What do randomized controlled trials of high-dose daily vitamin B12 supplementation show about its effects on cancer risk, death, and longevity?
In 2019, “Association of High Intakes of Vitamins B6 and B12 from Food and Supplements with Risk of Hip Fracture in Postmenopausal Women in [Harvard] Nurses’ Health Study’ was published. Note, however, that only a combined high intake of vitamins B6 (≥35 mg/day) and B12 (≥20 mcg/day) was associated with an increased risk of hip fracture. We know that high-dose vitamin B6 therapy can increase risk of hip fracture on its own. After about a decade, those taking high-dose B6 supplements (40 mg) had about a 40 percent higher risk of hip fracture, but not those taking B12, as you can see below and at 0:35 in my video Do vitamin B12 supplements cause bone fractures and lung cancer?.
This is what Harvard is studying I establishalso. High vitamin B12 intake alone was not associated with increased risk. Yes, some observational studies recommend slightly lower fracture risk at high blood B12 levels. What we’re most interested in, though, are the interventional studies, where people are randomized to B12, so we can see what happens, and when we look at them, find no increased risk of fracture among those given B12. In conclusion, based on randomized controlled trials, high doses of vitamin B12 have not been done it seems be associated with fracture risk.
OK, but what about this? In 2017, a study I establish that men who took vitamin B12 supplements appeared to have an increased risk of lung cancer. Now, the researchers found no such association in women, and the increased risk was mostly among men who smoked. It could have been that the B12 was feeding budding tumors? It’s hard enough to imagine a vitamin being carcinogenic by itself, especially if it somehow only affects men and not women as well. “Replication of these findings in additional prospective studies with careful measurement of B vitamin supplement use is warranted.” And, indeed, when you put together all the observational studies, there it is there is no significant association between lung cancer and blood B12 levels, whether you have smoked or not. If anything, most studies seemed to lean toward higher B12 levels being protective, as you can see below and at 2:03 in my video.
Then, in 2018, a new study I establish an association between overall lung cancer risk and higher circulating B12 levels, again seems to be of greater concern for smokers, as seen here and at 2:16 in my video.
Now, this it was another observational study. Those who had higher levels of B12 were just observed to have higher levels of cancer. Those of you who follow my work know the drill: There are two potential issues that arise in observational studies that prevent us from attributing cause-and-effect: confounding factors, also known as “hidden variables,” and reverse causality.
What could be a lurk variable in this case? What might be a third factor associated with both higher B12 levels and cancer that might be the real cause? So, who has higher levels of B12 circulating in their blood? Those who eat a lot of meat and dairy, which are, in fact, “the most important contributors to serum vitamin B-12,” meaning the B12 in our blood. And those who eat more meat tends to have more lung cancer: “Dose-response analysis showed that eating red meat for 120 g per day can increase the risk of lung cancer by 35%, and eating processed meat for 50 g per day can increase the risk of lung cancer by 20%. So, overall, we’re talking about a 35 percent higher risk for every quarter-pound burger eaten, and about a 20 percent increased risk for every breakfast sausage link. It is no wonder that those with higher levels of B12 in their blood could have more lung cancer. B12 could simply be an indicator for meat intake.
And, if you remember, reverse causation is when X may not lead to Y, but, instead, Y may lead to X. So instead of high B12 blood levels leading to cancer, perhaps cancer leads to high B12 blood levels. And, indeed, almost 75 percent of patients were diagnosed with cancer exhibit elevated B12 levels. So, elevated B12 levels can simply it is marker for cancer. In addition to taking extra B12, there hectare all kinds of reasons why your levels might be elevated, including liver problems, kidney problems, bone marrow problems, and cancer, as you can see below and at 3:50 in my video. So, high B12 levels can simply it is an indicator of brewing, but not yet diagnosed, cancer.
What about observational studies specifically? login B12 supplement use in lung cancer, though? They could too it is reverse causality: “The consequence of cancer risk is that patients will adopt healthier behaviors, including taking multivitamins (reverse causality). “The established causes, such as smoking, chronic obstructive pulmonary disease and previous cancers, are the real risks for lung cancer.” So we are left with this ‘chicken or egg causality dilemma’, so ideally we need randomized controlled trials to see if there is any cause and effect.
This became even more urgent with genetics suggesting that those born with higher lifetime levels may be at increased risk. Fortunately, as you can see below and at 4:47 in mine videowe have randomized controlled trials — more than a dozen randomized controlled trials randomization In fact, thousands of people up to 2,000 micrograms of B12 every day for years.
The findings? “B vitamin supplements have no effect on cancer incidence, cancer death, or total mortality.” And that specifically includes screening for lung cancer, as shown below and at 5:02 in my video. In fact, if anything, B vitamin supplements may actually reduce the risk of the most dangerous form of skin cancer.
If you missed my previous video, check out Vitamin B12 Supplements Cause Acne?.
For my other Updates B12see related posts below. All these videos can be found in one digital download: Latest recommendations for vitamin B12.
have also investigated the role of vitamin B12 in stroke risk. See related posts below. This series is also available for digital download: Why do vegetarians have a higher risk of stroke?.
