Paleo Diet pH: Does It Matter? – Part II

As I reported in Eskimo Osteoporosis?, I felt astonished when I found that a report by Mazess, commonly cited as documenting osteoporosis among precontact Inuit, actually reported that middle-aged Inuit had an apparently normal bone mineral density. As I said in that post, that report did not give good evidence one way or another for bone density of elderly Inuit. I decided to read some of the other papers published on this topic.

In 1972, Mazess and Jones published data documenting age-related bone loss in skeletons of extinct Sadlermiut Eskimos.[1] In this study 17% of the skeletal remains studied came from a stratum at least several hundreds of years old, 44% came from remains deposited before 1899, and 39% from remains deposited between 1899 and 1903. Contact had very little influence on Eskimo diet and lifestyle through these periods. In these skeletons Mazess and Jones found that skeletons from individuals probably aged 36 years or older showed a more rapid rate of bone mineral loss than comparably aged non-Eskimos.

In 1974, Mazess and Mather published another report, Bone Mineral Content of North Alaskan Eskimos.[2] This report looked at Inuit people living in Wainwright, Pt. Hope, and Pt. Barrow, ranging from age 5 years to 82 years, both male and female. This investigation found that Inuit have bone density comparable to age-matched Caucasians in the U.S. up until the age of 40, after which they show a more rapid loss of bone mass resulting in bone mineral densities averaging 10-15% lower than U.S. Caucasians. The process of bone loss starts in the third decade of life in Eskimos of both sexes, whereas in Caucasians in the U.S. it does not start until the forties in females and fifties in males. In the 70-82 year age group, Inuit men had bone density almost 16% lower than Caucasian men, and Inuit women had bone density almost 30% (29.8%) lower than Caucasian women.

Mazess and Mather state:

“Apparently some continuous process accompanies aging in Eskimos that accelerates and exacerbates the aging bone loss evident in so many other populations. In white females, the rate of bone loss between ages 45 and 74 is approximately 9.5% per decade, and there is a change to almost 4.5% per decade thereafter. In white males, the onset of loss is later, and the rate of loss after age 55 is nearly 4.5% per decade. The present results indicate that Eskimo males lost almost 6 to 7% per decade, and Eskimo females close to 10 to 12% per decade after the late thirties and early forties. The rate of loss in Eskimos appeared to approximate 2 to 3% per decade greater than that of corresponding whites. As the onset of loss was earlier than in whites by age 50, the Eskimos had substantially lower bone mineral than whites.”

Some advocates of Inuit-style diets have criticized this and similar studies, correctly pointing out that it looked only at partially modernized Eskimos. They suggest that Weston Price’s work documented excellent skeletal health among the primitive Inuit and these studies fail to contradict Price’s findings. I do not find this argument persuasive; in fact, I find it very flawed.

According to the diet surveys carried out by the International Biological Programme in 1971 and 1972 which is cited by Draper [3], Wainwright adults at that time (when Mazess collected skeletal data) obtained nearly half of their calories, three-quarters of their protein, and half of their fats from native foods. Carbohydrate provided 32 per cent of their calories, compared to an estimated 2 per cent in premodern Arctic Eskimos. Protein provided 25 per cent of calories, not much less than the estimated 32 per cent in the premodern Eskimos. For comparison, 12 per cent would be typical for US or Northern European populations.

Therefore, the Eskimos ate the most native and least modern foods when compared to Caucasians. Since Mazess and Mather found that the Caucasians (eating the most modernized diet) had the later onset and less severe progression of osteoporosis, their study actually showed that either modernization or Caucasian race protected against the accelerated loss of bone mass found in the partially modernized Eskimos.

I find it hard to imagine any adaptive value of early bone loss in humans, so I don't find it plausible to explain this difference via genetics.

Hence, if the Eskimo diet protected against osteoporosis, we should see the lowest rate of bone loss in the group with the most Eskimo-style diet and activity patterns and the highest rate of bone mass loss in people having the most modernized diet and activity patterns. In other words, Mazess and Mather should have found the greatest rate of bone loss in the Caucasians, not the Eskimos. However, they found the opposite. This means that the fully modernized diet consumed by the Caucasians protected against bone loss.

It follows that some feature of the primitive Eskimo diet accelerates aging-related bone loss, or that some feature of the modernized diet retards aging-related bone loss. According to Draper, at the time of data collection, the Eskimos got 32% of energy from carbohydrate, 43% from fat, and 25% from protein; whereas the modern U.S. diet supplied 46% of energy from carbohydrate, 42% from fat, and 12% from protein. Thus, compared to whites, Eskimos consumed a similar amount of fat, 30% less carbohydrate, and twice as much protein.

Hence this data would generate the reasonable and testable hypothesis that either reducing carbohydrate-rich foods or increasing protein intake promotes early onset and rapid progression of bone loss in Eskimos. It does not support the hypothesis that wild game protects against osteoporosis, because the group with the diet highest in wild game (the Eskimos) had the earliest onset and most rapid progression of osteoporosis. It also does not support the hypothesis that modern carbohydrates promote osteoporosis, because the group with the lowest intake of modern carbohydrates (the Eskimos) had the earliest onset and most rapid progression of osteoporosis.

In short, even if we didn’t already have the earlier Mazess study on precontact Eskimo skeletons showing the same accelerated loss of bone mass compared to modern U.S. citizens, the fact that these Eskimos were partially modernized in diet and lifestyle only more firmly points to their native diet -- specifically, its high protein content -- as the most probable dietary cause for their osteoporosis.

By comparing the Eskimos to fully modernized whites, Mazess demonstrated that the fully modernized diet reduces aging-related losses of bone mass compared to a partially modernized Eskimo diet, which effectively shows that the acceleration of bone loss did not result from the modernized portion of the Eskimo diet or lifestyle.

This does not conflict with Weston Price’s findings. Price focused his investigation on disorders of skeletal development), not disorders of skeletal aging. He did not investigate the effects of the Eskimo diet on the aging skeleton at all. Mazess and Mather also found that the Eskimos have normal bone development, but they found something Price missed, namely, accelerated bone aging, compared to non-Eskimos.

The evidence for the role of dietary protein (as a source of metabolic acid) in osteoporosis goes beyond Eskimos and includes clinical trials.

Stay tuned for the next installment.

Notes:

1. Mazess RB and Jones R. Weight and density of Sadlermiut Long Bones. Human Biology (September 1972) 44;3:537-548.
2. Mazess RB and Mather W. Bone Mineral Content of North Alaskan Eskimos. AJCN (1974) 27:916-925.
3. Draper HH. The Aboriginal Eskimo Diet in Modern Perspective. American Anthropologist, New Series, Vol. 79, No. 2 (Jun., 1977), pp. 309-316.