The Sunshine Vitamin: Why Vitamin D is Essential for Your Health

Dr. Andrea Klemes, Chief Medical Officer MDVIP
By Dr. Andrea Klemes , MDVIP
June 24, 2025

When it comes to keeping our bodies functioning, Vitamin D plays a starring role. Often called the "sunshine vitamin," it's one of the 13 essential vitamins our bodies need for growth and maintenance. Yet, despite its importance, more than 40 percent of American adults don't get enough of it. Here’s why Vitamin D matters so much and how you can ensure you're getting an adequate supply.

The Fundamental Role of Vitamin D

Vitamin D isn't just another over-the-counter supplement — it's a critical component in multiple bodily functions.

Bone Health - Perhaps the most well-known function of Vitamin D is its role in bone and teeth mineralization. Your body simply cannot absorb calcium properly without sufficient Vitamin D levels, making it essential for maintaining strong bones and preventing fractures. This becomes increasingly important as we age, when bone density naturally decreases.

Immune System Support - Vitamin D plays a vital role in strengthening your immune system. It helps your body recognize and fight off invading bacteria and viruses. During seasons when colds and flu are common, maintaining adequate Vitamin D levels can be one way to bolster your body's natural defenses.

Muscle Function - Those experiencing unexplained muscle pain or weakness might be suffering from a Vitamin D deficiency. The vitamin helps maintain proper muscle function and strength, which affects everything from daily activities to athletic performance.

Cognitive Function - Emerging research suggests Vitamin D helps maintain memory and cognitive function. While more studies are needed, this connection highlights yet another reason why adequate levels are important for overall health.

Nervous System Health - Vitamin D assists with nerve function, helping signals transmit properly throughout your body. This impacts coordination, sensation, and even mood regulation.

Causes of Vitamin D Deficiency

If your vitamin D levels are low, there are several possible causes. You might not get enough vitamin D in your diet or don’t get enough exposure to the sun. You take medications that interfere with your body’s ability to convert vitamin D or your kidneys or liver cannot convert enough vitamin D into the form it takes in your body. Being overweight or obese may also interfere with vitamin D levels.

The Consequences of Low Vitamin D Levels

When your body lacks sufficient Vitamin D, you might experience:

  • Bone and muscle pain
  • Increased risk of fractures
  • Muscle weakness
  • Fatigue
  • Compromised immune function

Vitamin D deficiencies have been linked to numerous other conditions, although these connections are tenuous. What's clear is that maintaining adequate levels is important for overall health and wellbeing.

Sources of Vitamin D

Unlike other nutrients, Vitamin D is somewhat unique in how we obtain it:

Sunlight - Our skin naturally produces Vitamin D when exposed to sunlight. This is why it's nicknamed the "sunshine vitamin." However, many factors affect this production, including:

  • Geographic location and season
  • Time of day
  • Cloud cover and air pollution
  • Sunscreen use (which blocks the UVB rays needed for Vitamin D production)
  • Skin pigmentation (darker skin requires more sun exposure to produce the same amount of Vitamin D)

Fear of skin cancer and premature aging has led many people to avoid sunlight, contributing to widespread Vitamin D deficiency. However, experts like Dr. Michael F. Holick suggest that sensible, unprotected sun exposure is important for health.

Food Sources - Dietary sources of Vitamin D are somewhat limited, but include:

  • Fatty fish (mackerel, salmon, sardines)
  • Cod liver oil
  • Egg yolks
  • Mushrooms
  • Fortified foods (milk, orange juice, cereals)
  • Supplements 

For many people, particularly those living in northern latitudes or with limited sun exposure, supplements may be necessary to maintain adequate Vitamin D levels.

How Much Do You Need?

The daily recommended intake for Vitamin D varies by age, but for most adults, recommendations range from 600-800 IU daily. However, many health professionals suggest that higher amounts may be beneficial, particularly for those who are deficient.

Before starting any supplement regimen, it's important to consult with your doctor. A simple blood test can determine your current Vitamin D levels and help guide appropriate supplementation.

But supplements simply 'supplement.' They are not a rescue from poor habits or a replacement for healthy eating. While supplements can help address deficiencies, they work best as part of an overall healthy lifestyle.

Additionally, supplements can interact with prescription medications, which is why discussing them with your healthcare provider is crucial.  

Vitamin D deficiency has become surprisingly common, and while some doctors may test for it, it’s not part of many annual exams. Vitamin D testing is part of the MDVIP Wellness Program.  

If your vitamin D levels are low, you and your doctor can discuss how to address them. Vitamin D levels that are too high are also a problem, which is why it’s a good idea to talk to your doctor about your Vitamin D status at your next checkup.

Vitamin D and the MDVIP Wellness Program

The MDVIP Wellness Program includes testing annually for vitamin D. The test, a 25-hydroxy vitamin D test, is the most accurate test for vitamin D levels. Because low levels of this nutrient are tied to so many chronic conditions, it’s an important test that’s not often covered by commercial insurance or given in traditional primary care practices. 


About the Author
Dr. Andrea Klemes, Chief Medical Officer MDVIP
Dr. Andrea Klemes, MDVIP

Dr. Andrea Klemes is the Chief Medical Officer of MDVIP. She also serves as the executive and organizational leader of MDVIP’s Medical Advisory Board that supports quality and innovation in the delivery of the healthcare model drawing expertise from the affiliated physicians. Dr. Klemes oversees MDVIP’s impressive outcomes data and research including hospital utilization and readmission statistics, quality of disease management in the MDVIP network and the ability to identify high-risk patients and intervene early. She is instrumental in the adoption of the Electronic Health Record use in MDVIP-affiliated practices and the creation of the data warehouse. Dr. Klemes is board certified in internal medicine and endocrinology and a fellow of the American College of Endocrinology. Dr. Klemes received her medical degree from the New York College of Osteopathic Medicine. She completed an internal medicine residency at Cabrini Medical Center in Manhattan, New York and an Endocrine and Metabolism Fellowship at the Medical College of Georgia in Augusta. Prior to joining MDVIP, Dr. Klemes worked at Procter & Gamble in the areas of personal healthcare, women’s health and digestive wellness and served as North American Medical Director for bone health. She spent 10 years in private practice specializing in endocrinology and metabolism in Tallahassee, Florida. In addition, Dr. Klemes held leadership roles with the American Medical Association, Florida Medical Association and as Medical Director of the Diabetes Center in Tallahassee and Panama City, Florida, as well as Chief of the Department of Medicine at Tallahassee Community Hospital. She has been a consultant and frequent lecturer and has completed broad clinical research in diabetes and osteoporosis and published extensively.

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