The term "Optimum Nutrition" can be defined as eating the right amounts of nutrients on a proper schedule to achieve the best performance and the longest possible lifetime in good health, assuming that external negative influences like accidents and infectious diseases can be avoided. Optimum Nutrition remains an elusive goal because the demands of the body change from minute-to-minute based on physical activity, and because medical science does not yet have a definitive set of comprehensive nutritional requirements for every human genetic variation.
Reduced calorie diets have been shown to extend the lifetime of mice and many other species. Optimum Nutrition, with regard to longevity, is thought to require a reduction of calories from what would normally be consumed. The term Caloric Restriction with Optimum Nutrition (CRON) refers to a reduced-calorie diet that supplies all the necessary nutrients. It is not unusual for male CRON practitioners to eat 1,800 Calories per day and for women to eat 1,300 Calories per day. The restricted calorie diets reduce basal metabolic rate and generally result in lower body temperatures.
In contrast, Optimum Nutrition for athletes emphasizes performance, rather than longevity. Bicycle riders of the Tour de France cover a distance of 3,000 to 4,000 kilometers in 20 races during a period of approximately three weeks with only two days of rest. During these races, participants consume from 6,500 to over 7,000 Calories per day. These diets attempt to build glycogen stores in the muscles quickly to be able to maintain a high degree of physical performance.
Timing of the Nutrients
The schedule for eating can be fairly flexible because the body is able to store nutrients for later use, but prolonged famines followed by episodes of gorging are not optimal. For the body to thrive, it is better if the nutrients are available in moderate amounts on a regular schedule. The timing of the administration of the nutrients is more important in competitive sports. Carbohydrate loading is a performance-enhancing strategy practiced by marathoners and other high-intensity endurance athletes. It is accomplished by first depleting the stored carbohydrate reserves a week before a competition, and then building up the glycogen reserves by increasing the percentage of carbohydrates in the diet while reducing physical activity for three days before the event. Bodybuilders also time their meals to maximize muscle growth. The muscles are stimulated to grow by exercising to exhaustion and then eating a high-protein meal immediately after the workout. To maintain their muscle mass, bodybuilders eat small high-protein meals throughout the day to keep the muscles from going into a catabolic state that destroys muscle tissue.
Inadequate diets can result in malnutrition and dietary deficiency diseases such as rickets, goiter, anemia, scurvy, etc. Similarly, diets with excessive calories and improper balance of protein, fat, and carbohydrates lead to obesity and may eventually result in metabolic syndrome, a combination of medical disorders that occur together: diabetes, cardiovascular disease, and high-blood pressure. Optimum Nutrition seeks to balance dietary nutrients to avoid diseases caused by deficiencies or excesses. The food that you eat should have the proper proportion of nutrients for your current stage of life. Women of reproductive age, for example, need more iron than post-menopausal women. Optimum Nutrition should provide the right quantities of protein, fat, carbohydrates, vitamins, minerals, fiber, and probiotic bacteria to maintain a healthy body and to sustain the desired level of activity for the best quality of life.
What to eat
The Food and Nutrition Board (FNB) is a unit of the Institute of Medicine (IOM), consisting of a group of biomedical scientists with expertise in various aspects of nutrition, food science, biochemistry, medicine, public health, epidemiology, food toxicology, and food safety. The FNB makes recommendations to promote public health and prevent diet-related diseases. The requirements for Optimum Nutrition, as far as they can be determined, are contained in a book published by the FNB entitled: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). These recommendations are a resource used to guide many government activities to promote public health. The information is also disseminated to the general public by the Center for Nutrition Policy and Promotion. The following paragraphs discuss the most important aspects of Optimum Nutrition.
Measuring Food and Counting Calories
The guidelines of the Food Pyramid established in 2005 emphasize finding a balance between food consumption and physical activity while making smart choices from every food group to get the most nutrition out of your calories. The steps of the pyramid represent physical activity, and the food groups are illustrated as colored wedges which include grains (orange), vegetables (green), fruits (red), dairy products (blue), meats and beans (purple), and oils (yellow). The width of the colored bands at the base indicate the proportions in which foods from the groups should be eaten.
The first step of planning any diet is to get an estimate of the number of calories required to maintain a normal weight based on your sex, height, weight, and level of physical activity using a Diet Calculator. Once you know how many calories your diet should have, you can select the proper portion sizes of pre-packaged products by reading the Nutrition Labels, or by weighing your food and using a diet-tracking program such as CRON-o-Meter to help you count the calories and determine the balance of nutrients. Learn how to count calories.
Alternative Healthy Eating Index (AHEI)
The current USDA food pyramid guidelines emphasize large amounts of carbohydrates, and do not make a distinction between types of fat or protein. Red meat, chicken, nuts and legumes are all under the same category. Harvard University researchers have developed an Alternative Healthy Eating Index (AHEI) by looking at dietary patterns and eating behaviors that were associated with lower rates of chronic disease. Unlike the USDA index, the AHEI emphasizes the quality of food choices: such as white meat over red meat; whole grains over refined grains; oils high in unsaturated fat over ones with saturated fat; and multivitamin use. Men whose diets most closely matched the AHEI were found to have a lower overall risk of major chronic disease by 20%, and women by 11%, compared with those whose diets least closely followed the AHEI guidelines. Also, men and women who followed the AHEI lowered their risk of cardiovascular disease by 39% and 28%, respectively. The characteristics of the AHEI diet associated with low rates of disease are:
Amino acids are the basic building blocks of proteins. Proteins in the body serve as structural components of cells, and they also function as enzymes and as hormones. The Recommended Dietary Allowance (RDA) for both men and women is 0.80 grams of protein per day per kilogram of body weight, which is 0.36 grams per pound of body weight. The RDA is an estimate of the minimum daily average dietary intake level that meets the nutrient requirements of nearly all (97 to 98 percent) healthy individuals. The upper range for total protein in the diet as a percent of total energy intake was set at 35 percent to decrease risk of chronic disease, but no Tolerable Upper Intake Level for total protein has been established. Using the criterion of 0.80 grams per kilogram, a person weighing 150 pounds should consume at least 55 grams of protein. The upper range of 35 percent of a 2000-Calorie diet corresponds to 700 Calories or 175 grams of protein because protein has 4 Calories per gram.
Fats or Lipids are compounds consisting of fatty acids and glycerol. Fats are structural components of the brain and cell membranes. Fats are also a major source of fuel energy for the body and carriers of fat-soluble vitamins and carotenoids. A Recommended Dietary Allowance for fat has not been established because there is insufficient data to determine a level of fat intake at which chronic disease occurs. However, an acceptable macronutrient range for total fat has been established at 20 to 35 percent of energy. This corresponds to a range of 400 to 700 Calories of fat for a 2000-Calorie diet, or 44 to 78 grams of fat per day because fat has 9 Calories per gram.
Essential Fatty Acids (EFA)
There are some fatty acids that are required in the diet because the body cannot make them from other fats. These are called omega-3 and omega-6 fatty acids, or sometimes n-3 and n-6 polyunsaturated fatty acids. These fats are found predominantly in seafood. Linoleic acid (LA) is an essential omega-6 polyunsaturated fatty acid that serves as a precursor to eicosanoids which act as mediators of inflammation. A lack of dietary omega-6 fatty acids can result in rough or scaly skin, and dermatitis. The Adequate Intake of 17 grams per day for men and 12 grams per day for women for linoleic acid is based on the median intake in the United States from samples of healthy individuals who do not have an omega-6 fatty acid deficiency. No upper limits have been set for omega-6 polyunsaturated fatty acids. The Adequate Intake corresponds to approximately one tablespoon of grapeseed oil per day.
Omega-3 polyunsaturated fatty acids are structural components of membrane lipids, particularly in nerve tissue and the retina, and are also precursors to eicosanoids. A lack of alpha-linolenic acid (ALA), an essential omega-3 polyunsaturated fatty acid, in the diet may manifest itself as scaly dermatitis. The Adequate Intake for alpha-linolenic acid is based on median intakes in the United States from samples of healthy individuals who do not have an omega-3 fatty acid deficiency. The Adequate Intake is 1.6 grams per day for men and 1.1 grams per day for women. The upper limit set by the FDA for omega-3 polyunsaturated fatty acids is 3 grams per day due to concerns about increased bleeding times that may be caused by greater amounts. The Adequate Intake corresponds to approximately one teaspoon of flax seed oil per day.
Carbohydrates may be simple sugars (monosaccharides), compounds of two simple sugars (disaccharides), or compounds containing a large number of simple sugars (polysaccharides). Sugars and starches provide energy to cells in the body, particularly the brain, which is the only carbohydrate-dependent organ in the body. The Recommended Dietary Allowance for carbohydrates is set at 130 grams per day for adults and children based on the average minimum amount of glucose utilized by the brain. This corresponds to approximately 520 Calories per day.
Dietary fiber consists of carbohydrates that cannot be digested in the human intestines. There are different types of fiber. Soluble fiber is highly viscous and may delay the gastric emptying of ingested foods into the small intestine, resulting in a sensation of fullness and reducing the level of glucose in the blood after a meal. Soluble fiber also may reduce blood cholesterol by interfering with the reabsorption of bile acids from the intestines. Insoluble fiber increases fecal bulk and may relieve constipation by promoting bowel movements. Some fiber is fermented in the intestines by anaerobic bacteria which produce short-chain fatty acids and some vitamins. The Adequate Intake for total fiber in foods is set at 38 grams per day for men, and 25 grams per day for women based on the intake level observed to protect against coronary heart disease.
The term "macronutrient" refers to the three major components of a diet: protein, fat, and carbohydrate. Acceptable Macronutrient Distribution Ranges have been set by the Food and Nutrition Board for protein, fat, carbohydrate, and essential omega-3 and omega-6 polyunsaturated fatty acids based on epidemiological evidence suggesting the prevention or increased risk of chronic diseases, and based on ensuring sufficient intakes of essential nutrients. The following table summarizes the acceptable ranges as a percent of energy for adults.
|Nutrient||Percent of Energy|
|Protein||10 to 35|
|Fat||20 to 35|
|LA (omega-6)||5 to 10|
|ALA (omega-3)||0.6 to 1.2|
|Carbohydrate||45 to 65|
It is worthwhile noting that the lower range of the percentage for carbohydrate is higher than the percentages in many popular weight loss diets. Dr. Sears' Zone Diet, for example, has macronutrient ratios of 30% protein, 30% fat, and 40% carbohydrate while the Atkins Diet reduces the amount of carbohydrates to about 13% of the total energy. Some traditional diets, such as those of Inuit natives living in the Nunavik villages in northern Quebec consist almost exclusively of meat or fish with more than 50 percent of the calories derived from fats. Yet, their cardiac death rate is about half that of other Canadians. Counterexamples like this emphasize that we still have a lot to learn about nutrition. The dietary guidelines for carbohydrates may need to be modified in the future to take into consideration gluconeogenesis, which is the ability of the body to produce glucose from noncarbohydrate sources, such as the glycerol portion of fats, and the use of ketone bodies derived from fatty acids as an alternative fuel for the central nervous system.
Vitamins and Minerals
A balanced diet does not require supplementation with vitamins and minerals. However, most nutritionists recommend supplementation with some vitamins or minerals and the government promotes enrichment of some foods with vitamins or minerals, e.g., salt is often supplemented with iodine, milk is enriched with Vitamin D, and water is supplemented with fluoride. The Recommended Dietary Allowances are revised as new research suggests that the health of the general public would benefit from the change.[3,4,5,6] In particular, the current RDA of Vitamin D is in the process of being revised upward to 1000 IU per day for adults because people in the northern latitudes do not get enough sunlight to synthesize the vitamin in their skin.
Variation in Foods
The nutritional values reported on food labels represent average values for foods collected from diverse locations. Mineral deficiencies can develop by eating vegetables that are grown on poor soils, specially when consuming low calorie diets. Nutritional deficiencies may also be caused by inadequate absorption in the intestines. Some vitamins can only be absorbed in the presence of fat, so it is important to eat meals that combine all macronutrients.