Yesterday I got an interesting email from The Vitamin D Council reporting on a new study that measures the vitamin D levels of the Masai and Hadzabe of Africa.
It seems there’s a good amount of epidemiology for vitamin D levels in people with various illness and disease; as well, there’s epidemiology for disease incidence by latitude (as surrogate for vitamin D levels), but not really anything measuring the vitamin D levels of a a group of normal people one might expect to have reasonably high levels.
Previously, there was only a 1971 study of 8 sunbathing, white lifeguards who maintained levels in the range of 50-80 ng/ml.
So here’s the abstract of the new study:
Dr. John Cannell explains the study thusly:
The Maasai are no longer hunter-gatherers but live, along with their cattle, either a settled or a semi-nomadic lifestyle. They wear sparse clothes, which mainly cover their upper legs and upper body, and attempt to avoid the sun during the hottest part of the day. They eat mainly milk and meat from their cattle, although recently they began to add corn porridge to their diet. Their mean 25(OH) vitamin D level was 48 ng/ml (119 nmol/L) and ranged from 23 to 67 ng/ml.
The Hadzabe are traditional hunter-gatherers. Their diet consists of meat, occasional fish, honey, fruits, and tubers. They have no personal possessions. They wear fewer clothes than the Maasai in that the men often wear nothing above the waist. Like the Maasai, they avoid the sun during the hottest part of the day. Their mean 25(OH)D was 44 ng/ml and ranged from 28 to 68 ng/ml.
It was also reported in the study that all subjects had black skin types that require the most sun to produce robust vitamin D.
So I guess if you unpack all of that, a 25(OH)-vitamin D level of 50 ng/ml that the Vitamin D Council has recommended is right about in the sweet spot.
But there’s a few other things this suggests to me:
- Since these subjects have the most difficult kind of skin to stimulate D production, that levels higher than 50 and perhaps even way higher might be less of a concern than others have suggested. Perhaps it’s less of an “experiment” now in the longer term.
- You really need to pay attention to what I called in my book, being a “fish out of water.” These subjects were on the equator where the sun is most effective, combined with skin that’s least effective. Things get dicey with modern migration and relocation where you have very efficient D generating white skin near the equator (too much D) and the less efficient dark skin at advanced latitudes (too little D).
But it seems to me that the latter situation is the far riskier one: a darker skin person at higher latitudes, such as northern Europe, Northern areas of the US, and Canada. The white skin person can always avoid over-exposure, use some sunscreen, etc., but the dark skin person suffers a double whammy of having less efficient skin for synthesis, combined with a sun that’s only effective in stimulating vitamin D for part of the year (the higher the latitude, the less effective).
How about the health of the Masai, in general? Do I really need to answer that question? I recommend Dr. Stephan Guyenet’s series:
- Diet and Body Composition of the Masai
- Masai and Atherosclerosis
- More Masai
- Nutrition and Infectious Disease
That 4th link wasn’t actually in the series but deals with the Masai, as well as vitamins A & D, which we now know work in synergy (along with K2). Here’s an excerpt:
…However, their colleagues had previously noted marked differences in the infection rate of largely vegetarian African tribes versus their carnivorous counterparts. The following quote from Nutrition and Disease refers to two tribes which, by coincidence, Dr. Weston Price also described in Nutrition and Physical Degeneration:
“The high incidence of bronchitis, pneumonia, tropical ulcers and phthisis among the Kikuyu tribe who live on a diet mainly of cereals as compared with the low incidence of these diseases among their neighbours the Masai who live on meat, milk and raw blood (Orr and Gilks), probably has a similar or related nutritional explanation. The differences in distribution of infective disease found by these workers in the two tribes are most impressive. Thus in the cereal-eating tribe, bronchitis and pneumonia accounted for 31 per cent of all cases of sickness, tropical ulcers for 33 per cent, and phthisis for 6 per cent. The corresponding figures for the meat, milk and raw blood tribe were 4 per cent, 3 per cent and 1 per cent.”
So they set out to test the theory under controlled conditions. Their first target: puerperal sepsis. This is an infection of the uterus that occurs after childbirth. They divided 550 women into two groups: one received vitamins A and D during the last month of pregnancy, and the other received nothing. Neither group was given instructions to change diet, and neither group was given vitamins during their hospital stay. The result, quoted from Nutrition and Disease:
“The morbidity rate in the puerperium using the [British Medical Association] standard was 1.1 per cent in the vitamin group and 4.7 in the control group, a difference of 3.6 per cent which is twice the standard error (1.4), and therefore statistically significant.”
This experiment didn’t differentiate between the effects of vitamin A and D, but it did establish that fat-soluble vitamins are important for resistance to bacterial infection.
So, there appears to be a dietary factor as well, which should make perfect sense, since we evolved over millions of years outdoors, at latitudes appropriate to our skin’s ability to produce vitamin D, and we ate real foods—not nutritionally bankrupt serial grains and all the processed crap they make from them now.
Just one more thing. How about cancer? While I looked but could find no references for cancer rates in the Masai, I do have some epidemiology for various cancers by vitamin D levels as well as latitude.
It’s from this very long and complex presentation: Dose-Response of Vitamin D and a Mechanism for Prevention of Cancer (PDF). Cedric F. Garland, Dr.P.H., F.A.C.E., Edward D. Gorham, M.P.H., Ph.D., Sharif B. Mohr, M.P.H., and Frank C. Garland, Ph.D., Department of Family and Preventive Medicine
UCSD School of Medicine and Moores UCSD Cancer Center, December 2, 2008.
This first slide is a plot of renal cancer rates in males (left) and females (right).
What do you make of that? Can anyone think of anything that might explain it better, with less assumptions (Occam’s Razor style) than vitamin D?
Dose-response relationships from cohort studies were used to estimate the number and percent of cancer cases that could be prevented worldwide by vitamin D3 supplementation:
Basically, what this estimates is that keeping your level of 25(OH) above 50 ng/ml dramatically reduces your risk of cancer.
And so now, given the above, I see no reason anyone should not be setting about to ensure it. And eat real food while you’re at it and better your chances even more.
Here’s the list of cohort studies that were used in that last graph:
- Gorham ED, et al. Am J Prev Med. 2007;32:210-6.
- Garland CF, et al. Am Assoc Ca Res Mtg San Diego April 14, 2008
- Li H, et al. PLoS Med. 2007;4:103.
- Tworoger SS, et al. Cancer Epidemiol Biomarkers Prev. 2007;16:783-8.
- Mohr SB, et al. Prev Med. 2007;45:323-4.
- Mohr SB, et al. Int J Cancer. 2006;119:2705-9.
- Purdue MP, et al. Cancer Causes Control. 2007;18:989-99.
- Lappe JM, et al. Am J Clin Nutr. 2007;85:1586-91.