The cardiovascular benefits of plant-based diets may be severely undermined by vitamin B12 deficiency.
Images thanks to Coolmikeol, Lisaclarke, Marcos Vasconcelos Photography, massdistraction and Rob Swatski via Flickr. Thanks to Ellen Reid for her image-finding expertise and Jeff Thomas for his Keynote help.
Other studies have also found less arterial wall thickening in those eating plant-based diets. This new study from China, for example, found that compared to omnivores, those that ate egg-free and meat-free diets, had all the typical benefits of eating more plant-based: remarkably lower body mass index, blood pressure, triglyceride, total cholesterol, and bad cholesterol; less free radicals; maybe better kidney function and blood sugar control, etc. But does all that translate to an actual difference in their arteries? Yes, indeed, the omnivores had comparatively thickened arterial linings, all of which suggests about a tripling in the probability of developing cardiovascular disease. They therefore recommend that more vegetables should be eaten instead of meat, and it is never too late to improve one’s diet.
Having said that, if those on plant-based diets don't get enough vitamin B12, levels of an artery-damaging compound called homocysteine can start to rise in the bloodstream and may counteract some of the benefits of eating healthy. In this study from Taiwan, the arteries of vegetarians were just as stiff as the omnivores and they had the same level of thickening in their carotid arteries, perhaps because of the elevated homocysteine levels. The negative findings of these studies should not be considered as evidence of neutral cardiovascular effects of vegetarianism, but do indicate an urgent need for modification of vegan diets through vitamin B12 fortification or supplements. Vitamin B12 deficiency is a very serious problem leading ultimately to anemia, neuropsychiatric disorders, irreversible nerve damage, and these high levels of artery damaging homocysteine in the blood. Prudent vegans should include sources of vitamin B12 in their diets.
One study of vegetarians whose B12 levels were really hurting even had thicker, more dysfunctional arteries than omnivores. How do we know B12 was to blame? Because when they were given B12 supplements they got better. Their arterial lining started to shrink back and the proper functioning of their arteries returned.
Without B12 fortified foods or B12 supplements, when omnivores are switched to a vegan diet, they develop vitamin B12 deficiency. Yes, it may take dropping down to around 150 picomoles per liter to develop classic signs of B12 deficiency, like anemia, and your spinal cord rotting away, but way before that you may start getting increased risk of cognitive deficits and brain shrinkage, stroke, depression, and nerve and bone damage, as well as having your homocysteine shoot through the roof. And that may attenuate the beneficial effects of a vegetarian diet on cardiovascular health. The beneficial effects of vegetarian diets on cholesterol and blood sugars need to be advocated, but at the same time efforts to correct vitamin B12 deficiency in vegetarian diets can never be overestimated.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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Make sure you see the “prequel” to this video: Arteries of Vegans vs. Runners.
I have dozens of videos on B12. For a quick cut-to-the-chase see my Q&A What is the best way to get vitamin B12? and for some context Vegan B12 deficiency: putting it into perspective. Vitamin B12 supplementation with fortified foods or supplements is critical on a plant-based diet.
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