Few people are vitamin D deficient
January 6, 2025
Slightly updated version of a post from January, 2024
Our skin uses sunshine to create vitamin D, and these short winter days make some wonder whether they could be vitamin D deficient. In most instances, adults who are not housebound, even in far northern (or southern) latitudes, are very unlikely to be deficient in vitamin D. Between hats, gloves and sunscreen, many of us in wintry climates might not get enough sunlight every day, but we have large stores of this vitamin in the liver that can be released in the winter. Sunscreen likely does not substantially reduce vitamin D production.
Many studies have shown an association between low vitamin D levels and a variety of serious conditions including heart disease, diabetes, strokes and cancer. Those with lower vitamin D levels were also more likely to die of COVID in the early months of the pandemic. However, supplementation has not shown to help prevent premature deaths. This is a classic example of association not representing causality. Most likely, those with poor health that predicts premature death have low vitamin D levels due to their underlying disease. Giving extra vitamin D doesn’t erase the risk of the underlying disease. A randomized study with over 25,000 participants published in 2019 found no evidence that vitamin D reduces risk of cancer or cardiovascular disease.
From a January, 2024 Scientific American article on this topic:
Think of it this way: there's a strong link between someone's wealth and the price of their car, but that doesn't mean buying an expensive vehicle will make you rich.
Nonetheless, there is a large industry built around promoting testing and vitamin D supplementation. Moreover, the standards to define low levels of vitamin D are a result of a misreading of the literature. As a result, vitamin D is one of the most frequently used low value tests in the United States. The Endocrine Society, the US Preventive Services Task Force, and the American Association of Clinical Endocrinologists do not recommend universal or routine screening of vitamin D levels. Clinical guidelines suggest that vitamin D testing should be restricted to those at high risk, including those with metabolic bone disease, abnormal calcium level, malabsorption, or chronic kidney or liver disease. Researchers in Canada decreased vitamin D testing by 92% by requiring one of these diagnoses, and some US health delivery systems have decreased their vitamin D testing by adding guidelines to their electronic medical record system.
Implications for employers:
Employers can support their carriers when they institute claims edits that will deny payment for vitamin D tests done on people without a diagnosis suggesting risk for vitamin D deficiency.
Providers likely would order fewer low value tests if they were paid through an alternative payment model where they bore the costs of such testing.
Thanks for reading. You can find previous posts in the Employer Coverage archive
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Illustration by Dall-E
Jeff,
The conversation around vitamin D is often oversimplified, treating it as just another nutrient and relying on population-wide deficiency statistics. But in reality, deficiency risk varies significantly by age, gender, ethnicity, body composition, and lifestyle, directly impacting productivity and quality of life for an INDIVIDUAL.
✅ Vitamin D isn’t just a vitamin—it’s a hormone. It is vital in immune function, inflammation regulation, musculoskeletal health, and cognitive function.
✅ Deficiency is not one-size-fits-all. Risk is significantly higher in darker-skinned individuals, postmenopausal women, and people with higher fat mass, as vitamin D is fat-soluble and less bioavailable in larger fat stores.
✅ Symptoms can be subtle but life-altering:
🚶🏽♀️ A young professional in their 30s struggling with chronic fatigue and brain fog—often misattributed to stress, but in reality, linked to vitamin D insufficiency.
🦴 A postmenopausal woman experiencing muscle weakness and joint pain, unknowingly increasing her risk of fractures and mobility issues.
🧑🏿⚕️ A Black or Brown-skinned individual working long hours indoors, facing an elevated risk of vitamin D deficiency due to melanin reducing natural synthesis.
💤 A shift worker dealing with frequent colds, poor sleep quality, and weakened immunity—all potentially connected to low vitamin D levels.
Precision Matters—Not Everyone Needs Testing
At Digbi Health, we take a precision biology approach to assess vitamin D risk—moving beyond blanket recommendations:
🔬 Genetics – Identifying those with a higher likelihood of vitamin D deficiency.
🌍 Zip Code & Work Patterns – Factoring in seasonal variations and sun exposure.
⚖️ BMI & Fat Mass – Considering how body composition affects vitamin D bioavailability.
📊 Symptoms & Quality of Life Impact – Chronic fatigue, muscle pain, immune dysfunction, and brain fog can significantly affect daily life and workplace performance.
But we don’t recommend unnecessary testing. Instead, we only recommend testing for vitamin D when an individual has both high composite risk and symptoms—ensuring a targeted, data-driven intervention rather than a generalized approach.
A Smarter, Food-First Approach
Before jumping to supplements, we focus on upregulating vitamin D-rich foods, ensuring sustainable, biologically aligned solutions.
Health is personal. Care solutions should be, too.