At a young age, we were told to eat our fruits and veggies for vitamin C, and drink our milk and play outside for calcium and vitamin D. We mostly did what we were told, but why exactly do we still need vitamins, in particular vitamin D? Most importantly, are we getting enough of the vitamin?

Growing up, our bodies require an adequate amount of vitamin D in order to absorb calcium and promote bone growth. It helps with calcium absorption in the gut and maintains blood calcium levels to allow the normal mineralization of bone, and prevent abnormally low blood calcium levels that can lead to tetany (involuntary contraction of muscles linked to various health conditions), according to the National Institutes of Health.

Too little vitamin D leads to soft bones in children (rickets), and fragile, misshapen bones in adults (osteomalacia). The recommended dose of vitamin D needed is contingent on our age: birth to 12 months need 400 International Units (IU); 1 to 18 years need 600 IU; adults 19 to 70 years need 600 IU; and those 71 years and older need 800 IU. The recommended amount for pregnant and breastfeeding women is 600 IU.

Vitamin D boosts our overall health and promotes strong and healthy bones. It's also seen as an important factor in ensuring our muscles, heart, lungs, and brain are functional, and preps the body to fight infection.

So, how do we get vitamin D?

Sunlight

There are a number of factors that influence how much vitamin D the body produces when the skin is in sunlight. Vitamin D, unlike other vitamins, can be made by the body when the skin is exposed to sunlight. Specifically, large amounts of vitamin D3 are made in the skin when all of our body is exposed to the summer sun, says the Vitamin D Council.

This happens very quickly; around half the time it takes for the skin to turn pink and begin to turn. It's all contingent on our skin color; someone with vary fair skin could take 15 minutes; yet, someone with a darker complexion may need a couple of hours. In fact, our body can produce 10,000 to 25,000 IU of vitamin D in just a little under the time it takes for your skin to turn pink. We make the most vitamin D when we expose a large area of our skin in the sun, such as our back.

Food

Typically, we get most of the vitamins and minerals we need from the food we eat. However, there are only a few foods that naturally contain vitamin D — even those foods only have small amounts, making it impossible to get an adequate amount from a food source. Possible foods to get some vitamin D intake include fatty fish, beef liver, egg yolks, fortified milk and orange juice, fortified cereals, and infant formula.

Supplements

The benefits of vitamin D supplements are still heavily debated. In a 2014 study, researchers evaluated the results of 268 previous studies of vitamin D. They concluded there is “highly convincing evidence of a clear role of vitamin D does not exist for any outcome, but associations with a selection of outcomes are probable.” Simply put: there’s no solid proof vitamin D has benefits outside of promoting strong bones.

However, another 2014 study found low blood levels of vitamin D were linked to increased risks of dying prematurely from cardiovascular disease, cancer, and other causes. It’s not clear if low vitamin D causes chronic conditions, or whether chronic conditions cause low vitamin D levels. We still need to do a little more research on the subject. 

The verdict? Take it at your own risk.

If you rarely get out in the sun, or just aren’t certain you are getting 600 to 800 IU of vitamin D a day, taking a supplement containing 400 to 1,000 IU can be a safe bet for your health.