Cancer: Eating Right During Cancer Treatment (cont.)

"We suggest that patients avoid high-dose multivitamins, because there is some concern that some of these, especially those with high-dose antioxidants, may interfere with treatment. As long as there remains controversy about this, we think it's prudent not to take high-dose multivitamins."

Plus, it's almost impossible to get "too much" of any given vitamin through food alone, while loading up on some vitamins in pill form can cause problems, like dangerous buildup in the liver. If a certain amount of a nutrient is good for you, twice or three times as much is not necessarily better.

Certain kinds of herbal supplements, like St. John's wort, can also interact badly with some types of cancer treatment. "Some complex herbal extracts may contain substances that can change drug metabolism, interfering with the way in which your body metabolizes chemotherapy," warns Deng. Talk to your doctor before taking any type of herbal product or supplement during cancer treatment.

Get Vitamins In Food, Not Capsules

Instead, say experts, focus on what you need most now: calories. When you're being treated for cancer, taking in enough calories to maintain your strength and keep your body going trumps pretty much everything else. "For many people undergoing chemotherapy, we're happy to tell them to eat whatever they like to eat. If it appeals to you and you can keep it down, then eat it," says Deng. "If you ask someone to eat too strict a diet, often they end up not eating enough."

If you have trouble eating enough at mealtimes, many experts recommend adding medical nutrition supplements -- like Ensure, Boost, and Instant Breakfast -- to the menu. These drinks can often help make up for some of the nutrition missed when you can't work up an appetite for dinner or the energy to prepare it.

"Go ahead and try to eat a meal, and when you've done your best, you can supplement it with one of these drinks to give you the calories, protein, and other nutrients you can't get in at mealtimes," advises Sally Scroggs, MS, RD, LD, senior health education coordinator at Houston's M.D. Anderson Cancer Center. Just don't rely on the drinks so much that you don't eat regular meals. "They're called supplements for a reason," she adds.

Next to getting enough calories in the first place, the most important nutritional rule for people with cancer is to focus on getting a well-balanced, healthy diet from natural sources, including fruits and vegetables, with a heavy emphasis on protein.

"Because the body is under stress from different treatments -- whether you're undergoing surgery, chemotherapy, radiation, or a combination of these -- we really need to emphasize proteins for healing and repair and strengthening of the immune system," says Scroggs. Red meat, fish, and poultry are excellent sources of protein (and iron as well, which is also important), but if you've lost your appetite for these, try other protein options like cheese, beans, peanut butter, eggs, nuts, milkshakes, and yogurt.