Do Vitamin Supplements Lower Cancer Risk?

By Carol L. Kornmehl, M.D, FACRO

Fruits and vegetables are known to protect people against lung, oral, esophageal, stomach, and colon cancer. The data that supports this statement has been borne out by a number of studies. In fact, fruits and vegetables are the best source of vitamins and minerals, including antioxidants. These healthful compounds probably work best in combination. Because we don’t know which of the many compounds in these foods are most helpful, the American Cancer Society advises the public to eat at least five assorted servings of produce per day.

Vitamin Supplements
It’s easier to persuade people to take vitamin pill supplements to fulfill their daily requirements than it is to convince them to change their diets. Yet, vitamin pills often contain only a fraction of what is capable of being assimilated by the body when compared to fruits and vegetables. Furthermore, there are likely to be significant compounds in the whole foods we have not yet identified, and therefore, cannot add to supplement pills.

Clinical Studies of Supplements

A study was performed to determine the benefits of beta-carotene and retinol (types of vitamin A) in lung cancer risk reduction. Ironically, the study found that beta-carotene and retinol supplements actually increased the lung cancer risk, especially among smokers. To more carefully evaluate the relationship, the researchers undertook another study to evaluate vitamin supplements and several types of cancer, with the focus being on lung cancer. The study group consisted of 77, 721 men and women aged 50 to 76 who lived in the state of Washington. Participants completed a 24-page survey on the kind of vitamin supplements, dose, and duration of use over the prior ten years. The cancer registry monitored the subjects of the study for the development of lung cancer over a nearly four-year period.

Summary of Findings

The investigators found 521 cases of lung cancer. Adjusting for risk factors for lung cancer, namely smoking, age, sex, previous cancer history, and other lung disease including a history of prior lung cancer, the researchers found the following:

  • There was no statically significant increased risk for lung cancer with increasing years of multivitamin use for all types of lung cancer (non-small cell and small cell).
  • There was no statically significant increased risk for lung cancer with increasing daily dose of vitamin C for all types of lung cancer.
  • There was no statically significant increased risk for lung cancer with increasing daily dose of folate (folic acid) for all types of lung cancer.
  • There was no statically significant increased risk for small cell lung cancer with increasing daily dose of vitamin E, but
  • There was a small but significant increase in non-small cell lung cancer risk with increasing daily dose of vitamin E.

The researchers then analyzed the effect of smoking status on multivitamins, vitamin C and folate, but found no associations. In contrast, for vitamin E use among current smokers (but not former smokers), there was an elevation of cancer risk.


These results suggest but do not prove that most vitamin supplementation is safe with respect to lung cancer. Oddly, some supplements may actually increase cancer risk. Nevertheless, the take home message of the study is: to reduce cancer risk, people should consume antioxidants through food sources, rather than through vitamin supplements, as there is strong evidence that a diet rich in fruits and vegetables may reduce the risk of cancer, while there is no proof that supplements can do so. Supplements, however, may be helpful for people with restricted dietary intakes. If one is taken, the best choice is a balanced multivitamin/mineral supplement containing no more than 100% of the “Daily Value” of most nutrients.

Also, the good news is that by consuming a wide variety of palatable fruits and vegetables, with a goal of eating at least five such servings per day, people have easy access to a natural way to help reduce their risk of developing cancer.

Dr. Kornmehl is a board certified radiation oncologist at St. Mary’s Passaic Hospital, Passaic, NJ and is the author of the critically acclaimed consumer health book, “The Best News About Radiation Therapy” (M. Evans, 2004). She may be contacted via

Copyright 2007 by Carol L. Kornmehl. All rights reserved. No part of this article may be reproduced without express written permission of the author.

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