Nutrition is a science that examines the relationship between diet and health. A Nutritionist is a professional who specializes in this area of study, and is trained to provide safe, evidence-based dietary advice and recommendations.
Deficiencies, excesses and imbalances in diet can produce negative impacts on your health, which may lead to diseases such as cardiovascular disease, diabetes, obesity or osteoporosis, as well as psychological and behavioral problems.
Many common diseases and their symptoms can often be prevented or alleviated with better nutrition. The science of nutrition attempts to understand how and why specific dietary aspects influence health.
Nutrients make up Nutrition
There are six main classes of nutrients that the body needs: carbohydrates, proteins, fats, vitamins, minerals, and water. It is important to consume these six nutrients on a daily basis to build and maintain health.
Carbohydrates - 4 kcal. /gram
Carbohydrates may be classified as monosaccharide, disaccharides, or polysaccharides by the number of sugar units they contain. Monosaccharide contains 1 sugar unit, disaccharides contain 2, and polysaccharides contain 3 or more. Polysaccharides are often referred to as complex carbohydrates because they are long chains of sugar units, whereas monosaccharide and disaccharides are simple carbohydrates. The difference is important to nutritionists because complex carbohydrates take longer to metabolize since their sugar units are processed one-by-one off the ends of the chains. Simple carbohydrates are metabolized quickly and thus raise blood sugar levels more quickly resulting in rapid increases in blood insulin levels.
Protein - 4 kcal. /gram
Most meats contain all the essential amino acids needed for people.
Protein is composed of amino acids. The body requires amino acids to produce new body protein (protein retention) and to replace damaged proteins (maintenance) that are lost in the urine. In humans amino acid requirements are classified in terms of essential (an individual cannot produce them) and non-essential (the individual can produce them from other nitrogen containing compounds) amino acids. Consuming a diet that contains adequate amounts of essential (but also non-essential) amino acids is particularly important for growing individuals, which have a particularly high requirement.
Fat - 9 kcal/gram
Fats are composed of fatty acids, long carbon/hydrogen chains bonded to a glycerol. Fat may be classified as saturated or unsaturated. Generally, saturated fat is solid at room temperature while unsaturated fat is a liquid. Unsaturated fats may be further classified as mono-unsaturated (one double-bond) or poly-unsaturated (many double-bonds). Trans fats are saturated fats which are typically created from unsaturated fat by adding the extra hydrogen atoms in a process called hydrogenation (also called hydrogenated fat).
Vitamins - 0 kcal/gram
Mineral and/or vitamin deficiency or excess may yield symptoms of diminishing health such as osteoporosis, weak immune system, disorders of cell metabolism, certain forms of cancer, symptoms of premature aging, and poor psychological health (including eating disorders).
Thirteen vitamins and about the same number of minerals are recognized as "essential nutrients", meaning that they must be consumed and absorbed - or, in the case of vitamin D, alternatively synthesized via UVB radiation. Thousands of different phytochemicals have recently been discovered in food (particularly in fresh vegetables), which have many known and yet to be explored properties including antioxidant activity.
Minerals - 0 kcal/gram
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. The term "mineral" is archaic, since the intent of the definition is to describe ions, not chemical compounds or actual minerals. Some health professionals 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. Sometimes these "minerals" come from natural sources such as ground oyster shells. Sometimes minerals are added to the diet separately from food, such as mineral supplements, the most famous being iodine in "iodized salt."
Water - 0 kcal/gram
About 70% of the non-fat mass of the human body is made of water. To function properly, the body requires between two to four liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well.
Normally, about 20 percent of water intake comes from food, while the rest comes from drinking water and beverages (caffeinated included). Water is excreted from the body in multiple forms; through waste, through sweating, and by exhalation of water vapor in the breath.
Poor health can be caused by an imbalance of nutrients, either an excess or deficiency, which, in turn, affects bodily functions cumulatively. Moreover, because most nutrients are involved in cell-to-cell signaling (e.g. as building blocks or as part of a hormone or signaling cascades), deficiency or excess of various nutrients affects hormonal function indirectly. Thus, because they largely regulate the expression of genes, hormones represent a link between nutrition and how our genes are expressed, i.e. our phenotype. Recent observations have demonstrated a pivotal role for nutrition in hormonal activity and function and therefore in health.
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