An epidemic of vitamin D deficiency appears to be sweeping the world. A large part of the population — from newborns to the elderly, and many in between — are deficient in this essential nutrient. An estimated 40%-75% of people are deficient. Studies suggests that healthy amounts of vitamin D play a role in bone health as well as reducing the risk of cancer, heart disease, stroke, diabetes, auto-immune diseases, decreasing inflammation, prevention and treatment of depression and more. The question many are asking is why are so many people lacking this vital nutrient?

Causes of Vitamin D deficiency

While researchers aren’t exactly sure why so many people are lacking vitamin D, much evidence is pointing to a lack of sun exposure. Known as the “sunshine vitamin,” vitamin D is produced by the body in response to sunlight. The combination of people spending more time indoors and slathering sunscreen on (to protect against the danger of skin cancer) when they do go outdoors, may be contributing to why so many people are deficient in this vitamin. Even if you do have some exposure to the sun, the total amount of vitamin D you can produce is affected by the season, time of day, ozone amount, latitude, and number of clouds in the sky.

Vitamin D deficiency can occur for other reasons such as:

Obesity: People with a body mass index of 30 or greater often have low blood levels of vitamin D.

Darker skin: The pigment melanin reduces the skin’s ability to make vitamin D in response to sunlight exposure.

Your kidneys cannot convert vitamin D to its active form. As people age their kidneys are less able to convert vitamin D to its active form, thus increasing their risk of vitamin D deficiency.

Your digestive tract cannot adequately absorb vitamin D. Certain medical problems, including Crohn’s disease, cystic fibrosis, and celiac disease, can affect your intestine’s ability to absorb vitamin D from the food you eat.

The negative effects of low blood levels of vitamin D have been associated with the following:

  • Increased risk of death from cardiovascular disease
  • Cognitive impairment in older adults
  • Severe asthma in children
  • Cancer
  • Osteoporosis


A simple blood test is all that is needed to determine your vitamin D level. Treatment for vitamin D deficiency usually involves getting more vitamin D through supplements.

Although more foods today are fortified with vitamin D, experts say it’s rarely possible to recoup a deficiency in vitamin D through the consumption of foods alone. Unless you enjoy a regular diet that includes fatty fish, fish liver oils and fortified food, it may be hard to get enough vitamin D naturally without taking a supplement. The main dietary sources are wild-caught oily fish (salmon and canned tuna), fish liver oils, egg yolks, fortified milk and baby formula, cereal and orange juice.

The amount of vitamin D that is needed to correct a deficiency will depend on the severity of the deficiency, but an optimum goal level should 40-70 nanograms per milliliter. Although it may differ depending on age and health conditions — a concentration of less than 30 ng/ml is generally considered inadequate, requiring treatment. A level less than 20 ng/mL indicates vitamin D deficiency.

If you’re concerned about whether you’re getting enough vitamin D, talk to your doctor about your diet and whether a vitamin supplement might benefit you. Always consult with your doctor before starting vitamin D supplements and routinely have your blood levels checked.