In February, the 2015 Dietary Guidelines Advisory Committee submitted the Scientific Report of the 2015 Dietary Guidelines Advisory Committee which gives recommendations to the U.S. Department of Health and Human Services (HHS) and the U.S. Department of Agriculture (USDA) for the upcoming Dietary Guidelines. The Advisory Report isnot the final Dietary Guidelines.
On February 20, the New York Times ran an opinion piece, The Government’s Bad Diet Advice, by Nina Teicholz. It’s the typical Weston Price-type, pro-animal-product piece, in the same vein as writings by Nina Planck (no, they are not the same person).
I don’t think it is a terrible article – there are nutrients that vegetarians and vegans have to pay attention to in order to achieve optimal health and he hits on most of them. However, he makes it seem like all vegetarians or vegans are going to have problems with all of those nutrients, which is not the case.
Vitamin B12 is one example of his overblown concern. He emphasizes the myriad of problems that can occur from B12 deficiency, which are quite frightening. In fact, if you allow vitamin B12 deficiency to go on long enough, you’ll die – and along the way some pretty bad things are going to happen. But all you need to know is to take a supplement and you’ll likely have a better B12 status than your average omnivore.
I’m not going to go through every nutrient he mentions and point out what I think he got right and wrong – but you can check out any of them at VeganHealth.org.
Kresser asks, “But don’t vegetarians live longer than omnivores?” He answers, “While it’s true that some observational studies suggest that vegetarians and vegans enjoy longer lifespans, these studies were plagued by the ‘healthy user bias’.”
He goes on to explain that people with healthy lifestyle habits choose to be vegetarian and so the lower mortality of vegetarians can be explained simply by other lifestyle factors.
Kresser singles out the Health Food Shoppers (HFS) study as being the one study that has risen above healthy user bias, and points out that it showed vegetarians to be no better off than non-vegetarians.
In fact, the HFS study is one of the weakest study designs of all the cohort studies comparing mortality rates of vegetarians. In the 1996 paper on the HFS that Kresser cites, the authors state:
“Another limitation is that the questionnaire was short and did not include several important food groups (for example, dairy products, fish, alcoholic drinks), did not allow us to estimate energy intake, and did not include other factors known to be associated with health (exercise, socioeconomic status, past smoking habits). We were therefore unable to explore whether the significant associations observed were partly due to confounding by other dietary or non-dietary variables.”
In contrast, the Adventist Health Study-2, which produced the most recently published paper on vegetarian mortality, adjusted for smoking, exercise, income, education, alcohol, geographic region, and sleep. They found that vegans had a 15% lower rate of early death than non-vegetarians (this finding was not statistically significant, though very close).
Additionally, there are good reasons why a vegan diet might lead to lower mortality – much lower LDL cholesterol levels, body mass index, and hypertension. There is very strong evidence to suggest vegans have only a fraction of the risk of type 2 diabetes, partly due to plant iron being harder to absorb (link).
Kresser says, “Still, while it may be possible to obtain adequate nutrition on a vegetarian diet, it is not optimal – as the research above indicates.”
I will agree that meat-eating is the more convenient choice for getting some nutrients – though sometimes it’s an all too convenient way to get too many, such as in the case of iron, saturated fat, and cholesterol.
While we don’t yet know for certain if a vegan diet increases the chance of living longer, when you consider the dearth of studies showing that meat-eaters live longer than vegetarians, it seems like a jump to conclude that meat-eating is the “optimal” choice.