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A healthy diet is one that helps maintain or improve health. It is important for the prevention of many chronic health risks such as: obesity, heart disease, diabetes, and cancer.[1] A healthy diet involves consuming appropriate amounts of all nutrients, and an adequate amount of water. Nutrients can be obtained from many different foods, so there are a wide variety of diets that may be considered healthy diets.
[edit] Dietary recommendationsThere are a number of diets and recommendations by numerous medical and governmental institutions that are designed to promote certain aspects of health. [edit] World Health OrganizationThe World Health Organization (WHO) makes the following 5 recommendations with respect to both populations and individuals:[2]
Other recommendations include:
[edit] DASH dietMain article: DASH diet [edit] Composition[edit] Macronutrients[edit] ProteinProtein is needed primarily for repair and growth of the human body. Protein consists of amino acids, some of which can be made from other proteins, some of which are essential amino acids. A healthy diet requires sufficient quantities of all essential amino acids. Increased requirements of amino acids occur for repair of muscles after strength training and a small amount is used for growth. Amino acid requirements are largely dependent on muscle mass; men generally require larger dietary protein intake for this reason. Some strictly epidemiological evidence shows an increased mortality with high red meat intake.[5] [edit] FatMain article: Fat Fat is used in the body for forming cell membranes, oxidized for energy, and can be stored by the body for later use if food intake is inadequate. Fats come in three main types: saturated fat, monounsaturated fat and polyunsaturated fat. Trans fat, a kind of unsaturated fat found in large quantities in foods such as margarine, is now known to be harmful. [edit] CarbohydrateCarbohydrates are chemicals that can be broken down in the body to simple sugars like glucose and fructose. Glucose is primarily used by the body in muscles but is the primary energy source used by the brain. If an excess of carbohydrate is consumed then it is stored with a large quantity of water as glycogen in the skeletal muscles and the liver. Fructose cannot be used by the skeletal muscles, but is converted into glucose by the liver. However, if large quantities of fructose are consumed, the conversion produces triglycerides which are thought to be unhealthy. One major source of fructose is sucrose (table sugar), fruits also contain substantial quantities, and so should not be taken in excess. [edit] EnergyThe human body creates energy from chemical reactions (mainly oxidation) of food. Due to conservation of energy if more energy is absorbed from food, then weight gain occurs (in the form of glycogen and its associated water) and fat. Some variation in weight can also occur due to hydration levels. Different components of the diet provide different number of net calories, roughly speaking proteins provide about 4.5 kCal, carbohydrates about 5 kCal and fats,9.5 kCal per gram. Research has showed that the idea of thin people having a 'fast metabolism' is false; human beings burn energy at quite predictable rates, and gain or loss of weight is mostly to do with calorie intake versus the bodies' basal metabolism (with people with more lean bodyweight burning more calories) as well as (usually to a lesser degree) activity levels; with any long-term excess being stored as fat. Energy is also used for growth and repair. [edit] Minerals[edit] SaltWhile a moderate amount of salt is required for health, a high salt diet can have detrimental effects on blood pressure[6] and long term high levels of salt intake is associated with increased risk of stroke and cardiovascular disease.[7] [edit] PotassiumPotassium is used by the body for a number of purposes, and tends to lower blood pressure. An inadequate supply can cause heart arrhythmias. [edit] MagnesiumMain article: Magnesium in biology#Food sources Magnesium salts are used in the nervous system, and tends to lower blood pressure. They are mostly water soluble and so are easily absorbed. [edit] CalciumCalcium is used by the body to form and maintain bones and teeth and is used in the nervous system. Inadequate supply can result in osteoporosis. [edit] IronIron is used by the body to form red blood cells, which carry the oxygen for the body. Lack of iron can cause anemia. High doses of iron in a short period cause death. [edit] CopperAlthough toxic in high doses, copper is an essential nutrient. Low levels cause progressive failure of the nervous system. Up to around half of the copper can be obtained from drinking water fed by copper pipes. [edit] ZincZinc is an essential component of many thousands of chemical processes throughout the body. A deficiency can cause skin problems, but also impairs the immune system and can cause impairment of repair and growth. [edit] ChromiumChromium is used by the body to process carbohydrates. High doses of chromium are toxic. [edit] SeleniumMain article: Selenium Although selenium is an essential trace mineral it is toxic at high doses. At normal levels it is used by the body to produce antioxidant chemicals, and some studies show an inverse relationship between intake and cancer, and the studies seem to show that it is unwise to be deficient in it. Few foods are high in selenium; one exception is Brazil nuts; one and half brazil nuts per day give the recommended intake. [edit] VitaminsMain article: Reference Daily Intake The target amount of vitamins that are thought to be needed for good health are expressed as RDA (Recommended Daily Allowance) or Reference Daily Intake (RDI). RDAs vary somewhat with age, sex and bodyweight and may be increased or reduced by medical conditions. [edit] FiberMain article: Dietary Fiber Fiber in the diet may be of benefit to health. There is some evidence that fiber lowers LDL cholesterol but does not lower HDL cholesterol.[8][9] [edit] Unhealthy dietsAn unhealthy diet is a major risk factor for a number of chronic diseases including: high blood pressure, diabetes, abnormal blood lipids, overweight/obesity, cardiovascular diseases, and cancer.[10] The WHO estimates that 2.7 million deaths are attributable to a diet low in fruit and vegetable every year.[10] Globally it is estimated to cause about 19% of gastrointestinal cancer, 31% of ischaemic heart disease, and 11% of strokes,[1] thus making it one of the leading preventable causes of death worldwide.[11] [edit] Food additive controversySome[who?] claim that food additives, such as artificial sweeteners, colorants, preserving agents, and flavorings may cause health problems such as increasing the risk of cancer or ADHD.[12] [edit] Fast foodExamples of fast food critics include Jamie Oliver, Morgan Spurlock and Eric Schlosser. [edit] Fad dietsMain article: Fad diet [edit] Public healthFears of high cholesterol were frequently voiced up until the mid-1990s. However, more recent research has shown that the distinction between high- and low-density lipoprotein ('good' and 'bad' cholesterol, respectively) must be addressed when speaking of the potential ill effects of cholesterol. Different types of dietary fat have different effects on blood levels of cholesterol. For example, polyunsaturated fats tend to decrease both types of cholesterol; monounsaturated fats tend to lower LDL and raise HDL; saturated fats tend to either raise HDL, or raise both HDL and LDL; and trans fat tend to raise LDL and lower HDL. Dietary cholesterol itself is only found in animal products such as meat, eggs, and dairy, but studies have shown that even large amounts of dietary cholesterol only have negligible effects on blood cholesterol. Media coverage of mass-produced, processed, "snack" or "sweet" products directly marketed at children has worked to undermine policy efforts to improve eating habits. The main problem with such advertisements for foods is that alcohol and fast food are portrayed as offering excitement, escape and instant gratification. Particularly within the last five years government agencies have attempted to combat the amount and method of media coverage lavished upon "junk" foods. Governments also put pressure on businesses to promote healthful food options, consider limiting the availability of junk food in state-run schools, and tax foods that are high in fat. Most recently, the United Kingdom removed the rights for McDonald's to advertise its products, as the majority of the foods that were seen have low nutrient values were aimed at children under the guise of the "Happy Meal". The British Heart Foundation released its own government-funded advertisements, labeled "Food4Thought", which were targeted at children and adults displaying the gory nature of how fast food is generally constituted. [edit] Cultural and psychological factorsFrom a psychological perspective, a new healthy diet may be difficult to achieve for a person with poor eating habits. This may be due to tastes acquired in early adolescence and preferences for fatty foods. It may be easier for such a person to transition to a healthy diet if treats such as chocolate are allowed; sweets may act as mood stabilizers, which could help reinforce correct nutrient intake. It is known that the experiences we have in childhood relating to consumption of food affect our perspective on food consumption in later life. From this, we are able to determine ourselves our limits of how much we will eat, as well as foods we will not eat - which can develop into eating disorders, such as anorexia, bulimia, or orthorexia This is also true with how we perceive the sizes of the meals or amounts of food we consume daily; people have different interpretations of small and large meals based on upbringing. While plants, vegetables, and fruits are known to help reduce the incidence of chronic disease,[citation needed] the benefits on health posed by plant-based foods, as well as the percentage of which a diet needs to be plant based in order to have health benefits is unknown. Nevertheless, plant-based food diets in society and between nutritionist circles are linked to health and longevity, as well as contributing to lowering cholesterol, weight loss, and in some cases, stress reduction.[citation needed] Indeed, ideas of what counts as "healthy eating" have varied in different times and places, according to scientific advances in the field of nutrition, cultural fashions, religious proscriptions, or personal considerations. [edit] See also
[edit] References
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