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In the news: Role of Vitamin D in COVID-19? Nutrients & Diabetic Retinopathy

Update: Vitamin D Status and Coronavirus

Over the last few months, the role of vitamin D in relation to COVID-19 has been the subject of debate. Some experts say the evidence is not strong enough to support recommending supplemental vitamin D beyond the Daily Value to help potentially protect against coronavirus. Others say that the available evidence is sufficient to act upon, particularly because the pandemic has curtailed outdoor activities (and hence the sunlight exposure needed to synthesize one’s own vitamin D), and that vitamin D is considered safe at supplemental levels of 1,000-2,000 IU daily, with a Tolerable Upper Intake Level of 4,000 IU.

Past intervention studies provide evidence that vitamin D can lower the risk of upper respiratory tract infections such as colds and the flu in people with low blood levels of the vitamin. There is also evidence that adequate levels are needed for proper immune system function, and that vitamin D stimulates the release of antimicrobial proteins and helps reduce inflammation.

But when it comes to COVID-19 specifically, the idea that vitamin D could influence susceptibility to the disease or affect the severity of symptoms is based on observational studies suggesting that deficiencies of the vitamin are common among groups that have been hard hit by the virus. Risk factors for vitamin D inadequacy include obesity, diabetes, hypertension, ethnicity – factors also associated with increased risk of severe COVID-19 illness.

Recently, a rapid review by the UK government looked at five published observational studies on vitamin D status and COVID-19 symptoms and mortality (1). The report indicates that four of the studies found an association between poor vitamin D status and subsequent infection with COVID-19, but that the studies didn’t account for confounders which may have independent correlations with the disease or with vitamin D status.

Another group of international medical societies issued guidance as well (2). They state that while the role of vitamin D in COVID-19 remains unclear, older and younger adults can safely take 400-1,000 IU daily to keep vitamin D levels within the range recommended by the US Institute of Medicine when they can't get 15-30 minutes of sunlight daily.

To provide further clarity about the potential role of vitamin D in COVID-19, Harvard researchers at Bingham and Women’s Hospital will be conducting a randomized controlled trial of supplemental vitamin D among patients recently diagnosed with COVID-19, to see if it can reduce the risk for developing severe illness or the need for hospitalization. The study will also assess whether supplementation can reduce the risk of developing the infection for others in the patient’s household.

Review: Nutrients and Diabetic Retinopathy

Researchers from the University of Miami Miller School of Medicine, Departments of Neurology and Ophthalmology, have reviewed the role of various nutrients in relation to elevated homocysteine and oxidative stress, two biological targets in the development of diabetic retinopathy (3).

The paper discusses deficiencies of various vitamins, minerals and related compounds that may lead to elevation of homocysteine and insufficiencies of co-factors for the release of neuro-trophic and neuroprotection growth factors.

The authors conclude that nutritional interventions provide safe and simple strategies that may help protect the retina and choroid, and support, not conflict with, conventional therapies for diabetic retinopathy.

References

1. COVID-19 rapid evidence summary: vitamin D for COVID-19. Evidence summary [ES28] June 29, 2020. https://www.nice.org.uk/advice/es28/evidence.
2. Joint Guidance on Vitamin D in the Era of COVID-19 From the ASBMR, AACE, ENDOCRINE SOCIETY, ECTS, NOF, and IOF. July, 2020. https://www.asbmr.org/ASBMRStatementsDetail/joint-guidance-on-vitamin-d-in-era-of-covid-19-fro
3. Shi C, et al. Nutritional and medical food therapies for diabetic retinopathy. Eye Vis (Lond). 7: 33, 2020.