FRIDAY, Nov. 19 (HealthDay News) -- Kidney disease patients, once cautioned against alcohol use, can relax and have a drink a two, but they also need to be mindful of their weight, two new Dutch studies show.

The researchers found that fears about moderate drinking by kidney disease patients may be unfounded, while concerns about weight are not.

Both studies, conducted by different researchers, were presented Thursday at the American Society of Nephrology's annual meeting in Denver.

One study focused on the effects of alcohol use among kidney transplant patients, who traditionally have been warned against drinking because it might interfere with medications that prevent the body from rejecting a new kidney. It found, instead, that a few drinks might actually help.

"Quality of life and long-term outcome after transplantation may benefit from advising moderate intake of alcohol," said study author Dorien Zelle, a Ph.D. Fellow in the department of nephrology at the University Medical Center in Groningen, The Netherlands.

The study followed 600 kidney transplant patients for seven years, recording deaths until 2009. Of those, 48 percent were alcohol abstainers, 35 percent were moderate drinkers, 16 percent were sporadic drinkers and 1 percent were heavy drinkers.

During the follow-up period, moderate drinkers were 67 percent less likely to develop diabetes and 44 percent less likely to die than those patients in the other groups.

Total post-transplant prevalence of diabetes in study participants was 12 percent. Less than a half a percent of those who developed diabetes were moderate alcohol users. During follow-up, 26 percent of abstainers, 24.5 percent sporadic drinkers and 25 percent of heavy drinkers died. Only 15.7 percent of moderate drinkers died.

The authors reported no financial conflicts of interest.

Dr. Kamyar Kalantar-Zadeh, a professor of medicine at Harbor-UCLA Los Angeles Biomedical Research Institute, said the medications that weaken the immune systems of kidney transplant patients were a concern in the past.

"These patients are susceptible to infections and are quite vulnerable," said Kalantar-Zadeh, who is also an associate professor-in-residence of medicine, pediatrics and epidemiology at the University of California, Los Angeles. "However, moderate alcohol consumption does not appear to interfere with immunotherapy."

The findings about alcohol consumption among transplant patients are consistent with research showing a positive impact of moderate alcohol use on the general population, said Kalantar-Zadeh, who was not connected to the study. Over the past 20 years, research has shown that moderate alcohol consumption helps prevent diabetes, heart attacks and early death, he said.

"It is welcome news. The findings are reassuring because in this population with chronic kidney problems hardly anything has been associated with better outcomes," said Kalantar-Zadeh.

About 19.2 million Americans -- or 11 percent of the population -- have chronic kidney disease, according to research funded by the National Institute of Health.

In the study examining the impact of weight on dialysis patients, researchers led by Dr. Ellen Hoogeveen of Jeroen Bosch Hospital compared patients who were over or under 65.

A higher risk of mortality for both the obese and the underweight was found for those under 65. There was no higher risk of death for obese patients over 65.

The study followed 1,749 dialysis patients until they had a transplant or died, or for a maximum of seven years. The average age was 49 for the younger group and 73 for the older group. All patients were to begin dialysis when the study started.

Both younger and older patients who were underweight had twice the risk of dying during follow-up than the obese patients, according to the research.

Kalantar-Zadeh noted that the mortality risk for underweight patients might be connected to the disease causing weight loss rather than weight loss leading to more deaths.

Younger patients were also at greater risk if they were obese. They were 1 1/2 times more likely to die than older obese patients and had a 50 percent greater chance of dying in seven years than young people of normal weight.

In populations with chronic diseases "something called the obesity paradox protects older obese patients," said Kalantar-Zadeh. Researchers "have looked at different age groups and have found older populations (among the chronically sick) in whom obesity is not bad. But if you're young, in your 30's or 40's, you're back to the situation where obesity plays against you."

The "nutritional reserves" of obese people may stand them in good stead when they become old and sick, he said.

Hoogeveen said the most important message from the study is that "young obese dialysis patients have a lower survival rate" than same-age patients of normal weight. "It is important to strive for normal weight in this age group," she said. "Maybe this can improve their life expectancy."

Because both studies were presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

More information

Find out more about chronic kidney diseases at the National Kidney Foundation.