Some people experience virtually no side effects from cancer chemotherapy, but this is rare. Most patients report at least some problems, including nausea, fatigue and diarrhea during the treatment.

Reason: The drugs that are used in chemotherapy are designed to kill fast-growing cancer cells. But they also damage fast-growing healthy cells, particularly in the mouth, digestive tract and hair follicles.

Good nutrition is critical if you’re undergoing chemotherapy. It’s estimated that up to 80% of cancer patients are malnourished. People who eat well before and during chemotherapy tend to have fewer side effects. They also are more likely to complete the full course of therapy than those who are poorly nourished and may feel too sick to continue. What to do…

  • Load up on nutrient-rich foods. In the weeks before chemotherapy, patients should emphasize nutrient-dense foods, such as whole grains, vegetables and legumes. The high nutrient load of a healthy diet helps strengthen healthy cells so that they’re better able to withstand — and then recover from — the effects of chemotherapy. Good choices…

    Dark leafy greens, such as spinach, kale and Swiss chard. They’re high in antioxidants, such as beta-carotene, lutein and other phytonutrients. These compounds help minimize the damaging effects of free radicals, tissue-damaging molecules that are produced in large amounts during chemotherapy. Kale is particularly good because it contains indole-3-carbinol, a compound that has anticancer properties.

    Olive oil, like green vegetables, is high in antioxidants. It’s one of the best sources of oleic acid, an omega-9 fatty acid that strengthens cell membranes and improves the ability of the immune system to fight cancer cells. I like extra-virgin olive oil because it has been exposed to the least heat.

    Garlic. The National Cancer Institute reports that people who eat garlic regularly seem to have a lower risk for intestinal and other cancers, including breast cancer. The strong-tasting sulfur compounds in garlic, such as allicin, have strong antiviral and antibacterial effects — important for chemotherapy patients because they’re susceptible to infection. In my recipes, I use fresh garlic. I smash it and let it sit for 10 minutes to allow the antiviral properties to become more accessible — then chop and cook. (To smash garlic, set the side of a chef’s knife on the clove, place the heel of your hand on the flat side of the knife and apply pressure.)

  • Increase protein. It’s the main structural component of muscle and other tissues. People who undergo chemotherapy need large amounts of protein to repair tissue damage that occurs during the treatments.

    Recommended: About 80 grams of protein daily. That’s nearly double the amount that healthy adults need. Cancer patients who increase their protein about a week before chemotherapy, and continue to get extra protein afterward, recover more quickly. They also will have more energy and less fatigue.

    Try this: Two or more daily smoothies (made in a blender with juice or milk, a variety of fresh fruits and ice, if you like) that are supplemented with a scoop of whey protein powder. The protein in whey is easily absorbed by the intestine. And most people can enjoy a nutrient-rich smoothie even when they have nausea or digestive problems related to chemotherapy.

  • Drink to reduce discomfort. Stay hydrated both before and after chemotherapy sessions to reduce nausea. Drink liquids until your urine runs clear — if it has more than a hint of yellow, you need to drink more.

    Helpful: Soups and broths provide water, as well as protein, minerals and vitamins.

  • Avoid your favorite foods two days before treatments. It’s common for chemotherapy patients to develop food aversions when they get nauseated from treatments and then to associate the nausea with certain foods. It’s sad when people develop aversions and can never again enjoy their favorite foods.
  • Eat lightly and frequently. People tend to experience more nausea when the stomach is empty. During and after “chemo days,” keep something in your stomach all the time — but not too much. Patients do better when they have a light snack, such as sautéed vegetables or a bowl of broth, than when they go hungry or eat a lot at one sitting.
  • Treat with ginger. When your stomach is upset, steep three slices of fresh ginger in a cup of simmering water for 10 minutes, then drink the tea. Or grate fresh ginger with a very fine grater, such as a Microplane, and put the shavings under your tongue. Ginger alleviates nausea almost instantly.
  • Overcome “metal mouth.” The drugs used in chemotherapy can damage the nerves that control the taste buds. Some people complain about a metallic taste in their mouths after treatments. Others notice that foods taste “flat” or that their mouths are extremely sensitive to hot or cold.

    These changes, known as transient taste changes, usually disappear a few weeks (or, in some cases, months) after treatments, but they can make it difficult for people to eat in the meantime.

    Helpful: The FASS method. It stands for Fat, Acid, Salt and Sweet. Most people will find that it’s easier to enjoy their meals, and therefore ingest enough nutrients, when they combine one or more of these elements in every meal.

    For fat, add more olive oil than usual to meals… lemons are a good source of acid… sea salt has less of a chemical aftertaste than regular salt… and maple syrup gives sweetness with more nutrients (including immune-building manganese and zinc) than table sugar.

  • Try kudzu root. Used in a powder form to thicken sauces, puddings and other foods, it soothes the intestine and can help prevent diarrhea. You also can dissolve one teaspoon of kudzu root in one teaspoon of cold liquid and drink that. Drink after meals, as needed. Kudzu root is available in most health-food stores.
  • Soothe mouth sores with soft, easy-to-eat foods, such as granitas (similar to “Italian ices”) or smoothies. The sores can be intensely painful, which makes it difficult to eat.

    Recommended: Watermelon ice cubes. Purée watermelon, and put it in a tray to freeze. Then suck on the cubes. The cold acts like a topical anesthetic — you can numb the mouth before eating a regular meal. And the juice from the melon is just as hydrating as water but provides extra nutrients, including the antioxidant lycopene.