Health & Nutrition

“Eat your fruits and vegetables” is one of the tried and true recommendations for a healthy diet. And for good reason. Eating plenty of fruits and vegetables can help you ward off heart disease and stroke, control blood pressure and cholesterol, prevent some types of cancer, avoid a painful intestinal ailment called diverticulitis, and guard against cataract and macular degeneration, two common causes of vision loss.

What does “plenty” mean? More than most Americans consume. If you don't count potatoes - which should be considered a starch rather than a vegetable - the average American gets a total of just three servings of fruits and vegetables a day. The latest dietary guidelines call for five to thirteen servings of fruits and vegetables a day, depending on one's caloric intake. For a person who needs 2,000 calories a day to maintain weight and health, this translates into nine servings, or 4½ cups per day.

Over the past 30 years or so, researchers have developed a solid base of science to back up what generations of mothers preached (but didn't always practice themselves). Early on, fruits and vegetables were acclaimed as cancer-fighting foods. In fact, the ubiquitous 5-A-Day message (now quietly changing to Eat 5 to 9 A Day) seen in produce aisles, magazine ads, and schools is supported in part by the National Cancer Institute. The latest research, though, suggests that the biggest payoff from eating fruits and vegetables is for the heart.

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“Eat a low-fat, low-cholesterol diet.” Most of us have heard this simple recommendation so often over the past two decades that we can recite it in our sleep. Touted as a way to lose weight and prevent cancer and heart disease, it's no wonder much of the nation - and food producers - hopped on board.

Unfortunately, this simple message is now largely out of date. Detailed research -much of it done at Harvard - shows that the total amount of fat in the diet, whether high or low, isn't really linked with disease. What really matters is the type of fat in the diet. New results from the large and long Women's Health Initiative Dietary Modification Trial showed that eating a low-fat diet for 8 years did not prevent heart disease, breast cancer, or colon cancer, and didn't do much for weight loss, either.

What is becoming clearer and clearer is that bad fats, meaning saturated and trans fats, increase the risk for certain diseases while good fats, meaning monounsaturated and polyunsaturated fats, lower the risk. The key is to substitute good fats for bad fats.

And cholesterol in food? Although it is still important to limit the amount of cholesterol you eat, especially if you have diabetes, dietary cholesterol isn't nearly the villain it's been portrayed to be. Cholesterol in the bloodstream is what's most important. High blood cholesterol levels greatly increase the risk for heart disease. But the average person makes about 75% of blood cholesterol in his or her liver, while only about 25% is absorbed from food. The biggest influence on blood cholesterol level is the mix of fats in the diet.

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Food companies make it more difficult than it should be to spot a whole-grain food. Aware that consumers are interested in whole-grain products, and that whole grains can improve health in a myriad of ways, companies often make foods sound like they're whole grain and healthy when they aren't.

That means you must read food labels carefully. True whole-grain products list as the main ingredient whole wheat, whole oats, whole rye, or some other whole grain cereal. If the label says "made with wheat flour" it may be an intact grain product or it may just be an advertising gimmick, since even highly processed cake flour is made with wheat flour.

The new whole grain stamp can simplify your search. It features a sheaf of grain on a golden background. Each stamp displays the number of grams of whole grain in a serving of the food. All foods bearing the whole grain stamp offer at least a half-serving (eight grams) or more of whole grain. Foods in which all the grains are whole grains — no refined grain is added—list 100% on the stamp.

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Carbohydrates are found in a wide array of foods—bread, beans, milk, popcorn, potatoes, cookies, spaghetti, soft drinks, corn, and cherry pie. They also come in a variety of forms. The most common and abundant forms are sugars, fibers, and starches.

The basic building block of every carbohydrate is a sugar molecule, a simple union of carbon, hydrogen, and oxygen. Starches and fibers are essentially chains of sugar molecules. Some contains hundreds of sugars. Some chains are straight, others branch wildly.

Carbohydrates were once grouped into two main categories. Simple carbohydrates included sugars such as fruit sugar (fructose), corn or grape sugar (dextrose or glucose), and table sugar (sucrose). Complex carbohydrates included everything made of three or more linked sugars. Complex carbohydrates were thought to be the healthiest to eat, while sugars weren't so great. It turns out that the picture is more complicated than that.

The digestive system handles all carbohydrates in much the same way—it breaks them down (or tries to break them down) into single sugar molecules, since only these are small enough to cross into the bloodstream. It also converts most digestible carbohydrates into glucose (also known as blood sugar), because cells are designed to use this as a universal energy source.

Fiber is an exception. It is put together in such a way that it can't be broken down into sugar molecules, and so it passes through the body undigested. Fiber comes in two varieties: soluble fiber dissolves in water, while insoluble fiber does not. Although neither type nourishes the body, they promote health in many ways. Soluble fiber binds to fatty substances in the intestines and carries them out as a waste, thus lowering low-density lipoprotein (LDL, or bad cholesterol). It also helps regulate the body's use of sugars, helping to keep hunger and blood sugar in check. Insoluble fiber helps push food through the intestinal tract, promoting regularity and helping prevent constipation.

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Take away the water and about 75 percent of your weight is protein. This chemical family is found throughout the body. It's in muscle, bone, skin, hair, and virtually every other body part or tissue. It makes up the enzymes that power many chemical reactions and the hemoglobin that carries oxygen in your blood. At least 10,000 different proteins make you what you are and keep you that way.

Twenty or so basic building blocks, called amino acids, provide the raw material for all proteins. Following genetic instructions, the body strings together amino acids. Some genes call for short chains, others are blueprints for long chains that fold, origami-like, into intricate, three-dimensional structures.

Because the body doesn't store amino acids, as it does fats or carbohydrates, it needs a daily supply of amino acids to make new protein.

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Those advertisements pushing milk as the answer to strong bones are almost inescapable. But does "got milk" really translate into "got strong bones?"

The pro-milk faction believes that increased calcium intake - particularly in the form of the currently recommended three glasses of milk per day - will help prevent osteoporosis, the weakening of bones. Each year, osteoporosis leads to more than 1.5 million fractures, including 300,000 broken hips.

On the other side are those who believe that consuming a lot of milk and other dairy products will have little effect on the rate of fractures but may contribute to problems such as heart disease or prostate cancer.

Which view is right? The final answers aren't in. But here is a summary of what's currently known about calcium and its effects on the body.

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Calcium is a mineral that the body needs for numerous functions, including building and maintaining bones and teeth, blood clotting, the transmission of nerve impulses, and the regulation of the heart's rhythm. Ninety-nine percent of the calcium in the human body is stored in the bones and teeth. The remaining 1 percent is found in the blood and other tissues.

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The body gets the calcium it needs in two ways. One is by eating foods that contain calcium. Good sources include dairy products, which have the highest concentration per serving of highly absorbable calcium, and dark leafy greens or dried beans, which have varying amounts of absorbable calcium.

The other way the body gets calcium is by pulling it from bones. This happens when blood levels of calcium drop too low, usually when it's been a while since having eaten a meal containing calcium. Ideally, the calcium that is "borrowed" from the bones will be replaced at a later point. But, this doesn't always happen. Most important, this payback can't be accomplished simply by eating more calcium.

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