Food and Nutrition zone

 Vitamin D Vitamin D food sources Vitamin D differs from the other nutrients in that the body can synthesize it, with the help of sunlight, from a precursor that the body makes from cholesterol. Therefore, vitamin D is not an essential nutrient; given enough time in the sun, people need no vitamin D from foods.  Also known as calciferol , vitamin D comes in two major forms. Vitamin D2 derives primarily from plant foods in the diet. Vitamin D3  derives from animal foods in the diet and from synthesis in the skin. These two forms of vitamin D are similar and both must be activated before they can fully function.  To make vitamin D, ultraviolet rays from the sun hit a precursor in the skin and convert it to pre-vitamin D3, which is converted to vitamin D3 with the help of body's heat. To activate vitamin D _whether made in the body or consumed from the diet _two hydroxylation reactions must occur. First, the liver adds an OH group, and then the kidneys add another OH gr...

 Vitamin A Vitamin A; most essential vitamin Vitamin A refers to the performed retinoids and provitamin A carotenoids that can be converted to vitamin A activity. Retinoids is a collective term for the biologically active forms of vitamin A. They are called performed vitamin A because, unlikely carotenoids, they do not need to be converted in the body to become biologically active. Retinoids exist in 3 forms; retinol, retinal and retinoic acid. The tail segment of the vitamin A structure terminates in 1 of these 3  chemical groups and determines the name or classification. To some extent, these can be interconverted . However, retinoic acid cannot be converted back to the other forms. the ability to interconvert forms helps maintain adequate amounts of each retinol form for its unique functions.  Carotenoids are yellow-orange pigmented materials in fruits and vegetables, some of which are provitamins __that is, they can be converted into vitamin A. Of the 600 or more kno...

  Vitamins: Essential Dietary Components Vitamins are essential, organic substances needed in small amounts in the diet. They are not a source of energy. Instead, they aid in energy metabolism as well as in the growth, development, and maintenance of body tissues.  During the first half of the 20th century, scientists identified each of the 13 vitamins now recognized as essential. For the most part, as the vitamins were discovered, they were named alphabetically: A, B, C, D and E. Later, some substances originally classified as B-vitamins were dropped from the list because they were shown to be non-essential substances. The B-vitamins originally were thought to have a single chemical form but turned out to exist in many forms. Thus, the label "vitamin B" now comprises 8 B-vitamins. Vitamins A, D, E and K dissolve in organic solvents, such as ether and benzene, and are referred as fat-soluble vitamins .  The B-vitamins and vitamin C, in contrast, dissolve in water and refe...

Triglycerides T riglycerides are the most common type of lipid found in foods and in the body. About 95% of the fats we eat and 95% of the fat stored in the body are in the form of triglycerides.  Structure: Triglycerides are built from a glycerol backbone and 3 fatty acids. Glycerol has 3 carbons in its chain. A triglyceride forms when each hydroxyl group on the glycerol backbone bonds with the hydrogen atom from the acid (carboxyl) end of a fatty acid. The bond between a fatty acid and glycerol is called an ester bond. One molecule of water forms each time an ester bond forms (this is called esterification), Thus, when a diglyceride (2 fatty acids attached to a glycerol backbone) forms, 2 molecules of water form. Similarly, forming a triglyceride will generate 3 water molecules. Esterification is a condensation reaction. A molecule of water is used when a fatty acid breaks away from a glycerol backbone (this hydrolysis reaction can be thought of as "de-esterification"). R...

 Lipids Fats and Oils Lipids (fats and oils) give food a creamy, luscious mouthfeel. Fat in foods has been considered the most satiating of all macronutrients. However, studies show that protein and carbohydrate probably provide more satiety. High fat meals do provide satiety because they are high in calories. They also add a great deal of flavor to foods __ think about the buttery taste of croissants or the savory flavor of beef. Most foods we eat contain at least some fat. Foods rich in fat and oils are vegetable oils, margarine, butter, avocado, and nuts.  All contain close to 100% of energy as fat. Many protein-rich foods, such as meat, cheese, and peanut butter, are high in fat too. In addition to providing flavor, texture, and energy, dietary fats supply fat-soluble vitamins (vitamin A, D, E, and K). They also are a compact source of calories __gram for gram, fats supply more than twice as many calories as both carbohydrates and proteins. Fat insulates the body and pads ...

 Vegetarian Diets Vegetarian Diet Vegetarianism has evolved over the centuries from a necessity into an option. Approximately, 2,5% of adults in the U.S and 4% of adults in Canada follow a vegetarian diet. Additionally, 20 to 25% of  Americans report that they eat at least 4 meatless meals a week. Most people choose vegetarian diets for religious, philosophical, ecological, or health-related reasons. Others adopt vegetarian practices because they are concerned about the economic and ecological impact of eating meat-based diets. They recognize that meat is not an efficient way of obtaining protein because it requires the use of approximately 40% of the world's grain production to raise meat-producing animals. Diets rich in fruits, vegetables, legumes, and grains frequently result in increased intakes of antioxidants nutrients (e.g., vitamins C and E and carotenoids), dietary fiber, and healthful phytochemicals and decreased intakes of saturated fat and cholesterol. Vegetarianis...

 Health Concerns Related to Protein Intake Many people living in developing countries suffer from malnutrition and disease because dietary protein supplies are limited. In contrast, the residents of developed countries tend to eat more protein than they need and may boost their intake even higher by consuming protein or amino acid supplements. Getting sufficient amounts of protein is required for good health, but getting too little or too much can have serious health problems. Protein-Energy Metabolism (PEM): Protein deficiency rarely develops as an isolated condition. It most often occurs in combination with a deficiency of energy and results in a condition known as protein-energy malnutrition (PEM), or protein-calorie malnutrition (PCM). In many developing areas of the world where diets are often low in protein and energy. PEM is a very serious public health concern. Although PEM can affect people of all ages, its most devastating consequences are seen in children. Without adequa...