Sun-seekers absorb an abundance of vitamin D, but not everyone gets enough of this essential ingredient. In fact, most Americans consume less than the recommended amount.

Why does this matter? Vitamin D helps the body in many important ways, including strengthening bones, in turn staving off osteoporosis and bone fractures and even supporting strong teeth. It also improves heart health, plays a role in healthy cholesterol levels and blood pressure and aids in glucose metabolism. Vitamin D also helps the immune system ward off bacteria and viruses.

Getting enough Vitamin D, also called calciferol, can reduce the number of falls and fractures in older adults because of its effect on strengthening bones and proximal muscles. Often, we think about a lack of calcium with osteoporosis, but since vitamin D helps the body absorb calcium, it’s also a crucial player in the health game.

So who’s at risk?

For starters, people who get very little sun exposure. This includes people with jobs and hobbies that keep them inside, as well as those who live in the northern part of the country. And the darker your skin, the higher your risk of deficiency, since the pigment melanin reduces the skin’s ability to produce vitamin D.

Being overweight also puts you at risk, since body fat stores more of the fat-soluble vitamin D, and doesn’t release as much into your bloodstream.

People over 50, as well as infants, also have cause for concern. Over the age of 50, our skin can’t make vitamin D as efficiently, and the American Academy of Pediatrics says that all breastfed infants need to be supplemented with 400 International Units (IU) of vitamin D daily.

Vitamin D deficiency often goes unnoticed, but it’s a simple problem to remedy.

We typically get 90% of our vitamin D from sunlight on the skin; it’s also found in foods and in over-the-counter supplements (look for vitamin D3 for maximum absorption). It’s nearly impossible to our daily dose of vitamin D through diet alone, however, since only a few foods are naturally good sources of vitamin D.

A single tablespoon of cod liver oil provides 1360 IU vitamin D, but you’ll only get 100 IU of vitamin D per ounce of salmon or cup of fortified milk.

Taking too much vitamin D is rare, but as always, consult with your healthcare provider before beginning any new supplement program.