macronutrients: Carbs, fats, proteins
Health,  Nutrition

Carbs, fats, and protein: The MacronutrientsThis article is a 6 min read

There are macronutrients and micronutrients that are generally considered to have beneficial effects for one’s health. The macronutrients are carbohydrates, proteins (amino acids), and lipids. Macronutrients are nutrients that provide energy and needed in larger quantities than micronutrients.

Carbohydrates

Carbohydrates are a class of nutrient that provides energy for high intensity exercise, fuel for optimal neurological function, as a primer for fat utilization, and sparing protein (McArdle, Katch, & Katch, 2012). Types of carbohydrates include monosaccharides, disaccharides and oligosaccharides, and polysaccharides. These are organized by their chemical complexity in regards to number of glucose units chemically bonded together (Wardlaw & Kessel, 2002). The latter is considered part of a class of carbohydrates considered as complex (vs. simple). From plant sources complex carbohydrates can be broken down into two forms, starch and fiber. Starch, the energy providing complex carbohydrate (about 4/kcalsžgram), can be divided into two categories, amylose and amylopectin. Starch is absorbed slower than simple carbohydrates and is made more available to digestion by cooking by making them more water soluble (Wardlaw & Kessel, 2002). Amylopectin will raise blood sugar more than amylose due to its branched chemical structure (Wardlaw & Kessel, 2002). This may have implications for pre-exercise, prolonged and post exercise recovery.

Fiber, the structural part of the polysaccharides, is a fibrous material and contains no available energy for humans as it is largely indigestible (McArdle, Katch, & Katch, 2012; Wardlaw & Kessel, 2002). However, it is very important to health. A diet rich in complex carbohydrates (mostly plant-based), is high in fiber, minerals, vitamins, and some fatty-acids (Wardlaw & Kessel, 2002). It is rich in antioxidants which may play a role in preventing various diseases such as coronary heart disease or cancer (Wardlaw & Kessel, 2002). It is high in folate lowering homocysteine, which has been inversely related to CHD (Wardlaw & Kessel, 2002). The fiber in complex carbohydrates promotes satiety via its bulk (Wardlaw & Kessel, 2002). It aids in proper digestion in the colon and rectum and may prevent cancer, appendicitis, hemorrhoids, and diverticulitis (Wardlaw & Kessel, 2002). A diet higher in fiber may lower fat intake and inhibit absorption of cholesterol from the small intestine, therefore possibly lowering blood cholesterol (McArdle, Katch, & Katch, 2012; Wardlaw & Kessel, 2002).

Fats

Lipids are essential to good health. These compounds do not readily breakdown in water (Wardlaw & Kessel, 2002). Lipid compounds are divided into three broad categories including simple, compound, and derived. From a diet perspective, these include fatty acids [i.e., saturated (SAFA), mono and polyunsaturated (PUFA)], sterols (i.e., cholesterol), and omega-3 fatty acids (McArdle, Katch, & Katch, 2012). All lipids provide about 9 kcalsžgram of energy. The role of lipids in the body include providing an energy reserve, protecting vital organs, thermal insulation, transportation of fat-soluble vitamins, and hunger suppression (McArdle, Katch, & Katch, 2012; Wardlaw & Kessel, 2002).

Recent research has questioned the role of saturated fat and its part in coronary heart disease, stroke, and myocardial infarction (MI). A 2015 scientific update speaks to SAFA consumption and lack of causation to CAD, MI, or stroke (Nettleton, Brouwer, Geleijnse, & Hornstra, 2017). But the authors recognize that the studies analyzed had limitations. However, the update does identify a positive relationship to SAFA and elevated LDL-C and probably more importantly LDL-P (Nettleton, Brouwer, Geleijnse, & Hornstra, 2017). The authors indicate that when SAFA are replaced by PUFA the greatest reduction in CHD risk takes place, suggesting that the effect of reducing SAFA is strongly influenced by the macronutrient replacing it (Nettleton, Brouwer, Geleijnse, & Hornstra, 2017), not simply reducing it. This could be supportive of using a polyunsaturated fat to saturated fat ratio as a recommended target which is purported as preferred 2:1 (McArdle, Katch, & Katch, 2012). In another review by Hooper and colleagues they found a benefit of reducing SAFA for lowering risk for heart disease and stroke (-17%), but not mortality (Hooper, Martin, Abdelhamid, & Davey-Smith, 2015). Like Nettleton and colleagues, Hooper found that replacing SAFA with MUFA and PUFA was a useful strategy for lowering risk (Hooper, et al., 2015). Replacing SAFA with carbohydrates or protein may not be useful in lowering risk for CHD or stroke (Hooper, et al., 2015).

Omega-3 and 6 fatty acids are long-string polyunsaturated fatty acids. These form essential fatty acids as the human body must obtain them through dietary sources (McArdle, Katch, & Katch, 2012). These fatty acids form the parts of vital body structures, involved in immunity, vision, assist in the formation of cell membranes and hormones (Wardlaw & Kessel, 2002). Omega-3 may be particularly important as it has been identified in blood platelet function (blood clotting) and as a vasodilator (Wardlaw & Kessel, 2002). Studies done on Greenland Eskimos found very high intake of fish oils (source of omega fatty acids) and a low incidence of CHD (Wardlaw & Kessel, 2002). Additionally, the population studied demonstrated reduced clotting ability and protracted clotting times (Wardlaw & Kessel, 2002) which are potentially beneficial for prevention of MI. One downside of too much omega-3 is the possible connection with hemorrhagic stroke due to blood clotting impairment (Wardlaw & Kessel, 2002). Deficiency in essential fatty acids have been identified and one may experience problems with skin, infections, reduced wound healing, and gastrointestinal problems (Wardlaw & Kessel, 2002). All lipids should be ingested in moderation with reduced SAFA and more mono and polyunsaturated acids.

An attempt to avoid trans fatty acids in the diet as much as possible.

Protein

From a dietary standpoint protein can be viewed from the types of amino acids from which out of the 20, nine are essential, meaning we need to derive them from food. More practically we can look at proteins as complete or incomplete. Complete proteins contain all the essential amino acids needed for adequate nitrogen balance and tissue anabolism (Wardlaw & Kessel, 2002). Conversely, incomplete proteins are missing one or more essential amino acids and need to be combined with other foods to form complete proteins (Wardlaw & Kessel, 2002). When proteins combine to make up for deficiencies in amino acids, they are termed complimentary proteins (Wardlaw & Kessel, 2002). A common misconception is that complimentary amino acids must be eaten during the same meal but this is not the case. For adults, even with plant-based foods, they do not have to be consumed during the same meal but rather over the course of a day (Wardlaw & Kessel, 2002).  A variety of plant foods eaten in concert can provide all needed essential amino acids which will produce high quality protein sources (McArdle, Katch, & Katch, 2012). Adequate protein intake is important as it is vital in maintaining body tissues and cells, blood clotting factors, blood transport proteins, enzymes, hormones, and more (McArdle, Katch, & Katch, 2012; Wardlaw & Kessel, 2002). Adequate protein aids in fluid balance, regulation pf blood pH, enhancing immune function, formation of glucose, and in specific instances provides energy (McArdle, Katch, & Katch, 2012; Wardlaw & Kessel, 2002).

References

Hooper, L., Martin, N., Abdelhamid, A., & Davey-Smith, G. (2015, June). Effect of cutting down on the saturated fat we eat on our risk of heart disease. Retrieved from http://www.cochrane.org/CD011737/VASC_effect-of-cutting-down-on-the-saturated-fat-we-eat-on-our-risk-of-heart-disease

McArdle, W. D., Katch, F. I., & Katch, V. L. (2012). Sports and exercise nutrition (4th ed.). Philadelphia, PA: Lippincott Williams and Wilkins.

Nettleton, J. A., Brouwer, I. A., Geleijnse, J. M., & Hornstra, G. (2017). Saturated Fat Consumption and Risk of Coronary Heart Disease and Ischemic Stroke: A Science Update. Annals of Nutrition and Metabolism, 70(1), 26-33. doi:10.1159/000455681

Wardlaw, G. M., & Kessel, M. (2002). Perspectives in nutrition (5th ed.). Boston: McGraw-Hill.

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