Lipids include fats, oils and cholesterol. They add flavor to food and provide a dense source of energy (i.e., nine calories per gram). Lipids are a necessary component for growth and maintenance and are carriers for the fat-soluble vitamins A, D, E and K. Most Americans consume excessive amounts of fat.[1,2] Constant overconsumption of high-fat, high-calorie foods can lead to obesity, heart disease and other chronic diseases. Note that any macronutrient (carbohydrate, protein and fat) can be stored as body fat when daily calorie needs are exceeded. There are three types of fats. Saturated fat, found mostly in animal products can increase “bad” (LDL) cholesterol levels and should be limited to no more than ten percent of total calories.[3] This means limiting the amount of butter, lard, high-fat meats such as bacon, sausage, poultry with the skin, fried foods and baked foods. Trans fats or “partially hydrogenated oils” are contained in stick margarine, baked goods, snack foods and fast foods. They can increase “bad” cholesterol and also lower “good” (HDL) cholesterol.[4,5,6] Nutrition and medical experts agree that trans fats should be limited as much as possible. Unsaturated fats are liquid at room temperature and include various oils including olive, corn, canola and peanut oil. The essential fats are often referred to as omega-3 and omega-6 fats which are required by the body. They may reduce the risk of heart disease by lowering cholesterol and/or blood triglycerides.[7,8] Fatty fish (e.g., salmon, tuna) and flaxseed are rich sources of essential fats.
Cholesterol is a lipid found in all animal tissue. It provides the structural components of cell membranes, helps form hormones needed for growth and various bodily functions, and are necessary for producing vitamin D and bile, which helps breakdown dietary fat. Excessive cholesterol accumulation in the blood can lead to plaque buildup in the arteries, increasing the risk of heart disease and stroke. Although saturated and Trans fats can increase “bad” cholesterol levels, essential fats in the proper ratios may have positive impacts on cholesterol levels.[7,8] The richest sources of cholesterol include organ meats, eggs and seafood. Daily intake should be limited to less than 300 milligrams per day and the recommended range for total fat in the diet is 20 to 35 percent. This can easily be met by choosing lean protein sources, dairy, nuts and oils as fat is contained in these foods.
References
1 Lissner L, Levitsky DA, Strupp BJ, Kalkwarf HJ, Roe DA. Dietary fat and the regulation of energy intake in human subjects. Am J Clin Nutr Dec 1987;46(6):886-92.
2 Paddon-Jones D, Westman E, Mattes RD, Wolfe RR, Astrup A, Westerterp-Plantenga M. Protein, weight management, and satiety. Am J Clin Nutr. 2008 May;87(5):1558S-1561S.
3 Lichtenstein AH. Dietary fat: a history. Nutr Rev. 1999 Jan;57(1):11-4.
4 Lichtenstein AH, Ausman LM, Jalbert SM, Schaefer EJ. Effects of different forms of dietary hydrogenated fats on serum lipoprotein cholesterol levels. N Engl J Med. Jun 1999;340(25):1933-40.
5 Tato F. Trans-fatty acids in the diet: a coronary risk factor? Eur J Med Res Nov 1995;1(2):118-22.
6 Ascherio, A, Willett, WC. Health effects of trans fatty acids. Am J Clin Nutr. Oct 1997;66(4 Suppl):1006S-1010S.
7 McKenney JM, Sica D. Role of prescription omega-3 fatty acids in the treatment of hypertriglyceridemia. Pharmacotherapy. 2007 May;27(5):715-28. Review.
8 Goldberg RB, Sabharwal AK. Fish oil in the treatment of dyslipidemia. Curr Opin Endocrinol Diabetes Obes. 2008 Apr;15(2):167-74. Review.