Women and Nutrition:
Breast cancer. Osteoporosis. Iron deficiency. Weight reduction. What do these things have in common? They are either unique to women, or are more prevalent in women. And they affect current recommendations on what women should eat for optimum health.
While new information on what's good and what's bad seems to surface almost daily, some basic guidelines have taken root over the past several years.
The bottom line (also known as the Dietary Guidelines for Americans, from the Departments of Health and Human Services and Agriculture) is:
Vitamins and Minerals
There are several vitamins and minerals essential to a healthy diet. A well-balanced diet will usually meet women's allowances for them. (See Recommended Dietary Allowances.) However, for good health, women need to pay special attention to two minerals, calcium and iron.
Both women and men need enough calcium to build peak (maximum) bone mass during their early years of life. Low calcium intake appears to be one important factor in the development of osteoporosis. Women have a greater risk than men of developing osteoporosis.
A condition in which progressive loss of bone mass occurs with aging, osteoporosis causes the bones to be more susceptible to fracture. If a woman has a high level of bone mass when her skeleton matures, this may modify her risk of developing osteoporosis.
Therefore, particularly during adolescence and early adulthood, women should increase their food sources of calcium. "The most important time to get a sufficient amount of calcium is while bone growth and consolidation are occurring, a period that continues until approximately age 30 to 35," says Marilyn Stephenson, a registered dietitian with FDA's Center for Food Safety and Applied Nutrition. "The idea is, if you can build a maximum peak of calcium deposits early on, this may delay fractures that occur later in life."
The recommended dietary allowance (RDA) for calcium for woman 19 to 24 is 1,200 milligrams per day. For women 25 and older, the allowance drops to 800 milligrams, but that is still a significant amount, says Stephenson. "The need for good dietary sources of calcium continues throughout life," she says.
How do you get enough calcium without too many calories and fat? After all, the foods that top the calcium charts--milk, cheese, ice cream--aren't calorie and fat lightweights.
"There are lots of lower fat choices," says Stephenson. "There's 1 percent or skim milk instead of whole milk. There's a good variety of lower fat cheeses, yogurts, and frozen yogurts, and there's a whole flock of substitutes for ice cream."
In addition to dairy foods, other good sources of calcium include salmon, tofu (soybean curd), certain vegetables (for example, broccoli), legumes (peas and beans), calcium-enriched grain products, lime-processed tortillas, seeds, and nuts.
For women, the RDA for iron is 15 milligrams per day, 5 milligrams more than the RDA for men. Women need more of this mineral because they lose an average of 15 to 20 milligrams of iron each month during menstruation. Without enough iron, iron deficiency anemia can develop and cause symptoms that include pallor, fatigue and headaches.
After menopause, body iron stores generally begin to increase. Therefore, iron deficiency in women over 50 may indicate blood loss from another source, and should be checked by a physician.
Animal products--meat, fish and poultry--are good and important sources of iron. In addition, the type of iron, known as heme iron, in these foods is well absorbed in the human intestine.
Dietary iron from plant sources, called non-heme, are found in peas and beans, spinach and other green leafy vegetables, potatoes, and whole-grain and iron-fortified cereal products. Although non-heme iron is not as well absorbed as heme iron, the amount of non-heme iron absorbed from a meal is influenced by other constituents in the diet. The addition of even relatively small amounts of meat or foods containing vitamin C substantially increases the total amount of iron absorbed from the entire meal.
Calories and Weight Control
The Food and Nutrition Board of the National Research Council recommends that the average woman between 23 and 50 eat about 2,200 calories a day to maintain weight.
The best way for a woman to determine whether she's eating the right number of calories is to "keep stepping on the scale," says FDA's Stephenson.
She cautions, however, that cutting back on calories isn't always the answer to losing weight. "You don't really want to cut back any more [calories] if you're down around that [1,500 calories] range," says Stephenson. She explains that the fewer the calories you have to work with, the harder it is to meet all your daily requirements for a healthy diet.
"If you find you are gaining weight, you need to think of not only cutting calories, but also about increasing exercise," she says. "Calories are only half the equation for weight control. Physical activity burns calories, increases the proportion of lean to fat body mass, and raises your metabolism. So, a combination of both calorie control and increased physical activity is important for attaining healthy weight.
"On the other hand, if you've been pigging out--well, you know what you have to do."
Women tend to have higher levels than men of a desirable type of cholesterol called HDLs (high-density lipoproteins) until menopause, leading some researchers to believe there is a link between HDLs and estrogen levels. But this doesn't let women off the hook--a diet high in saturated fat and cholesterol can still mean trouble.
For both women and men, blood cholesterol levels of below 200 milligrams are desirable. Levels between 200 and 239 milligrams are considered borderline, and anything over 240 milligrams is high. High levels of blood cholesterol increase the risk of coronary heart disease.
To keep levels in the good range, the National Cholesterol Education Program of the National Heart, Lung, and Blood Institute recommends eating no more than 300 milligrams of cholesterol a day. Cholesterol is found only in food from animal sources, such as egg yolks, dairy products, meat, poultry, shellfish, and--in smaller amounts--fish and some processed products containing animal foods.
Even more important than limiting cholesterol to under 300 milligrams is keeping saturated fat to under 10 percent of total calories, says Nancy Ernst, the nutrition coordinator for the National Heart, Lung, and Blood Institute.
"Don't even think about cholesterol in your diet," says Ernst. "Focus on reducing saturated fat."
In the United States, out of every 100,000 women, approximately 27 die from breast cancer each year. In Japan, breast cancer deaths are fewer than 7 per 100,000. Some scientists think that the difference in death rates may be related to the different amounts of fat in the average diet in each country--40 percent for American women versus 20 percent in Japan.
"We believe pretty strongly in the link [between high-fat diets and breast cancer]," says Jeffrey McKenna, director of NCI's Cancer Awareness Program.
Population studies have also linked high-fat diets to other cancers, particularly colorectal cancer.
Fat does, however, serve a purpose in the diet. Fats in foods provide energy and help the body absorb certain vitamins. But it is as easy as pie (and doughnuts, ice cream, and sirloin steaks) to eat too much.
For a healthy diet, the diet and health report of the National Research Council recommends reducing fat to no more than 30 percent of total calories. But that's not all. In terms of heart disease, the kinds of fat you eat are as important as how much.
There are three kinds of fat--saturated, polyunsaturated and monounsaturated. All three are equal when it comes to calories--9 per gram (compared to 4 calories per gram for protein or carbohydrate). But they aren't equal when it comes to how they affect your health.
More than anything else in the diet, saturated fat can raise your blood cholesterol level. Because of this risk, less than one-third of your daily fat intake (less than 10 percent of total calories) should come from saturated fats.
That's the bad news. The good news is polyunsaturated and monounsaturated may actually lower blood cholesterol levels. The diet and health report recommends that not more than 10 percent of total calories should be from polyunsaturated fat, and monounsaturated fat should make up the remaining 10 percent.
The foods with the highest amounts of saturated fat come from animals--meat, of course, and foods derived from animals, such as butter, cream, ice cream, and cheese. In addition to animal products, coconut and palm kernel oils are very high in saturated fat--over 90 percent.
The best sources for polyunsaturated fats are plant-based oils--sunflower, corn, soybean, cottonseed, and safflower. Monounsaturated fats are found in the largest amounts in olive, canola and peanut oils.
An apple a day--that is, a whole apple with the skin--will give you approximately 3.6 grams of fiber. That's a good start, but you still need a lot more fruits, vegetables, and whole grains to meet the daily level of 20 to 30 grams of fiber recommended by the National Cancer Institute.
Eating foods with plenty of complex carbohydrates and fiber (vegetables, fruits, and grain products) is part of a healthy diet for several reasons. A fiber-rich diet is helpful in the management of constipation and may be related to lower rates of colon cancer. These types of foods are generally low in fat and can be substitutes for fatty foods.
Fiber comes in two forms--insoluble and soluble. Insoluble fiber, mostly found in whole-grain products, vegetables and fruit, provides bulk for stool formation and helps move wastes more quickly through the colon. Another benefit is the full feeling fiber may create in the stomach, a possible deterrent to overeating.
Soluble fiber has been linked to lowering blood cholesterol levels, but that's still a research area according to the Surgeon General's Report on Nutrition and Health. There are many sources of soluble fiber, including peas and beans, many vegetables and fruits, and rice, corn and oat bran. There are even small amounts in pasta, crackers, and other bakery products.
Although foods containing fiber seem to exert a protective effect against some cancers, the diet and health report points out there is no conclusive evidence that dietary fiber itself, rather than other components, exerts this effect. Therefore, the report does not recommend the use of fiber supplements.
As important as fiber is to good health, it can be overdone. NCI recommends an upper limit of 35 grams a day. More probably won't further increase the benefits from fiber, and may interfere with the body's ability to absorb iron and other minerals.
When increasing the amount of fiber in your diet, do it slowly, so your body can become accustomed to handling it. Adding too much fiber too quickly may lead to uncomfortable side effects, including abdominal discomfort, flatulence and diarrhea.
Carefully selecting foods for a well-balanced diet can end up a wasted effort if equal care isn't used in the kitchen. Some important points to help make the most of healthy food: To help reduce fat, broil, bake or microwave food rather than frying or deep-fat frying. Cook vegetables in as little water as possible, or, instead of boiling food, try steaming. The steamer basket keeps the food above the water so the nutrients can't be washed away. Also, heat can destroy some nutrients, so don't overcook. Use fresh foods as soon as possible to avoid loss of vitamins. Season vegetables with herbs and spices instead of high-fat sauces, butter or margarine. Try lemon juice as a salad dressing. Substitute plain low-fat yogurt, blender-whipped low-fat cottage cheese, or buttermilk in recipes that call for sour cream or mayonnaise. Use skim or low-fat milk in place of whole milk in puddings, soups, and baked products.
Getting a Variety of Foods
The Dietary Guidelines say that the many nutrients you need should come from a variety of foods, not from a few highly fortified foods or supplements. A good way to ensure variety is to choose foods each day from the five major food groups. USDA has developed a daily food guide for a well-balanced diet that suggests the following:
Finally, the guidelines are meant for the average person, cautions Walter H. Glinsmann, M.D., FDA's associate director for clinical nutrition. "Almost nobody is average," he says. Lifestyle, genetics, and conditions such as pregnancy or disease can also affect a person's nutritional needs, he explains.
Dori Stehlin is a staff writer for FDA Consumer.
National Academy of Sciences/National Research Council
|Height*||Weight** (in pounds): age 19 - 34||Weight** (in pounds): age 35 and over|
Height without shoes
**Weight without clothes
The higher weights in the ranges generally apply to men, who tend to have larger body frames and more muscle; the lower weights more often apply to women, who have smaller body frames and less muscle. Weights even below the range may be appropriate for some small-boned people.
(Source: National Research Council, 1989)
Publication No. (FDA) 91-2247