day trial, I lost 8.0 pounds, about 1.9 pounds per week. I started at 186.0 and ended at 178.0. My body fat also dropped 1.8 percentage points. As of the morning of Feb 3rd, I weighed 174.0.”

“Before this trial I averaged about 2,000 calories a day on a cooked vegan food diet, so I actually lost weight even as I increased my daily calories by 15%.”

Unbeknownst to him, his weight loss despite increased food intake demonstrates how difficult it is for humans, by nature lacking cellulase, to extract nutrients from raw plant food.  

A Losing Proposition

Since Pavlina reports a loss of 8.0 pounds, we can calculate the bioavailability of calories from his raw diet. He reports that his body fat also dropped 1.8 percentage points, but he does not state his beginning and end body fat percentages so I don’t know if he lost only fat or also lost lean mass.   Generally caloric reduction results in weight loss that is at most 75% fat and at least 25% lean, but I will give him the benefit of the doubt and assume that he lost no lean mass at all. 

Eight pounds of fat lost would represent 28,000 calories if it was all fat, or a deficit of 933 calories per day.  Assuming 2000 calories as his maintenance based on his report, this indicates that his caloric absorption was only 2000 minus 933, or 1067 calories per day.  So, of the 2298 raw plant food calories he reports eating, he absorbed only 1067 calories, or 46%.  

That means his carbohydrate intake (into the blood) was nowhere near what he believed; he reports 532 g per day, but since we now know that he absorbed only 46% of what he ate, we can conclude that he probably only absorbed about 244 g of the 532g he ate. 

Let’s guess that his low-fat cooked vegan diet supplied 60% of its 2000 calories as carbohydrate (with 30% as fat and 10% as protein).  That would amount to 1200 calories from 300 grams of carbohydrate.  Hence, by going all raw, he may have actually reduced his total carbohydrate intake!

Further, since he reports consuming about 10% of those 1067 absorbed dietary calories as fat, and 933 calories each day came from his fat stores, we can calculate that each day he was actually burning at least 107 calories of dietary fat plus  933 calories of body fat, or 1040 calories of fat daily. Of the 1067 calories from food,  90% was not fat, or 960 calories. 

So his fuel mix was 960 non-fat dietary calories, and 1040 calories from total fat (dietary plus adipose), so during that month he obtained 1040÷2000 = 52% of his calories from fat.  In other words, he was running on a high fat fuel mix, most of the fat coming from his own adipose. 

He thinks he was running on a low fat diet, but if he was, he couldn’t have lost fat weight.  In fact, he was burning a fuel mix of which about 47% was the dreaded saturated animal fat, i.e. his own body fat.  So, if you feel good eating your raw vegan diet, its because you're burning animal fat!

Can you say "Crap!"?

By these calculations it appears that caloric absorption from a completely raw food vegan diet may be as low as 46%.  Given the data I showed above, this means that I would have to eat more than 20 pounds of raw vegetation daily to absorb enough calories to maintain my current body mass and activity levels.

Eating would be a full time job.  Given a 16 hour waking period, I would have to eat 1.25 pounds of food every waking hour to meet my energy needs.   I'd probably spend a good chunk of the time I wasn't eating sitting on the toilet excreting all the undigested carbage.  My life would consist largely of eating and crapping, just like other primates.  Not quite what I had in mind, how about you?

The Raw Deal

Pavlina's experience confirms previous research showing how much difficulty humans have getting adequate energy from raw vegetal foods. For example, Koebnick et al found BMI below 18.5 in 14.7% of males and 25.0% of females eating raw food diets.  Among these raw fooders, the more raw food they ate, and the longer they had been eating “raw,” the lower their body mass.

Beyond body mass,  Koebnick et al also found general malnutrition among the raw fooders resulting in young women losing their menstrual cycles:

“About 30% of the women under 45 years of age had partial to complete amenorrhea; subjects eating high amounts of raw food (90%) were affected more frequently than moderate raw food dieters.”

Most likely, these women were suffering severe iron and vitamin B12 deficiency, just like the subjects of another study by Koebnick’s team, which found B12 deficiency in at least 38% of raw food adherents.  These people also had low HDL concentrations and elevated homocysteine levels.  

If you believe that humans are designed to eat a diet that leaves 38% of people vitamin B12 deficient, 15% of males and 25% of females underweight,  and stops the menstruation in at least 30% of women in their reproductive years, good luck to you.

Who's Toxic Now?

Sadly, raw fooders claim that eating only raw food will detoxify your system.  Apparently they don’t know that by avoiding meat containing vitamin B12, they pump up their blood levels of homocysteine, a potent toxic by-product of protein metabolism. 

So, if you really want to detoxify, go eat a steak.

I shared this post at ParadigmShift Blogshare.

I wrote more on this topic:

The Raw Truth About Raw Vegan Diets

More Raw Truth About Raw Vegan Diets

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