Fruits and Vegetables
Because fruits and vegetables are loaded with both fiber and water, they enhance satiety, are low in calories, and may promote healthy weight management. Fruits and vegetables contain multiple nutrients and phytochemicals related to cancer reduction, and although it is not yet known which combination provides the best protection, the U.S. Centers for Disease Control and Prevention, along with the Department of Health and Human Services and the National Cancer Institute, recommend at least seven daily servings for women and nine for men.
Fresh, frozen, and canned fruits and vegetables can all be nutrient-dense food choices. Fresh produce typically has the greatest nutritional value, but long periods in transit, in grocery stores, and on home shelves all contribute to nutrient loss. For this reason, produce frozen immediately after harvest may contain more nutrients than some fresh produce. Canning and drying processes reduce heat-sensitive and water-soluble nutrient content, although foods preserved with these methods may pose less of an infection risk for patients undergoing immunosuppressive cancer treatment.4 Immunosuppressed patients also should avoid eating unpeeled raw fruits or vegetables because they may contain pathogens, which are destroyed in the cooking process. In terms of cooking methods, microwaving and steaming, instead of boiling, avoids nutrient losses that occur when nutrients leach into cooking water that is then discarded.
Juicing provides a means for increasing fruit and vegetable intake, particularly for those who have difficulty chewing or swallowing. For those concerned about overeating, however, juices do not match the satiety value of whole fruits and vegetables; additionally, when large juice servings are consumed, excess calories can contribute to weight gain. Only 100% juices should be chosen—added sugars detract from the nutrient density of any beverage.
The use of pesticides and herbicides has increased tremendously since the 1940s, and although many have been phased out, their residues may still be in foods eaten today.5 There is no epidemiological evidence that current exposure levels cause cancer,5 but for those interested in a cautionary approach, fruits and vegetables may be peeled or washed in lemon juice or vinegar baths to reduce residual surface pesticides. The Environmental Working Group (EWG), a research and advocacy organization based in Washington, D.C., has identified “Dirty Dozen” fruits and vegetables (pears, apples, bell peppers, celery, nectarines, strawberries, cherries, kale, lettuce, and imported grapes and carrots), which may have comparatively higher pesticide residues than other fruits and vegetables; as a result, consumers are advised to buy those raised organically. In contrast, they deem the “Clean 15” (onions, avocados, sweet corn, pineapples, mangos, asparagus, sweet peas, kiwi, cabbage, eggplant, papaya, watermelon, broccoli, tomatoes, and sweet potatoes) to be relatively free of pesticide residues. Given shifting patterns in agriculture and large-scale buying in the free market, it is unknown whether these categorizations will be useful to those seeking to minimize their exposure to pesticides over the long term.
The term organic commonly refers to plant foods grown without pesticides or genetic modifications, or to meat, poultry, and dairy products from animals raised without antibiotics or growth hormones. The FDA sets limits for produce exposure to agricultural chemicals, but as stated previously, it is unknown whether the choice of organic versus inorganic foods influences cancer incidence, recurrence, or progression. With regard to nutrient quality, a recent 50-year systematic literature review found no difference between organically and conventionally produced foodstuffs.