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As Japan westernized, their stroke rate plummeted. Stroke was the leading cause of death in Japan, but the mortality rate sharply decreased as they moved away from their traditional diets and started eating more like those in the west; so, maybe there was a protective effect of all the extra meat and dairy they started to eat. After all, their animal fat and animal protein intake were going up at the same time their stroke rates were going down.
“Protection from stroke by eating animal foods? Surely not!” commented a noted Loma Linda cardiology professor. “Many vegetarians, like myself have almost come to expect the data to indicate that they have an advantage, whatever the disease that’s being considered. Thus, it is disquieting to find evidence in a quite different direction for at least one subtype of stroke.”
Can dietary saturated fat, like that found in meat and dairy, be beneficial in the prevention of stroke risk? There appeared to be a protective association, but only in East Asian populations. High dietary saturated fat was found associated with a lower risk of stroke in Japanese but not in non-Japanese. So, what was it about the traditional Japanese diet where the Westernization of their diets made things better when it came to stroke risk? Well, at the same time their meat and dairy was going up, their salt intake was going down.
The traditional Japanese diet was packed with salt—in fact, they had some of the highest salt intakes in the world, like a dozen spoonfuls of salt a day. Before the widespread availability of refrigeration, they ate all sorts of salted, pickled, fermented foods from soy sauce to salted fish. And in the areas that had twice the salt intake, they had twice the stroke mortality, but when the salt intake dropped do did the stroke death rates, because when the salt came down their blood pressures came down, too. And high blood pressure is perhaps the single most important modifiable risk factor for stroke. So, it’s no big mystery why the westernization of the Japanese diet led to a drop in stroke risk.
When they abandoned their more traditional diets their obesity rates went up, their diabetes and coronary artery disease went up, but as they gave up the insanely high salt intake their insanely high stroke rates correspondingly fell. It’s like if you look at their stomach cancer rates, a cancer closely associated with excess salt intake. Their stomach cancer rates came down beautifully as they westernized their diets away from salt-preserved foods, but of course as they started eating more animal foods like dairy, their rates of fatal prostate cancer, for example, shot through the roof. Compared to Japan, not only does the U.S. have seven times more deaths from prostate cancer, but five times more deadly breast cancer, three times more colon cancer and lymphoma mortality, and six to twelve times the death rate from heart disease. Yes, Japanese stroke and stomach cancer rates were higher, but they were also eating up to a quarter cup of salt a day.
That would seem to be the most likely explanation, rather than some protective role of animal fat, as eventually acknowledged in the official Japanese guidelines for the prevention of cardiovascular disease.
Now, one of the Harvard cohorts found a protective association between both saturated fat and trans fat for hemorrhagic strokes, prompting a “sigh of relief throughout the cattle-producing Midwest,” even though the researchers clearly concluded that, of course, we all have to cut down on animal fat and trans fat for the heart disease benefit regardless, but looking at another major Harvard cohort they found no such protective association for any kind of stroke, and put all the studies together and zero protection across the board.
Observational studies have found that higher LDL cholesterol seems to be associated with lower risk of hemorrhagic stroke, raising the possibility that low cholesterol may be a double-edged sword, decreasing the risk of ischemic stroke but increasing the risk of hemorrhagic stroke. But low cholesterol levels in the aged may just be a surrogate for nutrient deﬁciencies, or a sign of debilitating diseases, or maybe they’re on a combo of cholesterol-lowering drugs and blood thinners, and that’s why we tend to see more brain bleeds in those with low cholesterol? You don’t know, until you: put it to the test. Put together about two dozen randomized controlled trials, and the lower your cholesterol the better when it comes to overall stroke risk, with no significant increase in the risk of hemorrhagic stroke with lower achieved LDL cholesterol levels.
The genetic data appears mixed, with some suggesting a lifetime of elevated LDL would give you a higher hemorrhagic stroke risk, and other data suggesting more of a double-edged sword effect, but any possible excess of bleeding stroke with lower cholesterol is greatly outweighed by the protective effect against the much more common clotting stroke, not to mention heart disease, perhaps on the order of 18 fewer clotting strokes for every one extra bleeding stroke with cholesterol lowering.
How about this as a candidate to explain the increased stroke risk found among vegetarians? This is the type of stroke that appeared higher in vegetarians, but the cholesterol levels in vegans were even lower and, if anything, they had a trend towards a higher clotting stroke risk; so, that doesn’t really make sense. If there is some kind of protective factor in animal foods, it is to be hoped that a diet can be found that still protects against killer #1, heart disease, without increasing the risk of killer #5, stroke. But first, we have to figure out what that factor is, a hunt that will continue, next.
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