Vitamin D, often called the “sunshine vitamin,” is known to promote bone health and support immune function. It is also important for the modulation of innate and adaptive immune responses.
Vitamin D liquid supplement is a convenient option for some people to help ensure they get adequate levels of vitamin D. These can be taken with food or independently and may be more accessible than gummies or tablets.
The most well-known function of vitamin D is bone growth. It helps the body absorb calcium, strengthening the bones and reducing osteoporosis risk. It also assists with muscle movement and nerve communication. However, it is important to note that this nutrient has many other functions, too.
It is crucial to the immune system’s innate and adaptive responses against viruses. In vitro studies have demonstrated the physiological role of vitamin D in immune modulation, inducing AMPs like cathelicidin to inhibit viral infection and promoting phagocytosis by neutrophils and monocytes/macrophages.
Vitamin D deficiency can lead to rickets in children and osteomalacia in adults. The condition leads to bowed or misshapen bones due to the breakdown of bone faster than it can form. It can also increase the risk of bone fractures. Vitamin D supplements can prevent rickets and osteomalacia and help to protect against the onset of osteoporosis.
The Institute of Medicine (IOM) recommends a minimum daily vitamin D intake of 600 IU for adults 19 or older. This amount is intended to ensure adequate serum 25(OH)D concentrations for optimal effects on calcium, bone, and muscle metabolism. The IOM also sets an upper tolerable intake level of 4,000 IU/day for adults to reduce potential adverse health effects.
Immune System Function
Vitamin D is important for bone health and essential to immune system function. It is a fat-soluble hormone created in the body by a reaction with UVB sunlight and can be found in several foods, including eggs, fish, milk, fortified breakfast cereals, and some mushrooms. The vitamin is also available as a supplement.
The endocrine system produces vitamin D through the action of CYP27B1, a key enzyme in this reaction. The active metabolite of vitamin D, 1,25(OH)2D, is then converted to its active form by the vitamin D receptor (VDR). Vitamin D is essential for immune system function as it activates the innate immune response providing the first line of defense against viral and bacterial infections. It also restricts the adaptive immune response, which, if unchecked, promotes inflammatory airway diseases such as acute respiratory distress syndrome and SARS-CoV2 pneumonia.
Vitamin D has been shown to increase monocyte expression of the antimicrobial peptide cathelicidin. This peptide is a potent inhibitor of the growth of many bacteria. It has been observed that patients with severe deficiency of vitamin D progressed to defined rheumatologic disease more frequently than those with normal levels. This is likely because the immune system requires vitamin D for proper cytokine and chemokine production.
People with anxiety disorders experience a higher risk of vitamin D deficiency. This is because broken down vitamin D produces calcidiol, which increases the activity of a receptor called PDE5. PDE5 reduces serotonin and dopamine levels in the brain, increasing feelings of stress. Vitamin D has also been linked to depression. Researchers have found that patients with depression may benefit from treatment with a high dose of Vitamin D.
Vitamin D has many other roles within the body as it impacts immunity via its interaction with receptors on innate immune cells (the first line of defense against pathogens). Vitamin D influences the innate immune response through several mechanisms and promotes protective immune responses such as cathelicidin production.
Studies suggest that low vitamin D levels are linked to certain types of depression, including postpartum depression (depression after giving birth). Low Vitamin D levels have also been linked to depression in women with rheumatoid arthritis, gout, spinal cord injuries, stroke, multiple sclerosis, and other diseases.
Vitamin D production is dependent on exposure to sunlight. Those living in northern latitudes with less sun or those who wear clothing that blocks the UV rays from reaching their skin will produce lower amounts of Vitamin D. Additionally, the use of sunscreen can inhibit Vitamin D production as it acts like a filter and limits UV penetration to only the outer layer of the skin.
Many people worldwide are deficient in vitamin D. This vitamin impacts the immune system and has been linked to cardiovascular disease. It is known to interact with cell receptors on innate immune cells, which form the body’s first line of defense. It suppresses B cell proliferation, alters T cell development by shifting away from the inflammatory Th1 phenotype, and encourages T regulatory cells to become active.
It is also known that vitamin D metabolites have antiviral effects and promote the production of the peptides cathelicidins and defensins, which enhance innate immunity. Vitamin D also interacts with dendritic cells and macrophages, strengthening the adaptive immune response against viruses and other microorganisms.
Observational studies have established the importance of vitamin D, and it has even been linked to a reduced risk of heart disease. Low concentrations of 25(OH)D are associated with an increased risk of hypertension and type 2 diabetes and an increased frequency of established cardiovascular disease risk factors such as high cholesterol and blood pressure.
However, clinical trials have not yet shown that vitamin D supplements can lower the risk of heart attack and stroke. This discrepancy is unclear, but it may be because vitamin D supplementation used in human trials did not reach the physiological concentrations required to affect innate and adaptive immune function.