With good reason carbohydrates (carbs) are the staple fuel source for most diets in the world. Not only are they plentiful and cheap to produce—created by plant photosynthesis—but also utilized easily by the body. The body’s process, in fact, according to Staci Nix, MS, RD, CD, is “far more efficient than any man-made machine (2005, p.16). There are different types of carbs: the simple, which are quickly absorbed by the body, and the complex, which are more slowly absorbed.
Simple carbs have one sugar molecule such as monosaccharides such as glucose, fructose and galactose, or disaccharides such as sucrose, lactose and maltose (Nix, 2005, pp. 16-17). The complex carbs (polysaccharides) include starches, glycogen, dietary fiber, cellulose, noncellulose polysaccharides and lignins. With the exception of dietary fiber and noncellulose polysaccharides, the body breaks down these carb types, turns them into glucose and distributes the glucose through blood circulation to all the cells that need it in the body.
The glucose—whether produced by simple or complex carbs—is not only important for energy, but for sparing the need to use stores of protein and fat, which can be used to sustain the body in other ways (Nix, 2005, p. 24). More important is glucose’s role in supplying adequate fuel to the nervous system including the brain (p. 24). Unlike carbs, protein and fat energy cannot supply a constant stream of glucose to the brain, giving carbohydrates a role that is vital for life.
The amount of carbohydrates needed in the diet, however, has been a hotly contested debate. Nix mentions that sugar is not “the villain,” but that too much of its use is problematic (2005, p.24). Harvard nutritionist and physician Walter Willet, Ph.D. Willet agrees that the USDA food pyramid should be modified to steer people away from refined carb foods. They provide little nutrients, he says, but more detrimentally, they spike blood glucose causing higher needs for insulin only to bring glucose “crashing down” (Discover, 2003, http://discovermagazine.com/2003/mar/breakdialogue). The scenario happening regularly adds to higher risk of Type II diabetes. His “Healthy Eating Pyramid” stresses more focus on whole grains and fruits and vegetables and not the refined carbs (President and Fellows at Harvard College, 2008, http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/pyramid/index.html).
Low-carb dieting for encouraging weight loss has been led partly by some who have developed theories surrounding the diet of early humans. According to Loren Cordain, Ph.D., (2002, Chapter 1 [digital version]) and Noel T. Boaz (2002, Location 2309, Table 7 [digital version]), both top-selling authors of books with collected research on human evolution and diet of Paleolithic populations, suggest that the body may be adapted to a diet of high-protein, high-fiber, and low-carbohydrates.
Significant health problems, however, can occur as a result of low-carb dieting and should not be overlooked. Without enough carbs the body has to use the body’s protein and fat supply for creating quick energy (p. 24). According to Nix, muscle may be catabolized for its protein, muscle maintenance prevented, and the break down of fat stores for fast fuel can result in “incomplete fat oxidation”, thus creating an excess of strongly acidic ketones (2005, p.24). The ketoacidosis that occurs can become toxic to the body.
Many may have found themselves with ketoacidosis when on an extremely low-carb diet. A report in The Lancet of a 40-year-old woman hospitalized while following the popular low-carb Atkins diet is just one of several reports (Groch, 2006,http://www.medpagetoday.com/PrimaryCare/DietNutrition/tb/2878.). She had eaten nothing but meat, cheese and salad for in the month before the event. Criticism along with the report included comments by Lyn Steffen, Ph.D., M.P.H. and Jennifer Nettleton, Ph.D., who said the ketoacidosis would lead to “constipation, halitosis, diarrhea, headache and fatigue,” and long-term ketoacidosis would create problems for the kidneys and bones. Note that the Atkins diet has since been revised, according to Atkins Nutritionals (2008, http://www.atkins.com).
Considered moderately low-carb, the Mediterranean diet, which includes plenty of fruits, vegetables, and monounsaturated oils may be a better choice. According to an Israeli study published in the New England Journal of Medicine on three typical diets—a typical low-fat diet, a pre-revised-Atkins diet and the Mediterranean diet (based on recommendations by Walter Willet)—all the diets were regarded as safe, both low-carbohydrate diets provided metabolism benefits, but only the Mediterranean diet showed significant improvement for glucose and insulin levels (Shai et al, 2008). When it comes to carbs, as Staci Nix points out, “moderation is once again is the key” (2005, p. 24).
References
Atkins Nutritionals Inc. (2008). “Thoughtful approach. Powerful science.” Retrieved on Sept. 12, 2008 from http://www.atkins.com.
Boaz, N.T. (2002). Evolving Health: The Origins of Illness and How the Modern World Is Making Us Sick [digital version]. New York: John Wiley & Sons.
Cordain, L. (2002). The Paleo Diet: Lose Weight and Get Healthy by Eating the Food You Were Designed to Eat [digital version].New York: John Wiley & Sons.
Discover [interview with Walter Willett]. (March, 2003). “Nutritionist and physician Walter Willett—a voice of reason on diet.” Retrieved on Sept. 12, 2008 from http://discovermagazine.com/2003/mar/breakdialogue.
Groch, J. (2006). Atkins dieter develops life-threatening complications. Medical News: Diet & Nutrition. Retrieved on Sept. 13, 2008 from http://www.medpagetoday.com/PrimaryCare/DietNutrition/tb/2878.
Nix, S. (2005). Williams' Basic Nutrition & Diet Therapy. Philadelphia: Mosby.
President and Fellows at Harvard College. (2008). “The nutrition source healthy eating pyramid.” Retrieved on Sept. 12, 2008 from http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/pyramid/index.html.
Shai, I., Schwarzfuchs, D., Yaakov, H., Sahar, D.R., Witkow, S., et al. (July, 2008). Weight loss with a low-carbohydrate, Mediterranean or low-fat diet. The New England Journal of Medicine, 359:229-241.
