Why You Should Pay Attention to Low Vitamin D

March 18, 2025

A woman enjoying the sunshine during the break between exercises

Vitamin D is essential to good health. It helps the body absorb calcium and phosphorus for bone health and supports the immune system.

An estimated 35 percent of U.S. adults are vitamin D deficient. Low vitamin D can raise the risk of bone disease and other health problems, says University Hospitals family medicine doctor William Hein, DO. Studies have shown vitamin D may also play a role in preventing diseases like cancer and heart disease.

Why Is Vitamin D Deficiency So Common?

The sun’s ultraviolet rays trigger vitamin D production in the body. The amount of sun a person needs varies widely and depends on geography, time of year, time of day, skin color and how much skin is exposed. And while it’s important to manage skin cancer risk from unprotected sun exposure, it’s clear that people with limited sun exposure due to climate or lifestyle are at higher risk for vitamin D deficiency.

“The latitude you live at is the largest contributor to vitamin D deficiency,” Dr. Hein says. “People who live in more northern latitudes tend to develop vitamin D deficiency more often than those who live more south.

Other common causes of vitamin D deficiency include:

Certain medical conditions and medications that can trigger low vitamin D, including Crohn’s disease, celiac disease, obesity, osteoporosis and kidney and liver disease.
Gastric bypass surgery can make it harder for the body to absorb vitamin D.
Darker skin tones reduce the amount of vitamin D production from the sun.
Breast-fed babies and older adults are at risk for vitamin D deficiency because the ability to synthesize vitamin D declines with age.

Symptoms of Vitamin D Deficiency

Research suggests that vitamin D can protect against cancer growth. Low vitamin D has also been linked to heart disease, depression and multiple sclerosis (MS). While vitamin D has been proven to support bone health, more research is needed about its effect on chronic diseases.

Symptoms of vitamin D deficiency include:

Osteoporosis
Bone or muscle pain or muscle weakness
Fatigue
Stress fractures
In extreme cases, babies and children can get rickets, which causes weak and soft bones and can lead to deformities.

How Much Vitamin D Do You Need?

For most people, vitamin supplements are the best way to get enough vitamin D. Foods that are rich in vitamin D include:

Fatty fish, such as salmon, tuna, sardines and swordfish
Beef liver
Swiss cheese
Egg yolks
Mushrooms
Fortified foods including cereals, dairy products and orange juice
Cod liver oil

The recommended daily amount of vitamin D varies by age:

Infants: 400 IU (international units)
Ages 1 to 70: 600 IU
Age 70+: 800 IU

These estimates may not be appropriate for people at risk for developing low vitamin D and higher supplemental amounts may be required, says Dr. Hein. “If you have concerns about vitamin D deficiency, always consult your physician first about what level of supplementation may be appropriate for you.”