KIN 311
Friday, March 22nd,
2002
Hypolactasia affects 70% of the world’s adult population, both male and female (Mahan & Escott-Stump, 2000). Afflicted individuals possess a deficiency in lactase, the enzyme that hydrolyzes the lactose disaccharide into galactose and glucose, which subsequently supply the body with a basic source of energy. Remaining lactose draws water into the gut and causes bloating, abdominal discomfort, and diarrhea (Whitey & Rolfes, 1999). Intestinal bacteria ferment the sugar, thereby producing irritating acids, short-chain fatty acids, and both carbon dioxide and hydrogen gases, which further contribute to diarrhea and discomfort (Whitey & Rolfes, 1999). Studies have not suggested that these symptoms affect the length of an afflicted person’s life span, except perhaps through dehydration associated with diarrhea and psychological stress associated with prolonged discomfort. However, lactose maldigesters suffer profusely upon intake of a standard glass of milk that contains approximately 12 g of lactose, and may therefore eliminate dairy products from the diet, which consequently presents a health challenge.
In the majority of human beings, lactase activity decreases exponentially through childhood and adolescence, and only 30% retain enough lactase to efficiently digest and absorb lactose through adult life, although the distribution varies among ethnic groups (Whitey & Rolfes, 1999) according to a specific DNA variant (Enattah et al., 2002). In fact, lactose intolerance has been suggested to be the norm, whereas lactose tolerance has resulted from a genetic mutation that proliferated predominantly through Western European lines (Mahan & Escott-Stump, 2000). Lactase deficiency may also arise from damage to intestinal villi (Whitney & Rolfes 1999) or prolonged disuse of the GI tract during total parenteral nutrition (Mahan & Escott-Stump, 2000). Lactose intolerance is diagnosed through a test in which individuals are given milk after a period of fasting and monitored for gastrointestinal symptoms, the failure of blood glucose significantly rising in response to lactose intake, and hydrogen gas in the breath (Mahan & Escott-Stump, 2000).
Individuals afflicted with lactose intolerance require dietary changes to compensate for reduction of intake of foods from the milk group. Often, total elimination of dairy products is not necessary, and most maldigesters can tolerate up to 6 g without symptoms (Whitey & Rolfes, 1999). Studies have demonstrated that maldigesters can adapt to the gradual intake of lactose and develop increased tolerance (Rizkalla et al., 2000). Therefore, one method of dealing with intolerance is increasing one’s intake of milk products gradually over time, taking them in conjunction with other foods, and spreading intake throughout the day. Lactose intolerant individuals can also often tolerate yogurt in which preparatory bacteria participates in lactose digestion, and hard cheeses or cottages cheeses from which lactose is removed with whey during manufacturing (Rizkalla et al., 2000). Some milk products are commercially prepared with enzyme treatments that break down lactose before being marketed and may be suitable for intolerant individuals. For example, Lactaid milk is available for use by adults (Whitey & Rolfes, 1999). Individuals also have the option of taking enzyme tablets or adding enzyme drops to their milk before consumption.
Tolerance levels vary widely among individuals. Therefore, lactose-restricted diets must be highly individualized, as well as controlled. In persons with more severe cases of intolerance, complete elimination of milk products may be necessary. However, lactose-free diets are quite difficult to prepare since the sugar is also found in a wide variety of nondairy products, such as breads, cereals, salad dressings and prescription drugs (Whitney & Rolfes, 1999). Labels must be read carefully and consultations with pharmacists are necessary in order to avoid intake of imperceptible lactose. Furthermore, excluding milk products may culminate in nutrient deficiencies, especially that of calcium, riboflavin, and vitamin D (Whitney & Rolfes, 1999). Meals must be planned cautiously to assure these needs are met. Important calcium sources may include broccoli, fortified soy milk, legumes, and supplements, as suggested by a doctor or dietition (Kemper, 2000). Contrary to the results of animal studies, lactose in humans neither decreases nor increases the absorption of calcium as expected (Zittermann et al., 2000) and, once again, is not directly essential for proper physiological functioning or survival.
Although lactose intolerance is
not a debilitating disorder, care must be taken in preventing nutrient
deficiencies when attempting to alleviate the distressing symptoms that
accompany dairy product intake. A
further question arises in the exact means by which the body of a lactose
intolerant individual adapts to a gradually increased intake of lactose and
dairy products. In other words, as
studies suggest that lactose tolerance can increase with gradually increased
lactose intake, it is unclear what mechanisms within the body permit the adaptation
and to what extent tolerance can be achieved.
The results of the research suggest that an individual who persists in
taking high amounts of dairy products throughout life would maintain a
relatively high level of lactose tolerance until death. Therefore, one must ask if this implication
is feasible and if tolerance levels close to those at birth can be maintained
by these means.
Works Cited
Enattah, N.S., Sahi, T., Savilahti, E.
Terwilliger, J.D., Peltonen, L., and Jarvela I. (2002). Identification of a
variant associated with adult-type hypolactasia. Nature Gentics. 30(2):
233-237.
Kemper, D.W. (2000). BC Health Guide. Healthwise Publication, B.C., Canada: 307.
Mahan, K.,and Escott-Stump, S., ed. (2000). Krause’s Food, Nutrition, and Diet Therapy. W.B. Saunders Company, Philadelphia, PA: 679-681.
Rzkalla, S.W., Luo, J., Kabir, M., Chevalier, A., Pacher, N., and Slama, G. (2000). Chronic consumption of fresh but not heated yogurt improves breath-hydrogen status and short-chain fatty acid profiles: a controlled study in healthy men with or without lactose maldigestion. American Journal of Clinical Nutrition. 72(6): 1474-1479.
Whitey,
E.N., and Rolfes, S.R. (1999). Understanding
Nutrition. Wadsworth Publishing
Co., Belmont, CA: 101-102, 383, 506.
Zitterman, A., Bock, P., Drummer, C., Scheld,
K., Heer, M., and Stehle, P. (2000). Lactose does not enhance calcium
bioavailability in lactose-tolerant healthy adults. American Journal of Clinical Nutrition. 71(4): 931-936.