Antioxidants


UCLA Center for Nutrition

  • The final common mechanism believed to mediate the effects of different diets on cancer and aging is the oxidation of the genome and other cellular and subcellular structures. Mutations induced by oxidative damage may then lead to increased cellular proliferation, reduced apoptosis or both. Therefore, genes confer susceptibility to oxidative damage through absence or malfunction of the extensive antioxidant defense and DNA repair mechanisms, while the diet can affect whether and to what extent that oxidative damage occurs.

    In aging, oxidative damage is increased and aging is the predominant risk factor for cancer. The demonstration of the effects of nutrition on cancer requires using age-adjusted incidences. Furthermore, dietary restriction with vitamin and antioxidant supplementation can extend maximum lifespan significantly in rodents. In epidemiologic studies in humans, the intake of 400 to 600 grams per day of fruits and vegetables is associated with a reduced risk of gastric and other cancers. The most common cancers in developed societies are breast, prostate and colon cancer. Obesity, high fat diets, and reduced intake of fiber from cereals, grains, fruits and vegetables comprise a high risk dietary pattern. For each of the most common cancers, there is extensive evidence of a variation in incidence as individuals move from low risk to high risk countries. For prostate cancer, there is an equal incidence of latent prostate cancer in the U.S. and Japan, but clinical cancer is five times more frequent in the U.S. In animal experiments, nutrition affects the growth, progression and metastasis of established tumors as well as the incidence of new tumors.

David Heber, MD, PhD - What Color is Your Diet?


  • "What Color Is Your Diet?" provides a color guide to fruits and vegetables and their benefits, as well as recipes to encourage an increased intake of produce. Heber says that counting servings may not be adequate if you are missing out on one or more major color categories. Not all members of the fruit and vegetable group are alike.

    They have unique properties that provide combinations of substances with unique effects on human biology. Therefore, simply eating five servings a day of fruits and vegetables will not guarantee that you are eating enough of the different substances needed to stimulate the metabolic pathways of genes in the different organs where fruits and vegetables have their beneficial effects.

    The colors represent 25,000 chemicals that are beneficial. There is evidence that interaction between the colors provides benefits, so it's important to have a diverse diet and eat different foods. We normally eat three color groups on average in this country. Heber believes in evolutionary terms, man started out on a plant-based diet.

    Fruits and vegetables are historically and biologically important. Our ancestors the hunter-gatherers ate over 800 varieties. The different colors represent families of compounds, and we have even selectively bred the colors we eat into an even narrower range. There are red carrots in India, we eat orange ones. There are 150 varieties of sweet peas, but only a few are available to us. We need to make an extra effort to eat many different foods to get the full range of benefits, he says

    Heber groups produce into seven color categories:

    Red Group
    (tomatoes, can of V8 juice, pink grapefruit, watermelon)

    These contain the carotenoid lycopene, which helps rid the body of free radicals that damage genes. Lycopene seems to protect against prostate cancer as well as heart and lung disease. Processed juices contain a lot of the beneficial ingredients. One glass of tomato juice gives you 50 percent of the recommended lycopene.

    Yellow/Green Group
    (spinach greens, collard greens, mustard greens, turnip greens, yellow corn, green peas, avocado, honeydew melon)

    These are sources of the carotenoids lutein and zeaxanthin. These are believed to reduce the risk of cataracts and age-related macular degeneration. Lutein is a yellow-green substance that concentrates in the back of your eye. It may also reduce atherosclerosis.

    Orange Group
    (carrots, mangos, apricots, cantaloupes, pumpkin, acorn squash, winter squash, sweet potatoes)

    These contain alpha carotene, which protects against cancer. They also contain beta-carotene, which the body converts to vitamin A.

    It protects the skin against free-radical damage and helps repair damaged DNA. Beta-carotene is also good for night vision. It's important to note that these beneficial nutrients can be received from other foods, too. For instance vitamin is found in dairy products and meat. But it's not as beneficial because you get high calories and fat along with it.

    Orange/Yellow Group
    (pineapple, orange juice, oranges, tangerines, peaches, papayas, nectarines)

    These contain beta cryptothanxin, which helps cells in the body communicate and may help prevent heart disease. Also, an orange contains 170 percent of the recommended daily vitamin C. It's interesting to note that the skin of an orange is high in a protective fat that has been found to kill cancer cells in humans and animals, which highlights the fact that two-thirds of all drugs come from the plant world.

    Red/Purple Group
    (beets, eggplant, purple grapes, red wine, grape juice, prunes, cranberries, blueberries, blackberries, strawberries, red apples)

    These are loaded with powerful antioxidants called anthocyanins believed to protect against heart disease by preventing blood clots. They may also delay the aging of cells in the body. There is some evidence they may help delay the onset of Alzheimer's disease.

    Green Group
    (broccoli, brussels sprouts, cabbage, Chinese cabbage or bok choi, kale)

    These contain the chemicals sulforaphane and isocyanate and they also contain indoles, all of which help ward off cancer by inhibiting carcinogens. It's a fact that ten percent of the population - like George Bush Sr. - doesn't like broccoli. But it is important in diets because of the beneficial chemicals it contains.

    White/Green Group
    (leeks, scallions, garlic, onions, celery, pears, white wine, endive, chives)

    The onion family contains allicin, which has antitumor properties. Other foods in this group contain antioxidant flavonoids like quercetin and kaempferol.