Vitamin D Deficiency and How to Avoid It

If you've ever wondered why you feel happy after spending an afternoon outdoors, the answer could be as simple as sun exposure. Vitamin D, supplied by sunlight, contributes to many aspects of our physical and mental wellbeing.

But many people do not get enough vitamin D. In fact, vitamin D deficiency is commonly reported worldwide. Read our guide to find out why vitamin D is so important to your health and how to make sure you’re getting enough.

Vitamin D is an essential nutrient required for healthy bones, teeth, immunity, and overall health.1 Unfortunately, in the past several decades, vitamin D deficiency has become a global epidemic, leading to increased risks of:2 3

Vitamin D contributes to the body’s ability to absorb calcium, which is why you’ll find many milk products fortified with it. It also aids cellular communication and immunity. Getting the right amount of vitamin D is crucial for physical and mental health.

The primary source of vitamin D is the sun. Direct, bare-skin sun exposure to UVB light provides adequate vitamin D for many people. Still, there are several reasons for deficiencies, including variations in skin type and residence location. Vitamin D supplements are the secondary source of attaining this nutrient, followed by diet. Few food sources provide adequate amounts of vitamin D, but you will find it in:1

• Fortified milk and milk alternatives (almond, soy, oat, etc.)
• Fortified breakfast cereals
• Mushrooms
• Beef liver
• Egg yolks
• Cheese
• Fatty fish (salmon, tuna, trout, mackerel)
• Fish liver oils

Vitamin D plays a vital role in many bodily functions, from cellular communication to calcium absorption. It supports bone and heart health and assists with blood sugar regulation. Some of the fundamental reasons to ensure you're getting sufficient vitamin D include:

Those with dark skin

Pale people absorb sunlight and produce vitamin D faster than darker-skinned individuals. Thus, vitamin D deficiency is more common for those with darker skin.

This is because melanin, the pigment that determines skin color, prevents ultraviolet UVB rays from penetrating and absorbing into the skin. People with more melanin need more sun exposure to attain the same amount of vitamin D as someone who is fair-skinned.

Those who live far from the equator

People who live in the upper regions of North America, including parts of the United States and Canada, experience less sun exposure, which often leads to vitamin D deficiency. This applies globally as well: the further you live from the equator, the less direct sunlight you receive, and in turn, you produce less vitamin D.

Sun exposure varies with the seasons, with those living in regions near the American Northeast (New York, Boston, etc.) unable to produce much vitamin D from November through March. You can produce vitamin D almost year-round in southern regions, including Florida.

In the southern hemisphere, you experience less sun exposure in June in places like Buenos Aires. In Cape Town, there's little sun exposure between mid-May and August, for example.

Older people

As we age, our skin becomes thinner and less capable of producing vitamin D from sunlight. Older individuals are also prone to weaker bones, so vitamin D supplementation is essential in preventing fractures.

Babies and pregnant people

When you're pregnant, your body can become depleted of vitamin D, leading to a deficiency in both you and your child. Vitamin D supplementation is recommended for those who are pregnant or nursing.

Vitamin D is crucial for children, as a deficiency can lead to rickets, a softening and weakening of bones that can lead to pain and deformity.

Obese individuals

Obesity correlates with a high prevalence of vitamin D deficiency, contributing to negative overall health impacts, including psychiatric, autoimmune, and neurodegenerative diseases.4

Those living in polluted or sun-deprived environments

Living in urban areas with significant smog cover or foggy areas with little sunlight can lead to vitamin D deficiency. Individuals living in environments without much sun exposure should consider vitamin D supplements and incorporate more fortified foods into their diet.

Symptoms of vitamin D deficiency include the following:3

• Fatigue
• Achy bones
• Muscle weakness and cramps
• Mood changes and depression

Some individuals may not experience any symptoms yet have a deficiency. Others may feel significantly debilitated from a lack of vitamin D. The only way to know if you have a deficiency is to ask your doctor to test you.

Your doctor can perform a vitamin D test that indicates your 25(OH)D levels. This simple blood test is easy and might be a standard assessment for blood work during your yearly physical. Today, you can also purchase at-home testing kits from many providers. These kits generally involve taking a finger-prick sample that you mail to the lab. You’ll receive your results in 2-3 weeks in most cases.

What do the numbers mean?

Having too little or too much vitamin D in your blood can indicate health risks. You should discuss your results with your doctor to determine the best path forward.5

• High vitamin D saturation: above 50ng/mL
• Adequate levels: 20 to 50ng/mL
• Inadequate levels: 12 to 20ng/mL
• Deficient levels: 12ng/mL or below

Sunlight

Direct sunlight exposure with at least 25% of your body uncovered is the best way to naturally produce vitamin D. However, several factors will affect how much vitamin D your body makes.

Lastly, you don't want to overdo it. You should aim to get half the sun exposure that it would take for a sunburn.

Indoor tanning

Indoor tanning beds are one option for individuals who live in locations where sun exposure is limited. Keep in mind: while the body does produce vitamin D from tanning beds, dermatologists no longer recommend their use based on skin cancer risks.6

Notes on skin protection

Spending too much time in the sun can burn the skin and increase the risk of skin cancer. You should spend a moderate but frequent time in sunlight, no more than half the time it takes you to burn, and then cover up and move to the shade.

Sunscreen that blocks UVA and UVB light may be necessary for fair-skinned and sun-sensitive individuals, but it has not proven effective in preventing basal cell carcinoma. Babies and young children are prone to burning in the sun, so dermatologists recommend giving them supplements instead of risking sun damage. The same applies to anyone with a history of cancer or sun sensitivity.

Supplements

Vitamin D supplements are an effective solution for most individuals with a deficiency. You'll see the daily recommended allowances for different age groups in the chart below.5

The recommended allowances above are from the Food and Nutrition Board and are the official recommendations from the US government. Other organizations, including the Vitamin D Council, recommend higher dosages.

The chart below indicates the upper limits for vitamin D supplementation. Again, these levels vary by organization. This chart shows limits set by the US Food and Nutrition Board.5

Vitamin D is fat-soluble, so your body has difficulty getting rid of excess. And while these upper limits may seem like a lot, it's essential to keep in mind that the body produces as much as 25,000IUs of Vitamin D from full-body sun exposure.

Vitamin D toxicity occurs when an individual intakes 40,000IU daily for over two months. And the Food and Nutrition Board allows pregnant or lactating women to intake higher amounts than non-pregnant individuals.

People with certain diseases and health conditions benefit from intaking higher levels of vitamin D, including those with prostate cancer and multiple sclerosis. If you live with these conditions or others that may benefit from a higher vitamin D intake, you should consult your doctor to determine a safe amount. Higher intake levels may also mean more frequent tests to ensure that your blood levels stay within a healthy range.

The Vitamin D Council and other organizations recommend taking Vitamin D3 supplements over Vitamin D2 supplements because the body more readily absorbs them. Vegans and vegetarians should be aware that Vitamin D3 supplements are not vegetarian. For these individuals, Vitamin D2 supplements may be a viable option.

Lastly, cod liver oil supplements contain vitamin D, but they also include high levels of vitamin A, which can be harmful.

Vitamin D does not occur naturally in many foods, so supplementation is essential if you live in an area with poor sunlight exposure. The chart below shows some foods that contain vitamin D.3