第 9 章
Phytochemicals: Nature's Protective Compounds
It seems almost like a conspiracy-the more animal foods people eat, the greater their risk of chronic diseases, while plant-based diets reduce these risks dramatically. Beyond the familiar nutrients, plants contain thousands of phytochemicals that provide flavor, color, and powerful protection. These naturally occurring chemicals not only defend plants against insects and fungi, but also offer remarkable health benefits to humans who consume them.
Phytochemicals are naturally occurring plant chemicals that provide flavor, color, texture, and odor while regulating growth and defense. Though vegetables and fruits are primary sources, legumes, whole grains, nuts, seeds, herbs, and spices also contribute significantly. There are thousands of phytochemicals, with phenolic compounds forming the largest category (over 4,000 chemicals), including flavonoids, phenolic acids, and tannins.
While all whole plant foods contain phytochemicals, certain foods stand out as particularly rich sources. Vegetables are the most protective and phytochemical-rich foods available. Particularly noteworthy are cruciferous vegetables (broccoli, cauliflower, cabbage, kale) containing indoles and isothiocyanates with anticancer and antiestrogenic activity; umbelliferous vegetables (celery, carrots, parsley) rich in coumarins, flavones, carotenoids and other compounds with antioxidant and anticancer properties; and allium vegetables (garlic, onions) containing allicin and its breakdown products with cardiovascular, anticancer and antimicrobial benefits.
Fruits, though not quite as impressive as vegetables in disease risk reduction, are close behind. Citrus fruits contain over 170 different phytochemicals including flavonoids, terpenes, and carotenoids with antioxidant, anticancer, and cardiovascular benefits. Berries are rich in phenolic compounds including anthocyanins (strong antioxidants that inhibit LDL cholesterol oxidation, promote connective tissue repair, and have anticlotting and anti-inflammatory properties).
Legumes, the protein powerhouses of plants, are rich in minerals, fiber, and phytochemicals including isoflavones (phytoestrogens with antiestrogenic activity), phenolic acids (antioxidants with anticancer properties), tannins like catechin (anticancer activity, especially high in lentils), and phytates (antioxidants that bind minerals). Soybeans reign supreme among legumes, containing isoflavones (mainly genestein and daidzein) that may reduce risks of estrogen-related cancers, menopausal discomfort, osteoporosis, and cardiovascular disease.
Nuts and seeds reduce cardiovascular disease risk partly due to their phytochemical content. They contain flavonoids (quercetin, rutin, kaemperol) with antioxidant, anticancer and anti-cardiovascular properties; phenolic acids (ellagic and caffeic acid) with antioxidant and anticancer activity; lignans with antiestrogenic activity; phytic acids with anticancer activity; and tocotrienols (vitamin E) with antioxidant, antitumor, and lipid-lowering effects. Flaxseeds stand out as champions, containing over 100 times the lignans of most plant foods, the highest alpha-linolenic acid content (57% omega-3 fatty acids), and rich amounts of boron, potassium, magnesium, and soluble fiber.
