By Jack Saari, U.S. Dept. of Agriculture, Human Nutrition Research Center
The most naturally colorful place in a supermarket is the produce department. Recent studies indicate that those colors are sending us a message. It seems that the color-producing chemicals in fruits and vegetables, nature’s packaging scheme, are advertising the health benefits of those plants.
What are these chemicals? A term coined to describe plant chemicals is phytonutrient, ‘phyto’ meaning plant-based. Some phytonutrients, colors or pigments, may already be familiar to you. These include lycopene, which makes tomatoes red; lutein, the color of corn; and beta-carotene, which gives carrots their orange color. The green color of chlorophyll is evident in leafy vegetables, but in many cases hides the presence of other pigments such as lutein and beta-carotene.
Other chemicals may be less familiar, for instance, the broad class of compounds called anthocyanins, which impart the vibrant reds (strawberries, cherries), blues (blueberries) and purples (grapes, plums) to many fruits. How do these colored chemicals protect us? A clue is provided by how they protect plants. While plants need light to survive, excess light energy can be destructive. In times of plant stress, light energy beyond what plants can use causes formation of highly reactive oxygen radicals. This so-called oxidant stress can damage the plant. In agricultural terms, this reduces yield.
Carotenoids in plants, in particular, lutein and zeazanthin, have been shown to prevent this damage by acting as antioxidants. Many of the colored phytonutrients have structures that make them good antioxidants. To increase yield, plant scientists are trying to find ways to increase the amounts of these naturally protective chemicals in crops.
Nutritionists in turn are trying to increase the amounts of plant-based foods in our diets. That’s because the colored phytonutrients can do for us what they do in plants. Many diseases have at their core the excess production of oxygen radicals. These radicals can mutate DNA to cause cancer. They can oxidize LDL (bad cholesterol) to promote atherosclerosis. Oxygen radicals can trigger clotting, which can lead to strokes and heart attacks.
Excess light, in addition to damaging plants, can damage the eye. In general, aging is thought by many scientists to result from accumulation of oxygen radical damage. Scientists are finding that consumption of plants with their high concentrations of antioxidant phytonutrients can combat many of the diseases mediated by oxygen radicals.
But fighting oxidant stress may not be all they do. Research is beginning to show effects of phytonutrients on cancer growth, hormone function, immune response, inflammation and blood vessel function that are independent of their antioxidant nature. From these findings, it is not surprising that consumption of tomato products has been linked to reduction of both cancer and cardiovascular disease.
Foods containing alpha- and beta-carotene, such as carrots and spinach, have been shown to reduce coronary heart disease. Lutein and zeazanthin, present in corn, carrots and dark green vegetables, are also components of the eye’s macula and thus essential for prevention of macular degeneration. Consumption of blueberries has been shown to improve memory, coordination and balance in aging rats. Strawberry extracts have been shown to prevent aging as simulated by a high oxygen environment in rats. Sour cherries appear to benefit arthritis sufferers by reducing inflammation.
And don’t ignore white. Though unpigmented vegetables such as garlic and white onions may lack colorful pigments, they nonetheless contain important protective phytochemicals.
Another side benefit of adding colorful plant-based foods to your diet is that they replace high-calorie foods in your diet. Along with exercise, this can contribute to weight reduction. As we know, excess weight is a risk factor for both cancer and heart disease.
How many servings of fruits and vegetables should we eat a day?
The U.S. Department of Agriculture recommendation (www.mypyramid.gov) actually is five to nine servings a day three to five of vegetables and two to four of fruit.
You may balk at the idea of nine servings, but don’t be distressed by the number. Serving sizes are not that big. Most would fit in the palm of your hand. The key is variety, not bulk.
So get healthier. Go out and color your diet.
Comments from the blog author Nutrition Breakthroughs: When deciding what to eat, seek out brightly colored fruits and vegetables for greater health. Good eating leads to good health for all parts of your body, including your heart and brain, and leads to higher levels of energy during the day and better, deeper sleep at night.
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