Midday naps have long been touted as a good thing, lowering blood pressure and driving down the risk of heart attack. And if you snooze long enough, researchers have now found, they also permit your memory banks to do their filing, leaving your brain cleared and ready to learn in the latter half of the day.

University of California at Berkeley researchers put 39 young adults through a demanding learning task and tested on it at noon. At 2 p.m., they divided the students into two groups and invited half of them to take a siesta for 90 minutes while asking the remainder to stay awake. At 6 p.m., both groups were returned to the day's learning task and tested again.

The siesta group went into the 6 p.m. task readier to learn and performed 10 percent better on the test than they had earlier. The no-nap group's performance declined by 10 percent, researchers reported.

Flu shots broadened The Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommended recently that all Americans over 6 months -- except those who are allergic to eggs -- should receive a seasonal flu shot every year, beginning this fall. The CDC has been slowly broadening the recommendations for flu shots over the past few years to the point where about 85 percent of the population is now covered. The primary exception now is adults 19 to 49 who do not have underlying medical conditions.

Little on lactose woes The National Institutes of Health recently convened a panel of experts to reach a consensus on what is known about lactose intolerance. Their consensus: There is no consensus. It is a real condition, but there are no good numbers for its incidence, little is known about its effects on health and even less is known about potential treatments.

Lactose is the primary sugar in all mammalian milk, including human milk. Virtually all babies are born with enzymes, called lactases, in their intestines that digest lactose, turning it into a form that can be used by the body. But beginning at about 5 or 6, many children, particularly those of African and Asian ancestry, begin to lose the ability to digest the sugar. If they continue drinking milk and eating dairy products afterward, bacteria in the gut often ferment the sugar, producing diarrhea, abdominal pain, flatulence and bloating.

Surprisingly, there are no good estimates of how many people have the problem, and the panel didn't try to make one.

"A lot of people who think they have lactose intolerance don't," said Dr. Frederick Suchy of the Mount Sinai School of Medicine, chair of the panel.

LOS ANGELES TIMES