The Science on Supplements

assorted pills, gelcaps and capsules spilled out onto white surface

You might have heard that certain vitamins, extracts, and other dietary supplements can prevent cancer “naturally.” But the truth is scientific research has not been able to back up such claims. For every study that finds a lower risk of cancer in people taking certain supplements, there’s another study showing a higher risk of cancer in people taking certain supplements.

Supplements include vitamins, minerals, herbs, protein powders, botanicals, and other extracts. Some manufacturers use the term “all natural” to describe supplements made from plant material. But that doesn’t make them safer or better than refined or manufactured substances. After all, plants are made up of many chemicals, and some plants in nature are harmful or poisonous if eaten, while others are nutritious or helpful.

What’s more, dietary supplements are not regulated by the US Food and Drug Administration, so the ingredients in them aren’t necessarily safe or within non-toxic levels. People who take supplements are at risk of taking more of a nutrient than they need or is even healthy. That’s because, unlike the vitamins and minerals we get through eating food, supplements usually include isolated nutrients, often in much higher doses, and sometimes with different chemical forms. You should always check with your doctor before you take any dietary supplements, especially if you are taking any prescription drugs.

So far, selenium, vitamin C, vitamin D, folate, and other supplements have not shown any promise in preventing cancer. Studies on a variety of supplements are ongoing, but much more research is needed before researchers can offer solid advice. 

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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