Good nutrition is vital for growth, health, and well-being throughout the life cycle. Nutritional status both preconceptionally and during pregnancy has an impact on pregnancy and infant outcomes. Good nutrition is essential during infancy-childhood, and adolescence, when nutrient needs are high, ensure optimal growth and development. Nutritional factors are important in the prevention of 4 of the leading 10 causes of death in the United States: coronary heart disease, certain cancers, stroke, and Type II diabetes. Nutrition is also related to other chronic health conditions such as obesity and osteoporosis. Relationships between dietary factors and health are becoming clearer. Thus, increased attention is being placed on the importance of preventive nutrition.
Many dietary components are involved in the link between nutrition and health. For instance, excessive intake of saturated fat is related to heart disease and inadequate intake of fruits and vegetables is associated with an increased risk for certain cancers. The 2000 Dietary Guidelines for Americans recommend that to stay healthy, persons aged 2 years and older should aim for a healthy weight, be physically active each day, choose a diet that is low in saturated fat and cholesterol and moderate in total fat, choose beverages and foods to moderate sugar intake, choose and prepare foods with less salt, and, if drinking alcoholic beverages (for adults), do so in moderation. The Dietary Guidelines for Americans also recommend selecting foods and portions based on guidelines outlined by the Food Guide Pyramid. The Food Guide Pyramid suggests consuming grains, fruits, and vegetables as the basis for healthy eating, accompanied by a moderate amount of low-fat foods from the milk and meat/beans groups and limited amounts of foods that are high in fat and sugars (Table 1).
Given the interrelationship between nutrition and health, it is important to review the priority nutrition-related concerns affecting Americans today. Healthy People 2010 is a National Health Promotion and Disease Prevention Agenda that was established by the U.S. Department of Health and Human Services. Several nutrition-related goals have been established through Healthy People 2010 to promote health and reduce chronic disease associated with diet and weight. Table 2 reviews the key nutrition-related objectives.
Priority Nutrition Concerns
Overweight and Obesity
Overweight and obesity have reached epidemic proportions in the United States. Currently, approximately two-thirds of U.S. adults are overweight or obese. There are also nearly twice as many overweight children and almost three times as many overweight adolescents as there were in 1980. These startling percentages are continuing to increase. Thus, the prevention and treatment of overweight and obesity is an important public health goal and is considered one of the leading health indicators in Healthy People 2010.
Overweight adults are at increased risk for morbidity and mortality from many acute and chronic medical conditions such as hypertension, coronary heart disease, Type II diabetes, certain cancers, and musculoskeletal disorders such as osteoarthritis. Approximately 300,000 deaths a year in the United States are associated with overweight and obesity. Overweight children are more likely to become overweight adults, and are also at increased risk for morbidity and mortality during adulthood. Overweight and obesity are increasing across all ages, among both genders, and in all population groups. However, they are particularly prevalent among Native Americans, Hispanics, and African-American females.
Overweight and obesity are caused by a complex variety of social, behavioral, cultural, environmental, physiological, and genetic factors. Nonetheless, a healthy diet consistent with guidelines recommended in the Dietary Guidelines for Americans and regular physical activity (30 min of moderate activity daily) are both essential for maintaining a healthy weight. Efforts to maintain a healthy weight should begin during childhood and continue throughout adulthood.
Inadequate or Excessive Dietary Intakes
Fruits, Vegetables, and Whole Grains
Dietary patterns characterized by a high intake of fruits, vegetables, and whole grains are associated with a variety of health benefits including a lower risk of developing heart disease, stroke, hypertension, and certain cancers. The Dietary Guidelines for Americans recommend consuming 3-5 servings of vegetables daily, 2-4 servings of fruits daily, and 6-11 servings daily of grain products with at least three being whole grains. Most Americans fail to meet these recommendations. Data from national food consumption surveys showed that only 28 percent of Americans consumed at least two servings of fruit daily, 3 percent of Americans consumed three servings of vegetables daily, and 7 percent of Americans consumed six grain servings daily with at least three being whole grains. A national survey found that although knowledge of the recommendation to consume five or more fruits and vegetables daily was associated with higher consumption, only 8 percent of the population was aware of this recommendation. Public health campaigns, such as the Five-A-Day for Better Health Program, to promote awareness and behavior change are underway.
The public health recommendation is that all healthy people aged 2 years and older reduce dietary fat intake to less than 30 percent of calories and dietary saturated fat intake to less than 10 percent of calories. However, results from population-based food consumption surveys indicate that consumption of total and saturated fat remains above recommended levels for a large proportion of the population. Only 30 percent of Americans consume diets containing no more than 30 percent of calories from total fat, and 36 percent of Americans consume diets containing less than 10 percent of calories from saturated fat. These findings are due in part to an increased reliance by Americans on takeout and restaurant foods, which are typically higher in fat.
Diets that are high in total fat are associated with an increased risk for obesity, certain cancers, and gallbladder disease. Diets high in saturated fat and cholesterol are associated with a greater risk for coronary heart disease. Saturated fatty acids, which are found in meats and dairy products that contain fat, and trans-fatty acids, which are found in hydrogenated margarine and shortening, raise blood low-density-lipoprotein cholesterol levels, thereby increasing the risk for heart disease. Monounsaturated fatty acids, found in olive and canola oil, and polyunsaturated fatty acids, found in corn, sunflower, and safflower oils, do not raise blood cholesterol levels and should replace saturated fats in the diet to lower health risks.
Excess sodium and salt intake has been linked to high blood pressure in many people. Food consumption survey data indicate that approximately 80 percent of Americans consume greater than the recommended maximum of 2,400 mg of sodium daily. Most dietary sodium is added to foods during processing. It is also added in the form of condiments such as table salt, soy sauce, ketchup, and mustard. The Dietary Guidelines for Americans recommend choosing a diet moderate in salt and sodium by limiting processed foods, added salt, and high-sodium condiments.
Calcium is essential for the formation and maintenance of bones and teeth. In fact, the level of bone mass achieved at full growth (peak bone mass) appears to be related to the level of calcium intake during childhood and adolescence. Achieving optimal peak bone mass is thought to protect against fractures and osteoporosis later in life.
The DRI (dietary reference intake) for adequate daily calcium intake is 800 mg for children aged 4-8 years, 1,300 mg for adolescents aged 9-18 years, 1,000 mg for adults aged 19-50 years, and 1,200 mg for adults aged 51 and older. The DRI for pregnant adolescents and women is not increased above prepregnancy levels because calcium absorption increases during pregnancy. Population-based survey data indicate that more than 50 percent of the population consumes less calcium than recommended. These findings are particularly prevalent among adolescents and adult females.
Approximately three-fourths of calcium in the American diet comes from dairy products such as milk, yogurt, and cheeses. Individuals who suffer from lactose intolerance can often tolerate smaller amounts of milk with meals, aged cheeses, yogurt with active cultures, and/or lactose-reduced milk. Other high-calcium food sources include fortified orange juice, cereals, breakfast bars, and breads.
Iron deficiency is the most prevalent nutritional deficiency disorder in the United States. Iron deficiency can progress to iron deficiency anemia and cause preterm births, low birth weight, and delays in infant and child development. Iron deficiency is most common among minority and low-income children, females of childbearing age due to blood loss during menstruation, and pregnant women due to increased iron requirements during pregnancy. Food consumption data indicate that only 25 percent of women of child-bearing age meet the RDA (recommended dietary allowance) of 15 mg of iron daily. Iron deficiency among women of childbearing age and children can be prevented by consumption of iron-rich foods such as meats, poultry, fish, leafy greens, dried beans, and iron-enriched grains and cereals. Vitamin C-rich foods (orange juice and other citrus foods) should be consumed with iron-rich foods, as they enhance iron absorption. Supplementation with 30 mg of elemental iron is recommended for all pregnant women during the second and third trimesters to prevent iron deficiency anemia during pregnancy. Also, exclusive breast-feeding during the first 4-6 months and the use of iron-fortified formulas for formula-fed infants is recommended to prevent iron deficiency during infancy.
Nutritional factors are important throughout the life span. Nutritional status before and during pregnancy has an impact on maternal and infant outcomes. During childhood, nutritional factors can affect growth and development, resistance to disease, and risk for future chronic diseases. Nutrition is also related to several acute and chronic health conditions such as overweight, hypertension, coronary heart disease, stroke, certain cancers, and Type II diabetes. Behaviors to promote good nutrition should begin during infancy and childhood, and the development of healthy eating habits should continue throughout life.
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