A Primer on Nutrition

One of the most important things for a diabetic to learn is the basics of nutrition. Unfortunately, it is also one of the fastest changing and controversial subjects today. Because of the controversy, we will attempt to fairly present the opposing views, but this page is aimed at diabetics, so how nutrition affects our blood glucose will be our emphasis.

All foods are made up of macro-nutrients, micro-nutrients, and inert ingredients like water.

Micro-Nutrients

Micronutrients are substances which cannot be synthesized by the body, and are typically needed in very small quantities. Therefore, they must be provided by our diets, or through supplementation. These micronutrients are essential for the body to maintain  its normal functions. All vitamins, most minerals, antioxidants and phytochemicals are micronutrients. 

Macro-Nutrients

All foods are made up of three macro-nutrients: Carbohydrates, Proteins, and Fats. Each is important to providing us energy under differing conditions, and to providing the building blocks to repair and create new cells.

Carbohydrates

Carbohydrates are composed of carbon, hydrogen and oxygen, which is the reason they are sometimes abbreviated as CHO. Carbs range from those with simple construction, like glucose (dextrose) and fructose (levulose), which are called mono-saccharides, to the di-saccharides like sucrose (table sugar) which is composed of equal parts of glucose and fructose. Increasingly complex carbs, like those found in grains, vegetables, legumes, etc., are called poly- or oligo-saccharides.

Simple carbs are almost immediately absorbed into our bloodstreams. The more complex the carb, the more the body needs to break them down before it can use them. This occurs in the stomach and intestine utilizing an enzyme called amylose. A measure of the speed at which the body makes glucose available from carbs is called the Glycemic Index or "GI" of that food. Sugar is a high-GI food, most legumes are lower-GI foods.

Carbs have the most profound impact on our blood glucose. Approximately 95% of carbohydrates in our diets are converted to blood glucose. A fast carb, like pure sugar, will raise BG very quickly causing a BG "spike".  A slower carb, like whole-grain bread, will raise it more slowly as it takes time for the body to break it down, but the Area Under the Curve (AUC) of blood glucose vs. time will be the same for both.

Since the fiber component listed on US (but not necessarily other countries') Nutrition Labels is included in the carb count, most deduct fiber from total carbs to arrive at Net Carbs, i.e., carbs that the body can use.

Proteins

Proteins contain amino acids, the "building blocks of life". Most importantly, proteins provide us with the seven essential amino acids, Tryptophan, Lysine, Methionine, Phenylalanine, Threonine, Valine, Leucine and Isoleucine. These are amino acids which the body is incapable of synthesizing and which must be gotten from diet.

Only about 53% of proteins eventually become blood glucose through the inefficient process of gluconeogenesis in the liver. Glucose from protein is also much slower to reach our bloodstreams.  Since even a fine piece of beefsteak is about 58% water and 14% fat, one ounce (28g) of steak only contains approximately 8g of actual protein. That amount, when converted to glucose, is only responsible for the equivalent of 4g of glucose which can appear in the bloodstream approximately 4-6 hours after ingestion. Therefore, most diabetics do not count protein as a source of BG when calculating bolus insulin doses.

Fats

Fats contain fatty acids, which are used in the body for energy storage, production of hormones, and cell repair. Fats are categorized by their degree of saturation with hydrogen atoms, from saturated, to poly-unsaturated, to mono-unsaturated. 

Like amino acids, there are Essential Fatty Acids (EFA) which the body cannot synthesize and which must be gotten from our diets. All EFAs are poly-unsaturated, and are further categorized as Omega-3 or Omega-6 by their chemical structures. The essential Omega-3 EFAs are alpha linolenic acid, docosahexaenoic acid, and eicosapentaenoic acid. The essential Omega-6 EFAs are arachidonic acid, dihomogamma linolenic acid, gamma linolenic acid, and linoleic acid.

Fats have gotten somewhat of a bad name in the popular press over the years. Newer research has shown that dietary fat consumption actually has little impact on serum cholesterol. However, it is always wise to limit saturated and trans-fats and replace them with poly- or mono-unsaturated fats. Research has shown that the optimum ratio of Omega-6 to Omega-3 fats is somewhere around 2:1 or 1:1. Since the average western diet is said to be about 20:1 Omega-6 to Omega-3, increasing Omega-3 fats is thought to be beneficial.

In terms of blood glucose, fats have little direct impact. Only about 9% of fat is converted to "glucose equivalents" in the body.

The Mix

None of us eats pure carbs, protein, or fat. All of our foods contain mixtures of the three macronutrients. It is important to know that both protein and fat will slow down the conversion of dietary carbs into blood glucose. In other words, if you ate a 15g piece of dry toast, which is almost pure carbohydrate, you would show a BG peak higher and quicker than if you used butter on that toast.

Of course, controversy has raged for years about what ratio of macronutrients constitutes good nutrition. On one hand, we have had the proponents of the Food Pyramid who insist that we should eat up to 65% of our calories as carbohydrates. On the other end of the spectrum are the Low Carb proponents, like Dr. Robert Atkins, with more moderate approaches like the Zone Diet and South Beach Diet taking the middle ground. Recently, Harvard has proposed a modified food pyramid, and new research is appearing which seems to vindicate the Atkins Diet and other lower carbohydrate plans.

Most diabetics should see a Registered Dietitian (RD) for assistance in developing a personalized Way of Eating (WOE). Anyone can call themselves a "Nutritionist", but an RD must meet official standards of training. However, be wary of an RD who hands you a copy of a canned diet. Rather, try to find one who will give you the individualized attention that you need, and who understands that diabetics have special needs.

In general, diabetics need to learn to manage their dietary carbohydrates to keep their BG readings in their target range. Instead of calling it Low Fat or Low Carb, which seem to inflame some, diabetics should strive to eat a Low Spike Diet which will assure them of adequate nutrition. Learning to "eat to your meter", in keeping with Jennifer's Advice to the Newly Diagnosed, is an excellent starting point.