If you're not getting all of the necessary nutrients you need from your diet, it seems easy to turn to supplements. While this can be a solution for some people who have nutrient deficiencies, it isn't always wise to just choose a supplement and take it because you heard it's healthy for you. And in the case of some vitamins, it can even be dangerous. According to a study from Cancer Epidemiology, Biomarkers & Prevention, folic acid and vitamin B12 supplements are actually linked to an increased risk of colorectal cancer.
This study evaluated over 2,500 participants over a two to three-year period of daily supplementation. Some took a daily supplement of folic acid (400 micrograms) and vitamin B12 (500 micrograms), while others took a placebo. The Netherlands Cancer Registry evaluated the data using the International Statistical Classification of Disease to search for all kinds of cancers, including colorectal cancer (and excluding skin cancer).
The results concluded that B vitamins (like B12 and folic acid, which is vitamin B9) were associated not only with a higher risk of overall cancer, but also "significantly associated with a higher risk of colorectal cancer." While researchers point out that further research would need to be done in order to confirm their findings, they conclude by stating that supplementation of folic acid and vitamin B12 should be limited to patients who have a known deficiency—and likely prescribed by a doctor.
Nevertheless, this study does contradict previous research that has been done—especially on folic acid. The Dietary Reference Intake (DRI) for folic acid is at 400 micrograms a day and rises to 600 micrograms during pregnancy. One previous study from Cancer Epidemiology actually concluded that folic acid supplementation before and during pregnancy did not have an effect on maternal cancer risk.
Secondly, this study had participants taking 500 micrograms of vitamin B12, which is incredibly high compared to the DRI that is recommended from B12 intake, which is just at 2.4 micrograms a day. While the toxicity of the vitamin has not been documented, deficiencies of this vitamin are uncommon. Unless a supplement is recommended by a doctor, one can easily get a sufficient amount of vitamin B12 in a day through consuming animal products (eggs, milk, cheese) and fortified foods (cereals, juices, tofu, milk alternatives, and more).
Folic acid can also be consumed through a variety of foods including dark leafy green vegetables, beans, peanuts, sunflower seeds, fresh fruits and juices, whole grains, liver, seafood, eggs, and other fortified items.
So what does this mean for supplementation—should you take a vitamin B12 or folic acid supplement at all? Researchers concluded that if there is a known deficiency and a doctor recommends supplementation, that would be the appropriate time to implement a supplement into your diet. But if this is not something the doctor is recommending to you, you can easily attain enough of these vitamins through dietary sources.
For more supplement tips, these are the Supplements You Should Give Up in 2022, Say Dietitians.
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