Just yesterday I learned that Ron Rosedale, Eric Westman, and John Konhilas published a retrospective clinical report in the January 2009 Journal of Applied Research entitled “Clinical Experience of a Diet Designed to Reduce Aging” (Full Text).
This article reports on the effects of a practically (i.e. almost) paleo diet on markers associated with aging, namely glucose, insulin, leptin, free T3 and serum triglycerides, all of which decline in response to caloric restriction and occur at lower levels in healthy centenarians than in people who do not live past 100 years.
The authors advised patients to consume a practically (i.e. almost) paleo diet with the following guidelines:
1. Eat unlimited fats
2. Restrict protein to 1-1.25g/kg lean body mass
3. Limit carbohydrate intake to non-starchy vegetables
4. Eat to satisfy hunger (no deliberate caloric restriction)
Patients receive instruction to obtain fats from raw nuts and seeds, avocados, olives and olive oil, flax oil and cod liver oil.
Based on lean body mass, most patients received instruction to consume 50-80g of protein per day from sardines, fish, eggs, tofu, chicken, turkey, wild meats, low-fat cheeses (cottage, ricotta, swiss), seafood, and veggie burgers. They recommended this relatively low protein intake in part because some of the benefits from caloric restriction appear to arise from protein restriction.
Obviously low-fat cheeses and veggie burgers don’t fit into my practically paleo scheme of things. Actually, it seems a bit odd that they recommended unlimited fat intake, and also use of low-fat cheeses and veggie burgers, also low in fat.
According to the report, the patients’ diet logs indicated that they averaged 20% of calories from protein, 20% from carbohydrate, and 60% from fat. Assuming an average 2000 kcalories per day, this would translate to 400 kcal from protein, 400 from carbohydrate, and 1200 from fat, which would come from 100g protein, 100g carbohydrate, and 133g fat. This may indicate that people consumed up to twice as much protein as the authors recommended.
They also advised the patients to take the following supplements: L-carnitine 2000mg, alpha-lipoic acid 400mg, coenzyme Q10 100 mg, 1 tbsp cod liver oil, magnesium 300mg, potassium 300mg, vitamin C 1000mg, vitamin E 800mg daily, and a multivitamin consisting of all essential B vitamins and minerals.
Results
The table below shows the effects of this regimen on body weight, insulin, glucose, leptin, triglycerides, HDL, creatinine, free T3, thyroid stimulating hormone, and blood pressure:
Insulin declined by 40%, glucose by 8%, leptin by 48%, triglycerides by 28%, free T3 by 11%, and blood pressure by 10% systolic and 11% diastolic.
All of these declines also occur with caloric restriction. Of note, free T3, the secreted form of thyroid hormone thought to mediate most of thyroid actions, declined by 11%. About this the authors point out:
“Paralleling this reduction in circulating free T3, 9 patients of this study cohort that had basal body temperatures measured before and after intervention showed a significant decrease (p=0.004) in basal body temperature of 0.182 degrees C. Similar findings were reported in caloric restricted rodents, monkeys, humans, and centenarians (31-34). It has been suggested that the reduction in T3 and body temperature could alter the aging process by reflecting a reducing metabolic rate, oxidative stress, and systemic inflammation (35, 36).”
In other words, contrary to the claims of some bloggers, the declines of thyroid levels and body temperature brought about by either caloric or carbohydrate reduction appear associated with improved health and longevity, not “wrecked metabolism.” Keep in mind that so-called “normal” thyroid levels occur in a population rife with degenerative diseases and a relatively short lifespan. Adjusting your dietary intake to raise thyroid and body temperatures to “normal” may simply put you in the “normal” health/acclerated aging category.
Edit 5/5/2010: Reading this last paragraph, I can see why some commenters got the idea that I was suggesting that hypothyroidism is a good thing. I want to emphasize that the drops in free T3 and basal body temperature recorded in this study were quite small (11% and 0.182 degrees C, respectively) and did not place any of the participants in the hypothyroid category. Such small reductions in metabolic rate appear associated with greater longevity and resistance to disease, whereas hypothyroidism reduces quality of life, increases risk of some diseases, and probably shortens lifespan. End edit.
So, this study suggests that people who follow a diet similar to what I practice (20% protein, 20% carbohydrate, and 60% fat) may achieve the metabolic benefits of caloric restriction without the hunger associated with caloric restriction.
I dare say, long live practically paleo people!
Edit 3/27/2012:
I missed some of the most important, and suspicious aspects of this study.
The authors clearly state: "The recommendation of a high fat, adequate protein, low carbohydrate diet resulted in a significant loss of body weight by 7.1 ± 0.8 lbs in this patient population."
That means this was a hypocaloric diet. The results were produced by a caloric deficit and weight loss. It does not follow that a eucaloric paleo diet producing weight maintenance will have the same results.
Also of interest, they state their outcome measures as: "Laboratory parameters included serum glucose, insulin, leptin, total cholesterol, LDL, HDL, triglycerides (TG), free T3 and thyroid stimulating hormone (TSH) following a 12 hour fast. "
But really interesting is they don't report total cholesterol or LDL in the Table 1B nor in the text. The fact that they left out this data makes me very suspicious. I would guess this means that the subjects did not have favorable changes in total cholesterol or LDL. If they did produce favorable changes in total cholesterol and LDL, they would have been sure to report those changes to support their case.
In the discussion they also state:
"Since this was a retrospective analysis of a clinical practice, there may be bias introduced in the patient sampling procedure. This study reflects the effect of recommending this diet in a clinical practice, so food intake was not directly measured. In addition, this sample population may reflect the results in highly motivated individuals. Though the metabolic improvements occurred in patients who had both high and low weight loss, the improvements in metabolic parameters may be all or partially due to the weight loss."
Thus, they even recognized themselves that 1) they probably used a biased sample, 2) they didn't adequately measure the food intake, and 3) the results might not have had anything to do with the dietary ratio.
Thus, this study failed to show any antiaging metabolic advantage of a calorically adequate low carbohydrate, high fat diet.
It doesn't show that paleo diet promotes longevity!
End of 3/27/2012 edit.
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