Lactose Intolerance
Individuals with idiopathic gastric complaints often assume, inappropriately, that they are lactose intolerant. Most people - even those who consider themselves to be severely lactose intolerant - can comfortably consume at least 250 ml milk (12g lactose).1-3 The best defence against lactose intolerance is the consumption of milk products. The human colon adapts to continues exposure to lactose, thereby reducing symptoms.3-7
The Facts About Lactose Intolerance
Colonic Adaptation
The Dose Counts
Overcoming the Bias
Why Is Dairy Important?
Key Messages about Lactose Intolerance
References
The Facts About Lactose Intolerance
Lactose is the principal carbohydrate in milk. Barring a rare congenital deficiency, virtually all mammals are born with high levels of lactase, a unique intestinal enzyme that breaks down lactose, enabling its absorption.3,8 In individuals with lactose maldigestion, the lactose that is not completely digested in the small intestine passes into the large intestine, where it is fermented by colonic microflora, producing short-chain fatty acids and gases, principally hydrogen.8
Testing
Gastrointestinal symptoms are often misdiagnosed as lactose intolerance by consumers and health professionals. The diagnosis can be confirmed by breath hydrogen analysis - an objective, noninvasive, inexpensive and easily performed test, appropriate for both adults and children.3 Symptoms of lactose intolerance are highly subjective and may or may not accompany lactose maldigestion.3
Primary Lactase Deficiency
Primary lactase deficiency can begin to develop after weaning. More common in certain racial or ethnic groups, including Africans, Asians and Native Americans, it is relatively rare in Caucasians.3 Offspring of Caucasians and African-Americans, however, have reduced prevalence of lactose maldigestion. The degree of lactose intolerance depends on a balance between the level of remaining lactase activity, the amount of lactose consumed, the adaptation of intestinal flora and the irritability of the colon.3
Secondary Lactase Deficiency
Secondary lactase deficiency is temporary. It is a response to gastroin-testinal factors that harm the intestinal mucosa (e.g., certain medical conditions, some medications, etc.). It can occur at any age and is reversible upon correction of the causative factor.3,9 Testing for other underlying conditions (such as Crohn's disease, infectious diarrheal disease and celiac disease) may be in order.
Colonic Adaptation
According to breath hydrogen tests, newborns are unable to completely hydrolyze the lactose in mothers' milk. Nevertheless, infants thrive on lactose-containing breast milk and formula, perhaps due to colonic absorption of the fermentation by-products of undigested lactose.3 Blinded, controlled, crossover studies have been conducted in adult lactose maldigesters to determine whether continuous lactose challenges could cause bacteria in the colon to metabolize lactose and reduce symptom severity.
Gradually increasing lactose intake significantly increased the ability of colonic bacteria to break it down.5 Subjects experienced a decrease in breath hydrogen (suggesting that the lactose was being digested) and, concomitantly, a significant reduction in flatulence,5 one of the principal symptoms of lactose intolerance. Often, despite a continued inability to digest lactose, confirmed by breath hydrogen testing, subjects can still tolerate more and more lactose with minimal symptoms.6,7
A recent 21-day intervention study assessed the effects of a dairy-rich diet in 14 African-American girls (11 to 15 years old). Confirmed lactose maldigesters, all were self-proclaimed non-drinkers of milk. The diet contained four servings of dairy products (primarily milk, some cheese and yogourt), providing about 33 g of lactose and 1,200 mg of calcium throughout the day. In addition to a significant decrease in breath hydrogen,8 gastrointestinal symptoms were negligible during the milk challenges and throughout the study period, likely due to colonic adaptation.8 The message is clear: Even individuals who are lactose intolerant can consume milk and milk products.
The Dose Counts
Colonic Adaptation
The Dose Counts
Overcoming the Bias
Why Is Dairy Important?
Key Messages about Lactose Intolerance
References
The Facts About Lactose Intolerance
Lactose is the principal carbohydrate in milk. Barring a rare congenital deficiency, virtually all mammals are born with high levels of lactase, a unique intestinal enzyme that breaks down lactose, enabling its absorption.3,8 In individuals with lactose maldigestion, the lactose that is not completely digested in the small intestine passes into the large intestine, where it is fermented by colonic microflora, producing short-chain fatty acids and gases, principally hydrogen.8
Testing
Gastrointestinal symptoms are often misdiagnosed as lactose intolerance by consumers and health professionals. The diagnosis can be confirmed by breath hydrogen analysis - an objective, noninvasive, inexpensive and easily performed test, appropriate for both adults and children.3 Symptoms of lactose intolerance are highly subjective and may or may not accompany lactose maldigestion.3
Primary Lactase Deficiency
Primary lactase deficiency can begin to develop after weaning. More common in certain racial or ethnic groups, including Africans, Asians and Native Americans, it is relatively rare in Caucasians.3 Offspring of Caucasians and African-Americans, however, have reduced prevalence of lactose maldigestion. The degree of lactose intolerance depends on a balance between the level of remaining lactase activity, the amount of lactose consumed, the adaptation of intestinal flora and the irritability of the colon.3
Secondary Lactase Deficiency
Secondary lactase deficiency is temporary. It is a response to gastroin-testinal factors that harm the intestinal mucosa (e.g., certain medical conditions, some medications, etc.). It can occur at any age and is reversible upon correction of the causative factor.3,9 Testing for other underlying conditions (such as Crohn's disease, infectious diarrheal disease and celiac disease) may be in order.
Colonic Adaptation
According to breath hydrogen tests, newborns are unable to completely hydrolyze the lactose in mothers' milk. Nevertheless, infants thrive on lactose-containing breast milk and formula, perhaps due to colonic absorption of the fermentation by-products of undigested lactose.3 Blinded, controlled, crossover studies have been conducted in adult lactose maldigesters to determine whether continuous lactose challenges could cause bacteria in the colon to metabolize lactose and reduce symptom severity.
Gradually increasing lactose intake significantly increased the ability of colonic bacteria to break it down.5 Subjects experienced a decrease in breath hydrogen (suggesting that the lactose was being digested) and, concomitantly, a significant reduction in flatulence,5 one of the principal symptoms of lactose intolerance. Often, despite a continued inability to digest lactose, confirmed by breath hydrogen testing, subjects can still tolerate more and more lactose with minimal symptoms.6,7
A recent 21-day intervention study assessed the effects of a dairy-rich diet in 14 African-American girls (11 to 15 years old). Confirmed lactose maldigesters, all were self-proclaimed non-drinkers of milk. The diet contained four servings of dairy products (primarily milk, some cheese and yogourt), providing about 33 g of lactose and 1,200 mg of calcium throughout the day. In addition to a significant decrease in breath hydrogen,8 gastrointestinal symptoms were negligible during the milk challenges and throughout the study period, likely due to colonic adaptation.8 The message is clear: Even individuals who are lactose intolerant can consume milk and milk products.
The Dose Counts
Double-blind, controlled studies have demonstrated time and again that primary lactase deficiency should not be an obstacle to meeting calcium needs with milk and milk products.1,2,8,11 Lactose intolerance is dose dependent. Most individuals with primary lactase deficiency - even adolescents and adults who perceive themselves to be severely lactose intolerant - can easily tolerate one cup (250 ml) of milk with a meal or two cups (500 ml) consumed in divided doses, for example with breakfast and dinner.1,2,8,12 Women with limited lactose digestion can comfortably consume enough milk, yogourt and cheese to provide up to 1500 mg of calcium/day.11 Interestingly, increased tolerance to lactose appears to be a by-product of pregnancy,13,14,15 possibly because intestinal transit time slows down.14,15 According to Dr. Denis Savaiano, an expert in lactose intolerance, people can recondition their digestive systems to accept dairy foods without discomfort.16 Smaller quantities, taken with meals or other foods and spread throughout the day, increases lactose tolerance.
Overcoming the Bias
Overcoming the Bias
Lactose intolerant or not, a significant portion of the population avoids milk products unnecessarily. Although the consequences may be similar - i.e., avoidance of milk products - there's a world of difference between lactose intolerance and milk intolerance. It is not unusual for individuals with milk intolerance to experience placebo-induced symptoms in double-blind studies. Sometimes intolerance to milk has absolutely nothing to do with lactase deficiency or the inability to digest lactose.3,8 Rather, it is affected by psychological factors or cultural attitudes.3,8 This phenomenon not only distorts clinical trial results, it exaggerates the prevalence of lactose intolerance and prevents too many people from reaping the nutritional benefits and enjoyment that milk and milk products provide.
Why Is Dairy Important?
Excluding milk products from the
diet for any length of time is not only unnecessary, it is unwise. Low intakes of milk result in concomitant low intakes of important milk nutrients: vitamins A, B 6 , B 12 and D; riboflavin, calcium, magnesium and protein.17,18 According to calcium expert Robert Heaney, MD, "a low calcium intake is generally a marker for a poor diet and… improving the calcium intake with food sources improves the total diet as well."19 Clinical trials assessing dairy-rich diets have demonstrated the health benefits associated with the consumption of milk products.
For example:
- Protection against vascular disease
The DASH (Dietary Approaches to Stop Hypertension) Study indicated that reductions in blood pressure of the magnitude achieved by the DASH diet - rich in milk products (3 servings), fruits and vegetables (8 to 10 servings) - could translate into a 15% reduction in ischemic heart disease and a 27% reduction in stroke.20 - Protection against cancerDairy foods (and/or calcium) appear be protective against colonic polyps and the risk of colorectal cancer. Conjugated linoleic acid (CLA) found in milk fat, identified as a potent cancer inhibitor, reduces breast cancer risk in adult women.22,23
- Protection against osteoporosisAvoidance of dairy foods is most likely an important factor in the increased osteoporosis risk observed in individuals who are, or simply believe themselves to be, lactose intolerant.24,25
Reconditioning the Gut3,26
Help your lactose intolerant patients find their own unique levels of tolerance. Offer them these tips that help the digestive process:
- Start Small
Start with less than 125 ml of milk, two to three times a day, and slowly increase the amount over a few weeks. - Enjoy with Other Foods
Drink milk with a meal or with other foods, not by itself. - Watch the Quantity
Avoid too much at one time. For some people two glasses of milk could be a lactose overdose. - Consume Other Dairy FoodsTry firm cheeses which contain small amounts of lactose.
Try yogourt with active cultures. - If All Else FailsTry lactose-hydrolyzed milk or take an oral lactase supplement before consuming dairy foods.
Key Messages about Lactose Intolerance
Its prevalence is grossly overestimated. Self-diagnosis is frequently inaccurate. Most lactose intolerant individuals can consume milk products with minimal symptoms.3-7 Lactose intolerant individuals who consume milk products have fewer symptoms than those who don't. The colon adapts to regular exposure, increasing tolerance.
Its prevalence is grossly overestimated. Self-diagnosis is frequently inaccurate. Most lactose intolerant individuals can consume milk products with minimal symptoms.3-7 Lactose intolerant individuals who consume milk products have fewer symptoms than those who don't. The colon adapts to regular exposure, increasing tolerance.
References :
1. Suarez FL et al. 1997. Tolerance to the daily ingestion of two cups of milk by individuals claiming lactose intolerance. Am J Clin Nutr 65:1502-1506.
2. Suarez FL et al. 1995. A comparison of symptoms after the consumption of milk or lactose-hydrolysed milk by people with self-reported severe lactose intolerance. N Engl J Med 333:1-4.
3. Miller GD et al. 2000. Lactose Intolerance. In: Handbook of Dairy Foods and Nutrition. 2nd ed. Chap. 8:311-354. CRC Press, Inc., Boca Raton, Florida.
4. Hertzler SR et al. 1997. Fecal hydrogen production and consumption measurements.
Response to daily lactose ingestion by lactose maldigesters. Dig Dis Sci 42:348-353.
5. Hertzler SR and Savaiano DA. 1996. Colonic adaptation to the daily lactose feeding in lactose maldigesters reduces lactose intolerance. Am J Clin Nutr 64:1232-1236.
6. Johnson AO et al. 1993. Adaptation of lactose maldigesters to continued milk intakes. Am J Clin Nutr 58:879-881.
7. Briet R et al. 1997. Improved clinical tolerance to chronic lactose ingestion in subjects with lactose intolerance: a placebo effect? Gut 41:632-635.
8. Pribila BA et al. 2000. Improved lactose digestion and intolerance among African-American adolescent girls fed a dairy-rich diet. Am J Diet Assoc 100:524-528.
9. Suarez FL and Savaiano DA. 1994. Lactose digestion and tolerance in adult and elderly Asian-Americans. Am J Clin Nutr 59:1021-1024.
1. Suarez FL et al. 1997. Tolerance to the daily ingestion of two cups of milk by individuals claiming lactose intolerance. Am J Clin Nutr 65:1502-1506.
2. Suarez FL et al. 1995. A comparison of symptoms after the consumption of milk or lactose-hydrolysed milk by people with self-reported severe lactose intolerance. N Engl J Med 333:1-4.
3. Miller GD et al. 2000. Lactose Intolerance. In: Handbook of Dairy Foods and Nutrition. 2nd ed. Chap. 8:311-354. CRC Press, Inc., Boca Raton, Florida.
4. Hertzler SR et al. 1997. Fecal hydrogen production and consumption measurements.
Response to daily lactose ingestion by lactose maldigesters. Dig Dis Sci 42:348-353.
5. Hertzler SR and Savaiano DA. 1996. Colonic adaptation to the daily lactose feeding in lactose maldigesters reduces lactose intolerance. Am J Clin Nutr 64:1232-1236.
6. Johnson AO et al. 1993. Adaptation of lactose maldigesters to continued milk intakes. Am J Clin Nutr 58:879-881.
7. Briet R et al. 1997. Improved clinical tolerance to chronic lactose ingestion in subjects with lactose intolerance: a placebo effect? Gut 41:632-635.
8. Pribila BA et al. 2000. Improved lactose digestion and intolerance among African-American adolescent girls fed a dairy-rich diet. Am J Diet Assoc 100:524-528.
9. Suarez FL and Savaiano DA. 1994. Lactose digestion and tolerance in adult and elderly Asian-Americans. Am J Clin Nutr 59:1021-1024.
10. Sampson HA and Metcalfe DD. 1992. Food allergies. JAMA 268:2840-2844.
11. Suarez FL et al. 1998. Lactose maldigestion is not an impediment to the intake of 1500 mg calcium daily as dairy products. Am J Clin Nutr 68:1118-1122.
12. Johnson AO et al. 1993. Correlation of maldigestion, lactose intolerance and milk intolerance. Am J Clin Nutr 57:399-401.
13. Villar J et al. 1988. Improved lactose digestion during pregnancy: a case of physiologic adaptation? Obstet Gynecol 71:697.
14. Szilagyi A et al. 1996. Lactose handling by women with lactose malabsorption is improved during pregnancy. Clin Invest Med 19:416.
15. Paige D et al. 1997. Lactose intolerance in pregnant African-American women. J Am Coll Nutr 16(Abstract 69):488.
16. Savaiano D. 2001. Managing lactose intolerance: a food lover’s guide. Presentation. The Smart Gourmet. Dairy Foods for Health and Pleasure. Montreal, Quebec (February 19, 2001).
17. Barger-Lux MJ et al. 1992. Nutritional correlates of low calcium intake. Clin Appl Nutr 2:39-44.
18. Fleming K and Heimbach JR. 1994. Consumption of calcium in the US: food sources and intake levels. J Nutr 124:1426S-1430S.
19. Heaney RP. 1996. Food: what a surprise! Am J Clin Nutr 64:791-792.
20. Appel LJ et al. 1997. A clinical trial of the effects of dietary patterns on blood pressure. N Eng J Med 336:1117-1124.
21. Holt PR. 1999. Dairy foods and prevention of colon cancer: human studies. J Am Coll Nutr 18(5):379S-391S.
22. Parodi PW. 1997. Milk fat conjugated linoleic acid: Can it help prevent breast cancer? Proc Nutr Soc NZ 22:137-149.
23. Aro A et al. 2001. Inverse association between dietary and serum conjugated linoleic acid and risk of breast cancer in postmenopausal women. Nutr Cancer (In press).
24. Heaney RP. 2000. Calcium, dairy products and osteoporosis. Am J Coll Nutr 19(Suppl):83S-99S.
25. Griessen M et al. 1989. Calcium absorption from milk in lactase-deficient subjects. Arch Inter Med 147:534.
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Ph.D., Justus liebig University, Giessen, West Germany. Professor,Department of Food Science. University of Ain Shams. Cairo, Egypt. Expert and consultant(dairy, food, water and nutrition |
