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Cedars-Sinai Blog

Understanding Vitamin D Deficiency

A man soaking in sunlight to get vitamin D.

Vitamin D, sometimes called the "sunshine vitamin," plays a key role in your health. Do you get enough of this vital nutrient?

"For younger people, if you eat a well-balanced diet, you can probably get enough vitamin D from your diet to maintain bone health."

Why do we need vitamin D?

Vitamin D is essential for bone growth and promotes calcium absorption in the gut. 

It’s produced when your skin is exposed to ultraviolet rays from sunlight, triggering vitamin D synthesis, and lack of sun exposure is a leading cause of vitamin D deficiency.

"We are seeing more patients with vitamin D deficiency," says Dr. Lacy Knowles, primary care physician at Cedars-Sinai in Los Angeles.

"People now spend more time indoors. Also, people are better about putting on sunscreen and wearing sun protection. This all leads to taking in less vitamin D."

Vitamin D is naturally found in some foods, such as salmon and egg yolks, and added to others, such as vitamin-D fortified milk. 

How much daily vitamin D you need?

For adults ages 18 to 65, make sure you're getting 800 international units (IU) of vitamin D daily. Adults over 65 need 1,000 to 2,000 IU of vitamin D every day.

At the same time, health experts caution against taking too much vitamin D. According to the National Capital Poison Center, a large excess intake of vitamin D over a long period of time can cause vitamin D poisoning—which can result in kidney damage and high blood pressure.

Dr. Knowles says dietary sources of vitamin D are the best absorbed and best utilized, but it can be difficult to get the full requirement from diet alone. Supplements can help make up for the deficiency in our diets.

"For younger people, if you eat a well-balanced diet, you can probably get enough vitamin D from your diet to maintain bone health," Dr. Knowles says.

Taking vitamin D supplements

Lack of vitamin D in the elderly population could lead to falls and minor fractures. A diet low in vitamin D may be one of the causes of osteoporosis.

If you're in your 60s or older, Dr. Knowles says you should take vitamin D supplements to support bone health.

"As we get older, we naturally spend more time indoors and don't synthesize vitamins as well," Dr. Knowles says.

In the winter months, Dr. Knowles says you don't necessarily need to take a vitamin D supplement, but you should try to include a little bit more vitamin D in your diet.

"If you don't like to eat foods high in vitamin D, taking 600-800 units of vitamin D in the winter is not going to hurt," Dr. Knowles says.