Should I be taking vitamins to fight cancer?

Man holding a pill and a glass of water

Multivitamins and other dietary supplements can be helpful for people who are deficient in specific nutrients or cannot meet their needs through food alone for various reasons. But can vitamins help you fight cancer?

Supplements for preventing cancer

If you don’t currently have cancer, vitamins or supplements may seem like a smart way to prevent it. Unfortunately, there is a lack of evidence regarding vitamins and cancer prevention. Instead of supplements, the American Institute for Cancer Research recommends getting your nutrients from food. 

For example, eating a single orange gives you almost all the Vitamin C you need daily and is quality source of fiber and potassium. So, eating an orange has more advantages than taking a vitamin C supplement, which often contains far more vitamin C than you need. 

Supplements during cancer treatment

You must talk with your health care provider before taking supplements during any cancer treatment, as vitamins and supplements could have adverse effects on your cancer treatment. These products can increase side effects or decrease the effectiveness of a given therapy. Still, if you want to take a supplement, a doctor can help you determine if it’s safe or recommend a supplement to meet a nutrient deficiency due to treatment. 

Checking a vitamin deficiency

If you're unsure whether you’re deficient in a particular vitamin, you should ask your health care provider to check. Those who are deficient can meet with a registered dietitian (RD) to find ways to increase your intake of the necessary vitamins you’re lacking through changes in your diet. For example, an RD might suggest that someone low in iron adds more lean beef or beans to their diet.

Consuming vitamins safely

The U.S. National Institutes of Health (NIH) recommends getting nutrients from food instead of supplements. However, if you wish to supplement safely, you must read the label before purchasing a multivitamin to avoid products with greater than 100% of your daily value for any nutrient listed. 

Be an informed consumer and look for third-party verification testing, like NSF, USP or ConsumerLab, as the FDA does not approve safety or effectiveness of supplements. 

Maddie Holland, medical nutrition graduate student