June 13, 2006

Got Milk? Don't Let Dairy Get You Down

June 13, 2006 (AIDSmeds)—Chronic diarrhea remains a common problem for people living with HIV, and many doctors advise restricting the intake of dairy products to prevent or reverse symptoms. But a recent Canadian study has concluded that moderate dairy ingestion does not worsen diarrhea in HIV-positive people with chronic diarrhea, regardless of their lactose-tolerance status.

According to the American Dietetic Association, approximately 30 to 50 million Americans are lactose intolerant – an inability to digest lactose, a sugar found in milk and dairy products. People with lactose intolerance do not have enough of the enzyme lactase in their small intestine, which is needed to break down lactose into forms of sugar (glucose and galactose) that can be absorbed easily. If lactose is not converted into these simple sugars, it can cause flatulence (gas), bloating, stomach cramps, and diarrhea.

While there have been some studies suggesting the people with HIV are more likely to suffer from lactose intolerance, there haven't been any studies suggesting that dairy avoidance is beneficial. In fact, there is some concern about a diet that severely limits dairy products, as they may be needed to help prevent weight loss and fragile bones (osteoporosis) – two potential problems for those with HIV.

The new study, conducted by Dr. Jill Tinmouth of the University of Toronto and her colleagues, evaluated 49 HIV-positive people with chronic diarrhea, defined as having at least three loose/watery bowl movements per day for the previous four weeks. Approximately 80% of the volunteers were on a stable anti-HIV drug regimen and none of the patients had evidence of an infection known to cause chronic diarrhea (intestinal parasites, etc.).

On one day of the study, all of the volunteers – ten of whom had documented lactose intolerance – ingested 240 mL of lactose-free milk. On another day, they ingested 240 mL of low-fat milk containing 12.5 grams of lactose. For eight hours after taking the lactose-free and lactose-sweetened milk, the researchers weighed the total amount of stool excreted by each volunteer. The higher the weight, the researchers suggested, the greater the diarrhea.

According to the research team's report, published in the June 12th issue of Archives of Internal Medicine, the average total stool weight within eight hours after ingesting lactose-sweetened milk was 126.3 grams. The average total stool weight after ingesting lactose-free milk was 167.6 grams. While there appeared to be slightly more stool excretion after ingesting lactose-free milk – a surprising finding – the difference was not statistically significant (it could have been due to chance).

Another surprising finding was that the lactose-tolerant volunteers had significantly great stool excretion after ingesting lactose-free milk compared to the lactose-intolerant volunteers. Stool excretion decreased by 11.3 grams in the lactose-intolerant volunteers after taking lactose-free milk, compared to a stool excretion increase of 54.8 grams in the lactose-tolerant volunteers after taking lactose-free milk. However, the researchers questioned the real-world significance of the increased stool in the lactose-tolerant volunteers. "This difference represents approximately three tablespoons of stool and is unlikely to be clinical significant," Dr. Tinmouth and her colleagues wrote.

While Dr. Tinmouth's group pointed out that there are limitations to their study – for example, there is no "gold standard" method to evaluate diarrhea symptoms in clinical trials – the researchers concluded that ingesting moderate quantities of milk containing lactose did not significantly increase stool excretion or worsen symptoms in HIV-positive people with chronic diarrhea. These results, they write, echo those of studies involving HIV-negative volunteers, which also found that moderate lactose ingestion does not worsen symptoms.