Wednesday, January 6, 2016

Not all vegetarian diets the same, and full vegan's not the best for long life

Eat vegetarian and you’ll live longer. No brainer, right? 

Actually, it’s complicated.

Most studies suggest that a vegetarian lifestyle gives you longer life. But some vegetarians do better on some measures than meat eaters—but there are also some vegetarians who do far better than other vegetarians. 

Spoiler alert: based on our review of the biggest studies, you should eat mostly vegetarian, but eat some dairy and fish, too. You’ll live longer than by eating a pure vegan diet.

Certainly not what we expected. So, what’s going on?

Heart disease is a major killer. It seems clear from most studies that a vegetarian or largely vegetarian diet is associated with lower heart disease, especially in men. A famous series of British studies found that 1 in 20 vegetarian men have hypertension, while 3 in 20 meat eaters do. The numbers are less stark for women, but they still hold. American studies have similar results.

But ultimately, one way of looking at the data with respect to heart disease is that this particular study did not find that the vegetarian diet made all the difference—rather that body weight did. “Non-meat eaters, especially vegans, have a lower prevalence of hypertension and lower systolic and diastolic blood pressures than meat eaters, largely because of differences in body mass index.”

So, what’s going on there?

This related study found that if you’re eating a high-fiber diet that’s low in protein, you’re less likely to be fat. And the previous study says if you’re less likely to be fat, you’re less likely to have high blood pressure. 

But here is perhaps the more interesting and perplexing study result: Despite a higher death rate for people with high blood pressure, the British studies on more than 50,000 individuals showed that the overall death rate of vegetarians studied wasn’t much different than that of meat eaters. 

That’s weird, right? Because it flies in the face of accepted logic.

Well, there are a couple of things going on. One is that even the British non-vegetarians in these studies may have been eating better than the average Brit, since meat-eaters in this study have better health outcomes than the national average. (One clue: part of the study involved meat-eaters who shop at health food stores.)

When the massive British study is paired with an even bigger study of American Seventh-Day Adventists, the picture gains some clarity, but some more complexit.

It seems that British vegetarians eat a different vegetarian diet than American Seventh-Day Adventist  vegetarians do. Maybe not as good a vegetarian diet, in terms of promoting long life.

The British results, from what’s known as the EPIC-Oxford studies, are very different in overall mortality from American ones in the American Seventh-Day Adventist study by Loma Linda University School of Public Health researchers. This one was on more than 96,000 American Seventh-Day Adventists, half of whom follow some version of a vegetarian diet, but about half of whom don’t.

The American study found death rates among vegetarians was significantly lower than among meat-eaters, but that the rates differed between different kinds of vegetarians.

The American Loma Linda researchers knew about the British study, and looked into the differences. Their finding: “It appears that British vegetarians and US Adventist vegetarians eat somewhat differently.”

And that matters. “Although vegetarian diets are healthful and are associated with lower risk of several chronic diseases, different types of vegetarians may not experience the same effects on health.” So says this study.

A big difference: American Seventh-Day Adventist vegetarians  ate far more fiber, and far more vitamin C. Close to 70 percent more fiber and Vitamin C in the Americans. Maybe there are other differences, too. But those stood out.

“… the vegetarians in our study consume more fiber and vitamin C than those of the EPIC-Oxford cohort: mean dietary fiber in EPIC-Oxford vegans was 27.7 g/d in men and 26.4 g/d in women compared with 45.6 g/d in men and 47.3 g/d in women in AHS-2 vegans; mean vitamin C in EPIC-Oxford vegans was 125 mg/d in men and 143 mg/d in women compared with 224 mg/d in men and 250 mg/d in women in AHS-2 vegans,” the Loma Linda study says. 

Loma Linda researchers also noted that there are a lot of different kinds of vegetarian eaters. Here’s the list Loma Linda used to describe their sample: vegan (No red meat, fish, poultry, dairy or eggs); lacto-ovo vegetarian (Consume milk and/or eggs, but no red meat, fish or poultry); pesco-vegetarian (Eat fish, milk and eggs but no red meat or poultry); semi-vegetarian (Eat red meat, poultry and fish less than once per week); non-vegetarian (Eat red meat, poultry, fish, milk and eggs more than once a week). 

In general, the more meat you eat, the poorer your outcome in these studies—with one major caveat. People who ate fish with their vegetarian fare, even when they included milk and eggs, were even less likely to die early than vegans.

© Jan TenBruggencate 2016

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