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Multivitamin supplements and cancer: is there a role?

man and woman looking at a bottle of supplements and its label

Contributed by Nancy Burke, R.D., Danielle Karsies, M.S., R.D., and Melissa Shannon-Hagen, R.D., CSO
U-M Rogel Cancer Center Symptom Management and Supportive Care Program

It is well known that the appropriate intake of vitamins and minerals is essential to overall health. This is likely the driving force behind the 49% of U.S. adults who are taking at least one dietary supplement. Most people assume that multivitamin supplements are harmless, since they are perceived as natural. But a recent review of the research, which has been well represented in the media, has actually shown that there can be harm with nutrition supplement use in healthy populations.

The U.S. Preventative Services Task Force, which bases its recommendations on the potential benefit, harm and overall balance between the two, does not feel there is sufficient evidence to promote or avoid multivitamin supplements. It does, however, recommend the avoidance of beta-carotene and vitamin E supplements, which can increase the risk of certain types of cancer and death, and it warns against vitamin A supplementation due to its potential harm. These recommendations only apply to healthy adults without special nutritional needs in relation to the prevention of cardiovascular disease and cancer.

Other organizations including the Academy of Nutrition and Dietetics, the American Cancer Society, the American Institute of Cancer Research and the American Heart Association do not promote the use of dietary supplements to prevent cancer or heart disease.

If you are a cancer survivor, you do not fall into the recommendation above, but to date, there are not specific nutrition supplement recommendations for you that are supported by evidence.

Supplementation recommendations during cancer care should be individually recommended by a qualified, medical clinician to ensure it is necessary and to avoid potential interactions with your treatment. For example, almost 1/3 of people with cancer have vitamin D deficiency and would benefit from a vitamin D3 supplement for repletion, but vitamin D supplementation is not recommended for all cancer patients.

Additionally, while antioxidants can potentially decrease the negative effects from radiation and chemotherapy drugs that rely on free radicals, it may come at the cost of increased return of disease and death. To ensure that cancer treatments are as effective as possible, antioxidant supplements are not recommended during treatment.

The problem with focusing on this supplement debate is that the real issue is being ignored.

We are so focused on an easy fix for cancer and this is supported by statistics. In one study, 50% of breast cancer patients were taking a multivitamin, but 70% of these individuals had an unhealthy BMI, one of the main risk factors for increased risk of breast cancer.

The real focus should not be on supplements, but on eating a healthy diet focused on whole grains, vegetables, fruits, and legumes that will nourish your body with all the nutrients you need to prevent cancer and other chronic diseases.

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