Vitamin D Deficiency: What You Should Know

Vitamin D is an extremely important vitamin for your skin and beauty, bones and strength, and overall health and immunity. When an estimated 1 billion people worldwide have a vitamin D deficiency, it’s important to know what vitamin D is, how to know if you are lacking this vital vitamin, and what you can do about it.

What is Vitamin D?

Vitamin D is a fat-soluble vitamin, meaning it can travel into your blood circulation and be stored in your body’s tissues. It is the only vitamin that can be produced in the body on its own, making it more of a hormone than a vitamin. It does so when your skin has direct sun exposure, and it can also be found in some food sources as well as vitamin D supplementation.

The Sunshine Vitamin D3

Once your body takes in vitamin D, chemical processes in your liver allow it to be absorbed into your blood. Your blood then directs it through your tissues and in your kidney where it turns into activated vitamin D, also known as calcitriol. In this activated form, it now supports the calcium supply and absorption by your blood, bones and gut, and helps the cells in your body grow and function properly. Here’s how vitamin D works in the body from any of the 3 sources.

How the body processes vitamin D

How To Know If You Are ‘D’eficienct?

As vitamin D plays a pivotal role in your body, it is important to ensure your body gets enough of it. However, research has shown that a large percentage of people do not.

Your geographic region plays a large role on your ability to get vitamin D from sunshine. The Harvard Health blog states that outside of summer there is little to no chance of getting vitamin D from the sun for those at latitudes above 37 degrees north (a high percentage of the US), or below 37 degrees south of the equator. See the map of the US below to see if your area falls into this category.

Latitude and vitamin D deficiency

But it’s not just those below the 37th degree that can be vitamin D deficient. Even in sunshine states like southern California deficiency is prevalent due to the extensive use of (and need for) sunscreen. Also, anyone who does not spend sufficient time in the sunlight (and the recommended time varies due to a variety of factors) can have a vitamin D deficiency. For instance, those with darker skin have a greater chance of being deficient because skin pigments act as natural sun protection. One study showed that a black man in Chicago needs at least 90 minutes, 3 times a week in the sun to produce the same amount of vitamin D as a white man in Chicago can in 15 minutes, 3 times a week. When sun exposure is simply not an option, natural food sources, vitamin D fortified foods and supplementation are options.


5 Signs you May Have a Vitamin D Deficiency

Because of the prevalence of vitamin D deficiency and the role it plays in your body, it’s important to know the signs. If you think you might be missing out on vitamin D, connect with your doctor about getting tested for the next steps. Here are 4 signs that your body might have a vitamin D deficiency.

1. Weak Bones or Muscles

Vitamin D has been most heavily researched for its connection to bone and muscle strength, concluding that vitamin D deficiencies increase the risk of fractures in older adults. Vitamin D ensures the body is able to absorb calcium and phosphorus, critical elements to building strong bones. In a review of 12 fracture prevention trials with 40,000 elderly individuals, researchers found that high intakes of vitamin D supplementation (800 IU per day) reduced hip and non-spinal fractures by 20%. Muscle strength to prevent falls and fractures was greater in those with sufficient vitamin D. [1]

2. Depression

SAD, or Seasonal Affective Disorder, is a mood disorder characterized by depression that usually occurs during the winter months. It is related to the decrease in sunlight your body is getting. This can cause a drop in serotonin, our body’s chemical contributor to well-being and happiness, which studies have found rise with exposure to bright light and fall with reduced exposure to light. However, the drop in mood doesn’t only relate to the drop in serotonin, but can also be due to the vitamin D your body is missing during winter months. One longitudinal study from 2006 on 80 elderly participants found that those with the lowest levels of vitamin D were 11 times more prone to depression. [2]

3. Poor Skin Health

Vitamin D plays an important role in protecting skin cell health, reducing wrinkles, improving skin softness and maintaining a smooth, glowing complexion. At the same time, UV rays from extensive sun exposure can harm the health of your skin cells and in fact be dangerous to your health. It is important to be careful to find the right balance, and we’ll discuss more on this below.

Calcitriol, the activated form of vitamin D, is essential to skin cell growth, repair and metabolism in the renewal process. As your skin cells are constantly dying, keratinocytes (which account for 95% of all the cells in your epidermis) are the center that keep your skin cells dividing and differentiating in order to constantly regenerate. This activity creates the structure of your skin that locks in moisture and keeps your skin hydrated. Vitamin D is vital to keep this process running smoothly so your cells are renewing and your skin appears healthy and smooth. [3]

4. Acne or Eczema

Part of this process extends to issues with acne or eczema when you have a vitamin D deficiency. Because vitamin D is a hormone, a deficiency can likely have an affect on your other hormones and a hormone imbalance is possible. In addition, proper vitamin D levels stimulate your T-cells to fight infection, including the acne bacteria. Vitamin D is also known to cool inflammation and control your insulin response, helpful in reducing severe skin conditions such as acne or eczema.

One study on oral vitamin D supplementation found the clinical improvement of patients with atopic dermatitis, or the inflammation of skin known as eczema. Vitamin D may also impact sebocytes, cells in your body that that excrete oil, by producing proteins with antibacterial properties. [4]

5. Weakened Immunity

A vitamin D deficiency can play a role in autoimmune diseases (when the immune system attacks its own organs and tissues) such as Multiple Sclerosis (MS), Type 1 Diabetes, or Irritable Bowel Syndrome. Researchers have found MS rates to be higher far north or far south of the equator where exposure to sunlight is more limited. One Finnish study found that children who regularly took vitamin D supplements during infancy had a 90% lower risk of developing type 1 diabetes than those who did not.

Vitamin D can also play a role in your body’s response to infectious diseases like the flu, common cold, or tuberculosis. Calcitriol is known to boost the immune cell production of microbe-fighting proteins, and researchers found that adults with low D levels were more likely to report having a recent cold, cough, or upper respiratory infection. [5]

Vitamin D supplementation can prove further benefits for women. One study by researchers in Iran found that a bacterial infection in the vagina, Bacterial Vaginosis (BV), was effectively cured with vitamin D supplementation. [6]


What to Do if you Have a Vitamin D Deficiency

If you believe you may have a vitamin D deficiency, we recommend speaking with your doctor to get your vitamin D levels tested. Here are a few preventative and restorative steps you can take naturally on your own.

Sun Exposure

Of course direct sun exposure makes the most sense in terms of boosting your vitamin D levels but there are a number of factors that can make this not a viable option. Winter months, cold climates and busy workdays can make the daily recommended sun exposure impossible. Even during the summer, SPF greater than 8 blocks the ability of your skin to absorb vitamin D3 so it can be difficult to get the sun nutrients without exposing yourself to the dangers of overexposure.

The best way to prevent a vitamin D deficiency by getting it from sunlight is spending just enough amount of time exposed to UV rays without the need to tan or burn your skin. Here are a few factors to consider:

– Time of year & time of day: The closer to midday, the more vitamin D your body is exposed to. Here’s a tip: make sure your shadow is shorter than your actual height to get optimal D exposure.

– Color of your skin: As mentioned earlier, the fairer your skin the less time you need to be in the sun to absorb UV rays and the darker the skin, the more time you will need scaling from 15 to 90 minutes.

– Amount of skin you expose: The more skin you expose, the more vitamin D you can produce. Forearm exposure is best for vitamin D uptake (not your face.)

– Factors the block UVB: Glass blocks UVB but not UVA, so it is not safe to attempt to get your daily sunshine vitamin from through a window. In addition, sunscreens with SPF ratings greater than 8 effectively block the synthesis of vitamin D in the skin.

– Note for tanning: Use low-pressure beds with a good amount of UVB light rather than high-intensity UVA light.

Food Sources

It is possible to get some vitamin D from a few food sources, though it can be extremely difficult to get your recommended levels. Fish is an especially helpful supply, particularly salmon and mackerel from wild seas and when low in mercury. In addition, mushrooms grown with exposure to UV light (vs. the many mushrooms grown in the dark which would not provide vitamin D) are also a food source. In addition to these, some milk and yogurt fortified with vitamin D (nearly all cow’s milk in the US is fortified) can help you reach your recommended levels, but likely not on their own: an 8 oz. glass of milk contains at least 100 IUs, and a 6 oz. yogurt usually contains 80 IUs.


In cases when it is not possible to get vitamin D through sun exposure, supplementation is recommended for a vitamin D deficiency. There are 2 forms of vitamin D used in supplements: D2 (ergocalciferol) or D3 (cholecalciferol). The D3 is the same chemically as produced in the body and so the preferred form.

Vitamin D is measured in IU, the International Unit which is usually used to measure fat soluble vitamins including A, D and E. Although the recommended dose of vitamin D is up for debate among medical professionals, the upper limit notes the degree to which safety is assumed an is at 4,000 IU per day. At HUM, based on an analysis of the research and recommendations by our top nutritionists on efficacy, our vitamin D supplement Here Comes the Sun contains 2,000 IU per day of the superior form of cholecalciferol.

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