What was healthy (and not so healthy) in 2010

With the new year just days away, Americans are resolving once again to live healthier lives. Luckily, in 2010, scientists offered up a bevy of new information as to what makes for a (supposedly) healthy and unhealthy existence. Here's what they discovered:

SOME OF THE THINGS THEY SAID WERE GOOD FOR US...

Naps make you smarter. Subjects in a study at the University of California at Berkeley were given a learning task designed to challenge their short-term memory; they took the test at noon and a similar one at 6 p.m. Those who were allowed to take a midafternoon nap fared far better on the second test. Sleep seems to "reboot" the brain, clearing short-term memory and making room for new information, says study author Matthew Walker. "It's as though the e-mail inbox in your hippocampus is full, and until you sleep and clear out those fact e-mails, you’re not going to receive any more mail.”

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Dreaming makes you smarter still. Harvard researchers asked people to navigate a maze, and found that those who both napped and dreamed about their maze experience in any way showed a tenfold improvement when they did the maze a second time. "Dreams are the brain's way of processing, integrating, and really understanding new information," says neuroscientist Robert Stickgold. That process isn't necessarily rational or literal — one of the test subjects dreamed about being lost in a cave — but reflects a deeper process in which the unconscious mind consolidates what it has learned and produces new insights.

Laughter improves your appetite. Repeated bouts of "mirthful laughter" — produced by watching funny, 20-minute video clips — were found to trigger a rise in the hormone ghrelin, which cues hunger, and a drop in leptin, which cues satiety. In fact, laughter can offer some of the same benefits as exercise, such as lower blood pressure and cholesterol levels. Study author Lee Berk says laughter therapy might be a viable option "for patients who cannot use physical activity to normalize or enhance their appetite," including elderly patients with so-called wasting disease or even widowers, who commonly suffer depression and lose their appetite following the death of a spouse.

Good-luck charms give you an advantage — if you believe they work. In a series of experiments, people who carried a lucky charm set higher goals and felt more confident than those who left their rabbit's foot at home. It's that confidence — not magic — that makes the difference. In one test, subjects who'd been told that a golf ball was "lucky" tended to perform better than those who were simply handed the ball. "Superstitious behavior won’t help you win the lottery," says psychologist Barbara Stoberock. "But it could help you win a sporting event or pass a test."

Getting older makes you happier. A study found that after age 50, people report being consistently happier, less stressed, and less worried than their younger counterparts. Because of life experience, older people may be “more effective at regulating their emotions than younger adults,” says psychiatrist Arthur Stone. They also seem more likely to forget or let go of bad memories. "If you were to do a survey and say, 'How many of you would like to be 25 again?'" Stone says, "you don’t get a lot of takers."

Sighing helps you breathe easier. A Belgian study found that after volunteers spontaneously sighed — defined as a breath with twice the mean volume — the dynamics of their breathing changed to become more effective. Under stress, our breathing becomes less variable from breath to breath, which makes the lungs stiffer and less effective at exchanging gas. But a sigh shakes up the system and “acts as a general re-setter of the respiratory system," says study author Elke Vleminckx.

A good massage boosts your immune system. An hour after receiving a 45-minute deep-tissue Swedish massage, study volunteers had lower levels of the hormones cortisol, which causes stress, and arginine vasopressin, which can elevate cortisol; they also showed a rise in white blood cells, which aid the immune response. Massage also produced an increase in the “love hormone,” oxytocin, which makes people feel pleasantly "high." The results are "very, very intriguing and very, very exciting," says Cedars-Sinai psychiatrist Mark Hyman Rapaport, "and I'm a skeptic."

AND SOME OF THINGS WE WERE TOLD TO AVOID...

Daydreaming makes you unhappy. Harvard researchers randomly contacted volunteers throughout the day and had them describe what they were doing, what they were thinking about, and how they felt on a scale of zero to 100. People who were daydreaming often reported feeling sad or worried. When people's minds wander, says study co-author Matthew Killingsworth, they tend "to wander toward negative thoughts," regardless of the activity in progress. People who are intensely focused on what they are doing at that moment — especially sex — tend to report feeling much happier.

Lack of sleep will keep you fat. Two groups of study subjects were put on a reduced-calorie diet; one group was allowed to sleep just five hours a night and the other had a full night’s sleep. Both groups lost the same amount of weight, but the well-rested subjects lost twice as much of that weight in the form of fat. The sleep-deprived group lost more muscle mass and water, and woke up starving. "If your goal is to lose fat," says University of Chicago researcher Plamen Penev, “skipping sleep is like poking sticks in your bicycle wheels.”

Sitting for prolonged periods shortens your life span. Epidemiologists found that people who sat for more than six hours a day were nearly 20 percent more likely to die over the 14-year study period than those who sat for less than three hours daily. Standing burns calories, boosts the ability of insulin to lower glucose, and activates an enzyme that sucks fat out of the bloodstream. “Sitting is hazardous,” says Marc Hamilton, a physiologist. “It’s dangerous.”

Too much television hurts your kid in every possible way. Every hour of TV beyond average that younger toddlers watched made them, by fourth grade, 7 percent less engaged in class, 6 percent worse at math, and 10 percent more likely to be bullied; they also snacked more, exercised less, and had higher ratios of body fat.

Eating too much salt can subtract years from your life. Americans eat far more than the recommended amount of sodium, mostly in processed foods. Reducing the daily intake by three grams, or just half a teaspoon, would cut the number of heart attacks by 99,000 — a 13 percent decline; strokes and new cases of heart disease would decline too, by 8 percent and 11 percent, respectively.

Cash receipts can be toxic. Forty percent of receipts from ATM machines, supermarkets, gas stations, and other major retail outlets carry significant traces of bisphenol A, or BPA, a chemical that has been linked to heart ailments, cancer, and behavioral and reproductive problems. Often found in plastics, BPA is also used as coating in the paper used to make receipts; it transfers easily to fingers and may penetrate the skin. Although the health risk is probably greater to cashiers than to shoppers, says researcher Frederick vom Saal, “I won’t touch receipts now.”

Running shoes can hurt your knees. An analysis of people running on a treadmill found that the use of running shoes led to 38 percent more torque, or twisting, around parts of the knee where osteoarthritis develops than barefoot runners experienced. In fact, the shoes put more strain on the knee than women’s high heels do. Unshod, a runner naturally runs on the balls of the feet, which allows the foot itself to absorb more of the impact. People who run on streets and hard pavement, of course, may not have the option of going barefoot, so for them researchers suggested a minimal running shoe with less padding.

Dogs and cats may be good companions, but they can break your leg. A new analysis of emergency-room data found that 86,000 people a year wind up in the hospital after tripping over a pet, its bowls, or its toys. Dogs cause nearly eight times more injuries than cats, mainly because they’re bigger and stronger, and can yank people down stairs or into holes when pulling on their leashes during walks.