Care During Chemotherapy and Beyond

Vitamins and Cancer: What About Taking Diet Supplements and Vitamins

Should I consider taking vitamins and nutritional supplements before, after, or during chemotherapy?

Ask your physician, nurse, or dietitian about using nutritional supplements such as Boost, Ensure, and Carnation Instant Breakfast to help meet nutritional needs and maintain or gain weight.  There are many products available that can't be purchased at the grocery store.  Call 1-877-4WebMed to order products for home including those that are found at the grocery store.  A dietitian can help you add commercial supplements to your current diet, or if necessary, comprise your entire diet to meet all your estimated nutritional needs.
Will taking vitamins during chemotherapy help?
Diet vs. supplements - the preferred choice to meet nutritional needs is from the diet.  The vitamins, minerals and phytochemicals (a variety of compounds produced by plants) needed to help our bodies fight cancer are found in a well-balanced diet emphasizing plant-based foods.  According to the nutrition-based literature available, an inverse association has been noted between fruit and vegetable consumption and cancer risk.  In other words, eating more fruits and vegetables may lower your cancer risk.

It is difficult to determine if a specific nutrient is protective, or a specific combination and ratio of phytochemicals.  The ultimate goal is to maintain a well-balanced, plant-based diet, low in fats and sugars to help lower the risk of cancer.  Recommendations include at least 5 servings per day of a variety of fruits and vegetables with breads and starch consumption including 2-3 servings of whole grains.

In cancer research, the intake of individual vitamin supplements, as opposed to consuming fruits and vegetables, has not shown increased protection from these supplements.  In fact, three clinical studies were done examining the protective effects of beta-carotene and lung cancer, two of which found a higher association among cigarette smokers when beta-carotene was supplemented.  The third study showed neither benefit nor harm from the beta-carotene.  
Phytochemicals refer to a wide variety of compounds produced by plants.  They are found in fruits, vegetables, beans, grains, and other plants.  There are thousands of phytochemicals and they fall into groups such as the polyphenols (subgroup flavonoids), antioxidants (including carotenoids), and sulfides.  Phytochemicals have either antioxidant or hormone-like actions.

Flavonoids are found in soy beans, soy products, garbanzo beans, chickpeas, licorice, and tea.  These are estrogen-like substances from plants called phytoestrogens.

Antioxidants are commonly found in vegetables such as broccoli, brussel sprouts, cabbage and cauliflower.  There are many phytochemicals that fall into this category including carotenoids which are founds in carrots, yams, cantaloupe, butternut squash, and apricots.  The term antioxidant is often associated with vitamins and cancer protection. Antioxidants include vitamin C, vitamin E, selenium, and carotenoids.  These nutrients are associated with a reduced cancer risk due to their ability to scavenge free radicals from our body.  Free radicals are reactive compounds that can damage normal cells.

Sulfides are found in garlic and onions and may have a role in reducing risk of stomach cancer.   These nutrients are found naturally in many fruits and vegetables.  Due to their protective association in food, researchers are trying to determine if this benefit exists with supplemental phytochemicals.
Herbs have been used for hundreds of years to treat disease.  Many are safe, and others may have severe and harmful side effects, and possibly interfere with cancer therapies such as chemotherapy, radiation therapy and recovery from surgery.  A recent example has been the discovery that levels of chemotherapy were reduced in the body in people who were using the herb St. John's Wort.

Safety considerations are to tell your health care team about any herbal products you are using or are planning to use before, during, or after chemotherapy.  Ask your physician, nurse, or dietitian for reliable information about dietary supplements.  Stop taking the products immediately and contact your physician if you experience side effects such as wheezing, itching, numbness, or tingling in limbs. 
The jury is still out regarding supplementation of various phytochemicals and herbs to help prevent or fight cancer.  There are many studies being conducted regarding supplementing and/or megadosing different phytochemicals or herbs.  It appears that much of the encouraging herb / vitamin / cancer  data has been seen in animal studies, which do not necessarily cross over to human studies.  There isn't enough consistent and significant data at this point to draw any strong conclusions or associations to recommend the use of supplements.
Vitamins, Minerals, Herbs and Chemotherapy / Radiation Therapy for Cancer

Research is underway to determine the safety and possible benefits in using herbs, antioxidants, vitamins, and minerals during treatments.
Megadoses - The literature available has not proven that taking vitamins in small or large doses helps to prevent or reverse cancer.  Megadoses of vitamins can prove to be toxic or harmful in some instances.

Water-soluble vitamins are generally harmless due to our body's ability to excrete the excess vitamins as waste.  In some instances there can be negative effects, for example, high doses of Vitamin C can increase the risk of oxalate kidney stones, posing an increased risk for individuals with renal failure.  B6 (pyridoxine), even in moderate dosages, could result in nerve damage.

Quite the opposite of fighting diseases such as cancer, fat-soluble vitamins in large doses can become toxic, because they are stored in the body.  Vitamin A toxicity can lead to changes in bone development, an enlarged liver, anemia, and loss of hair.  High doses of Vitamin D can produce high calcium levels with calcifications in the kidney and blood vessels, and possibly result in osteoporosis.

Note:  We strongly encourage you to talk with your health care professional about your specific medical condition and treatments. The information contained in this website is meant to be helpful and educational, but is not a substitute for medical advice. is designed to provide the latest information about chemotherapy to patients and their families, caregivers and friends. For information about the 4th Angel Mentoring Program visit