Although vitamin D is called a “vitamin” (i.e., a required nutrient obtained from the diet), it is not truly a vitamin. It acts more like a hormone since the body can synthesize it from cholesterol after the skin is exposed to UVB rays from the sun. Vitamin D is estimated to be involved in the regulation of up to 2000 genes—that’s a lot of input into the critical processes happening in every cell throughout the entire body! Consequently, this vital nutrient has been linked to almost every health condition under the sun, from bone and muscle health, to brain health, pregnancy, immune activity, cardiovascular functions and more. In contrast, vitamin D deficiency can lead to significant health consequences, and it’s estimated that 42%(it’s higher) of American adults are deficient. Below are some of the many aspects of health which vitamin D has been shown to impact.
Vitamin D benefits and the consequences of deficiency
When many people think about vitamin D, they likely think about their bones. Vitamin D is known for helping to balance minerals like calcium, phosphorus, sodium, and magnesium for healthy bone formation and mineralization. Although vitamin D plays a significant role in skeletal health, its benefits go well beyond bone health to all parts of the body. Because of the abundant presence of these minerals, along with vitamin D receptors in the body, vitamin D’s benefits are vast, directly and indirectly influencing countless physiological functions. For example, vitamin D can act as an antioxidant, regulate immune activity, support cardiovascular health, modulate blood sugar balance, regulate neurotransmitter synthesis and more.
Vitamin D from food, supplementation, or sun exposure, is originally in an inactive form. It must shuttle first through the liver, to become 25(OH) vitamin D, and then to the kidney, to become biologically active 1,25(OH)2 vitamin D. Once biologically active, vitamin D travels to organs throughout the body. Because vitamin D receptors are found in most organs in the body (e.g. intestines, pancreas, kidney, lungs, thyroid, etc.), vitamin D affects their health and functions. Below are some of the organ systems that benefit from vitamin D, and the negative consequences of vitamin D deficiency in select health conditions.
Vitamin D and musculoskeletal health
Vitamin D supports the normal structure and function of bones and muscles. Historically, the consequences of chronic vitamin D deficiency have been on full display in cases of rickets, a skeletal disorder that results in weakening and distortion of bone growth in children without food sources of vitamin D and low sun exposure. Vitamin D deficiency also affects adults, as evidenced by an increased risk in certain types of fractures and forms of muscles weakness.
Vitamin D and brain and nervous system
Vitamin D substantially affects the brain and nervous systems. Studies have shown that supplemental vitamin D may enhance mood during the winter season when vitamin D synthesis from the sun is extremely low. In addition, research suggests that low vitamin D levels may be associated with increased sleepiness and sleep difficulties.
Vitamin D and pregnancy
Growing evidence also supports the benefits of vitamin D during pregnancy. Recent studies have found that during pregnancy, vitamin D may reduce the risk of many pregnancy complications.
Vitamin D and immunity and respiration
Since vitamin D plays a role in regulating the immune system, it may also have a positive influence on immune-related conditions such as acute and chronic respiratory complications and may help to diminish their symptoms when they occur. For example, adequate amounts of vitamin D during childhood and adulthood have been shown to decrease the risk of the exacerbation of chronic respiratory issues and their symptoms. Studies have also shown that pregnant women taking 4,400 IU of vitamin D per day may reduce the risk of respiratory issues in their newborn to three-year-old children, compared to pregnant women who took just 400 IU per day. Self-reported incidences of seasonal respiratory complications have shown to be significantly lower in women taking 800 IU per day compared to placebo.
Vitamin D and cardiovascular health
In addition to the respiratory system, research shows that vitamin D plays a role in the health of the cardiovascular system as well, helping to reduce the risk of various complications of the heart and blood vessels. For example, researchers reported that daily vitamin D supplementation using a wide range of doses (i.e. 600 IU, 2,000 IU, 4,000 IU) decreased stiffness of specific blood vessels after only eight weeks, compared to placebo. Even more compelling, the influence of vitamin D was observed in a dose-response relationship, meaning that as more vitamin D was taken, more improvement in blood vessel structure was observed.
Vitamin D and metabolism
Vitamin D is involved in numerous metabolic processes throughout the body, with research showing that vitamin D can positively influence blood sugar imbalances and metabolic complications. Obesity is a significant risk factor for many metabolic and cardiovascular imbalances. Research suggests that the prevalence of vitamin D deficiency may be higher among people with obesity (and to a lesser degree in people who are overweight) and those with blood-sugar imbalances. Importantly, the association between vitamin D and metabolic complications may be dose-dependent—the better one’s vitamin D status, the lower the risk of many of these imbalances.