The Latest and Straightest on Sources of Energy
 by Carolyn McClanahan

                 This month we review and update our thinking about the three sources our body uses for energy.

 Carbohydrates

          Complex or simple are the two terms we are familiar with in discussing carbohydrates. We think of simple as those sweet things not to eat too much of, such as candy and sugary cereals. Complex carbohydrates are all the good stuff runners are supposed to eat: vegetables, pasta, cereal, potatoes.  Technically, a simple carbohydrate is three or fewer sugar molecules hooked together, and a complex carbohydrate is more than three sugar molecules hooked together. That sounds pretty arbitrary to me.

          Another way to think of carbs has been around a long time but not widely used. This is the glycemic index. The glycemic index is how fast and how high food will raise the glucose level in your bloodstream, which will determine how much insulin is secreted. Diets filled with high-glycemic foods have been linked to an increased risk of diabetes and heart disease. The American Diabetes Association didn’t want to use glycemic index in the past, thinking it would add more confusion to the already difficult diabetic diet. Now we realize it is a great adjunct in helping diabetics with food choices, and I bet we hear much more about it in the future.

          A glycemic index less than 55 is considered low. Most vegetables (except peas and corn), legumes and many types of fruit (berries, peaches, grapefruit, oranges, but not bananas, pineapple or raisins) fit this category. Whole-grain and protein-enriched pasta are also in this category. What is high? Most breads, cereals and potatoes. A great website for determining the glycemic index of most foods is www.glycemicindex.com.

          In general, these factors will determine glycemic index:

·        How highly processed the food is.

·        Fiber content.

·                    Ripeness (ripe foods have more sugar).

·                    Type of “starch” (for example, potatoes have a very high glycemic index).

·                    Fat and acid content of food. These slow the absorption, lowering the glycemic index.

·                    Physical form. The work your body has to do in breaking a food down lowers the glycemic index. Coarse-ground grain is broken down more slowly than finely ground. Eating an orange is better than drinking the juice. Also, cooking pasta al dente lowers the glycemic index more than boiling it to death.

Proteins

          Not much has changed in how we think about protein. Protein comes from a variety of sources: animal products, nuts, beans and certain other vegetables. Complete protein comes from animal sources and provides us with every type of essential amino acid that we need. Incomplete proteins come from plant products and by themselves do not provide all of our essential amino acids. A vegetarian must be careful to choose a good variety of food to get all of the essential amino acids. 

          Many people are concerned about eating too much protein. In general, people with healthy kidneys do fine with any amount of protein and no one has shown any bad long-term effects from high protein consumption. The exception to this is that processing protein requires the use of calcium, and diets high in protein long term may contribute to osteoporosis. So if you eat large amounts of protein, you may want to increase the calcium in your diet.

Fats

          Contrary to the belief of many (including my husband), not all fats are bad. They provide essential fatty acids needed to produce our hormones and they are a good energy source. We now classify fats into four basic types.

The Good                                 The Bad                       The Ugly

Monounsaturated                      Saturated                         Trans fats

Polyunsaturated

          Diets containing mono- and polyunsaturated fats lower the risk of heart disease by raising HDL (good cholesterol) and lowering LDL. Diets containing saturated and trans fat raise the risk of heart disease by raising LDL.

DIETARY FATS

Type of Fat                   Main Source                   State at Room                    Effect on  Levels                                                                        Temperature                    Cholesterol

Monounsaturated           Olives, olive oil,                         Liquid                          Lowers LDL
                                    canola oil, peanut oil,                                                      Raises HDL
                                    cashews, almonds,
                                    peanuts, and most
                                    other nuts; avocados                  

Polyunsaturated           Corn, soybean, safflower,             Liquid                          Lowers LDL      
                                    and cottonseed oils; fish                                                   Raises HDL

Saturated                   Whole milk, butter, cheese,             Solid                            Raises LDL & HDL
                                    ice cream, red meat, chocolate,
                                    coconuts, coconut milk,
                                    coconut oil                  

Trans                           Most margarines, vegetable shortening,         Solid or semi-solid        Raises LDL
                                        partially hydrogenated vegetable oil,
                                        deep-fried chips, many fast foods,
                                        most commercial baked goods                  

           Trans fat is the new thing on the block to watch out for. In 2006, food products will be required to list trans fat in the ingredients. For now, just watch out for the words “partially hydrogenated” in the ingredients. That means it contains those ugly trans fats you should avoid.

           Carolyn McClanahan, M.D., is a family physician, runner and expert dieter.