A dietary supplement is a product that is added to the diet. It is usually taken by mouth, and usually has one or more dietary ingredients. Cancer patients may take dietary supplements to improve their symptoms or treat their cancer.

Vitamin C

• Vitamin C is a nutrient that the body needs in small amounts to function and stay healthy. It helps fight infection, heal wounds, and keep tissues healthy.
• Vitamin C is found in fruits and vegetables. It can also be taken as a dietary supplement.

Probiotics

• Probiotics are live microorganisms used as dietary supplements to help with digestion and normal bowel function. They may also help keep the gastrointestinal tract healthy.
• Studies have shown that taking probiotics during radiation therapy and chemotherapy can help prevent diarrhea caused by those treatments. This is especially true for patients receiving radiation therapy to the abdomen.
• Cancer patients who are receiving radiation therapy to the abdomen or chemotherapy that is known to cause diarrhea may find probiotics helpful.

Melatonin

• Melatonin is a hormone made by the pineal gland (tiny organ near the center of the brain). Melatonin helps control the body’s sleep cycle. It can also be made in a laboratory and taken as a dietary supplement.
• Several small studies have shown that taking a melatonin supplement with chemotherapy and/or radiation therapy for treatment of solid tumors may be helpful. It may help reduce side effects of treatment.
• Melatonin does not appear to have side effects.

Herbal Products

• Some studies suggest that certain herbs may help with side effects of cancer
• No herbal products have however been confirmed to cure or treat cancer
• Some herbal supplements may even interfere with cancer treatment and could have negative consequences.

Antioxidants

• Antioxidants are chemicals that prevent free-radicals from damaging our cells
• Antioxidants are found in healthful foods, including fruits, vegetables, and whole grains
• However, antioxidants in the supplement form have not been proven to reduce cancer risk

Calcium

• Research has shown that increased calcium intake may reduce risk of colorectal cancer
• However, other studies also suggest increased calcium intake may increase risk of prostate cancer.

Vitamin D

• This vitamin works with calcium and phosphorus to promote bone health
• Some studies show that vitamin D intake may reduce risk of colorectal cancer, but results are inconclusive.

Cruciferous vegetables

• Cruciferous vegetables, including broccoli, Brussels sprouts, or cauliflower, contain a chemical called "glucosinolates," which may be broken down into anti-cancer compounds
• These compounds may reduce risk of cancer in animal studies, but show mixed results in human trials.