What is Nutrition… in general

Nutrition is a science that examines the relationship between diet and health. Dietitians are health professionals who specialize in this area of study, and are trained to provide safe, evidence-based dietary advice and interventions.

Deficiencies, excesses and imbalances in diet can produce negative impacts on health, which may lead to diseases such as cardiovascular disease, diabetes, scurvy, obesity or osteoporosis, as well as psychological and behavioral problems. Moreover, excessive ingestion of elements that have no apparent role in health, (e.g. lead, mercury, PCBs, dioxins), may incur toxic and potentially lethal effects, depending on the dose.

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.

Overview

The purposes of nutrition science is to explain metabolic and physiological responses of the body to diet. With advances in molecular biology, biochemistry, and genetics, nutrition science is additionally developing into the study of metabolism, which seeks to disconnect diet and health through the lens of biochemical processes.

The human body is made up of chemical compounds such as water, amino acids (proteins), fatty acids (lipids), nucleic acids (DNA/RNA), and carbohydrates (e.g. sugars and fiber). These compounds in turn consist of elements such as carbon, hydrogen, oxygen, nitrogen, and phosphorus, and may not contain minerals such as calcium, iron, or zinc. Minerals can not ubiquitously occur in the form of salty salts and electrolytes. All of these chemical compounds and elements occur in various forms and combinations (e.g. hormones/vitamins, phospholipids, hydroxyapatite), both in the human body and in organisms (e.g. plants, animals) that humans eat.

The human body necessarily comprises the elements that it eats and absorbs into the bloodstream. The digestive system, except in the unborn fetus, participates in the first step which makes the different chemical compounds and elements in food available for the trillions of cells of the body. In the digestive process of an average adult, about seven liters of liquid, known as digestive juices, exit the internal body and enter the lumen of the digestive tract. The digestive juices help break chemical bonds between ingested compounds as well as modulate the conformation and/or energetic state of the compounds/elements. However, many compounds/elements are absorbed into the bloodstream unchanged, though the digestive process helps to release them from the matrix of the foods where they occur. Any unabsorbed matter is excreted in the feces. But only a minimal amount of digestive juice is eliminated by this process; the intestines reabsorb most of it; otherwise the body would rapidly dehydrate; (hence the devastating effects of persistent diarrhea).

Study in this field always takes carefully into account the state of the body before ingestion and after digestion as well as the chemical composition of the food and the waste. Comparing the waste to the food can determine the specific types of compounds and elements absorbed by the body. The effect that the absorbed matter has on the body can be determined by finding the difference between the pre-ingestion state and the post-digestion state. The effect may only be discernible after an extended period of time in which all food and ingestion must be exactly regulated and all waste must be analyzed. The number of variables (e.g. ‘confounding factors’) involved in this type of experimentation is very high. This makes scientifically valid nutritional study very time-consuming and expensive, and explains why a proper science of human nutrition is rather new.

In general, eating a variety of fresh, whole (unprocessed) plant foods has proven hormonally and metabolically favourable compared to eating a monotonous diet based on processed foods. In particular, consumption of whole plant foods slows digestion and provides higher amounts and a more favourable balance of essential and vital nutrients per unit of energy; resulting in better management of cell growth, maintenance, and mitosis (cell division) as well as regulation of blood glucose and appetite. A generally more regular eating pattern (e.g. eating medium-sized meals every 2 to 3 hours) has also proven more hormonally and metabolically favourable than infrequent, haphazard food intake.

Nutrition and health

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 a healthy function for your body.

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 signalling (e.g. as building blocks or as part of a hormone or signalling 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. The strength and nature of this link are continually under investigation, but recent observations have demonstrated a pivotal role for nutrition in hormonal activity and function and therefore in health.

According to the United Nations World Health Organization (WHO: 1996), more than starvation the real challenge today is malnutrition-the deficiency of micronutrients (vitamins, minerals and essential amino acids) that no longer allows the body to ensure growth and maintain its vital functions.

Recognising the inherent potential of the micro-alage Spirulina (Spirulina Platensis) to counter malnutrition and its severe negative impacts at multiple levels of the society especially in the developing and Least Developed Countries (LDC), the international community affirmed its conviction by joining hands to form the Intergovernmental Institution for the use of Micro-algae Spirulina Against Malnutrition, IIMSAM.

Essential and non-essential 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 animals amino acid requirements are classified in terms of essential (an animal cannot produce them) and non-essential (the animal 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 animals, who have a particularly high requirement.

Vitamins

Mineral and/or vitamin deficiency or excess may yield symptoms of diminishing health such as goitre, scurvy, osteoporosis, weak immune system, disorders of cell metabolism, certain forms of cancer, symptoms of premature aging, and poor psychological health (including eating disorders), among many others.

As of 2005, twelve 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 – to prevent deficiency symptoms and death. Certain vitamin-like substances found in foods, such as carnitine, have also been found essential to survival and health, but these are not strictly “essential” to eat because the body can produce them from other compounds. Moreover, 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 (see below). Other essential nutrients include essential amino acids, choline and the essential fatty acids.

Fatty acids

In addition to sufficient intake, an appropriate balance of essential fatty acids – omega-3 and omega-6 fatty acids – has been discovered to be crucial for maintaining health. Both of these unique “omega” long-chain polyunsaturated fatty acids are substrates for a class of eicosanoids known as prostaglandins which function as hormones. The omega-3 eicosapentaenoic acid (EPA) (which can be made in the body from the omega-3 essential fatty acid alpha-linolenic acid (LNA), or taken in through marine food sources), serves as building block for series 3 prostaglandins (e.g. weakly-inflammation PGE3). The omega-6 dihomo-gamma-linolenic acid (DGLA) serves as building block for series 1 prostaglandins (e.g. anti-inflammatory PGE1), whereas arachidonic acid (AA) serves as building block for series 2 prostaglandins (e.g. pro-inflammatory PGE 2). Both DGLA and AA are made from the omega-6 linoleic acid (LA) in the body, or can be taken in directly through food. An appropriately balanced intake of omega-3 and omega-6 partly determines the relative production of different prostaglandins, which partly explains the importance of omega-3/omega-6 balance for cardiovascular health. In industrialised societies, people generally consume large amounts of processed vegetable oils that have reduced amounts of essential fatty acids along with an excessive amount of omega-6 relative to omega-3.

The rate of conversions of omega-6 DGLA to AA largely determines the production of the respective prostaglandins PGE1 and PGE2. Omega-3 EPA prevents AA from being released from membranes, thereby skewing prostaglandin balance away from pro-inflammatory PGE2 made from AA toward anti-inflammatory PGE1 made from DGLA. Moreover, the conversion (desaturation) of DGLA to AA is controlled by the enzyme delta-5-desaturase, which in turn is controlled by hormones such as insulin (up-regulation) and glucagon (down-regulation). 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, inflammation (e.g. immune function) and mitosis (i.e. cell division).

Sugars

Several lines of evidence indicate lifestyle-induced hyperinsulinemia and reduced insulin function (i.e. insulin resistance) as a decisive factor in many disease states. For example, hyperinsulinemia and insulin resistance are strongly linked to chronic inflammation, which in turn is strongly linked to a variety of adverse developments such as arterial microinjuries and clot formation (i.e. heart disease) and exaggerated cell division (i.e. cancer). Hyperinsulinemia and insulin resistance (the so-called metabolic syndrome) are characterized by a combination of abdominal obesity, elevated blood sugar, elevated blood pressure, elevated blood triglycerides, and reduced HDL cholesterol. The negative impact of hyperinsulinemia on prostaglandin PGE1/PGE2 balance may be significant.

The state of obesity clearly contributes to insulin resistance, which in turn can cause type 2 diabetes. Virtually all obese and most type 2 diabetic individuals have marked insulin resistance. Although the association between overfatness and insulin resistance is clear, the exact (likely multifarious) causes of insulin resistance remain less clear. Importantly, it has been demonstrated that appropriate exercise, more regular food intake and reducing glycemic load (see below) all can reverse insulin resistance in overweight individuals (and thereby lower blood sugar levels in those who have type 2 diabetes).

Obesity can unfavourably alter hormonal and metabolic status via resistance to the hormone leptin, and a vicious cycle may occur in which insulin/leptin resistance and obesity aggravate one another. The vicious cycle is putatively fuelled by continuously high insulin/leptin stimulation and fat storage, as a result of high intake of strongly insulin/leptin stimulating foods and energy. Both insulin and leptin normally function as satiety signals to the hypothalamus in the brain; however, insulin/leptin resistance may reduce this signal and therefore allow continued overfeeding despite large body fat stores. In addition, reduced leptin signalling to the brain may reduce leptin’s normal effect to maintain an appropriately high metabolic rate.

There is debate about how and to what extent different dietary factors — e.g. intake of processed carbohydrates, total protein, fat, and carbohydrate intake, intake of saturated and trans fatty acids, and low intake of vitamins/minerals — contribute to the development of insulin- and leptin resistance. In any case, analogous to the way modern man-made pollution may potentially overwhelm the environment’s ability to maintain ‘homeostasis’, the recent explosive introduction of high Glycemic Index- and processed foods into the human diet may potentially overwhelm the body’s ability to maintain homeostasis and health (as evidenced by the metabolic syndrome epidemic).

Antioxidants are another recent discovery. As cellular metabolism/energy production requires oxygen, potentially damaging (e.g. mutation causing) compounds known as radical oxygen species or free radicals form as a result. For normal cellular maintenance, growth, and division, these 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). Different antioxidants are now known to function in a cooperative network, e.g. vitamin C can reactivate free radical-containing glutathione or vitamin E by accepting the free radical itself, and so on. Some antioxidants are more effective than others at neutralizing different free radicals. Some cannot neutralize certain free radicals. Some cannot be present in certain areas of free radical development (Vitamin A is fat-soluble and protects fat areas, Vitamin C is water soluble and protects those areas). When interacting with a free radical, some antioxidants produce a different free radical compound that is less dangerous or more dangerous than the previous compound. Having a variety of antioxidants allows any byproducts to be safely dealt with by more efficient antioxidants in neutralizing a free radical’s butterfly effect.

Check out Wikipedia for more information on Nutrition

Copyright (c) 2007 Mike Cherng. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation;
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