Vitamin D and its role in health has been studied for over a century. Vitamin D helps the gut absorb calcium, is involved in bone health, muscle contraction, reduction in inflammation, immunity, and glucose metabolism. However, with the current Covid 19 pandemic Vitamin D’s role in immunity has been the focus of more recent studies which reach similar conclusions that Vitamin D deficiency is associated with respiratory infections such as Influenza A and Covid 19 and that Vitamin D supplementation reduces the risk of these infections and associated poor outcomes (Brenner, Holleczek, Schöttker, 2020; Martineau, et al, 2017; Mitsuyoshi, et al, 2010; Urashima, et al, 2010). In fact one study found that over 80% of Covid 19 cases had vitamin D deficiency (Hernández et al, 2020). But what is Vitamin D and what are the sources? Who is at risk for Vitamin D deficiency? What is the recommended daily dose?
What is Vitamin D?
Vitamin D (Calciferol) is known as the “sunshine vitamin” and is a fat soluble, steroid hormone. Many vitamin D receptors are found in the immune cells such as leukocytes making it play an important role in immunity (Li & Li, 2020)
Sources of Vitamin D
1. Sun. When our skin is exposed to the sun our skin produces vitamin D. Major causes of Vitamin D deficiency is inadequate exposure to sunlight (Moan, Porojnicu, Dahlback,& Setlow,2008). Our sun exposure is generally not enough to produce sufficient vitamin D levels because we spend on average only 7.6% of the day outdoors (National Human Activity Pattern Survey).
Cod liver oil, Rainbow trout, Salmon, white raw mushrooms, Vitamin D fortified milk, Soy/almond/oat milk, vitamin D fortified cereal, eggs, and liver.
Vitamin= “Vital” + “Amine”
*Most of us require supplementation.
Who is at risk for Vitamin D deficiency?
As we get older our ability to make Vitamin D decreases
(Maclaughlin & Holick, 1985)
Those who are obese are at greater risk for vitamin D deficiency (Wortsman, Matsuoka, Chen, Lu, & Holick, 2000) because Vitamin D is fat soluble-the more fat the less available active vitamin D.
People with darker skin tones are at greater risk for vitamin D deficiency because they require more sun exposure time to produce vitamin D (Gutiérrez, Farwell, Kermah & Taylor, 2010).
Living in Northern latitudes
People living North of the 37th parallel are at greater risk for Vitamin D deficiency (Huotari & Herzig, 2008). Perhaps due to less sunshine in the winter months.
Vitamin D 25(OH)D levels in the blood
*Levels targeted to prevent fractures (30-40 ng/ml) according to the Endocrine society.
Optimal Vitamin D levels=51-70 ng/ml
*Treatment for heart disease or Cancer=71-100 ng/ml
Vitamin D3 supplementation
Currently there is no International consensus on optimal Vitamin D supplementation levels and the daily recommendations vary from 400IU to 10,000 IU daily. Evidence indicates that vitamin D3 increases and maintains serum 25(OH)D levels to a greater extent and longer than vitamin D2, even though both forms are well absorbed in the gut (Logan, Gray, Peddie, Harper & Houghton, 2013; Tripkovic et al, 2017)
***Vitamin D toxicity is very rare. A study involving Canadian adults who ingested 20,000IU daily had vitamin D levels of up to 60ng/ml but without evidence of toxicity. In another study involving healthy adults who received 50,000IU once every 2 weeks for up to 6 years had vitamin D blood concentrations of 40-60ng/ml and no signs of toxicity.
(Marcinowska-Suchowierska, Kupisz-Urbańska, Łukaszkiewicz, Płudowski & Jones,2018).
***The Endocrine Society states, for example, that to maintain serum 25(OH)D levels above 30 ng/mL, adults might need at least 1,500–2,000 IU/day of supplemental vitamin D, and children and adolescents might need at least 1,000 IU/day (Binkley et al, 2011).
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