The U.S. Department of Agriculture makes it relatively easy to eat for optimal nutrition, spelling out caloric and food group requirements for age and gender and targeting areas of special concern for some individuals. You can follow their guidelines exactly or simply concentrate on nutrient-dense foods with a minimum of trans and saturated fats, cholesterol, refined sugar and sodium.
While more precise ways are available to determine your personal calorie needs, the USDA offers some general rules of thumb. A teen girl needs between 1,800 and 2,400 calories a day, depending on her level of activity, while a teen boy requires between 1,800 and 3,200 a day. A woman in her 30s should be able to maintain her weight on an 1,800-calorie-a-day diet if she is not active. A man of the same age, equally as active, needs approximately 2,200 calories for optimal energy without weight gain. The USDA defines an inactive lifestyle as one in which you expend only enough energy for routine day-to-day activities. If you walk more than three miles per day at three to four miles per hour or the equivalent, you have an active lifestyle.
Ideally, you should consume some food from each of six groups on a daily basis. On an average 2,000-calorie-a-day diet, the USDA recommends that you have two cups from the fruit group; 2.5 cups from the vegetable group; 6 oz. of grains; 5.5 oz. of meats, beans or a protein equivalent; three cups of milk or the equivalent; and 6 tsp. of oils. Half of your grains should be whole grains, and meat should be limited to lean beef, poultry or fish. Eggs, peanut butter, nuts and seeds are included in this group, as well. Milk includes only those products that retain their calcium value, and cream cheese, butter and cream do not. Choose cheese, milk or yogurt. Oils are any fats that are liquid at room temperature, such as corn and olive oils.
Beyond eating 2.5 cups of vegetables a day for a 2,000-calorie-per-day-diet, the USDA further specifies exactly what kind of vegetables you should eat. Three cups per week each should come from dark green vegetables, legumes and starchy vegetables such as potatoes. Two cups should come from orange vegetables. Once you’ve reached those quotas, however, the choice as to what to eat for the remaining servings is yours.
Even if you eat the correct amounts of all the right things, and you get your recommended daily allowances, or RDA, of vitamins and minerals from food sources, RDA amounts are only sufficient to prevent a deficiency, according to the website Safe Slimming. You may want to supplement for optimal health, but too much of any single vitamin can be unhealthy as well, so talk to your doctor to find out what is best for you.
People over 50 should monitor their intake of vitamin B12, according to the USDA. Their bodies are not as easily able to digest this vitamin from food sources so they might needs supplements. Older adults also need more vitamin D, as well as those with dark skin and people who are housebound and do not get much sunlight. Women of childbearing age should make sure they get enough iron and folic acid. The USDA indicates that many women and teen girls are iron-deficient, and folic acid helps to prevent neural tube birth defects.