Vitamin D Deficiency and HealthVitamin D foods

Vitamin D deficiency is rapidly emerging as one of the most significant risk factors for a wide range of diseases. It is also one of the most common nutritional deficiencies—especially here in the Northwest. Fortunately, it is easy to identify and treat.

Low Vitamin D levels have been linked to at least 17 types of cancer, neurological diseases such as multiple sclerosis, bone and calcium metabolism disorders, muscle pain and weakness, cardiovascular disease, depression, diabetes, autoimmune conditions, and increased susceptibility to colds and flu. Research suggests Vitamin D plays an important role in both disease prevention and overall health.

People with adequate Vitamin D levels have a 30–50% lower risk of developing many cancers. In those who do develop cancer, studies show higher Vitamin D intake is associated with improved survival rates, including significantly better outcomes in lung cancer.

Vitamin D deficiency is also strongly associated with chronic musculoskeletal pain, particularly low back pain. One study found chronic pain was three times more common in people with the lowest Vitamin D levels. Geriatric facilities increasingly supplement Vitamin D because it helps prevent muscle weakness and significantly reduces falls.

Low Vitamin D levels have also been linked to depression. Individuals with higher levels report a greater overall sense of well-being. In addition, Vitamin D plays a crucial role in immune function. Seasonal deficiency may help explain why illnesses like colds and flu are more common in winter. In one study, supplementing with 2,000 IU of Vitamin D daily virtually eliminated self-reported colds and influenza.

How We Get Vitamin D

Vitamin D comes from sunlight exposure, diet, and supplementation. Sun exposure is the most efficient source—fair-skinned individuals can produce up to 20,000 IU in less than 30 minutes of summer sun. However, excessive exposure increases skin aging and cancer risk.

Diet alone typically provides only 250–300 IU per day, even from Vitamin D–rich foods such as fish oil, liver, and fortified milk. Supplementation is often necessary. Most adults require 2,000–4,000 IU daily to maintain healthy levels. Research shows no credible evidence of toxicity with doses up to 10,000 IU per day when using Vitamin D₃ (cholecalciferol).

Vitamin D Levels and Testing

Most people have blood Vitamin D levels between 10–18 ng/mL in winter or with limited sun exposure. Disease risk decreases significantly at levels above 30 ng/mL, while natural levels in sun-exposed populations range from 50–70 ng/mL.

Vitamin D levels are influenced by location, skin color, sunscreen use, age, body weight, and diet. Blood testing is the most reliable way to assess status. Ask your provider for a 25-hydroxy Vitamin D test.

Bottom Line

Vitamin D deficiency is extremely common and contributes to many serious health conditions. Testing is simple, supplementation is affordable, and maintaining adequate levels is one of the easiest ways to support long-term health.