Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Two cases of young strictly vegetarian individuals with no known vascular risk factors—yet suffering a stroke, or multiple strokes. Why? Most probably because they weren’t taking vitamin B12 supplements, which leads to high homocysteine levels, which can attack your arteries.
So those eating plant-based failing to supplement may increase one’s risk of both heart disease and stroke. Now vegetarians have so much heart disease risk factor benefit that they are still at lower risk overall, but this may help explain why vegetarians were found to have more stroke. Presumably this disparity would disappear with adequate B12 supplementation and this benefit, would grow even larger.
Compared with non-vegetarians, vegetarians enjoy all these other advantages: better cholesterol, blood pressures, blood sugars, and obesity rates. But, like what about that stroke study? And even among studies that show benefits, they’re not as pronounced as one might expect, which may be a result of poor vitamin B12 status. Vitamin B12 deﬁciency may negate some of the cardiovascular disease prevention beneﬁts of vegetarian diets; so, in order to further reduce the risk of cardiovascular disease, vegetarians should be advised to use vitamin B12 supplements.
How can you determine your B12 status? By the time you’re symptomatic with B12 deficiency it’s too late, and initially the symptoms can be so subtle you might even miss them. And well before you develop clinical deficiency, you develop metabolic vitamin B12 deficiency: a missed opportunity to prevent strokes, where you have enough B12 to avoid deficiency symptoms, but not enough to keep your homocysteine in check. Underdiagnosis of the condition results largely from failure to understand that a normal B12 blood level may not reflect an adequate functional B12 status. The levels of B12 in your blood does not always represent the levels of B12 in your cells. You can have a severe functional deﬁciency of B12 even though your blood levels are normal or even high.
Most physicians tend to assume that if the B12 level in your blood is “normal”, there is no problem. But, within the lower range of normal, 30% of patients could have metabolic B12 deficiency, with high homocysteine levels.
Measuring methylmalonic acid levels or homocysteine directly are a more accurate reflection of vitamin B12 functional status. Methylmalonic acid can be a simple urine test; you’re looking for less than a value of 4 (micrograms per milligram of creatinine). “Elevated MMA is a specific marker of vitamin B12 deficiency while homocysteine rises in [the context of] both vitamin B12 and folate deficiencies”; and so, metabolic B12 deficiency is defined by an elevation in MMA levels or by elevation of homocysteine in people getting enough folate. Even without eating beans and greens, which are packed with folate, folic acid is added to the flour supply by law; and so, high homocysteine levels these days may be mostly a B12 problem. Ideally, you’re looking for a homocysteine level in your blood down in the single digits.
Measured this way, “the prevalence of functional vitamin B12 deficiency is dramatically higher than previously assumed,” like 10%-40% of the general population, and more than 40% in vegetarians, and the majority of vegans who aren’t scrupulous about getting their B12. Some suggest that those on plant-based diets check their vitamin B12 status every year, but you shouldn’t need to if you’re adequately supplementing, and evidently there are rare cases of vitamin B12 deficiency that can’t be picked up on any test; so, better to just make sure you’re getting enough. If you do get your homocysteine tested and it’s still up in the double digits even despite B12 supplementation, I do have a suggestion in the final videos of this series, which we’ll turn to, next.
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