It's long been known that getting too little of vitamin D weakens bones. But when it comes to heart health, the role vitamin D may play is less clear.

Vitamin D deficiency may be linked to heart disease and an increased risk of high blood pressure (hypertension). However, more research is needed. It's too early to say whether a lack of vitamin D causes high blood pressure, or whether vitamin D supplements may have any role in the treatment of high blood pressure.

Still, vitamin D remains an important nutrient for overall good health. The National Academies of Sciences, Engineering, and Medicine recommends 600 international units (IU) of vitamin D a day for adults ages 19 to 70. For adults age 71 and older, the recommendation increases to 800 IU a day.

Some doctors question whether these levels are adequate and think that getting more vitamin D would benefit many people. But the National Academies of Sciences, Engineering, and Medicine recommends that adults avoid taking more than 4,000 IU a day.

If you're concerned that you're getting too little — or too much — vitamin D, contact your doctor. He or she may recommend a blood test to check the level of vitamin D in your blood.

Screening for vitamin D deficiency is important in African Americans and others with dark skin. Darker skin has higher levels of melanin, the pigment that gives skin its color. The more melanin you have, the harder it is for your skin to make vitamin D from sunlight.

Others who may benefit from screening for vitamin D deficiency include:

• People who don't spend a lot of time in the sun
• Older adults
• People with certain health conditions that make it difficult to absorb vitamin D