Vitamin D deficiency affects around 42 percent of American adults, and multiple studies have linked low levels of this vitamin to increased risks of serious health conditions, such as cardiovascular disease.
Though technically a prohormone, vitamin D acts as a hormone in the body. It undergoes chemical changes in the kidneys and is secreted to regulate blood calcium levels, enhance calcium absorption, inhibit the release of parathyroid hormone (crucial for bone health), and fortify the immune system, among many other functions.
Vitamin D is also vital for muscle and bone health, as it helps regulate calcium and phosphate in the body. Without enough vitamin D, children risk developing rickets (soft and weak bones), while adults can experience osteomalacia, a condition causing bone pain and muscle weakness. Too much vitamin D, however, can lead to high calcium levels, potentially causing heart and kidney issues.
While sunlight is the primary source of vitamin D, food and supplements can also provide this nutrient, which is absorbed in the intestines, processed by the liver, and then activated in the kidneys as calcitriol.
Here are the most common modifiable risk factors that can contribute to vitamin D deficiency:
- Sedentary lifestyle
- Calcium intake
- Body weight and composition
- Improper sunscreen use
Non-modifiable risk factors include:
- Female sex
- Older age
- Non-white ethnicity (higher risk for Black and Latino populations)
- Conditions such as inflammatory bowel disease or cystic fibrosis
Despite these factors, other hidden causes can also lead to deficiency. Here are some often-overlooked reasons:
1. Lack of Sunlight
Inadequate sunlight exposure is a major cause of vitamin D deficiency. However, correct application of sunscreen should not significantly impact the skin’s ability to synthesize this vitamin.
2. Age
Aging can reduce the skin’s ability to produce vitamin D. Older adults may benefit from taking vitamin D supplements.
3. Crohn’s Disease
As an inflammatory bowel disease, Crohn’s disease can interfere with the absorption of vitamin D. Inflammatory conditions like ulcerative colitis can similarly impact levels of this nutrient.
4. Darker Skin
People with darker skin (such as Latinos and African-Americans) are more prone to vitamin D deficiency, as higher melanin levels can inhibit vitamin D synthesis.
Conditions affecting the kidneys can impede vitamin D metabolism, especially in advanced disease stages where certain proteins block vitamin D processing.
6. Obesity
Higher body fat can absorb excess vitamin D, reducing the available levels in circulation.
7. Cystic Fibrosis
This genetic disease causes lung and digestive issues, which can interfere with fat absorption and lead to vitamin D deficiency, as vitamin D is fat-soluble.
8. Gastric-Bypass Surgery
This weight-loss surgery can alter the digestive system’s ability to absorb vitamin D, as it removes a significant portion of the intestine.
9. Whipple’s Disease
This rare bacterial infection disrupts nutrient absorption, including that of vitamin D, and blocks intestinal openings.
10. Celiac Disease
An immune response to gluten, celiac disease can lead to a variety of digestive problems, including difficulty absorbing nutrients like vitamin D.
A blood test is the most common way to assess vitamin D levels, and a reading below 20 ng/mL is considered deficient.
Improving Vitamin D Levels:
To boost vitamin D, consider sun exposure for 10 to 30 minutes daily, several times a week. Dietary sources include fish, egg yolks, fortified dairy, grains, and fish liver oils. According to the George Mateljan Foundation, notable sources of vitamin D include:
- 4 oz of wild-caught Alaskan sockeye salmon (128% of RDA)
- 3.2 oz of sardines (44% of RDA)
- One egg (11% of RDA)
- Shiitake mushrooms (5% of RDA)
The Institute of Medicine recommends a daily intake of 600 IU of vitamin D for individuals aged 1 to 70 and 800 IU for those over 70. However, a safe upper limit for most people is around 4,000 IU per day.
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Additionally, magnesium is necessary for proper vitamin D activation. Without enough magnesium, vitamin D may not be fully effective. Ensuring sufficient magnesium intake may lower the need for vitamin D supplements, promoting better health overall.
