Here comes the sun — at last. But don’t get too complacent. Although it may feel great that we are now beginning to see more daylight, it still may not be enough to supply your daily dose of D. Vitamin D, also known as the sunshine vitamin because of our ability to absorb it from the sun’s rays, is necessary for health and well-being.

Vitamin D is a nutrient that serves many important functions in your body. By helping to absorb calcium, it is vital for bone health.  Muscles need vitamin D for movement, nerves need it to carry messages, and the immune system needs it to fight bacteria and viruses.

In fact, in a 2010 article in Genome Research, a geneticist and his colleagues at Oxford University reported that more than 200 genes are awakened or silenced by vitamin D binding to its receptor. Additional evidence suggests the number of genes indirectly affected by vitamin D could exceed 2,000!

Without a decent amount of D, you may feel generally “off,” with tiredness, aches and pains, and general malaise. Significant D deficiencies will cause rickets in children, and osteomalacia and other bone conditions in adults.

But is getting a daily dose of D even doable in New England in January? One can absorb vitamin D naturally from the ultraviolet B (UVB) rays that come from the sun. Sounds easy, but not so fast. 

Turns out, up to 40 per cent of the world’s population is vitamin D deficient. Unfortunately, during the winter, the sun may not be able to supply enough. You may have already guessed that bundling up has a major effect on how much of the sun’s rays can reach your skin. Other factors, such as where you live, time of day, and even color of your skin, also affect your ability to get enough vitamin D from the sun.

The Vitamin D Council confirms these concerns: “During the winter months in Boston, it’s not possible to make enough vitamin D no matter the skin type.” In summertime the living in easy, since only 15 minutes to a few hours are needed to get your daily dose of D.

But in winter, the angle of the sun plays a role. Morning and evening aren’t the best times to try to soak up the sun — a rule of thumb is that if your shadow is longer than your height, you aren’t able to make vitamin D.  Middle of the day is your best bet.

Standing by a sunny window is not a solution either, since the UVB rays can’t get through. Nor can you just eat your way to vitamin D health. Most foods do not provide it. However, some, such as fatty fish, beef liver, egg yolks and fortified foods like milk, juice and breakfast cereals, can help.

The easiest way to insure that you are getting enough vitamin D is with supplements. Nobel Prize-winning chemist Linus Pauling concurred, saying: “I believe that you can, by taking some simple and inexpensive measures, lead a longer life and extend your years of well-being. My most important recommendation is that you take vitamins every day in optimum amounts to supplement the vitamins you receive in your food.”

Putting it more succinctly, well-known wrestler Hulk Hogan told his young followers “Say your prayers, take your vitamins, and you will never go wrong.”

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.