Vitamin D is a nutrient needed by the body to aid in calcium absorption and prevent muscle cramps and involuntary spasms. It is necessary for proper bone growth and repair during injury. If vitamin D is lacking, bones become weak, brittle, or deformed. Many people associate weak bones with osteoporosis in adults and rickets in children. Vitamin D also plays a role in reducing inflammation in the body.
What is vitamin D deficiency?
Vitamin D deficiency occurs when the body does not get enough vitamin D over a long period. Deficiency results when the amount of vitamin D stored in the body is below the designated level, which may vary depending on where the patient resides.
What causes vitamin D deficiency?
Vitamin D deficiency occurs when someone has a low dietary intake of vitamin D, limited sun exposure, their intestines do not absorb it correctly, or the kidneys or liver do not use it properly.
Other risks include:
- Age: The ability to absorb vitamin D through the skin and organs decreases with age, particularly after age 65.
- Mobility: People who have difficulty moving around struggle to get enough sun exposure to the sun. For example, people who are homebound or living in facilities.
- Location: Areas further from the equator receive less sunlight at certain times of the year, plus people are less likely to spend time outdoors due to cold temperatures. As a result, they cover their skin and cannot absorb vitamin D from the sun.
- Skin color: Dark-colored skin is less able to absorb vitamin D from the sun than fair-colored skin.
- Breast milk: Breast milk only contains a small amount of vitamin D. Infants who are breastfed are at risk of not receiving enough, especially those who receive only breast milk.
- Medications: Some medications cause vitamin D to be processed and passed out of the body too quickly to be used.
- Obesity: Vitamin D deposits in fat tissues and is not used by the body as needed.
- Diseases: Certain diseases can alter the body’s ability to absorb vitamin D, particularly those that affect the digestive system, such as Crohn’s disease, irritable bowel, and liver disease.
- Surgeries: Removal or bypassing the intestines can result in vitamin D deficiency due to altered fat absorption.
- Sunscreen: While sunscreen use is important, it blocks UVB light and vitamin D from the sun.
Symptoms in adults are not easy to spot. Symptoms can include:
- Muscle weakness, aches, cramps, or spasms
- Altered mood, including depression
- Bone pain
In children, symptoms are even harder to see. Muscle weakness can be common. Bone pain can occur, but children cannot report it as easily. Bone deformities cannot require proper testing. Severe vitamin D deficiency leads to rickets in children, which causes altered growth and development.
How is vitamin D diagnosed?
Testing for vitamin D deficiency is not necessary unless low levels are suspected. People who complain of the symptoms above or have medical conditions that put them at risk of deficiency may require a blood test to check their level. Patients with osteoporosis, low calcium or phosphate, or those who have a history of breaking a bone without a reasonable traumatic injury should also warrant testing.
As mentioned above, accepted vitamin D levels may vary depending on where the patient resides. However, most experts agree that levels lower than 20 nanograms/milliliter is less than adequate for bone health.
Treating low vitamin D
When vitamin D is low, it is essential to return levels to at least adequate. Low vitamin D does not allow the body to absorb sufficient amounts of calcium and phosphate, which are needed to help the bones grow and stay strong. These minerals also prevent muscle pain and cramps. Treating low vitamin D is required to avoid pain and injury.
Prevention. Preventing low vitamin D can help maintain optimal bone health for children and adults. Your healthcare provider can advise you to take vitamin D supplements. Supplements are beneficial when diets are poor, and food sources lack sufficient vitamin D (See recommended Nutrition below).
More sun, but not too much. This recommendation often comes with caution, as people tend to overdo sun exposure, do not use proper skin protection, and risks of sunburn and skin cancer are high. However, 10 to 15 minutes of sun exposure two to three times per week may be enough to absorb vitamin D. Prolonged periods in the sun without proper skin protection are not recommended.
Nutrition. Vitamin D levels in food are often low, another reason for inadequate levels. The highest levels are in fatty fish and fortified foods:
- Fish: Salmon, tuna, swordfish, cod liver oil, mackerel, sardines
- Dairy products (fortified with vitamin D)
- Egg yolk
- Fortified cereals
- Orange juice (fortified)
If necessary, your healthcare provider may recommend you use a supplement for low vitamin D or vitamin D deficiency. Supplements are available for children in liquid form and adults in tablets. There are two types of supplements, ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Doses can vary depending on the significance of the deficiency. Your healthcare provider will advise you on the most appropriate and how much to take, most commonly cholecalciferol with a calcium supplement. Supplements are measured in international units (IU), which measure how a substance affects the body and is a consistent measurement across all types around the world.
While rare, too much vitamin D can cause toxicity, meaning a high amount can lead to damaging effects such as:
- Weight loss
- Irregular heartbeat
- Poor appetite
- Hardening of blood vessels
- Increased calcium levels
- Heart and kidney damage
Vitamin D is an important nutrient needed to help the bones grow and stay strong throughout life. Low vitamin D, known as vitamin D deficiency, leads to low calcium and can result in medical problems, including broken bones or deformities. Your healthcare provider can monitor and treat deficiency through supplements. You can take steps to prevent low vitamin D by eating fortified foods and watching sun exposure.
U.S. Department of Health & Human Services. Vitamin D
UpToDate. Patient education: Vitamin D deficiency (Beyond the Basics)
Cleveland Clinic. Vitamin D Deficiency
Harvard T.H. Chan. Vitamin D
American Family Physician. Recognition and Management of Vitamin D Deficiency
National Library of Medicine. Vitamin D Deficiency