Vitamin D: deficiency and source in food, the sun, and supplements.

How to Prevent Vitamin D Deficiency with Food, Sun, and Supplements

Vitamin D deficiency is a common worldwide problem and a nutrient deficiency of concern according to the Center for Disease Control and Prevention (1). This article explores the role of vitamin D in health, symptoms of deficiency, and sources of vitamin D — naturally occurring and fortified in food, the sun, and supplements.


Vitamin D is also known as calciferol and is found in some foods or added to others. It is also available in supplement form. Additionally, it comes from the sun — when ultraviolet rays contact the skin, vitamin D production is triggered. Many bodily functions require vitamin D (2, 3).

  • Bone health: Vitamin D is needed for bone growth and helps calcium, the main component of bone, get absorbed in the gut. 
  • Maintains a steady amount of calcium and phosphate levels to strengthen bones and prevent involuntary muscle contraction.
  • Reduces inflammation.
  • Regulates cell growth, blood sugar breakdown, muscle, and immune function. 


The table below shows the Recommended Dietary Allowance (RDA) for Vitamin D, listed in both micrograms (mcg) and international units (IU); 1 mcg of vitamin D = 40 IU (3). The RDA assumes that people get minimal sun exposure.

0-12 months*10 mcg (400 IU)10 mcg (400 IU)
1-13 years15 mcg (600 IU)15 mcg (600 IU)
14-18 years15 mcg (600 IU)15 mcg (600 IU)15 mcg (600 IU)15 mcg (600 IU)
19-50 years15 mcg (600 IU)15 mcg (600 IU)15 mcg (600 IU)15 mcg (600 IU)
51-70 years15 mcg (600 IU)15 mcg (600 IU)
> 70 years20 mcg (800 IU) 20 mcg (800 IU) 
RDAs for vitamin D by age group

*Adequate Intake (AI) is established when evidence is insufficient to develop an RDA. 


Adequate vitamin D, but not too much, is important for health. Vitamin D deficiency presents as rickets in children. In adolescents and adults, deficiency leads to osteomalacia, a condition that softens the bones. Signs and symptoms of these conditions include (2, 4, 5).

Symptoms of vitamin D deficiency: bone deformities, developmental delays in children; muscle pain, weakness, and spasms; joint pain; mood disorders, fatigue, seizures, dental abnormalities

People at risk for deficiency

Consumption of vitamin D through diet and sun exposure may be enough to maintain optimal vitamin D levels. However, the following groups are at risk for deficiency and would benefit from a dietary supplement (3, 6):

  • Breastfed infants: The mother’s vitamin D status affects vitamin D content in human milk.
  • Infants younger than 6 months: Parents avoid direct sun exposure for babies per expert guidelines.
  • Older adults: The skin’s ability to make vitamin D diminishes with age and older people are likely to spend more time indoors compared to younger people.
  • Limited sun exposure: This includes people who are homebound and patients in hospitals and nursing homes. 
  • Darker skin: Higher melanin pigment in the skin lessens the skin’s ability to make vitamin D from the sun.
  • People with fat malabsorption: Medical conditions such as celiac disease, Crohn’s disease, cystic fibrosis, certain forms of liver disease, and ulcerative colitis affect the gut’s ability to absorb fat. Fat is needed because vitamin D is a fat-soluble vitamin.
  • Weight loss surgeries: Reduction and/or bypassing of the stomach and small intestine make it difficult to absorb adequate nutrients.
  • Higher fat stores: Vitamin D is a fat-soluble vitamin and higher fat stores can keep it isolated from the bloodstream.
  • Kidney and liver disease: These conditions reduce the amount of enzyme required to convert vitamin D to the active form used by the body.


Food is a vitamin D source that can help prevent deficiency. However, vitamin D doesn’t naturally occur in many foods. This is why some foods are fortified with vitamin D.

While foods that naturally have vitamin D help increase vitamin D levels, it is not sufficient enough without the use of fortified foods or supplements in the absence of sun exposure (7).

The infographics below show select foods and their vitamin D content in micrograms (mcg) and international units (IU). The percent daily value (%DV) is also listed.

The % DV is how much a single serving of a nutrient in a packaged food or supplement contributes to your daily diet. A percent daily value of 20% or more is considered high. However, foods with lower amounts still help provide some vitamin D and have other health benefits.


Fish is a natural source of vitamin D. However, the amount of vitamin D in fish varies by type of fish and even by species as feed, growth, and season are also factors (7).

Vitamin D in food - fish: cod liver oil, trout, salmon, sardines, tuna

Other animal and animal products

Other animals and animal products: milk, egg yolk, beef liver, cheddar cheese, chicken breast

Plant sources

Plant and cereal - mushrooms; oat, soy, and almond milk; fortified cereal

Other foods with vitamin D

Other foods typically fortified with vitamin D include yogurt and orange juice and range from 10-20% of daily value. Read the food label so you know how much you’re getting.


  • Add fish to your rotation of protein entrees. 
  • Egg, salmon or tuna salad on toast, crackers, or leafy greens. 
  • Include milk or yogurt with breakfast or snack. 
  • Make a dip with plain yogurt and seasonings or herbs. 
  • Add raw mushrooms to salad.  
  • Cook mushrooms with eggs, pasta, or stir fry. 
  • Use up vegetables and add to eggs to make a quiche or frittata.


The sun is a natural source and is another way to prevent vitamin D deficiency. The sun’s UV-B light makes vitamin D when exposed to skin.  While most people get some vitamin D through sun exposure, the following factors affect how much vitamin D your skin can make (3): 

  • Season 
  • Location — places near the equator get more sun
  • Time of day
  • Clouds 
  • Smog 
  • Melanin content in your skin
  • Age — the skin’s ability to produce vitamin D diminishes with age
  • Sunscreen 

Researchers and experts recommend getting 5-30 minutes of sun exposure daily or twice a week at minimum, without sunscreen. Sitting indoors by a window that gets sun won’t count as UV-B rays cannot penetrate glass. Beyond that, experts recommended wearing sunscreen and limiting sun exposure to prevent skin cancer and aging skin (3).


What’s the difference between vitamin D2 and D3?

Supplementation for high-risk groups and people who don’t get enough sunlight and vitamin D in their diet can help prevent deficiency (3, 8). Vitamin D supplements come in two forms, D2 and D3; the table below compares the two:

Vitamin D2Vitamin D3
also known as ergocalciferolalso known as cholecalciferol
plant basedanimal based
need a prescription to getavailable over the counter
Vitamin D2 and D3

Both forms of vitamin D raise the body’s vitamin D levels. But most research shows that vitamin D3 raises vitamin D levels to a higher degree and lasts longer in the body compared to vitamin D2 (3, 9). There is ongoing debate and research on this topic (3, 10). Discuss any concerns you have about supplementation with your doctor.

Supplement interactions with medications

Vitamin D supplements may interact with some medications listed below (3). Speak with your doctor if you’re on these medications.

  • Orlistat: a weight loss medication that when combined with a low-fat diet, can reduces vitamin D absorption.
  • Statins: medications that lower cholesterol. Cholesterol is needed to make vitamin D and statins may reduce vitamin D production.
  • Steroids: medications that reduce inflammation. Steroids may reduce calcium absorption and interrupt vitamin D metabolism.
  • Thiazide diuretics: a type of diuretic. Thiazide diuretics and vitamin D both increase calcium absorption. Taken together may result in an abnormally high level of calcium in the body and affect the kidneys.


Consuming foods that contain vitamin D and getting sun exposure helps prevent vitamin D deficiency. However, supplementation is needed for people in at-risk categories and those who don’t eat enough vitamin D in their diet or get enough sun. Talk to your doctor if you have any concerns with your vitamin D status.

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