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Thursday, April 01, 2010

Report from the LI Conference, part 18

Back at the NIH LI Conference, the presenters were ready to tackle question 3.

What Amount of Daily Lactose Intake Is Tolerable in Subjects With Diagnosed Lactose Intolerance?

Adaptation to Lactose Intolerance
Andrew Szilagyi, M.D., FACN, FRCPC
Assistant Professor of Medicine
McGill University School of Medicine
Department of Medicine
Division of Gastroenterology
The Sir Mortimer B. Davis Jewish General Hospital

Szilagyi is pronounced something like Siz-lah-ee.

What does it mean to be adapted to LI? It all relates to the big gap between people who have undergone testing to show that they don't digest lactose and the people who report symptoms of lactose intolerance. Some people who do digest lactose report symptoms in any case. But most people with lactase malabsorption - the technical term - aren't really all that bothered by milk.

I've covered some of these already, but we went over the list again. Having certain types of bacteria in the colon mean that less lactose is fermented and less gas created. Slowing the transit time through the intestines means that whatever small amounts of lactase remain have more chance to work on the lactose.

He also cited some studies that said that pregnant women have fewer symptoms, but worse symptoms after delivery. I've received email from women who are on both sides: some say their symptoms lessen, some say that pregnancy made it worse. But the evidence from these studies is interesting.

Improved lactose digestion during pregnancy: a case of physiologic adaptation?

Obstet Gynecol. 1988 May;71(5):697-700.
Villar J, Kestler E, Castillo P, Juarez A, Menendez R, Solomons NW.

Loss of intestinal lactase activity among adults could theoretically limit milk consumption and hence dietary availability of calcium during pregnancy. The present study sought to define, using breath hydrogen (H2) production as an index of incomplete carbohydrate absorption, the prevalence during pregnancy of lactose maldigestion of 360 mL of milk (18 g of lactose), and to determine whether lactose digestion improved as pregnancy advanced. The prevalence of lactose maldigestion among 114 pregnant women tested before the 15th week of gestation was 54%. By term, 44% of those originally classified as maldigesters had become digesters. There was a significant reduction in the four-hour sum of the changes in breath H2 concentration from the period before 15 weeks (116.6 +/- 9.6 ppm) to the time after 36 weeks (54.4 +/- 7.3 ppm; P less than .01). This apparent adaptive improvement in intestinal handling of milk lactose during gestation has implications for calcium intake and absorption.

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