Fruits and Veggies: Powerful Armor

From Spanish explorers to modern-day scientists, the secret to preserving youthfulness has been pursued for centuries. Could the answer be antioxidants?

The effects of aging are influenced by multiple genetic and environmental factors. Reactive oxygen species (ROS, also known as oxidants) are considered major culprits in aging and disease. ROS are byproducts of energy generation in normal metabolism and increase during infection and inflammation, exercise and stress, and with exposure to external pollutants, radiation and sunlight. When high levels of ROS exist with inadequate antioxidants to neutralize them, oxidative stress increases and exacerbates aging and disease.

The consequences of ROS damage depend on the molecules they attack and on the body's prevailing levels of protective antioxidants. 1-4 When the target molecule is DNA, the resulting ROS-induced chemical changes (mutations) can lead to cancer.2 Oxidation of lipids and proteins injures cell membranes, increases blood vessel fragility, damages immune cells and modifies enzymes. 1,2 ROS oxidation of cholesterol and other blood lipids increases their ability to form atherosclerotic plaques that can detach, block arteries and lead to heart attacks and stroke. 5 Stroke can be followed by dementia, when brain cells deprived of oxygen and blood (ischemia) during blockage die by apoptosis. 6

Dietary Antioxidants and Aging

Dietary antioxidants include essential vitamins and minerals as well as phytochemicals present in plant food. Antioxidants can prevent cancer-causing DNA damage, protect blood vessels against atherosclerosis, help optimize blood flow to the heart and brain, and protect brain cells against oxidative death that can lead to Alzheimer's disease, Parkinson's disease and other neurodegenerative conditions that increase in age. 4,5,7

Table 1 (on p. 3) lists some nutrients and phytochemicals that have anti-aging potential. The most important essential dietary antioxidants are vitamin C, vitamin E and the cofactor minerals selenium, zinc, copper, manganese and iron. These are necessary for antioxidant enzyme activity. Vitamin A itself has some antioxidant activity, but provitamin A, known as beta carotene, is a particularly powerful antioxidant.

Vitamins have additional actions that may be unrelated to their antioxidant activity. 2 For example, vitamin E is a lipid-soluble antioxidant that protects membranes and helps prevent cataracts and age-related macular degeneration. 8,9 It also increases immunity. 10 Vitamin C, a water-soluble antioxidant that is protective against cataract and macular degeneration, is also essential for producing collagen in bones, joints and skin. 8,9,11 Vitamin E, vitamin C and selenium are needed in higher amounts in older years, when the absorption of dietary components is not as efficient. 12

Coenzyme Q10

Coenzyme Q10 (CoQ10) is an antioxidant that protects lipids and other cell components from oxidation. Classified as a ubiquinol because it is ubiquitous in plant and animal products (particularly sardines and spinach), CoQ10 shows promise as a cardioprotective agent. CoQ10 supplements can help restore CoQ10 activity that diminishes with age and protect against heart disease. 13,14

CoQ10 supplementation is also important for people taking cholesterol-reducing statin drugs. Because CoQ10 and lipids share an enzymatic pathway, cholesterol reduction with statins is accompanied by a reduction in CoQ10 synthesis. 15

Folate and Vitamin B12

Although they are not antioxidants, vitamin B12, vitamin B6 and folate protect the body against the toxicity of homocysteine, an ROS-generating substance linked to dementia and an increased risk for cancer and cardiovascular disease. 16

Green leafy vegetables, calf liver and kidneys, wheat germ and beans all contain high amounts of folate. When ingested in supplement form, 400 mcg/day are necessary for adequate intake. Vitamin B12 is present in animal food, so vegetarians must obtain it in supplement form. Intake of garlic in the form of aged garlic extract supplement can also protect against homocysteine toxicity by fighting folate deficiency. 17

Phytochemicals

Phytochemicals are important substances that add to the body's armament against disease and aging. Phytochemicals are divided into several chemical classes. 2,18-20 Some act as antioxidants (carotenoids, flavonoids and organosulfur compounds in garlic). Among the flavonoids, isoflavonoids in soy and other legumes, as well as the lignans in grain, have estrogen-like activities.

Other phytochemicals alter biochemical pathways in cells to help eliminate carcinogenic substances (isocyanates in the cabbage family and the organosulfur compounds in garlic). 20,21

Carotenoids

Carotenoids in green, yellow, red and orange fruits and vegetables can help reduce cancer and heart disease risk. 2,20 Beta carotene is converted to vitamin A when the body needs more of it. Although beta carotene is the most studied carotenoid, it is by no means the most efficient antioxidant.

For example, Lycopene, found in abundance in tomatoes, is at least 10 times more effective as an antioxidant compared with beta carotene and may protect against prostate cancer. 22

Lutein and zeaxanthin, found in high levels in spinach and other green leafy vegetables, can protect the eyes from age-related macular degeneration that causes blindness. 23