You will add years to your life by increasing your intake of fruits and vegetables rich in alpha-carotene, according to researchers at the U.S. Centers for Disease Control and Prevention in Atlanta.
Alpha-carotene belongs to the carotenoid family, a group of yellow, orange and red pigments produced by plants. Other carotenoids include beta-carotene (found in carrots and sweet potato), lycopene (in tomatoes and pink grapefruit) and lutein (in spinach and kale).
It is widely believed that free-radical damage to DNA, proteins and fats in cells plays a role in the development of heart disease, cancer and Alzheimer's disease, as well as many other chronic illnesses. As potent antioxidants, carotenoids counteract free-radical damage. (Free radicals are produced naturally when we breathe, but ultraviolet light, cigarette smoking and alcohol consumption are other sources.)
While previous research has linked higher intakes of carotenoid-rich foods with lowering the risk of chronic disease, randomized trials have generally found that beta-carotene supplements have no effect. It's possible that carotenoids other than beta-carotene - such as alpha-carotene - guard against disease.
In the 14-year study, published online this week in the Archives of Internal Medicine, researchers investigated the relationship between alpha-carotene blood levels and the risk of dying among 15,318 adults aged 20 and older.
Higher alpha-carotene blood levels were associated with a lower risk of dying from cancer, cardiovascular disease and all other causes. Compared with people with lower alpha-carotene blood levels, those with the highest had a 39-per-cent lower risk of dying over the 14-year period.
The protective effect of alpha-carotene on the risk of death was particularly strong for cancers of the upper digestive tract (esophagus, larynx, pharynx), type 2 diabetes and chronic lower respiratory disease.
Although alpha-carotene is chemically similar to beta-carotene, it's thought to be more effective at blocking the growth of cancer cells in the brain, liver and skin. What's more, previous research has found that yellow-orange and dark-green vegetables - plentiful in alpha-carotene - do a better job of guarding against lung cancer than all other types of vegetables.
The only way to increase your blood level of alpha-carotene is to eat more fruits and vegetables. Canadians are advised to consume seven to 10 servings of fruit and vegetables each day, a target that many of us do not hit.
Seven to 10 servings might sound like a lot, but a serving size isn't that large. If it fits in your hand, it's probably one serving - a medium-sized fruit, ¼ cup dried fruit, ½ cup of cooked or raw vegetables, one cup of salad or ½ cup 100-per-cent vegetable or fruit juice.
If you forgo your fruits and vegetables until the end of the day, you won't come close to meeting your target. The key is incorporating fruits and vegetables into all of your meals and snacks.
Choose orange and green To consume more carotenoids, include one yellow-orange and one dark-green vegetable in your diet each day. Excellent sources of alpha-carotene include pumpkin, carrots, carrot juice, winter squash, collard greens, dandelion greens, plantains, vegetable soup, vegetable juice and tangerines.
In addition to yellow-orange vegetables, you'll find plenty of beta-carotene in spinach, kale, beet greens, turnip greens, dandelion, broccoli, red bell peppers, cantaloupe, apricots and mangos.
Enhance absorption Carotenoids are fat-soluble, which means you'll absorb more of these antioxidants if you include ½ to 1 teaspoon of oil with your meal.
You'll also get more carotenoids if you eat your vegetables cooked instead of raw. Cooking breaks down cell walls in the plant, making more of these antioxidants available for absorption.
Plan ahead In order to get at least seven servings a day, plan to add fruit and vegetables to each meal. At breakfast, include one or two fruit servings. Sprinkle chopped banana, raisins or dried cranberries over whole-grain cereal. Or blend blueberries and strawberries with low-fat milk or soy beverage to make a breakfast smoothie.
Include at least one vegetable serving with lunch. Add sliced tomatoes, grated carrot and spinach leaves to a sandwich. Add a handful of baby carrots or raw red-pepper strips to a brown-bag lunch. Or serve vegetable soup or low-sodium vegetable juice with your meal.
Carry fruit for a midday snack - a tangerine, an apple or a pear. Pack a single serving can of unsweetened fruit or applesauce into your briefcase. Or prepare snack-size bags of dried apricots, raisins and almonds.
Include at least two vegetable servings at dinner. Use Romaine and other dark-green lettuces in salads (they're higher in carotenoids than iceberg lettuce). Serve sweet potato as a change from white potatoes.
Add quick-cooking greens like spinach, kale, rapini or Swiss chard to soups and pasta sauces. Roast or grill eggplant, peppers, asparagus, fennel, onion and mushrooms. Add the leftovers to the next day's lunch.
Increase portion size Boost your vegetable intake by eating larger serving sizes. Instead of ½ cup of sweet potato, have 1 cup for two servings.
Opt for convenience If prep time prevents you from meeting your daily fruit and vegetable target, take advantage of packaged, ready-to-eat produce sold in the grocery store - pre-washed salad greens, shredded cabbage, broccoli florets, carrot sticks and so on.
Because pre-chopped and pre-washed vegetables are subject to more food handling - and the fact they are often eaten raw - they are a potential source of food poisoning. Always wash these vegetables - like any others - under cool running water before eating.
Choose frozen When produce is out of season, choose frozen. Frozen produce is quick to prepare and often outshines fresh as a source of vitamins and minerals. That's because processing and packaging take place almost immediately after harvest, locking in nutrients.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.