The body also needs micronutrients (such as vitamins and minerals) in smaller amounts, but macronutrients provide it with calories (energy) and the building blocks of cell growth, immune function, and overall repair. We need essential amino acids, carbohydrates, essential fatty acids, and a variety of vitamins and minerals to maintain life and health. However, nutritional needs vary from one stage of life to another. During intrauterine development, infancy and childhood, for example, the recommended intake of macronutrients and most micronutrients is greater relative to body size, compared to macronutrient intake during adulthood.
In older people, some nutritional needs (for example, nutrients) are classified as carbohydrates, fats, proteins, vitamins, or minerals. Water and dietary fiber are also essential. Each nutrient has specific functions and is made available to the tissues of the body through the processes of digestion and absorption. The nutrients proteins, carbohydrates, and fats in foods serve as energy sources for the body.
Of the three nutrients, we're least concerned about protein. Not because it's not important that 50% of our body weight is made up of protein, but because teenagers in the United States get twice as much protein as they need. Unless blood tests and a pediatrician's evaluation reveal a specific deficiency, getting nutrients from food rather than dietary supplements is preferred. On food labels, the amount listed for “calories” is actually equivalent to each calorie multiplied by a thousand.
More than 200 million children suffer from protein-energy malnutrition (PEM) and every year nearly 13 million children under five die as a direct or indirect result of hunger and malnutrition. First of all, the predominant nutritional problem in developed countries is overnutrition, at least when it comes to energy and macronutrients. The FAO and WHO Nutrition Advisory Group has determined that, on average, a daily diet of around 2,200 calories is sufficient to meet basic nutritional needs. Malnutrition is usually the result of diets that lack specific nutrients, but it can also be caused by so-called excess diets.
Nutrition Essentials by Stephanie Green and Kelli Shallal is licensed under a Creative Commons Attribution-Noncommercial-ShareAlike 4.0 international license, except where otherwise noted. Anemia, largely due to iron deficiency, is the most widespread nutritional problem affecting 2 billion people worldwide. From arctic tundra to tropical forests, and from large cities to remote islands, diverse populations demonstrate that human nutritional needs can be met with a wide range of foods and dietary habits. Doctors can help patients make the dietary changes needed to prevent overnutrition and its after-effects.
While the expectant mother must provide nutrition for both herself and her developing baby, the increase in energy needs during pregnancy is modest. However, while nutritional and lifestyle factors can directly affect fertility, they also influence the risk of several diseases that impair fertility, such as polycystic ovary syndrome, endometriosis and uterine fibroids (see relevant chapters). The role of nutrition in fertility has been the subject of a limited amount of research, focusing particularly on the role of antioxidants, other micronutrients and alcohol. Each of these stages has slightly different requirements when it comes to nutrition, although some needs may remain the same.
Nutritional interventions should emphasize healthy foods first, and supplements should play a sensible secondary role. When trying to figure out what foods to include in your diet plan, the easiest way to do that is to eat according to the nutritional recommendations for your age.