Dietary supplements are intended to help people meet nutritional needs. When used correctly, they may help reduce your risk of certain diseases, minimize discomfort and improve your quality of life. But are they appropriate to take if you're undergoing cancer treatment? 

"The short answer is we don't really know enough about how dietary supplements interact with cancer treatment, and until we know more, it's hard to recommend their use broadly for anyone being treated for cancer," says Nebraska Medicine cancer doctor Christopher D'Angelo, MD.

Read on to learn more about dietary supplements, their risks and what to consider if you're being treated for cancer. 

What are dietary supplements?

Dietary supplements refer to a wide range of nutritional products, including vitamins, minerals, herbs, amino acids and enzymes. You can find them in many forms, such as pills, gummies, powders and liquids. Unlike prescription or over-the-counter medications, dietary supplements are not intended to treat, prevent or cure diseases.

Are all supplements regulated?

Herbal supplements fall under the category of dietary supplements and are regulated by the U.S. Food and Drug Administration. However, they are not regulated as strictly as prescriptions or over-the-counter medication. In fact, supplement manufacturers can say whatever they want about their products if they follow these rules:

• Ensure supplements are free of contaminants and accurately labeled
• Have research to support claims that a product addresses a nutrient deficiency or supports health, and include a disclaimer that the FDA hasn't evaluated the claim
• Avoid making specific medical claims, such as reducing urinary frequency

What are the risks of taking supplements during cancer treatment?

Most people can use dietary supplements safely if they don't take too much, but supplements are not totally safe. For example, guidelines released by the U.S. Preventive Services Task Force recommend against taking beta carotene, a compound that converts to vitamin A in the body, which may increase the risk of lung cancer in patients who smoke tobacco or have been exposed to asbestos. 

If you have been taking supplements and want to continue taking them, it's important to discuss them with your doctor. Some supplements may interact with your cancer treatment and increase side effects or decrease effectiveness. 

When might a cancer patient need to take supplements?

If you're getting all the nutrients you need through the food you eat, it's unlikely you need a dietary supplement. However, if you can't get the essential nutrients in your diet, a general multivitamin may be beneficial, even during cancer treatment. 

Additionally, your doctor may prescribe a supplement if you have or may develop a vitamin deficiency caused by cancer treatment. For example, certain cancer therapies can weaken bones and contribute to osteoporosis. So, your doctor may prescribe calcium and vitamin D to support your bone health. Also, some chemotherapy can decrease potassium and magnesium, so your doctor may also recommend you supplement those during treatment.

Otherwise, it's best to peel back the use of dietary supplements until after you have completed your cancer treatment to minimize pill burden and conflicting effects on the body. Some data suggest ginseng can help support fatigue in cancer patients following treatment. Even then, it depends on a variety of factors. Therefore, it's best to work with your doctor to determine what's best for you.

What are some common misconceptions about supplements?

One misconception is that we must take supplements. Most of the vitamins and minerals we need are adequately provided in our diet. If not, it's an excellent opportunity to change your diet to be healthier. Your doctor can refer you to a dietitian who can work with you to ensure you're getting the nutrients you need.

Additionally, many people believe that all supplements are created equal. That's not true. The quality of nutritional supplements varies widely, and it's important to do your due diligence to verify the ingredients and understand how those will affect you. Working with your doctor can help, but the bottom line is if a product sounds too good to be true, it likely is.

Another misconception is that when you take a multivitamin, your body will use what it needs and get rid of the rest naturally. In truth, it's best not to introduce anything into our bodies that we don't need. Unless you have a history of a specific vitamin deficiency or are at risk for one, aim to get your nutrients through food.

"A supplement must be overwhelmingly safe for me to consider recommending its use during cancer treatment," says Dr. D'Angelo. "I often tell patients, ‘If these supplements aren't important to you, I wouldn't recommend taking them.'"