Vitamin D is commonly known as the “sunshine vitamin.” It’s critical for a range of bodily processes — yet much of the US population isn’t getting enough of it.
From healthy bones to a boosted immune system, vitamin D helps ensure your body stays healthy in several ways.
Getting enough vitamin D can be challenging. Consuming it through food isn’t always reliable. Plus, while sunlight exposure encourages your body to produce vitamin D, exposing your skin to sunlight has risks.
Working an office job, having a darker skin tone, living in a cooler climate, and certain medical conditions can all contribute to low vitamin D stores.
Find out about vitamin D deficiency and how you can avoid it.
Vitamin D deficiency is more common than you might think. Globally, studies suggest roughly one billion¹ people are vitamin D deficient.
In the US alone, 42%² of adults are deficient, while 50%³ of children aged between one and five and 70% of children aged between six and 11 have low vitamin D stores.
The statistics are even higher for people with dark skin. Nearly 63% of Hispanic adults and 82% of African American adults are vitamin D deficient.
Despite high rates, many people don’t know they are vitamin D deficient. This is because the deficiency can mimic other conditions, and general tiredness and symptoms often appear many months or even years after you become deficient.
Vitamin D’s primary role in the body is to help you absorb and maintain calcium and phosphorus. These nutrients are essential for bone growth.
Vitamin D has also been shown⁴ to reduce cancer cell growth, inflammation, and your chance of developing infections.
A study⁵ in 2011, for example, found deficiency correlates with increased autoimmunity and susceptibility to infections.
Long-term vitamin D deficiency is also associated with a range of serious health conditions, including:
Rickets: This condition is commonly associated with infants who do not get enough sunlight. It generally occurs in children and can cause skeletal deformities and soft bones.
Osteomalacia: This condition is linked to severe vitamin D deficiency. Osteomalacia occurs in adults and is associated with weak and softened bones.
Depression: Studies show people with low vitamin D levels are more than twice as likely to be diagnosed with depression. The cause is unknown, but some experts⁶ believe vitamin D alters hormones associated with mood regulation.
Type 1 diabetes: Low vitamin D levels may play a role in type 1 diabetes. Studies have found vitamin D can reduce the risk of developing type 1 diabetes earlier in life. It can also improve glycemic control and insulin sensitivity in people who already have the condition.
Asthma: The severity of asthma and increased inflammatory markers are linked⁷ to low vitamin D levels.
It can be hard to know whether you’re deficient in vitamin D. While there are some common symptoms, many mimic other illnesses, and deficiencies. These include:
Muscle weakness, aches, and cramps
Joint pain (particularly in your back)
The only way to truly know if you’re vitamin D deficient is to speak to your doctor and have blood work done. Your doctor will likely check other nutrient deficiencies and irregularities too. This will give you a greater understanding of your overall health.
Avoiding high doses of vitamin D on the assumption that you are deficient is important. High levels can also harm your health.
To find out if your blood levels are safe, your doctor will assess the amount of vitamin D in your blood.
Vitamin D is measured per liter (nmol/L) or nanograms per milliliter (ng/mL). For most people, 50nmol/L (20ng/ml) or above is a healthy level. Levels below 30nmol/L (12ng/mL) and above 125nmol/L (50ng/mL) may cause health issues.
Your doctor will likely recommend supplementing to boost your intake if you are deficient in vitamin D. Only ever take more than the typical daily limit under your doctor’s guidance.
You may want to ensure you’re getting enough vitamin D, even if you’re not currently deficient. The amount you need depends on your age and how much sun exposure you get.
People aged over 70 years have the highest requirements. Infants have the lowest.
The National Institutes of Health (NIH)⁸ recommends that people aged up to 70 get a rough daily intake of 600 IU (15mcg).
Infants should get 400 IU (10mcg) per day.
People over 70 years should get 800 IU (20mcg) per day.
The NIH considers 4,000 IU daily a safe upper limit of vitamin D.
You should consider the type of vitamin D you supplement with. Two forms of vitamin D exist:
Vitamin D2 (ergocalciferol)
Vitamin D3 (cholecalciferol)
A 2017 study⁹ found vitamin D3 is more readily absorbed. Researchers found D3 raised blood levels of the vitamin significantly more than D2.
You’ll need to consider a few key vitamin D sources to ensure you’re getting enough.
Some foods naturally contain vitamin D, while others are fortified with it. As we’ve seen, the body also produces vitamin D when the skin is exposed to UV rays.
Try these methods for upping your vitamin D intake:
Supplementing is the most reliable and widely recommended method of ensuring you maintain healthy vitamin D levels.
Try to follow the NIH recommendations above when supplementing vitamin D. Follow local recommendations if they exist, as sun exposure varies in different locations and at different times of the year.
Vitamin D is found in some multivitamins in addition to separate supplements. If using a multivitamin, ensure its vitamin D content is sufficient for your needs.
Ask your doctor for their product recommendations.
Skin exposure is another simple and effective way to encourage your body to produce vitamin D.
When you expose your skin to sunlight, the sun’s UV rays interact with a skin protein known as 7-DHC. This is naturally converted into vitamin D.
Ensuring you don’t damage your skin or put yourself at risk of skin cancer during exposure is essential. Consider the UV index in your climate before heading outside.
When the UV index is at three or above in sunny climates or during the summer months, incidental skin exposure for a few minutes each day is likely enough to produce sufficient vitamin D levels.
People who live further from the equator need more sun exposure. You may also need more during the cooler months. In these cases, you might need two to three hours of sun exposure per week.
When the UV index is at three or higher, the Cancer Council recommends using sun protection when spending time outdoors. Consult your doctor before any sun exposure if you already have existing skin damage.
Check for relevant government advice in your local area to decide the best level of skin exposure for you. Wear skin protection if you’re unsure.
People with darker skin tones need more sun exposure. In these cases, supplementation (particularly in climates with less sunshine) will be more important.
Some foods contain vitamin D, but few are reliably high in nutrient. For this reason, it’s generally recommended to focus on supplements or sun exposure to maintain healthy stores rather than foods alone.
The following foods contain vitamin D:
Some fish, including tuna and salmon
Cod liver oil
Getting enough vitamin D is important for your health, but taking too much can lead to toxicity.
The risk of toxicity is generally associated with taking supplements. This is because most foods contain relatively little vitamin D. When it comes to sun exposure, your body naturally prevents the overproduction of vitamin D.
For people over the age of nine, the NIH recommends a safe upper limit of 4,000 IU per day when supplementing, unless you are under medical supervision. Taking more than the recommended dose can lead to health complications.
In 2017, a study¹⁰ found 18% of adults taking vitamin D supplements were taking more than 1,000 IU per day. 3% were taking more than the safe limit of 4,000 IU per day.
Avoid megadosing (taking higher amounts of vitamin D than recommended). Taking too much vitamin D puts you at risk of toxicity.
Some symptoms of toxicity include:
Hypercalcemia: Vitamin D plays a critical role in helping your body absorb calcium. Taking too much vitamin D can cause excessive calcium in the blood. Confusion, apathy, drowsiness, and depression are all signs of hypercalcemia.
Kidney stones: Calcium deposits caused by megadosing vitamin D can result in nephrocalcinosis. This can lead to kidney failure in severe cases.
Bone weakness: Too much vitamin D can prevent the natural interaction of vitamin K2 in the body. This is essential for keeping calcium inside the bones. Megadosing is associated with an increased risk of bone fractures.
Gastrointestinal issues: High levels of vitamin D can lead to gut issues. These include vomiting, ulcers, and abdominal pain.
Other risks of megadosing include headaches, dizziness, appetite loss, thirst, nausea, and fatigue.
Without supplementing, access to sunlight is essential for vitamin D production. People with limited sun exposure have more risk of being deficient.
Office workers, people with darker skin tones, and people who live far from the equator are all at risk. Certain medical conditions can also play a role.
Risk factors for vitamin D deficiency include:
Working in an office during typical work hours means you may get limited sun exposure during the day. This means you may have a higher risk of developing vitamin D deficiency.
A systematic review¹¹ in 2017 found occupations with a high risk of deficiency included:
Understandably, the review found outdoor workers had reduced risk.
If you work indoors, try taking walks outside during sunlight hours. Making an effort to increase your sunlight exposure can be beneficial, and supplementation can also help.
People with darker skin need more sun exposure to produce enough vitamin D. This is because the melanin pigment associated with darker skin tones can absorb UV radiation. Melanin pigment is useful in protecting you from skin damage, but it can also prevent vitamin D production.
Supplementation can be a good option for people with darker skin tones, especially for those who have limited access to sunlight.
Living far away from the equator, whether north or south, can increase your risk of vitamin D deficiency. People who live in climates with limited sunshine hours should consider supplementation and get blood work done regularly — especially during winter.
Absorbing fat is challenging for people with inflammatory bowel disease (IBD). Vitamin D is a fat-soluble vitamin, so absorption depends on your intestine’s ability to process fat.
A report¹² found up to 70% of patients with IBD had insufficient vitamin D levels.
Other health conditions may also affect vitamin D absorption. Talk to your doctor and ask for their advice about managing vitamin D levels with health conditions like IBD.
Vitamin D is critical for a range of bodily processes. It helps maintain bone health and immune function.
Vitamin D deficiency is associated with fatigue, muscle aches, and a range of serious health conditions. It affects roughly one billion people globally, but many are unaware they are deficient.
Request blood work from your doctor to find out if you have vitamin D deficiency. Your doctor will likely recommend supplementation if your levels are too low.
Supplementation is a quick and easy method to ensure you maintain healthy vitamin D levels.
For most people, the recommended daily vitamin D intake is 600 IU.
Getting safe sun exposure is another way to ensure you maintain healthy vitamin D levels, but the length of exposure needed will vary depending on your location’s UV index. Take care when exposing your skin to the sun.
Vitamin D can be toxic when you take too much. Don’t exceed the safe upper limit of 4,000 IU per day unless recommended by your doctor.
Vitamin D (2022)
Vitamin D | Harvard T.H. Chan
Vitamin D | NIH: National Institutes of Health
Daily supplementation with 15 μg vitamin D2 compared with vitamin D3 to increase wintertime 25-hydroxyvitamin D status in healthy South Asian and white European women: a 12-wk randomized, placebo-controlled food-fortification trial (2017)
Vitamin D | Cancer Council
Vitamin D brochure | Cancer Council
Vitamin D | Harvard T.H. Chan
Sun protection and vitamin D | Skin Cancer Foundation
Can too much vitamin D cause hypercalcemia? | CENTER for Advanced Parathyroid Surgery
Chloe Garnham is a writer exploring a broad range of topics, including healthcare, education, and technology.
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