Vitamin supplements are mostly non-effective, potentially harmful.

Vitamin supplements became a part of everyday life for many people. But are they really helping? The new findings from University of Colorado Cancer Center, which follows the study from 2012: “Dietary supplements and cancer prevention: balancing potential benefits against proven harms.”, suggests it is not necessarily true. One of the researchers, Tim Byers, reported: “we have discovered that taking extra vitamins and minerals does more harm than good.” Study concludes, that the amount of vitamins from the natural sources are sufficient for most of worlds population.

What about the research on the connection between different vitamins and cancer? Are these topics interesting for scientists? What we can learn from wast amounts of unstructured research data available?

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Vitamin D supplements

When we look at the figure above, we can see that the highest number of publications is for the research on vitamin D – cancer relation. Vitamin D helps the body use calcium and phosphorus to stronger our bones and teeth. After fairly brief exposure to sunlight, the body can make vitamin D for several hours. Dietary sources include a few foods that naturally contain vitamin D, such as fatty fish, fish liver oil, and eggs. However, most dietary vitamin D comes from foods artificially enriched with vitamin D, such as milk, juices, and breakfast cereals. Researchers suggest, that vitamin D can be beneficial in prevention of breast, prostate and colorectal cancer, but the evidence is not yet sufficient. However, anaverage person will get his daily vitamin D dose naturally, and vitamin D supplements are mostly non-effective. The researcher with the most publications about effects of vitamin D on organism is William B. Grant. The most cited research paper is “Vitamin D.” with 131 citations.


Vitamin E supplements

A number of studies in men have reported that vitamin E supplements are associated with an increased risk of cancer. One study (read – “only one so far”) had even reported, that taking vitamin E supplements it could double the risk of prostate cancer. On the other hand, the deficiency of vitamin E in the body is rare and associated with diseases or starvation. What is important, the clinical studies in general show that vitamin E supplements do not have any overall health benefit, do not reduce risk of heart disease or cancer, and may even lead to increased risk of heart failure. Available scientific evidence does not support claims, that vitamin E positively and significantly affects the growth of cancer cells that have already formed. When we look at the data, we can see that the number of publication about vitamin E and cancer is less than a half of the number for vitamin D. As opposed to the research about vitamin D, the research on vitamin E suggests, that it can be more harmful than helpful when consumed via vitamin supplements. If we look at the number of publications per country, we can see the majority of research done in USA (871). The global research effort spreads through four continents from USA to India,@ Italy to Australia. The most cited research paper on this topic is: “Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT).”

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B-complex supplements

In terms of B-complex publication rate, the folic acid (vitamin B9) gets all the attention. In 2006, folic acid supplements were found to increase the risk of developing breast cancer by 20%. In another trial researchers found that it increased the number of polyps, in the colon. Although many of these are harmless, some can become cancerous. As usual, the highest number of publications on this topic comes from USA(459), but China follows with nearly half as much (202). The most cited study for folic acid is: “Folic acid for the prevention of colorectal adenomas: a randomized clinical trial.” which is a good example of its potentially harmful effects. Vast majority of studies on folic acid supplements suggest, that the excessive exposure to this vitamin can cause more harm than good.


Vitamin C

High-dosage og vitamin C has been studied as a treatment for patients with cancer since the 1970s. So far, there is 11 150 studies on vitamin C – cancer relation. Most of the studies suggests that vitamin C helps to ease the side effects of chemotherapy and increase the quality of life for cancer patients. Some studies report positive effect of vitamin C on pancreatic and other cancers. Although high doses of vitamin C are used by many cancer patients, it is known, that more than 1g of vitamin C a day can damage kidneys by forming kidney stones. If you would like to read more about this topic, Kay-Tee Khaw is the researcher with the biggest contribution in the vitamin C – cancer research. The most cited research paper is: “Vitamin C pharmacokinetics: implications for oral and intravenous use.”


Vitamin K supplements

Looking at the first figure again, we can see that the research of the links between vitamin K and cancer is the least explored one, but the trend is rising in the past years. Vitamin K is necessary for normal blood clotting and other activities. The human body gets vitamin K from certain food and bacteria living in our intestines. Available scientific evidence does not support the use of vitamin K supplements for cancer treatment or prevention. The vitamin K is studied also in context of newborns, because in many countries it’s common to give vitamin K to newborns. The researchers conclude that the use of vitamin K does not influences the risk of children developing leukemia or any other cancer. The highest number of publications comes from USA(88) followed by Japan (66).

After looking at the results of our research overview, we can report only one thing: Vitamins are good for our bodies, as long as we obtain them from their natural sources. In majority of cases, vitamin supplements are more likely to harm us than to help us. Eat healthy, consult with your GP, don’t buy supplements unless adviced by medical professionals.

  • Henry Lahore

    60 health problems prevented or treated by vitamin D
    details on every study is at

    • Martin Majernik

      Yes, vitamin D, as all vitamins helps our bodies to prevent and treat many problems. However – that doesn’t mean, that one should take vitamin D supplements. What this article communicates is the scientific evidence, that most people manage to get their vitamin D doses in natural fashion. Supplements are useful for people with vitamin deficiencies – diagnosed by their GP.