Over the last 25 years it seems that the consensus opinion of what constitutes good nutrition is constantly changing. Scientists have known since the 1960′s that the saturated fat in red meat and dairy products can raise cholesterol. Whether or not that leads to coronary heart disease is debatable. Initially these findings were downplayed to appease the cattle and dairy industries. Later, the synthetic fats (trans-fats) were invented to replace saturated fats, but scientists have recently determined that the newer fats are more detrimental to health than saturated fats. These trans-fats are still being used by the food industry, however, because they are inexpensive and increase the shelf life of processed foods. Nutritionists are now sternly warning us about the perils of simple sugars, yet because of sugar’s pervasiveness and somewhat addicting properties, the use of simple sugars and high fructose corn syrup continues to grow. There is a constant debate about whether a low-fat diet or a low-carbohydrate diet is better for losing weight. Asking your doctor for their opinion is often no better than asking your babysitter. Until very recently, nutrition was very rarely taught in medical school.
The calories we get from food either come from protein, carbohydrates, or fats. A gram of protein or carbohydrate has four calories, whereas a gram of fat has nine calories. Because food was not as plentiful as it is today and famines were frequent occurrences, our ancestors and many animals evolved a desire to consume as many calories as possible, so the craving for fatty foods was an important inherited trait. Now food is plentiful but unfortunately we cannot reverse our evolutionary desires. Today Americans eat too much, and as a result, about two thirds of Americans are overweight or obese. Clearly, we need to eat smaller portions.
When carbohydrates are digested, they enter the bloodstream as glucose and become an instant energy source for all tissues in the body. Carbohydrates can be subdivided into “good” carbohydrates and “bad” carbohydrates. “Good” carbohydrates consist of fruits, vegetables, and unprocessed starches (whole grain breads and cereals, wild brown rice). “Good” carbohydrates provide dietary fiber and some essential vitamins and minerals. Fiber is the structural part of fruits and vegetables that cannot be digested. Fiber is important in preventing constipation and colon cancer. Societies that eat the highest percentage of fiber have the lowest incidence of colon cancer. Fiber also gives us a sense of fullness, which helps us from over eating. Fiber removes bile acids and some sugars from the small intestine, resulting in lower cholesterol and blood sugar levels.
The main difference between “good” and “bad” carbohydrates is how rapidly each carbohydrate is absorbed as glucose into the bloodstream. This is what nutritionists call the “Glycemic index” of each food. The “good” carbohydrates have a low glycemic index whereas the “bad” carbohydrates have a high glycemic index. When glucose enters the bloodstream a surge of insulin is released from the pancreas. Insulin is the hormone that enables the glucose to enter the cells within the muscle and other tissues. At times of activity glucose is immediately consumed by muscle cells. This is why carbohydrates are an excellent source of fuel during exercise, especially high glycemic carbohydrates. At times of rest insulin still causes cells to absorb glucose, but the glucose is stored away in fat and muscle cells. The intake of carbohydrates, especially “bad” carbohydrates, needs to be limited at times of inactivity. Low glycemic foods such as hard whole fruits and vegetables are broken down much slower in the digestive tract compared with high glycemic foods such as cakes and candies so the surge of glucose and insulin is not as drastic.
“Bad” carbohydrates consist of simple sugars, refined pasta, white rice, and white bread. These are the most important items to be removed from our diets. They have a high glycemic index. These foods give the surge in glucose, which then cause the surge in insulin. The surge in insulin can also cause us to over eat because after the insulin surge our blood glucose falls rapidly, increasing our craving for more glucose. Increased insulin levels also decrease the ability for the body to metabolize fat. Not only does this cause us to gain weight but cells become resistant to insulin, which can lead to diabetes. High insulin levels inhibit the activity of glucagon. Glucagon is a hormone that is responsible for releasing stored fuels when blood sugar is low. Without glucagon our body cannot self regulate its blood glucose level, causing the hunger signal to set in. Eating another high glycemic snack then results in a continuous cycle of high blood sugars followed by low blood sugars, then the craving for sugar again. The simple sugars consist of anything sweet: sodas, cookies, candies, cakes, etc.
Proteins are made up from combinations of the twenty amino acids. There are eight essential amino acids that the body needs through nutrition. The remaining amino acids can be made by your body from the eight essential amino acids. Protein is important for building muscle mass. All protein sources are good for you but some have a higher percentage of fat in them and therefore more calories. The low fat sources of protein are: turkey and chicken breasts, dry beans, most fish, shell fish, egg whites, tofu and reduced fat dairy (cheese, yogurt, milk). Proteins with a higher fat content are: red meats, liver, sausage, bacon, hot dogs, ribs, poultry leg and thigh, egg yolks, dairy products. A diet that is excessive in protein can put stress on the kidneys, resulting in kidney stones or renal failure.
Fats role in heart disease led to the fat phobia. Fats are nutritionally very important. Fat is essential for the growth and maintenance of the nervous system. Fat is also integral in proper functioning of the fat soluble vitamins, vitamins A, D, E, and K. Fats can be broken down into saturated and unsaturated fats. Saturated fats are solid at room temperature, whereas unsaturated fats are in a liquid form at room temperature. Too much saturated fat in a diet can be bad for us due to its ability to increase inflammation. Saturated fats also promote insulin resistance. Saturated fats are found in fats from animals (dairy products, poultry, and red meat) and tropical oils (coconut and palm oils). Unsaturated fats are typically better for us and they consist of monounsaturated and polyunsaturated fats. Unsaturated fats can lower cholesterol and are felt to be protective to the heart. We should never eat foods deep-fried because even if it is fried in unsaturated fat, the heat can break the double bonds of unsaturated fat, changing it into a saturated fat. The oils in olives and peanuts are monounsaturated. Polyunsaturated fat sources are the oils that come from corn, soybean, sunflower, and safflower. Omega-3 fatty acids are polyunsaturated fats and are protective to the heart. Foods that are rich in omega-3 fatty acids include tuna, salmon, mackerel, walnuts, flax and canola oils. It is smart to eat good fats in moderation because of their high caloric content. Additionally, the body easily stores dietary fats as body fat. Trans-fatty acids are synthetic fats that are common in processed foods, labeled as “partially hydrogenated” or “vegetable shortening”. Like saturated fats, trans-fatty acids raise LDL cholesterol and lower HDL cholesterol, which may contribute to heart disease and strokes. It is best to avoid all trans-fats.
In the 1980′s the general population learned that we got more than twice as many calories from fat, and was told that saturated fats were partially responsible for heart disease. As a result, the fat free diet became popular. Products were coming up overnight with their “fat free” or “low fat” slogans and they were a huge economic success. Unfortunately these products were loaded with simple sugars and as a result had nearly as many calories. These products had a psychological effect on people as well because we felt we could eat more than the usual serving because they were good for us. Instead of losing weight, people gained weight by eating these products. A low fat diet can be good for us, as long as high glycemic foods are not replacing the fat calories.
Today we are seeing low-carbohydrate products saturating the food industry, similar to the fat free gimmick of the 1980′s. The problem with this diet is that one can eat unlimited amounts of fatty meats, butter, and cheese. Though this diet has been successful for weight loss, it does not promote healthy eating. This diet is high in saturated fats and causes the body to go into ketoacidosis, a disturbed acid balance. This diet can also cause bone loss and increased uric acid levels, leading to gout. The Atkin’s diet causes rapid early weight loss, but most of this is water and some lean muscle weight. After one year, people regained more weight on the low carbohydrate diet compared to those on low fat diets. The problem with a lot of diets is that they are very hard to adhere to. I prefer diets for lifelong health, not short-term weight loss. The key to this is giving up processed foods in favor of natural foods and avoiding high glycemic carbohydrates along with excessive calories.
One proposed solution is The Paleolithic Diet by Boyd Eaton, M.D. His solution is to eliminate processed grains from our diet and replace them with fruits and vegetables favored by our early ancestors. He also advises against mass produced meats and favors lean free-range animals like those hunted by our forebears. Not only are the meats we buy in the supermarket fatter, but they are usually injected with hormones to make the animals grow bigger. I also recommend trying to limit milk products, such as butter, cheese, and cream. Milk products are high in calories and saturated fats. We are the only mammals who continue to use milk products after weaning from breast milk. Another good book is “The Complete Idiot’s Guide to Glycemic Index Weight Loss”, by Lucy Beale.
The most important thing is moderation. Eating more calories than you burn off is still the biggest issue whether you are on a particular diet or not. Instead of crash dieting, reduce certain foods from your permanent diet. Avoid the “bad” carbohydrates to prevent the blood sugar yo-yo effect and to avoid excessive hunger while reducing your caloric intake. Avoid the unhealthy trans-fatty acids altogether. Reduce the amount of saturated fats and increase the amount of omega-3 fatty acids in your diet. Eat plenty of fiber or take a fiber supplement and drink plenty of water. Avoid carbonated beverages, regular and diet sodas.