If you spend most of your time indoors or live in regions of the Northern Hemisphere, you may be at a greater risk of vitamin D deficiency. Even with adequate sun exposure and a varied diet, vitamin D deficiency is very common and affects over 40% of people in North America. (6)(17) Keep reading to identify the signs of vitamin D deficiency, and find out if you might be at risk.
What is Vitamin D?
Vitamin D is a fat-soluble vitamin that can be absorbed in the small intestine along with dietary fats and stored in the liver and body’s fat tissues for long-term use. (17) It’s also one of the few vitamins the body can make on its own. Vitamin D helps the body absorb and regulate calcium levels in the blood, which is especially important for maintaining strong, healthy bones. Beyond bone health, vitamin D supports immune, heart, and cognitive function. (17)(19)
What is Vitamin D deficiency, and what are the signs?
Low vitamin D status can occur in individuals who do not spend enough time in the sun or don’t consume enough vitamin D through their diets. Vitamin D deficiency symptoms include bone and muscle pain, chronic fatigue, hair loss, and general weakness. (10)(1)
Deficiency is directly linked to several health concerns, including osteoporosis, heart disease, cancer, and impaired immune function. (17) A simple blood test can help determine whether you have vitamin D deficiency. Consult your healthcare practitioner for testing and an appropriate treatment plan if necessary.
Vitamin D Sources
Vitamin D comes from three main sources, including sun exposure, diet, and supplements.
UVB rays from the sun react with a cholesterol precursor in the skin, where 7-dehydrocholesterol is converted to cholecalciferol, also known as vitamin D3. The liver and kidneys are then responsible for converting cholecalciferol to calcitriol, the active form of vitamin D3. (17)
Vitamin D is primarily found in animal-derived foods, including beef liver, cheese, eggs, and fatty fish. (17) Certain mushrooms, such as maitake and UV-treated portabella, also contain small amounts of vitamin D. (16) Some foods, including breakfast cereals, dairy products, non-dairy beverages (e.g., almond and soy milk), and orange juice, may be fortified with vitamin D. (15)
Vitamin D is also available in supplement form and may be necessary if you’re not getting enough through diet and regular sun exposure. There are two forms of vitamin D in food and supplements, D2 (ergocalciferol) and D3 (cholecalciferol). Both can help you meet your daily vitamin D needs; however, D3 has been shown to be better absorbed by the body. D2 is often less expensive to produce than D3 and, therefore, frequently added to fortified foods. (15)
Most vitamin D supplements are derived from lanolin, a waxy substance secreted from the sweat glands of sheep. (20) An alternative source is lichen, derived from a combination of fungus and algae, making it a suitable alternative for individuals following a strictly plant-based diet. (20)(3)
Health Effects of Vitamin D Deficiency
Altered immune function
The immune system, which is the body’s primary defense against foreign invaders, is enhanced by vitamin D. Without adequate vitamin D, immune cells (e.g., macrophages, B-cells, and T-cells) can’t properly fight off infection. (5) Research has determined that individuals with vitamin D deficiency are more likely to contract upper respiratory tract infections, such as the common cold or seasonal flu, compared to individuals with normal vitamin D status. (2) Low vitamin D levels are also associated with an increased incidence of certain autoimmune diseases, conditions in which the body misidentifies its own cells as invaders. (2)
Increased risk of cardiovascular disease
Vitamin D deficiency is associated with an increased risk of cardiovascular disease and heart failure. Other cardiovascular disease risk factors that are also influenced by low vitamin D status include high blood pressure, type 2 diabetes, high BMI (≥30), and high triglyceride levels. (9)
Increased risk of cancer
Certain cancers, including breast, colorectal, and prostate cancer, may be linked to vitamin D deficiency. (7) Deficiency may contribute to tumor growth and metastasis in breast cancer. (23) When comparing levels of vitamin D and colon cancer risk, levels less than 12 ng/mL increased risk by 31% in comparison to levels of at least 20 ng/mL. (12) Another study suggests a link between vitamin D deficiency and aggressive forms of prostate cancer in African-American and European-American men. (14)
When vitamin D levels are low, calcium is pulled from the bones to maintain blood calcium homeostasis (balance). Vitamin D deficiency in children can lead to a condition called rickets, characterized by softened bones and bowed legs. Additionally, vitamin D deficiency can cause osteomalacia and osteoporosis in adults, making bones more vulnerable to fracture. (21)
Increased risk of Alzheimer’s disease and dementia
Low vitamin D status is related to an increased risk of neurodegenerative disease, including Alzheimer’s disease and dementia. This relationship is positively correlated; the risk of developing Alzheimer’s disease increases as the severity of vitamin D deficiency increases. (9)