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Antioxidants, especially abundant in fruits and vegetables, are powerful compounds that cancel out cancer-causing free radicals before they damage cells.
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updated 10/2/2009 9:54:24 AM ET 2009-10-02T13:54:24

Science has confirmed that the nutrients in our food can slow down and even reverse aging. When you eat well, the repair starts immediately on a cellular level, but some benefits take years. "Certain effects may happen quickly, but it's best to take a long-term perspective when you're trying to change your body," says Tamas Horvath, PhD, a neurobiologist at Yale University. So when will those antioxidants in your salad start attacking the free radicals ravaging your body? How many fish dinners before you reap the brain-boosting benefits of omega-3s? And how long till that daily vitamin D supplement leads to stronger bones? Here's exactly how and when you can expect the health payoff you want.

In hours you can...

Beat stress
Vitamin B6 deficiency has been linked to anxiety, stress, and depression, and women are more likely to become deficient in B6 as they age, according to researchers at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. "When B6 makes its way to your brain, it facilitates synthesis of neurotransmitters, such as dopamine, which makes you feel calm and happy," says Hanjo Hellmann, PhD, a plant biologist at Washington State University. "But if you have a B6 deficiency, your brain may not be able to make enough dopamine." The vitamin is found in a variety of foods, but it's especially high in potatoes, bananas, red meat, poultry, and chickpeas. Once eaten, B6 is quickly distributed throughout the body but isn't stored well, so we need a consistent daily supply. Hellmann recommends getting 1 to 2 mg of B6 every day — the amount in about one medium russet potato and a chicken breast — to help you produce enough stress-busting dopamine.

Prevent cell damage that causes cancer
Antioxidants, especially abundant in fruits and vegetables, are powerful compounds that cancel out cancer-causing free radicals before they damage cells. "Antioxidants begin working almost immediately upon absorption — as soon as they find a free radical to interact with," Hellmann says. But don't think you're set for the week after eating a big salad. Antioxidants remain active for only a few hours and need to be continually replenished. "Plus, they are a diverse group and don't all have the same functions," says Hellmann. "The key is always having plenty in your body to take on anything that comes along." That means eating as much produce as possible and mixing up the types as often as you can.

In one week you can...

Lower your blood pressure naturally

Potassium supplements are an effective treatment for hypertension, but they can be dangerous for you as you age, according to the American Heart Association. Scientists at St. George's Hospital Medical School in London found that food sources of potassium are as effective as supplements in fighting high blood pressure — without side effects. The mineral is found in clams and in almost every fruit and vegetable but especially in potatoes, dried peaches, avocados, and bananas. Study participants with high blood pressure ate 3,754 mg of potassium per day and lowered their blood pressure to prehypertension levels after just 1 week. "If you have normal kidneys, you'll use and excrete potassium within hours, which is why getting plenty of fruits and vegetables a day is so important — a steady stream of potassium will control your blood pressure," says Christine Gerbstadt, MD, RD, of the American Dietetic Association. Just be sure to discuss dietary changes with your doctor if you're on blood pressure medications.

In five weeks you can...

Boost your memory

An Australian study found that folate boosts memory in as little as 35 days. Women who participated in the study, published in the Journal of Nutrition, saw improved memory performance after taking 750 mcg of folate daily — that's about 1 cup of cooked spinach and 1 cup of cooked lentils. Though folate supplements (folic acid) are recommended during pregnancy to help prevent birth defects, you should otherwise get your folate from food, says Gerbstadt.

In six weeks you can...

Lower dangerous homocysteine levels

An analysis of 25 studies on B vitamins and homocysteine in the American Journal of Clinical Nutrition concluded that taking 800 mcg of folate supplements daily for 6 to 8 weeks reduces homocysteine concentrations up to 23 percent. Don't exceed 1,000 mcg per day, however, or you could trigger symptoms of a B12 deficiency. Good food sources of folate are meat, fish, eggs, and dairy.

In two months you can...

Improve heart health
Omega-3s, essential fatty acids in which Americans are known to be deficient, have a wide range of impressive health benefits — from smoothing your skin and aiding weight loss to boosting your mood and minimizing the effects of arthritis. However, the ability of omega-3s, found in oily fish (like salmon, mackerel, and anchovies) and in plant sources (flaxseed, walnuts, and spinach), to prevent heart disease is perhaps best understood. Although some of the heart-health benefits kick in shortly after you digest your salmon, the effects won't last unless you eat these essential fatty acids consistently so that your body reaches a healthy saturation level, says Susan Raatz, PhD, RD, an associate professor of medicine at the University of Minnesota: "If you are deficient in omega-3s and begin eating at least two 3-ounce servings of fatty fish a week, your heart will see significant benefits in 4 to 8 weeks."

In three months you can... 

Fight dementia
Omega-3s are also crucial to brain health and development, says Stephen Cunnane, PhD, an omega-3 expert at the University of Sherbrooke's Research Center for Aging in Quebec. Many studies have found that variations in Alzheimer's rates across countries can be predicted by the quantity of fish in the diet. A study published in Neuroscience Research found that patients with mild dementia improved their short-term memory after taking omega-3s daily for 3 months. Another recent study found that depressive feelings in suicidal patients diminished after taking 2.1 g of omega-3s daily for 3 months. A 3-ounce serving of wild salmon contains nearly 2 g of omega-3s.

In one year you can...

Improve your vision
Lutein, a natural plant pigment known as a carotenoid, concentrates in the retina and lens to protect and strengthen your eyes. "Lutein is important to eye health," says Elizabeth Johnson, PhD, a scientist who studies vision at Tufts University. In a study conducted at North Chicago VA Medical Center, researchers found that patients with age-related macular degeneration improved in multiple measures of vision after taking 12 mg of lutein daily for a year. You can easily get that dose from food, particularly green leafy vegetables such as 1/2 cup of cooked spinach, Johnson says. Other top sources of this antioxidant are peas, broccoli, and corn.

Build stronger bones
Vitamin D allows your body to absorb the calcium needed to build stronger bones and reduce your risk of osteoporosis. An analysis of multiple vitamin D studies in JAMA found that a daily supplement of 700 to 800 IU of vitamin D combined with calcium reduces the risk of bone fractures by 26 percent after 2 years. D is found in fortified milk and cereals as well as in fish and eggs, yet supplements are generally accepted as safe.

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