Fat and Cholesterol

Fat and cholesterol limitation should be a primary goal in the diets of all people with diabetes. Specifically, saturated fats should be limited to less than 10 percent of the total calories in the diet because they are the primary cause of increased LDL (harmful) cholesterol in the blood. People with diabetes appear to be more affected by dietary cholesterol than those without diabetes. This means that higher levels of dietary cholesterol will more likely result in higher levels of blood cholesterol. Increased cholesterol levels are associated with increased risk of heart attacks and strokes. It is recommended that the amount of cholesterol in the daily diet be no more than 100 mg/dl.

It is known that a diet low in saturated fats and cholesterol leads to improvements in total cholesterol, a decrease in the harmful type of cholesterol (LDL), and a decrease in triglycerides; it also may improve the beneficial type of cholesterol (HDL) in most people. And we also know that if this type of diet is used in conjunction with exercise, it can significantly increase these benefits. Although there have been no specific studies comparing the effects on those with diabetes and those without the disease, the findings are likely similar. Therefore, the low-fat diet recommendations are the same for those with and without diabetes. In addition, a person can achieve better glucose control by adhering to a reduced-fat diet (Swinburn et al. 2001); this is independent of race, age, gender, BMI, total food intake, and exercise (Marshall et al. 1994).

What about diets that are low in saturated fat and high in carbohydrates? We've seen that glucose, insulin, and triglyceride levels are elevated as a result of such diets. However, it has been shown that in diets in which some of the saturated fats are replaced with monounsaturated fats, the levels of blood glucose, insulin, and triglycerides are improved. But it appears that a diet high in monounsaturated fat stimulates the hunger centers of the brain, resulting in increased consumption of food and weight gain. Therefore, if you replace saturated fats with monounsaturated fats, you should pay close attention to your caloric intake to ensure that you do not gain weight, as I discussed earlier. Again, your dietitian will be able to help you decide what types of food you can use to achieve the right balance of fat, protein, and carbohydrate. The following are other types of fats that you should be aware of.

• Polyunsaturated fats, particularly omega-3 polyunsaturated fat such as that found in fish, seem to lower total cholesterol but not to the same extent as monosaturated fats. Omega-3 fat is found in higher amounts in cold-water fish such as salmon, herring, and tuna. Polyunsaturated fats should be roughly 10 percent of the total caloric intake of fat in your diet. Eating two to three servings of fish per week will provide adequate amounts of omega-3 polyunsaturated fats. Supplements are available as well, but you should discuss this with your dietitian.
• Trans-unsaturated fats, or trans-fatty acids, come from processed vegetable oils commonly found in margarine and fast foods such as french fries. This type of fat has properties similar to saturated fat; that is, it raises LDL cholesterol levels. It also decreases the good cholesterol (HDL). Therefore, you should consume trans-unsaturated fats sparingly. Note that many crackers that are not high in sugar or total calories are high in trans-fatty acids.
• Sterols and stanols, which are substances from plants, are compounds that can be used to restrict the absorption of cholesterol from your gastrointestinal tract into your blood. These work because their structure is very similar to cholesterol and they bind to cholesterol transport on cells in the intestine, but they are not absorbed into the blood. Thus, the more stanols or sterols that bind to the transporters, the less cholesterol will be absorbed into the blood. The recommended amount of stanols is 3.4 grams per day; for sterols, it is 1.3 grams per day. These are typically available in concentrated forms such as spreads, since they are present in such low amounts in normal servings of fruits and vegetables. Benecol margarine contains stanols and Take Control margarine contains sterols; both are approved by the FDA. Salad dressings, nutrition bars, and dietary supplements containing these substances are also available. Before adding sterols and stanols to your diet, discuss them with your health care team.
• Fat substitutes, which the FDA has approved, deserve a brief mention. The goal of using fat substitutes is to decrease the amount of fat in the diet by substituting it with a lower-calorie substance with similar food properties. One such product is Olestra, which is nonfat cooking oil that has been used in popular food products such as potato chips. However, despite FDA approval, this product has been associated with gastrointestinal problems including cramping. At this point it is not known how much of the fat supplement is required to provide beneficial effects of decreased cholesterol levels and weight loss while still allowing the diet to be of significant nutritional value.