Both Regina and Stephan have some good commentary on this recent study:
Daily energy expenditure and cardiovascular risk in Masai, rural and urban Bantu Tanzanians
Regina's first post is really worth reading here
Here we have evidence that a high-fat, low-carbohydrate diet, consumed habitually does not lead to obesity, high blood pressure and dyslipidemia, and it may, in fact, lead to beneficial long-term health and increased levels of activity in those habitually eating such a diet.She also comes back to the topic here.
there is a simple explanation for why the Masai do not develop atherosclerosis despite consuming a high-fat diet that the authors did not consider: high-fat diets (not containing man-made fats) are not atherogenic.
Stephan also examines the study really helpfully in this post: What to do if your study contradicts conventional wisdom.
13 comments:
It's a good study and reading comments show biases from both sides of the fence and how we filter results according to these biases. Those in the low carb camp are always quick to point out that maybe it wasn't the large energy expenditure maybe it was just the fact that high fat/low carb diets don't cause cardiovascular disease. Well, probably kinda true, but high energy expenditure is a huge plus. That's why the same followers will say "I follow a HF/LC diet why is this or that reading up" or "why did I have a heart attack." Well, good reason you eating the way the way the Masai or other indigenous people are eating or have the high activity level they do. In fact, the Masai don't eat that much and can travel for very long times just searching for food to eat. A huge part of their diet is cow's blood. Remember, Jack Lalanne said that exercise is king and nutrition is queen and together you have a kingdom.
But the Masai do suffer from extensive CHD. George Mann, one of the original researchers that popularized the Masia and a great doubter of the lipid hypothesis, acutally preformed autopsies on Masia men and discovered extensive blood vessel disease. Luckily they were proteced by their exceptional large cornaary arteries (due their genetics and large volumne of medium intensity aerobic exercise).
Regards
Randy
Here's the ref:
ATHEROSCLEROSIS IN THE MASAI1
GEORGE V. MANN, ANNE SPOERRY, MARGARETE GARY and DEBRA JARASHOW
Mann, G. V. (Vanderbilt Univ. School of Medicine, Nashville, Tenn. 37203), A. Spoerry, M. Gray, and D. Jarashow. Atherosclerosis in the Masai. Am J Epidemiol 95: 26–37, 1972.–The hearts and aortae of 50 Masai men were collected at autopsy. These pastoral people are exceptionally active and fit and they consume diets of milk and meat. The intake of animal fat exceeds that of American men. Measurements of the aorta showed extensive atherosclerosis with lipid infiltration and fibrous changes but very few complicated lesions. The coronary arteries showed intimal thickening by atherosclerosis which equaled that of old U.S. men. The Masai vessels enlarge with age to more than compensate for this disease. It is speculated that the Masai are protected from their atherosclerosis by physical fitness which causes their coronary vessels to be capacious.
atherosclerosis; autopsy; cholesterol; coronary artery disease; diet; exercise
--------------------------------------------------------------------------------
1 From the Nutrition Division, vanderbilt University, Nashville, Tennessee 37203 (G. V. Mann and D. Jarashow), and the Aftrican Medical and Research Foundation, Nairobi (A. Spoerry and M. Gray). Reprint requests to Dr. Mann.
Randy and Chris,
I've gotten my hands on the full text of that paper, as well as several others on the Masai from that time period. They're all great, thorough, old school science. It's a lot to sort through so I'll make my next blog post about it.
Here's a little taste to whet your appetite though: everyone seems to agree that the Masai eat tons of fat and don't suffer from cardiovascular disease or most of its proxies like high BP, abnormal EKG. There is some disagreement over whether they have athersclerosis, with some studies falling on either side.
One thing I didn't realize is that their milk is a lot higher in fat and lower in lactose than American milk.
Stephan Wrote:
"everyone seems to agree that the Masai eat tons of fat and don't suffer from cardiovascular disease"
Randy Write:
Not true. They do suffer from CVD as reported in the Mann study. Other studies have only look at surogate markers, HDL, LDL, total and Tris, but the final test is too crack open a chest and take a look. The only time that's been done it was found that the Masai suffer from "extensive CVD". See the Mann study.
The same test have been done on the Bantu and their arteries have been found free of disease. Let me know if you want references and I'll dig them up.
Surogate markers can be very usefull but the final determination is the state of what the surogates are pointing too. And in this case the Masai were diseased despite positive suragotes.
The final test of CVD is a pathology report on the condition of the cornary arteries.
It interesting to note that Mann was NOT a supporter of the "lipid hypothesis" but nevertheless reported the facts as he saw them. He was actually expecting to find clean arteries. I respect that he reported the facts as he found them.
Regards
Randy
Hi Randy,
I just read the full text of the Mann et al study. Here is a quote from Mann himself: "We have found no anatomical evidence of myocardial infarction in [Masai] hearts and we have seen only one man with ECG evidence".
They did find atherosclerosis; we are in agreement about that. But they did not have cardiac events, nor was there any indication that they were on that path, even at ages of 50+.
Furthermore, the atherosclerosis generally occurred AFTER the warrior males went off the milk/meat/blood-only diet and began to include white flour, sugar, and hydrogenated fat in their diet. This is all discussed in the full version of the paper, but is not reflected in the abstract. I will have a more thorough discussion of the paper on my blog soon: http://wholehealthsource.blogspot.com
Best,
Stephan
Hello Stephen,
I appologize in advance if I offend or seem in polite. You seem to to be an intelligent person with a genuine interest in these topics. I do appreciate the discourse.
Stephan Wrote:
They did find atherosclerosis; we are in agreement about that. But they did not have cardiac events, nor was there any indication that they were on that path, even at ages of 50+.
Randy Writes:
Sorry Stephan, but you seem to be down playing what Mann acutally indicated.
Here's Mann's words:
"Measurements of the aorta showed extensive atherosclerosis with lipid infiltration and fibrous changes but very few complicated lesions. The coronary arteries showed intimal thickening by atherosclerosis which equaled that of old U.S. men."
Please note the Mann's use of the descriptive "extensive atherosclerosis ".
Stephan Wrote:
"Furthermore, the atherosclerosis generally occurred AFTER the warrior males went off the milk/meat/blood-only diet and began to include white flour, sugar, and hydrogenated fat in their diet. "
Randy Writes:
I've got a very difficult time beliving that Mann mantains what you are claiming. Mann's data were obtained after the men were dead surely Mann wouldn't claim that the changes happened after they went off the diet. There is no way this could be proved and Mann's too good of a scientist to make such a claim.
Please prove me wrong, but how can you prove that the changes only happened when these men went off their traditional diet?
Stephen Wrote:
They did find atherosclerosis; we are in agreement about that. But they did not have cardiac events, nor was there any indication that they were on that path, even at ages of 50+.
Randy Replies:
If you are implying that the Masia traditional diet prevented them from getting heart disease inspite of extensive diseased arteries, you'll find no support of this from Mann's paper. In fact Mann discusses this issue and his stance is quite clear. These guys bypassed heart attacks because of unusally wide coranary arteries due to alot of mild aerobic exercise.
Here's a quote from Mann:
"The Masai vessels enlarge with age to more than compensate for this disease. It is speculated that the Masai are protected from their atherosclerosis by physical fitness which causes their coronary vessels to be capacious."
What's especially interesting in this discussion is the the "Bantus"
,whose traditional diet is High Carb, High Fiber, Low Fat and Moderate to Low Protein have CLEAN arteries on autopsy.
Regards
Randy
Randy,
No offense taken. I also appreciate the discussion.
The ultimate outcome of heart disease is occlusion of blood vessels resulting in a heart attack. The Masai men had neither, thus they did not have the most relevant measure of CVD in my mind. You could say it was the exercise, or you could say it was diet, or both. Here's what the authors think is most likely, which they state in the discussion but not the abstract:
"We believe... that the Muran [Masai warrior male on an exclusive milk/meat/blood diet] escapes some noxious dietary agent for a time. Obviously, this is neither animal fat nor cholesterol. The old and young Masai do have access to such processed staples as flour, sugar, confections and shortenings through the Indian Dukas scattered about Masailand. These foods could carry the hypothetical agent."
I will post two figures to support this assertion on my blog.
best,
Stephan
Stephen,
I too enjoy the back and forth.
Stephan Wrote:
"The ultimate outcome of heart disease is occlusion of blood vessels resulting in a heart attack. The Masai men had neither, thus they did not have the most relevant measure of CVD in my mind."
Randy Writes:
Well, your defintion of CVD does not match the long standing defintion used in medical science. By the standards in 1972 and now (and accepted by Mann) these folks had severe CVD. They had gross lesions on their coranary arteries. I doubt you could find one MD or PHD that would say you have to suffer a heart attack before you've got CVD. The diagnostic criteria are qaunitativley defined.
Stephan Wrote:
"You could say it was the exercise, or you could say it was diet, or both."
Randy Writes:
No you couldn't say that. I know of no data that indicates any diet can widen coranary arteries in the face on increasing lesions.
There is some imaging data showing that some diets can reduce lesions, but only if the diets are very low in saturated fat.
On the other hand there is ample evidence showing the exercise can increase the diameter of coranary arteries.
Also, as I have remarked before, the Bantu show no CVD when you crack their chest open inspite of lower HDL and smaller LDL particles not to mention their low fat high fiber high carb diet.
Regards
Randy
Hi Randy,
I encourage you to take a look at my blog post. You will see from the figures that the Masai men only develop atherosclerotic lesions after they stop eating a diet of exclusively milk, meat and blood.
Once they include flour, sugar and shortening in their diets (which lowers their fat %, incidentally), their cholesterol skyrockets and their atherosclerosis progresses in a sudden way that is not consistent with simple aging. While they are eating 66% fat by calories, 33% from saturated fat, they have very low levels of atherosclerosis. Please read the author's comments that I have quoted as well; I feel the conclusions he draws flow very logically from the data.
Stephan
Thanks Stephan!
I did read your comments on your site and also obtained a copy of the full paper. I most strongly disagree with your conclusions. You present as certaintudes what neither the authors or the data indicate.
Stephan Wrote:
"You will see from the figures that the Masai men only develop atherosclerotic lesions after they stop eating a diet of exclusively milk, meat and blood."
Randy Writes:
No, this is not supported by the paper. Mann clearly states that this conclusion cannot be made.
From the paper:
"While there is a suggestion
of a decrease of sudanophilia with age from ages 10 through 30, this is not statistically supportable with the variance encountered
within these age groups. Neither was it possible to show an increase of sudanophilia
after age 30."
Your stating something as a certainly that neither the authors or data support.
What's especially noteworthy to me is the next line in the paper:
"It is remarkable, however, that
this degree of sudanophilia is found in a population where cholesteremia averages
125 mg per cent."
The authors are refering to the accept datum that low cholesterol levels (<150) are almost always associted with clean arteries, but in NOT with the Masia. In other words low cholesterol levels in high saturated fat diets break the rule, and CVD results. This is a crucial point that needs futher research. There's no doubt that low carb/high fat diets improve lipid levels, but if these levels do not reduce CVD(as they do in some high fiber high carb diets) then the low carb community is in for a big surprise. We really need imaging studies to settle this issue. The few imaging studies (admittedly not the best designs) I've seen do not bode well for high saturated fats diets.
The authors were so struck by this contradictory result that they remark latter in the paper in an even stronger way:
Mann Write:
"The most striking thing about the Masai data is the extent of arterial lesions in a
population with consistently low levels of cholesteremia."
Could the improved lipid numbers associated with high saturated fat low carb diets be a mirage?? It's an open question for me, but a question that this paper brings to the fore. We need imaging studies. Lets see whats going on inside peoples chest instead of just assuming that great numbers mean clean arteries. It certainly doesn't with the Masia and that's a conclusion that this paper does support.
You are partially correct that the authors do "muse" ("not conclude") that that some "noxious agent" absent from the murin period might be responsible the lack of occulsion and infarctions, but this one of several possibilities they consider along with exercise and life style. In no way do the authors present these as conclusions as you imply but as possibilities. They have no evidence that this guys were gorging in pastries fried in transfat.
As far as the protection form occlusions and infarcs the authors clearly give their view here:
"One obvious explanation for the Masai immunity to occlusive disease is the compensatory
increase of coronary vessel size
with age resulting in a net increase of lumen size despite a tripling of intimal thickness
during this time. This we attribute to high levels of exercise but we have no direct
proof. There are scattered bits of experimental evidence to support this thesis"
Finally when we compare the Masia data to the Bantu as regards CVD the Bantu win.
1. Masai- No heart disease, diseased arterise.
2.Bantu - No heart dieases, healthy arteries.
Seems like a no brainer for me.
Thanks for the discourse and glad I discovered your site. We share alot of common interests and I appreciate the generousity of sharing your time and knowledge.
Regards
Randy
Discussion continued at:
http://wholehealthsource.blogspot.com/2008/06/masai-and-atherosclerosis.html
thanks Stephan
My pleasure; thanks for triggering this extremely fruitful line of investigation!
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