Originally posted in 2021 / Updated October 2024

What Does Vitamin D Do In The Body?

Vitamin D plays a crucial role in maintaining overall health, particularly in supporting bone health, immune function, and mood regulation. It helps the body absorb calcium and phosphorus, essential for building and maintaining strong bones and teeth. Additionally, Vitamin D supports the immune system, helping to fend off infections and reduce inflammation. Playing a key role in mood regulation, vitamin D deficiencies are linked to increased risks of depression and anxiety.

Vitamin D is essential for calcium absorption, which is crucial for maintaining strong bones and teeth. Vitamin D helps the body absorb calcium from the diet, ensuring that bones remain dense and resilient, reducing the risk of fractures and conditions like osteoporosis.

The importance of Vitamin D goes beyond bone health. Studies show that Vitamin D also supports the immune system by enhancing the pathogen-fighting effects of monocytes and macrophages, white blood cells that are critical for immune defense, and reducing inflammation. This anti-inflammatory property also helps in preventing chronic diseases such as cardiovascular disease and diabetes.

Additionally, according to research, the health benefits of Vitamin D include its known ability to improve mood and combat conditions like seasonal affective disorder (SAD). SAD is a type of depression that occurs at certain times of the year, usually in the winter when sunlight exposure is limited. Ensuring adequate Vitamin D levels through sunlight exposure and dietary sources is vital for overall health and well-being.

‌‌‌‌How Much Vitamin D Do You Need?

The recommended daily intake (RDI) of Vitamin D varies based on age. For instance, infants up to 12 months need 400 IU, children aged one through adults aged 70 need 600 IU, and adults 71 and over need 800 IU. Studies show the RDI for Vitamin D is generally the same for both men and women.

Vitamin D can be obtained from two main sources: sunlight and food. Sunlight triggers the production of Vitamin D in the skin, while dietary sources include egg yolks, shiitake and maitake mushrooms, and canned tuna. Fortified foods like orange juice, milk, cereal, and tofu are also rich sources of vitamin D in food.

According to research, getting adequate Vitamin D from sunlight alone can be challenging, especially during winter months when UVB rays are weaker, and daylight hours are shorter. This is particularly true for individuals living in higher latitudes or those who spend most of their time indoors. Therefore, relying solely on sunlight may not be sufficient, and incorporating dietary sources or supplements is often necessary to meet the body’s Vitamin D needs.

Top Foods High in Vitamin D

Here are some foods that are naturally high in Vitamin D.

Fatty Fish

The best fish for Vitamin D include fatty fish like salmon, mackerel, sardines, and tuna. These fish are among the richest sources of Vitamin D due to their high-fat content, which allows them to store more of this fat-soluble vitamin. Studies show these fish accumulate Vitamin D through their diet, which includes plankton and smaller fish that also contain Vitamin D.

A typical serving of fatty fish high in Vitamin D can provide a substantial amount of calciferol; for example, a 3.5-ounce (100-gram) serving of cooked salmon can deliver around 526 IU of Vitamin D, which is about 66% of the daily value. Similarly, mackerel can provide approximately 643 IU per 3.5-ounce serving, and sardines offer around 272 IU per 3.5-ounce serving. This makes fatty fish an excellent dietary source of Vitamin D, especially for individuals with limited sun exposure.

Egg Yolks

Egg yolks are a valuable source of Vitamin D, providing smaller but still beneficial amounts of this essential nutrient. A typical large egg yolk contains about 37 IU of Vitamin D, which contributes to your daily intake.

Free-range eggs, however, offer even higher levels of Vitamin D compared to conventional eggs. This is because free-range hens have more exposure to sunlight, allowing them to produce more Vitamin D naturally. Studies have shown that free-range eggs can contain up to 42% more Vitamin D than those from hens kept indoors. Therefore, incorporating free-range eggs into your diet can be an effective way to boost your Vitamin D intake.

Consider eating egg yolks for Vitamin D and not just egg whites because yolks are the best sources of vitamin D in eggs.

Fortified Foods

Fortified milk, orange juice, cereals, and plant-based milk alternatives like soy, almond, and oat milk are the best-fortified foods for Vitamin D because they are enriched with this essential nutrient during processing. This fortification process involves adding precise amounts of Vitamin D to these foods to help individuals meet their daily nutritional needs.

Fortified milk typically contains about 100 IU of Vitamin D per cup, while fortified orange juice can provide around 137 IU per cup. It’s important to read labels carefully to ensure you’re getting adequate Vitamin D, as the content can vary between brands and products.

By incorporating fortified foods with Vitamin D into your diet, you can help maintain optimal Vitamin D levels and support overall health.

Mushrooms

Certain mushrooms, such as shiitake and maitake, have the unique ability to produce Vitamin D when exposed to sunlight or ultraviolet (UV) light. This process occurs because these mushrooms contain ergosterol, a compound that converts into Vitamin D2 upon exposure to UV light. Research shows that when mushrooms are exposed to sunlight for some time, their Vitamin D content can increase dramatically, making them an excellent plant-based source of this essential nutrient.

UV-exposed mushrooms can provide a substantial amount of Vitamin D2, comparable to the daily requirements recommended for humans. This makes UV-exposed mushrooms a valuable dietary option, especially for individuals who have limited sun exposure or follow a vegan diet.

Mushrooms high in Vitamin D are a great option for people who prefer plant-based Vitamin D foods.

Cod Liver Oil

Cod liver oil is one of the richest sources of both Vitamin D and omega-3 fatty acids. Extracted from the liver of Atlantic cod, it is one of the best supplements for Vitamin D, and omega-3 fatty acids, which are known for their anti-inflammatory properties and benefits for heart health.

Each teaspoon of cod liver oil contains about 56% of the daily value for Vitamin D and 890 milligrams of omega-3 fatty acids. For individuals at risk of Vitamin D deficiency, studies show taking cod liver oil can help maintain adequate levels of this vital nutrient. Additionally, studies show the omega-3 fatty acids in cod liver oil can help reduce inflammation and support cognitive function.

These are all great reasons to support a decision to take cod liver oil for Vitamin D.

‌‌‌‌What Are The Signs and Symptoms of Vitamin D Deficiency?

What are the best ways to get an adequate amount of vitamin D? One way is through exposure to sunlight. Just 10-15 minutes of sunlight exposure can provide 3,000-20,000 IU. The problem is that the amount of vitamin D we get from sun exposure varies considerably depending on several factors including geographic latitude and skin color. Sunlight is generally weaker in northern latitudes, leading to less vitamin D synthesis. Also, people with darker skin tones generally need a lot more sun exposure to synthesize vitamin D, as melanin reduces the skin’s ability to produce vitamin D from sunlight. 

Vitamin D deficiency has reemerged as a global health concern. About one billion people worldwide have vitamin D deficiency. Some experts believe that low intake of the vitamin coupled with behaviors that limit UV-light exposure (such as time spent indoors, the use of sunscreen, and the use of protective clothing to fully cover the skin) have resulted in widespread inadequate vitamin D status. Elderly people and individuals who are hospitalized or reside in nursing homes are especially at risk. Not only do many of them have inadequate sun exposure, but they also may have limited dietary intake and/or impaired kidney function, which limits the conversion of vitamin D to its active form.      

Many patients with vitamin D deficiency are asymptomatic. Others may experience signs or symptoms such as muscle pain or cramps, bone pain, weakness, fatigue, and mood changes. With prolonged vitamin D deficiency, infants and children can develop rickets, a condition characterized by soft bones and skeletal deformities such as bowed legs. In adults, prolonged vitamin D deficiency can cause osteomalacia, which is characterized by weak, soft bones and can result in frequent fractures.

‌‌‌‌Vitamin D Supplements

If you are concerned that you are still not getting enough vitamin D through sun exposure and food sources, you can take a vitamin D supplement. The vitamin D found in supplements comes in two different forms: vitamin D2 (ergocalciferol), which comes from plant sources, and vitamin D3 (cholecalciferol), which comes from animal sources. Both are well absorbed in the gut and increase vitamin D levels in the blood. However, most evidence indicates that vitamin D3 raises blood levels of the vitamin more and sustains those levels longer than D2.

Who Needs More Vitamin D?

Certain groups are at higher risk for vitamin D deficiency and should consider taking a supplement. These groups are: 

• Breastfed infants: Human milk is a poor source of vitamin D.
• Older adults: Their skin is less efficient at making vitamin D when exposed to the sun and their kidneys don’t convert the vitamin to its active form as well. 
• People with limited sun exposure, such as individuals who are homebound, hospitalized, or nursing home residents, those who wear sun-protective clothing, and those with occupations that limit time outside. 
• People with dark skin: Melanin in the skin reduces the skin’s ability to make vitamin D.
• People with conditions that limit fat absorption, such as cystic fibrosis, Crohn’s disease, or celiac disease: Vitamin D needs fat to be absorbed properly in the gut.
• People who are obese: Body fat binds some of the vitamin D, preventing it from getting into the blood.
• People who have had gastric bypass surgery: Part of the upper small intestine where vitamin D is absorbed gets bypassed after surgery.

Vitamin D deficiency risk groups include people who live in northern latitudes or areas with little sunlight, individuals with darker skin tones, older adults, pregnant women, and those with health conditions like celiac disease or Crohn’s disease.

Research shows that these populations may struggle to produce sufficient Vitamin D from sunlight or absorb it effectively from their diet. Monitoring Vitamin D levels in these groups is crucial to prevent deficiencies that can lead to serious health issues such as osteoporosis, weakened immune function, and other chronic conditions. Regular testing and appropriate supplementation can help maintain optimal health and prevent long-term complications.

‌‌‌‌Vitamin D Toxicity

Vitamin D can be harmful when amounts in the blood become too high. The Tolerable Upper Intake Level (UL) is the maximum daily intake of a nutrient that’s unlikely to cause harmful effects on health. The UL for vitamin D for adults and children ages 9+ is 4,000 IU. 

When vitamin D toxicity occurs, it is typically from taking supplements. The low amounts of vitamin D found in foods are unlikely to reach a toxic level. And prolonged sun exposure is unlikely to cause toxicity because the body has inherent mechanisms to limit the amount of vitamin D it produces. 

Symptoms and signs of vitamin D toxicity include nausea, vomiting, lack of appetite, constipation, weight loss, weakness, confusion, irregular heartbeat, and damage to the heart and kidneys. It is advised to not take daily vitamin D supplements containing more than 4,000 IU unless it’s under the supervision of your doctor.

Conclusion

In this article, we discussed how to increase Vitamin D levels and natural ways to get Vitamin D. Incorporating Vitamin D-rich foods, such as fatty fish, egg yolks, mushrooms, and fortified foods into your diet is essential for maintaining optimal health.

If you find it challenging to get enough Vitamin D from food alone, especially during winter or in areas with low sunlight exposure, consider taking Vitamin D supplements to ensure you meet your daily requirements and Boost vitamin D naturally.

Maintaining optimal Vitamin D levels is crucial for long-term health benefits, including strong bones, a robust immune system, and overall well-being. Regularly monitoring your Vitamin D levels and making necessary dietary or supplemental adjustments can help you stay healthy and vibrant.

References:

1. Office of Dietary Supplements. Vitamin D - Health Professional Fact Sheet. National Institutes of Health. Updated March 24, 2023. Accessed September 25, 2024. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
2. Chauhan K, Shahrokhi M, Huecker MR. Vitamin D. [Updated 2023 Apr 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441912/
3. Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532266/
4. Office of Dietary Supplements. Vitamin D - Consumer Fact Sheet. National Institutes of Health. Updated March 24, 2023. Accessed September 25, 2024. https://ods.od.nih.gov/factsheets/VitaminD-Consumer/
5. Cortese M, Riise T, Bjørnevik K, et al. Timing of use of cod liver oil, a vitamin D source, and multiple sclerosis risk: The EnvIMS study. Mult Scler. 2015;21(14):1856-1864. doi:10.1177/1352458515578770
6. Cardwell G, Bornman JF, James AP, Black LJ. A Review of Mushrooms as a Potential Source of Dietary Vitamin D. Nutrients. 2018;10(10):1498. Published 2018 Oct 13. doi:10.3390/nu10101498
7. Institute of Medicine (US) Committee to Review Dietary Reference Intakes for Vitamin D and Calcium; Ross AC, Taylor CL, Yaktine AL, et al., editors. Dietary Reference Intakes for Calcium and Vitamin D. Washington (DC): National Academies Press (US); 2011. 3, Overview of Vitamin D. Available from: https://www.ncbi.nlm.nih.gov/books/NBK56061/
8. Martens PJ, Gysemans C, Verstuyf A, Mathieu AC. Vitamin D's Effect on Immune Function. Nutrients. 2020;12(5):1248. Published 2020 Apr 28. doi:10.3390/nu12051248