In the news: “Med’ Diet & Lower Risk of Late AMD; Low Vitamin D a Factor in Covid-19 Severity?

Med Diet, Fish Intake Influence Late AMD

Closer adherence to the Mediterranean (Med) diet lowers the risk for late AMD, more so for geographic atrophy (GA) than wet AMD, according to the authors of a new analysis of AREDS and AREDS2 data (1).

The researchers aimed to determine whether more closely following the Med diet (and its individual food components) alters the risk of progression to late AMD and its sub-types. Additionally, they analyzed progression to large drusen and assessed interactions with AMD genotype.

Over a median follow-up of about 10 years, 34% of the total 13,204 eyes from both studies with no late AMD at baseline had progressed to late AMD.

Comparing the greatest adherence to Med diet vs. the lowest (tertile 3 vs. tertile 1) showed a 22% reduction in relative risk for late AMD, a 29% reduction for GA (p< 0.0001 for both), and a 16% reduction for neovascular AMD (p=0.005).

Consuming more fish contributed to the Med diet’s protective effect. Comparing the highest fish intake vs. the lowest (quartile 4 vs. quartile 1) indicated a 31% lower risk for late AMD in AREDS (p<0.0001) and an 8% risk reduction in AREDS2 (p=0.28).

The benefit of greater adherence to the Med diet and higher fish intake was more pronounced in participants with the CFH protective genotype. In separate analyses, closer diet adherence was also associated with a 21% lower risk of progression to large drusen.

These findings lend further support to the ocular benefits of the Mediterranean-type diet.

Vitamin D Status and Covid-19 Severity

Researchers in Dublin, Ireland propose that improving vitamin D status in the population could possibly reduce serious COVD-19 complications (2).

Synthesized in the body with sunlight exposure, vitamin D plays a role in regulating the immune system. At the cellular level, it modulates both the adaptive and innate immune system through cytokines and regulation of cell signaling pathways. It’s the impact of vitamin D deficiency on cytokine response that is potentially important in context of Covid-19 “cytokine storms” according to the authors.

Although there are currently no randomized controlled trials to prove that vitamin D supple-mentation beneficially influences COVID-19 outcomes, the researchers present data that higher vitamin D status is associated with better outcomes.

The team analyzed European studies, completed since 1999, that measured vitamin D status in older adults. Countries were selected by severity of Covid-19 infection (high and low) and mortality data was gathered from the WHO.

Counter-intuitively, lower latitude and typically ‘sunny’ countries such as Spain and Italy had low mean plasma vitamin D concentrations and high rates of vitamin D deficiency. These countries have experienced the highest infection and death rates in Europe.

Northern latitude countries (Norway, Finland, Sweden) which receive less UVB sunlight than southern Europe (but where supplementation is common), had much higher mean blood vitamin D, low levels of deficiency and for Norway and Finland, lower infection and death rates.

The vitamin D status-covid19 association has also been reported in a study from Northwestern University that has not yet been published. Analyzing patient data from 10 countries, a correlation was found between low vitamin D levels and hyperactive immune systems.

The notion that vitamin D strengths innate immunity and prevents overactive immune responses in Covid-19 deserves attention and further study. 

References

1. Keenan TD, et al. Adherence to the Mediterranean diet and progression to late age-related macular degeneration in the Age-Related Eye Disease Studies 1 and 2. Ophthalmol. Epub ahead of print April 26, 2020
2. Laird E, et al. Vitamin D and inflammation: Potential implications for severity of Covid-19. Irish Med J. 113:81, May, 2020.
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