What Does Vitamin D do for Your Body?

August 28, 2023


by: Claudia Cesarotti

Home / Blog / What Does Vitamin D do for Your Body?

In recent years, a spotlight has been shone on Vitamin D, often dubbed the “sunshine vitamin.” Despite its essential role in bone health, immune function, and overall well-being, a staggering number of US children and adults find themselves deficient.

Approximately 42% of adults and up to 70% of children between the ages of 6 and 11 fall short of the recommended Vitamin D levels. But why is this deficiency so widespread in a developed nation like the US?

Several factors contribute to this widespread deficiency. For one, modern lifestyles often mean more time spent indoors, away from the natural sunlight that helps our bodies produce Vitamin D. While certain foods contain Vitamin D, they are not always a staple in the average American diet.

As the implications of Vitamin D deficiency become clearer, from weak bones in children to fatigue and mood changes in adults, it is crucial to address this silent yet pervasive issue. Recognizing the factors leading to this deficiency is the first step towards ensuring everyone receives their daily dose of Vitamin D from the sun, diet, or supplements.

Benefits of Optimal Vitamin D Levels

1. Bone Health:
  • Calcium Absorption: Vitamin D facilitates calcium absorption in the gut, essential for maintaining healthy bones and teeth.
  • Bone Remodeling: Vitamin D plays a role in bone remodeling, replacing old bone tissue with new tissue.
  • Prevention of Osteoporosis: Adequate Vitamin D levels can help prevent osteoporosis, a condition characterized by brittle and fragile bones.
2. Mood Regulation and Brain Health:
  • Evidence suggests that Vitamin D can regulate mood and ward off depression. Some studies have found that low levels of Vitamin D seem to be correlated with increased symptoms of depression.
  • Vitamin D receptors are found throughout the brain, indicating its role in brain health.
3. Supporting Diabetes Management:
  • There’s emerging evidence that Vitamin D might play some role in the regulation of insulin and the management of diabetes.
4. Muscle Function:
  • Adequate Vitamin D levels are essential for muscle function, and deficiency can lead to muscle weakness and pain.
5. Immune System Support:
  • Vitamin D enhances the pathogen-fighting effects of monocytes and macrophages — white blood cells that are essential immune system defenders.
  • It also decreases inflammation.

How do you know if you are getting enough Vitamin D? A simple blood test can identify your system’s Vitamin D level. A physician should review the results with you and make recommendations to help you reach optimal levels.

Vitamin D Levels and What They Mean

Low Vitamin D – If you fall into the less than 30 ng/mL category, you are considered vitamin deficient. You could experience bone pain, fatigue, muscle twitching, hair loss, depressor, low-quality sleep, and muscle weakness. Our MDLifespan providers recommend vitamin supplementation to achieve optimal levels between 60 to 100mg/mL.

High Vitamin D – If your bloodwork shows you are over 150 ng/mL, you may have vitamin D toxicity. This can be harmful and cause nausea, vomiting, confusion, loss of appetite, dehydration, excessive urination and thirst, kidney stones, and pain. Talk to one of our MDLifespan providers if you are experiencing these symptoms.


The daily Vitamin D intake chart below includes intakes from all sources – food, beverages, and supplements. Note that your healthcare provider may recommend higher doses of Vitamin D for a brief period to treat a vitamin D deficiency.

AgesRecommended Vitamin D Intake (Upper Limit)
Birth to 6 Months1,000 IU
Infants 7 – 12 Months1,500 IU
Children 1 – 3 Years2,500 IU
Children 4 – 8 Years3,000 IU
Children 9 – 18 Years4,000 IU
Adults 19 Years and Older4,000 IU
Pregnant and Breastfeeding Women4,000 IU

How to Get Enough Vitamin D

Now we know the benefits of Vitamin D and what levels are best for our body’s needs. Where can Vitamin D be found to keep our levels where they are supposed to be?

Here are some suggestions:

1. Food:

Vitamin D is naturally present in a limited number of foods. Some of the best sources include:

  • Fatty Fish: Salmon, mackerel, sardines, and tuna are among the top sources. A single serving of salmon can provide close to a day’s recommended intake.
  • Fortified Foods: Many dairy products, plant-based milk alternatives, and cereals are fortified with Vitamin D. This means that Vitamin D has been added to them. Always check the nutrition label to see if Vitamin D has been added.
  • Egg Yolks: The yolk of an egg contains Vitamin D, so consider this when preparing your eggs.
  • Beef Liver and Cheese: While not as potent as fatty fish, they offer a Vitamin D dose.
2. Sun:

The sun is a natural source of Vitamin D. Exposing your skin to UVB is an excellent way to increase your Vitamin D levels.

  • Time of Day: The best time to get sunlight is midday when the sun is highest.
  • Duration: About 10-30 minutes of midday sun exposure at least twice a week can lead to sufficient Vitamin D synthesis. The exact time varies based on skin tone, location, and season.
  • Skin Exposure: Expose arms, legs, or back without sunscreen. However, always be cautious and avoid sunburn.
  • Location and Season: People living farther from the equator or in cloudy places might need more sun exposure.
3. Supplements:

Supplements are essential for those who cannot get enough Vitamin D from food or sunlight.

  • Types: There are two types of Vitamin D supplements: D2 (ergocalciferol) and D3 (cholecalciferol). D3 is the more potent and preferred option.
  • Dosage: It is essential to take the right amount. The recommended daily amount varies based on age, but always consult with a healthcare professional before starting a supplement regimen.
  • Absorption: Taking Vitamin D with a meal containing fats can enhance absorption. Remember, while Vitamin D is essential, it is possible to have too much. Always aim for a balanced approach and consult with a healthcare professional if unsure about your Vitamin D levels or intake.

Do You Want to Know Your Vitamin D Levels?

Click the link below to schedule a call and speak with a Patient Service Advisor. They can help you get started and schedule your Initial Visit + Labs appointment with an MDLifespan Provider. We require all new patients to fill out a questionnaire with over 400 questions to help provide a clear picture of their health. Once that is complete and your labs have been processed, we will schedule a virtual 90-minute consultation to review your results.