Few of us need to be convinced to perk up when the sun comes out -- we perk up automatically. We set off on vacations, have cookouts and enjoy the outdoors. We tend to be more social and get more exercise. Time spent in the sun is time well spent, and research confirms that sunlight -- so long as it's enjoyed in moderation -- makes us happy and keeps us healthy.

Vitamin D

The sun is a natural source of vitamin D. Vitamin D helps us absorb calcium and other minerals that keep our bones, muscles and joints strong. We find it naturally, in eggs and in fatty fish like salmon, tuna and sardines. Some foods like milk or yogurt are fortified with vitamin D. But the easiest way to get it is through direct exposure to sunlight. In just 10-15 minutes a day, our skin absorbs enough sunlight to provide our daily requirement of vitamin D.

The Mayo Clinic lists vitamin D as one of three preventative measures against osteoporosis (the other two being adequate calcium intake and exercise). Osteoporosis is age-related and characterized by the loss of bone tissue. As bones age, they shed cells more quickly than they add new cells, making them brittle and more fragile. People with osteoporosis are more likely to experience fractures and other serious complications when they fall. A lack of vitamin D prevents us from absorbing calcium and regenerating bone tissue.

Want to have healthy bones? Combine a weight-bearing exercise with sunlight. Even a brief walk in the early morning or late afternoon will keep your bones strong, while ensuring that you get your daily dose of vitamin D.

Recently, researchers have taken a closer look at vitamin D and its effects on the immune system. They found that vitamin D3 -- a type of vitamin D we get from sunlight -- sends signals to cells in the immune system to break up a harmful protein in the brain called beta-amyloid. Beta-amyloid is a marker of Alzheimer's Disease. It forms plaques that interfere with cell-to-cell communication, and is thought to play a role in cognitive decline. Exposure to the sun may help ward off this harmful protein buildup.

Sunlight and Mental Health

Most of us feel a surge of well-being when the sun comes out after a long dark winter. This is because sunlight causes our brains to produce more serotonin, a chemical that elevates mood. One study found that production levels of serotonin increased in proportion to the amount of sun exposure. Typically, the longer people spend in the sun, the happier they feel.

A recent study published in the American Journal of Preventative Medicine used internet search data to track mental health throughout the seasons. The researchers tracked searches for various mental health ailments, and saw that people were less concerned about those ailments in the summer. Searches for eating disorders decreased by 37 percent during the summertime, and those related to bipolar disorder were 17 percent lower. The study also found that searches for attention deficit disorder, obsessive compulsive disorder, and other mental illnesses all decreased when the sun came out.

Weighing the Pros and Cons

Too much of a good thing can be dangerous, and the sun is no exception. If you're planning on spending hours outside, be aware of the following risks:

-- Sunburns: The lighter your skin, the more careful you need to be. Lighter skin is more susceptible to the sun's UV rays and burns more easily. Be sure to use UV-blocking sunscreen when you go out, especially during midday when the sun is at its hottest.

-- Skin cancer: In some cases, UV rays from the sun can alter DNA and lead to skin cancer. Skin cancer is the most common form of cancer, affecting roughly two million people per year in the U.S. Your risk increases if you have fair skin, light hair, and/or a history of sunburns. Talk to your doctor if you're concerned about cancer or want to know more about the risks.

-- Eye Damage: Protect your eyes. UV rays from the sun can harm the retina and the lens of your eye and may lead to cataracts. Keep your eyes safe with UV blocking sunglasses.

-- Dehydration: Hot weather causes us to lose water more quickly through perspiration. The older you are, the greater your risk of losing too much water. Dehydration can cause dizziness and confusion, and may increase your risk of falling. While everyone's filtration system is different, men should generally drink 6-8 eight ounce glasses of water a day. Women should drink around five eight ounce glasses a day. Remember that even if you don't feel thirsty, you may still be dehydrated.

This summer -- provided we're not in the middle of a heat wave -- do yourself a favor and spend some time in the sun. Remember to use sunscreen and wear sunglasses for longer outings. Stay safe, stay hydrated, and enjoy the outdoors!

Adam Johnson writes for Youville Assisted Living Residences, member of Covenant Health Systems, a Catholic, multi-institutional health and elder care organization serving New England. See www.youvilleassistedliving.org.