Vitamin D is responsible for regulation of calcium and phosphate metabolism and maintaining a healthy mineralized skeleton. It is also known as an immunomodulatory hormone. Experimental studies have shown that 1,25-dihydroxyvitamin D, the active form of vitamin D, exerts immunologic activities on multiple components of the innate and adaptive immune system as well as endothelial membrane stability. Association between low levels of serum 25-hydroxyvitamin D and increased risk of developing several immune-related diseases and disorders, including psoriasis, type 1 diabetes, multiple sclerosis, rheumatoid arthritis, tuberculosis, sepsis, respiratory infection, and COVID-19, has been observed. Accordingly, a number of clinical trials aiming to determine the efficacy of administration of vitamin D and its metabolites for treatment of these diseases have been conducted with variable outcomes. Interestingly, recent evidence suggests that some individuals might benefit from vitamin D more or less than others as high inter-individual difference in broad gene expression in human peripheral blood mononuclear cells in response to vitamin D supplementation has been observed. Although it is still debatable what level of serum 25-hydroxyvitamin D is optimal, it is advisable to increase vitamin D intake and have sensible sunlight exposure to maintain serum 25-hydroxyvitamin D at least 30 ng/mL (75 nmol/L), and preferably at 40-60 ng/mL (100-150 nmol/L) to achieve the optimal overall health benefits of vitamin D.

This abstract and article was published in Nutrients, 2020: 12(7), 2097

In light of the current Covid-19 pandemic, questions are raised and answers sought about the role of nutrition in the prevention of infectious diseases. In this case, vitamin D (a fat soluble vitamin stored in the body) is examined.

Vitamin D Facts:

RDA Women: 600 IU; Men: 600 IU; UL: 4000 IU. Toxicity possible with long-term use of 10,000 IU daily. 1 microgram (mcg) vitamin D = 40 IU.

Primary Functions: Needed for absorption of calcium and phosphorus for bone formation nerve and muscle activity. Inhibits inflammation and is involved in insulin secretion and blood glucose level maintenance.

Consequences of Deficiency: Weak, deformed bones (children), loss of calcium from bones (adults), osteoporosis.

Concenquences of Overdose: Mental retardation in young children, abnormal bone growth and formation. Nausea, diarrhea, irritability, weight loss. Deposition of calcium in organs such as kidneys, liver and heart.

Primary Food Sources: Vitamin D – fortified milk, cereals, and other foods. Fish

Highlights: Vitamin D3, the most active form is manufactured from a form of cholesterol in skin cells upon exposure to ultraviolet rays from the sun. Inadequate vitamin D status is common. Breast-fed infants with little sun exposure benefit from vitamin D supplements. People with very dark skin, especially from Asian and Afro-Carribbean descent find it difficult to make vitamin D from limited sunlight.

NOTE: It’s important to know that megadoses of any vitamin or mineral are never recommended, unless there is a medical reason for doing so. In this case, a Canadian study reported that among 303 middle-aged and older adults (who were not vitamin D deficient), those who were randomly assigned to get 4,000 IU  of vitamin D  a day for 3 years lost more bone in their arms  than those who got 400 IU a day. Those who got 10,000 IU a day lost more bone in their arms and shins than those who got 400 IU a day.  See the consequences of overdose.