How well do you know clinical nutrition: Basic review (1)

Clinical nutrition is very important for our health. We hear lots of medical education on nutrition with diverse philosophies. In fact, some are even confused on what to eat and not to eat.

I believe this article will help the lay man make the right choices on nutrition on what to eat.

The energy required to maintain good health is derived from macronutrient food sources – carbohydrates proteins, and fats. Some forms of these foods are more nutritious than others; some, in fact, can contribute to the disease process rather than support the self-healing process

Macronutrient Proportion

The percentage of calories from carbohydrates, proteins, and fats in the diet is still under debate. Most nutritionists-agree that fat should comprise less than one third of the calories in a healthy diet. Some heart disease diets aim for only 10%. Calories from carbohydrates should comprise 30-50%, while calories from protein should comprise 20-30% of total calories.

The human body generates energy through the oxidative phosphorylation process that occurs in the mitochondria and, to a lesser degree, through the anerobic breakdown of glucose. Every cell in the body requires the constant influx of oxygen and Kreb's cycle intermediaries. The Kreb's cycle produces high energy compounds, such as NADH, which can contribute electrons to the electron transport chain. This ultimately results in the formation of ATP, the energy currency of the body.

Energy Needs

Without this constant supply of energy, the replication of DNA, translation of DNN and assembly of proteins would cease. Glucose, certain amino acid carbon skeletons, and lipids can be used to generate ATP.

This means that dietary macronutrients - carbohydrate, protein, fats and oils - can all contribute to total energy. However what proportion of each of these macronutrients constitutes a healthy diet is debateable. In practicing clinical nutrition, naturopathic physicians need to determine the proportion of macronutrients that benefits a particular patient.

This is not an exact science, but rather a well-informed clinical decision. Another decision concerns the make-up of each major energy source. Carbohydrates, for example, can be simple or complex and appear in many forms, such as glucose, fructose, lactose, and glucose polymer constituting starch. Fats can be saturated, monounsaturated, or polyunsaturated.

Proteins can be derived from animal or vegetable sources, as intact protein or as individual amino acids. Yet another decision is to determine how many calories a day patients require to meet their energy needs and maintain a healthy weight, not lose or gain weight, unless needed to improve their health.

Carbohydrates

Carbohydrates are needed to provide glucose to be used in powering reactions that derive energy from protein sources. Carbohydrates are considered to be "protein sparing," in that an adequate supply of carbohydrates can allow amino acids to be used for the manufacture of proteins in the body, as opposed to being catabolized for their energy value.

Forms of Carbohydrates

*Monosaccharides, such as glucose and fructose *Disaccharides, such as sucrose and lactose *Polysaccharides, such as starch (digestible) and dietary fiber (not digestible)

Simple and Complex Carbohydrates.

In general, naturopathic physicians recommend that the majority of calories from carbohydrates be derived from complex carbohydrate sources. Simple carbohydrates, while easy to digest and absorb (with some exceptions), tend to enter the bloodstream very quickly. This results in a rapid rise in blood sugar levels, followed by a compensatory surge in insulin secretion. High insulin levels are thought to be linked with the gradual development of obesity and insulin insensitivity, which can lead to diabetes mellitus.

Complex carbohydrates tend to be digested more slowly, not provoking insulin secretion to such a great a degree. Complex carbohydrates can take many forms. Naturopathic physicians tend to encourage patients to choose "whole grain" or unrefined carbohydrates - for example, brown rice rather than white rice or whole meal flour rather than white flour.

In wholegrain foods, the bran and germ of the grain are still present. Refined grains tend to be stripped of their nutrients, fiber, and antioxidants. Although fortification of grains with nutrients, such as thiamin (vitamin B-1), riboflavin (vitamin B-2), and niacin (vitamin B-3), has enriched these foods, not all nutrients that are stripped during food processing have been added back.

Early naturopathic practitioners observed that patients who relied heavily on refined carbohydrates (sugar and white flour) were less healthy because the very nutrients needed to metabolize these substances are missing or reduced in refined foods. During their metabolism, these foods use up more B complex vitamins and trace minerals than they contribute. On a mixed diet with a variety of whole foods, a certain amount of these highly refined foods can be consumed, but in large quantities they crowd out more nutritious alternatives.

Recommended Daily Carbohydrate Intake:

250 g carbohydrate for a 2000 kcal diet. These intakes must be adjusted for body mass, activity level, glycemic tolerance, and other individualizing factors. PROTEINS Amino acids make up proteins and are needed for the assembly of proteins in the cell. Protein present in amounts greater than that needed for cellular functions is broken down and the nitrogen component excreted in the urine. Protein is always being lost due to turnover of skin, mucosal surfaces, and the secretion of bile, pancreatic enzymes, saliva, and antibodies. Life events, such as pregnancy, rapid growth, or the repair of injury, require increased levels of proteins.

Disease conditions can increase protein needs, such as the sloughing off of the intestinal mucosa in inflammatory bowel disease or the loss of skin in a major burn.

Recommended Daily Protein Intake: The World Health Organization has calculated that basic protein needs are 0.6 g/kg body mass/day of a high quality protein. This includes eggs, fish, or meat, which contain all of the "essential" amino acids.

These amino acids cannot be assembled from other amino acids and thus are essential in the diet. Using a value of 25% above this figure to meet the needs of 97% of the population, the recommended daily allowance (RDA) becomes 0.75 g/kg/day.

Since this is in relation to "reference protein" - that is, high quality protein - the actual recommended requirements are higher, since not all protein consumed will be the same as the reference protein. It may be low in certain essential amino acids compared to the reference protein.