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Nutrition and health

Ill health can be brought about by an imbalance of nutrients, producing either an excess or deficiency which in turn affects body functioning in a cumulative manner. In addition, as mentioned, the type and amount of foods Pharmacy Health Topic we eat affect the body's hormonal environment directly, and a persistent intake of (a certain amount of) certain foods may induce hormonal imbalance and thereby disease. Moreover, because most nutrients are, in some way or the other, involved in cell-to-cell signalling (e.g. as building block or part of a hormone), deficiency or excess of various nutrients affects hormonal function also 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 observations especially in recent years have demonstrated a pivotal role for nutrition in hormonal activity and function and therefore in health.

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). The list goes on and on; for reference, see Modern Nutrition in Health and Disease by Shils et al.

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 discovered and yet to be discovered properties including antioxidant activity (see below). Other essential nutrients include essential amino acids, choline and the essential 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 unsaturated fatty acids are substrates for a class of eicosanoids known as prostaglandins). Alpha-linolenic acid (LNA) serves as the building block for the less-inflammatory PGE3 series of prostaglandins, whereas linoleic acid (LA) (and specifically its product, arachidonic acid, AA) serves as the building block for either the PGE1 (anti-inflammatory) or the PGE2 (pro-inflammatory) series. (The omega-6 fatty acid LA is the building block for the omega-6 fatty acid AA, but AA can also be obtained directly in the diet). The Pharmacy Health Topic conversions of AA into the respective prostaglandins (PGE1/PGE2) have importantly been discovered to be under hormonal control, as certain hormones such as insulin and glucagon regulate the function of the enzymes responsible for the conversions. 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 is now known to determine health implications in relation to essential fatty acids, inflammation (e.g. immune function) and mitosis (i.e. cell division).

Several lines of evidence indicate lifestyle-induced insulin malfunction, referred to as insulin resistance, as a decisive factor in many disease states. Researchers have for long assumed that overfatness/obesity causes insulin resistance, which in turn causes type 2 diabetes (virtually all obese and diabetic individuals have marked insulin resistance). More recent evidence has however demonstrated that insulin resistance may well be the cause of overfatness/obesity as well as type 2 diabetes and possibly other lifestyle-related diseases. For example, it has been demonstrated that appropriate exercise, more regular food intake and reducing glycemic load all can reverse insulin resistance in overfat individuals, which means that lifestyle rather than the fact of being fat promotes insulin resistance.

Nonetheless, overfatness can unfavourably alter hormonal and metabolic status seemingly especially via the hormone leptin, and a vicious cycle may occur in which insulin/leptin resistance and overfatness aggravate one another. There is debate to what extent different dietary factors, such as intake of processed carbohydrates, total protein-, fat-, and carbohydrate intake, intake of trans fatty acids, and low intake of micronutrients, contribute to develop insulin- and leptin resistance. Most importantly, insulin- and leptin resistance are both 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 over-expressed cell division (i.e. cancer).

A persistent high intake of processed carbohydrate-dense foods (high glycemic load) resulting in repeatedly high release of insulin and leptin seems to readily make cells less responsive to both of these crucial hormones (perhaps especially in combination with high intake of saturated fat/trans fatty acids and sedentary living). This type of negative feedback is ubiquitous in any biological system, all of which depend on appropriate hormonal regulation for survival and proper function. However, certain cell types appear to more readily become resistant to the effects of certain hormones (e.g. insulin, leptin) than others; certain fat cells (e.g. abdominal subcutaneous fat) may respond well to the fat-storing signal of insulin while other cells fail to properly receive/transduce the signal meant to induce important cellular and systemic effects. Why certain cells develop resistance to certain signalling molecules remains unclear, but it seems plausible that hormone resistance serves to protect cells from excess circulating amounts of the given hormone. 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, for example, the obesity 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 may form. Pharmacy Health Topic For normal cellular maintenance, growth, and division, these free radicals must be sufficiently neutralized by antioxidant compounds, such as certain vitamins (vitamin C, vitamin E, vitamin K and the aforementioned phytochemicals as well as other compounds, some of which the body itself produces. 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.

It is now also known that the human digestion system contains a population of a range of bacteria which are essential to digestion, and which are also affected by the food we eat. The role and significance of the intestinal bacterial flora is under investigation.

It is now commonly accepted amongst the medical profession that a diet high in fresh fruit and vegetables but low in animal fat helps to prevent heart disease and cancer.