What's your (Glycemic) Index?

The kinds of food you eat have a direct effect on your health. Our body uses the food we eat for many things, but the primary use is as a fuel. The calories we take in are used to run out bodies. The common denominator of this fuel is glucose, a six carbon sugar.
Our bodies try to maintain a constant blood glucose level in order to deliver a steady stream of energy to cells. Insulin is the primary regulator of blood glucose.
Carbohydrates and fats are the primary sources of energy. My last two posts have discussed the metabolism of carbohydrates and fats. In short, fats are absorbed into the bloodstream with minimal processing whereas carbohydrates must be broken down into simple sugars such as glucose before they are absorbed. The result is that fats are absorbed and can be easily stored for use when needed but the sugars that come from our food must be dealt with immediately. They must be either used by cells or converted into stored energy (fat or glycogen).

Insulin

Insulin regulates our blood sugar by directing cells to take up glucose where it can be burned or stored. The problem is that if you take in a lot of sugar at one time, your pancreas must make a lot of insulin to keep your blood sugar from going too high. If you eat foods such as starches which a large complex carbohyddrates, these are broken down by your digestive system more slowly and absorbed into your bloodstream over a longer period of time. This places smaller demands on the pancreas for insulin.

Glycemic Index

It turns out that a big jump in blood sugar and insulin is bad for you. It contributes to high blood pressure, cardiovascular disease, and, of course, diabetes.  It's much better to eat foods that are digested slowly and don't require a large insulin response. There is a way to measure this trait called glycemic index (GI). Simple sugars such as glucose, fructose, sucrose have a high glycemic index meaning that they are absorbed quickly and cause a large rise in insulin. Glucose has the highest glycemic index which is defined as 100. Foods such as white bread, white rice and other sugars have a GI of over 70 and cause a severe insulin reaction. Foods such as whole wheat flour, whole rice and most fruits are medium GI foods and are healthier. Even better, foods with a GI of less than 55 such as beans, vegetables, nuts and seeds as well as intact whole grains are least challenging to your insulin response and are the healthiest.
You can easily find the GI of most foods online. Try to eat a diet that includes mostly low GI foods and avoid high GI foods. This will help prevent diabetes and cardiovascular disease.

Another plug for hummus

I can't resist mentioning my favorite food, hummus. It has a glycemic index of only 6... even more reason to eat more hummus!

The Many Faces of Fat

Of the three main nutrients (fat, protein, carbohydrate), fat is the most complex and interesting and gives us the most latitude to improve our nutrition.
Protein consists of long chains of amino acids which fold into useful shapes to provide structure and function such as enzymes and muscles. There are 21 different amino acids and these can be assembled into countless combinations to form complex shapes. However, from the nutrition standpoint, all protein is pretty much the same. Whatever the source of protein, our digestive system disassembles the long chains into individual amino acids which are then absorbed into the blood stream. Our body then uses these amino acids to build the proteins it needs.
Carbohydrates are also simple. They are short or long chains of sugars. The digestive system breaks these down into simple sugars; they are absorbed and used as fuel.
However, fats are more complex. There are many different kinds of fats and they are metabolized differently.

Why fat?

Osmotic pressure.
Since we already have fuel in the form of sugars, why do we need fat? Can't we just store sugar or starch? The answer is that sugar and starch are water soluble and are osmotically active so in order to store significant amount of fuel, we would need lots of molecules and each of these molecules attracts water. We would literally bloat up with water.
Fat has the advantage in that it is not water soluble so you can store lots of fuel in a glob of fat and not have to worry about attracting water.
Fats are long chains of hydrocarbons with oxygen molecules at crucial locations which repell water. These are large molecules with lots of different shapes and variations. Animal fat has more hydrogen bonds and is said to be "saturated". Vegetable fats are "unsaturated". Cholesterol is a special type of saturated fat.

Digesting all of this...

Fats that we eat are handled differently than protein or carbohydrates. Fats are broken down only into triglycerides which are absorbed directly into the blood stream. Therefore, the types of fat you eat make a difference since they are absorbed directly into the blood. A common test for "blood lipids" is to measure these in the blood. They can be roughly separated into "high density lipoproteins (HDL)", cholesterol and "low density lipoproteins (LDL)". There are many different kinds of fatty acids and these are only the large groupings.
We know from lots of research that the body handles different kinds of fat differently and that when you eat large amounts of animal fat (saturated fat), this leads to high cholesterol and high LDL. This is associated with heart disease, high blood pressure, diabetes, stroke and other medical problems.
Trans fat has been in the news recently because they have been banned by the FDA. Trans fats are a type of synthetic fat manufactured by taking vegetable oil and adding hydrogen. Unfortunately, it took many years of research to confirm that these synthetic fats are as bad for you as saturated fat. Unfortunately, the food industry has come up with new synthetic replacements (interesterification) which are not proven safe and show some of the same problems (increase in LDL and increase in blood sugar and insulin) as trans fat. I fear we may confirm that these are also dangerous years from now.
Vegetable fat (unsaturated) does not tend to cause these problems and should be preferred. Olive oil and peanut oil are mono-saturated fats which are also known to be healthy. Fish oil (omega fatty acids) are also know to be beneficial and protective from heart disease.

You are what you eat

So, while protein and carbohydrates are broken down completely, fat comes through to your blood stream and reflects its source. Animal fats are saturated and cause health problems. Vegetable fats and fish oils are healthy.

White Death

Don't eat white food.

White Death

It's complicated. We have to make decisions about what food to eat many times a day. It's good to have a few rules of thumb to make it easier to choose.

One good rule is "don't eat white food".

There are very few foods in nature that are white. Foods in nature are green or brown or yellow or red or purple. These colors are made by vitamins, minerals, antioxidants and phytonutrients. The darker the color the better.

The grocery store is different. There are lots of white foods. How did they get that way? They were processed (mechanical or chemical) to make them white. Why? Sometimes to improve shelf life. Sometimes to make them more attractive. Making food white never improves it.

Let's look at some different foods and their nutritional value.

Glycemic Index

First we should discuss glycemic index. This is a measure of how quickly blood sugar levels rise after eating each kind of food. Glucose is 100 and most sugars are also 100. This is bad. You want a low glycemic index in the food you eat. Hummus (my favorite food) has a glycemic index of only 6. Most beans are about 25. Eating lots of high glycemic index food leads to diabetes, heart disease, stroke, and excess weight gain. A high number is bad. A low number is good.

Grains

Wheat is the most common grain in our diet. Wheat is brown. Industrial food production and storage found that if they removed the brown outer layer (and the "germ"), the resulting white flour could be stored and shipped long distances. Of course, in removing the outer layers, they also removed a lot of the nutrition leaving just starch and a little protein. The outer layers provide fiber, vitamins and minerals. White flour also has a much higher glycemic index (71) than whole wheat flour (50).

Rice another common grain. Same problem here. Food processors who are interested in storage life remove the outer covering and "germ" to make white rice. White rice has a glycemic index of 89 whereas brown rice is only 50. Black rice (available in Asian markets) is also very high in phytonutrients and antioxidants.

Legumes

Beans, lentils, etc. are all good. Fortunately, they are not usually stripped of nutrients during processing and they retain their natural color and nutrients. Darker colored beans (black beans and kidney beans) are high in phytonutrients. You can buy most beans dry and soak then cook them easily, thus avoiding the excess salt that is usually found in canned beans and also avoid the BPA coating in cans.

Fruits

Here again, you have lots of options. Dark colored fruits such as blueberries and dark red cherries have more phytonutrients and antioxidants and are very healthy. Most fruits have a glycemic index of about 40.

Vegetables

Vegetables come in all colors of the rainbow. The more colorful, the healthier. Most vegetables have a low glycemic index (30 to 50). Eat your vegetables!

A note about cooked food

You know that frying or baking food makes it brown. If you take white bread and bake it or white flour breading and fry it, it will turn brown. However, it is still white food. Cooking doesn't magically put back all of the nutrients that were lost when the food was made white.

So, the next time you get hungry... avoid the white stuff.