Nutrition is the provision, to cells and organisms, of the materials necessary (in the form of food) to support life. It is the intake of food, considered in relation to the body's dietary needs. Nutrition is one matter that takes a backseat with lifestyle enthusiasts around the world. In its basic sense, nutrition refers to the intake of nourishment; specifically the fluids and fuels we need to survive.

Diet and Fiber

Dietary fiber consists mainly of cellulose that is indigestible because we do not have enzymes to digest it. Dietary sources of protein include meats, eggs, grains, legumes, and dairy products such as milk and cheese. Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen which are present in common organic molecules. Dietary Guidelines for Americans, published jointly by the Department of Health and Human Services (HHS) and the Department of Agriculture (USDA), provides advice about how good dietary habits for people aged 2 years and older can promote health and reduce risk for major chronic diseases. While pizza really can't be a staple part of a healthy diet, you can make healthier pizzas that are lower in fat, higher in fiber and actually offer some good nutrition by choosing whole grain crusts and lots of vegetables. Poor diet can have an injurious impact on health, causing deficiency diseases such as scurvy, beriberi, and kwashiorkor; health-threatening conditions like obesity and metabolic syndrome, and such common chronic systemic diseases as cardiovascular disease, diabetes, and osteoporosis. In general, eating a wide variety of fresh, whole (unprocessed), foods has proven favourable compared to monotonous diets based on processed foods. Fruits and vegetables are rich in dietary fiber.

Importance of dietary fiber:

- Provides bulk to the intestinal contents.

- Stimulates peristalsis (rhythmic muscular contractions passing along the digestive tract).

Lack of dietary fiber in the diet leads to constipation (failure to pass motions). Consuming a diet that contains adequate amounts of essential (but also non-essential) amino acids is particularly important for growing animals, who have a particularly high requirement. Some dietitians recommend that these heavier elements should be supplied by ingesting specific foods (that are enriched in the element(s) of interest), compounds, and sometimes including even minerals, such as calcium carbonate.

Nutritional Supplements

Sometimes minerals are added to the diet separately from food, such as mineral supplements, the most famous being iodine in "iodized" salt. Sodium is not generally found in dietary supplements, despite being needed in large quantities, because the ion is very common in food. Supplements containing vitamins or dietary minerals are recognised by the Codex Alimentarius Commission (the United Nations' highest authority on food standards) as a category of food. Supplements, most especially anti-oxidants, can help our body keep toxins to a minimum. Supplementation with both single vitamins and vitamin mixtures have been studied in children with Down syndrome. Supplemental L-Tyrosine has been studied as an athletic enhancement aid and in the treatment of depression, drug dependence, narcolepsy, Parkinson's, Alzheimer's, phenylketonuria, and many other conditions.

Nutritional maintenance

For normal cellular maintenance, growth, and division, the free radicals must be sufficiently neutralized by antioxidant compounds, some produced by the body with adequate precursors (glutathione, Vitamin C in most animals) and those that the body cannot produce may only be obtained through the diet through direct sources (Vitamin C in humans, Vitamin A, Vitamin K) or produced by the body from other compounds (Beta-carotene converted to Vitamin A by the body, Vitamin D synthesized from cholesterol by sunlight). Most fatty acids are non-essential, meaning the body can produce them as needed, however, at least two fatty acids are essential and must be consumed in the diet. Because different types and amounts of food eaten/absorbed affect insulin, glucagon and other hormones to varying degrees, not only the amount of omega-3 versus omega-6 eaten but also the general composition of the diet therefore determine health implications in relation to essential fatty acids.