In the news: Egg Intake Tied to Healthy Vision New Studies on Vitamin D & COVID-19

Egg Consumption, Serum Lutein & MPOD

Observational studies have shown that dietary consumption of lutein and zeaxanthin are inversely associated with age-related macular degeneration (AMD) risk. Eggs are one of the richest sources of lutein and zeaxanthin, with one egg yolk providing approximately 200 mcg of lutein. Due to their fat content, eggs have greater lutein and zeaxanthin bioavailability relative to other carotenoid-rich foods, including vegetable sources such as spinach and kale.

To date, five clinical trials have been conducted to assess the influence of egg-rich diets with varying concentrations of lutein on serum lutein levels, and its effect on macular pigment optical density (MPOD). The results of these trials have been mixed, leading researchers to perform the first meta-analysis or systematic review of these studies. The aim of the study was to determine the effect of egg consumption on MPOD and serum lutein levels in those with AMD and in healthy subjects(1).

The authors used a random-effects model to obtain pooled weighted mean differences and standard deviations for each outcome. Using the Cochrane Collaboration’s tool to assess the quality of eligible studies, five trials (296 participants) were included.

Egg consumption was found to significantly increase MPOD (weighted mean difference +0.037, P = .027) and serum lutein (weighted mean difference +0.150 µmol , P = 0.009). A subgroup analysis revealed that egg consumption increased MPOD to a greater extent in a healthy population than in AMD patients.

The findings also indicate that daily egg consumption is associated with reduced AMD progression, according to the authors who also caution that further long-term trials are necessary to confirm their findings.

Eggs are a good source of protein (about 6 g/egg), vitamin D and choline. Years ago, the advice was to eat no more than 1-2 whole eggs per week. But that advice has changed, with the American Heart Association currently suggesting one egg per day for those who can eat them and as part of an overall healthy diet. Eggs, which contain about 200 mg cholesterol, have been found to consistently raise HDL cholesterol without increasing total or LDL cholesterol. However, since individual response to dietary cholesterol can vary, those with high blood cholesterol should check with their physician.

Vitamin D & COVID-19: New Findings

Two new studies addressing the influence of vitamin D status on COVID were recently published. The first(2), a systematic review and meta-analysis, reports that vitamin D insufficiency worsens COVID-19 infections.

The analysis, which included 27 epidemiological studies, found 64% more vitamin D deficiency present among severe cases compared with mild cases. In addition, insufficient blood levels of the vitamin significantly increased odds of hospitalization and mortality. No association between vitamin D deficiency and a higher chance of COVID-19 infection was seen.

In contrast to the lack of a link between vitamin D status and increased chance of infection in the meta-analysis, the results of another newly published study(3) suggests that deficiency of the vitamin is associated with increased COVID risk.

Analyzing data from a University of Florida database, the investigators found that those deficient in vitamin D were 4.6 x more likely to be positive for COVID-19 than those with sufficient levels of the vitamin. The vitamin D-COVID association decreased after adjustment for race, diabetes, obesity and periodontal disease status, but still remained robust (P < 0.001). Importantly, the risk of developing COVID increased by a factor of 5 after adjusting for age, the authors wrote.

References

1. Sikaroudi MK, et al. A positive effect of egg con-sumption on macular pigment and healthy vision: a systematic review and meta-analysis of clinical trials. J Sci Food Agric. Jan. 24, 2021.
2. Pereira M, et al. Vitamin D deficiency aggravates COVID-19: systematic review and meta-analysis. Crit Rev Food Sci Nutr. 1-9 published online Nov 4, 2020.
3. Katz J, et al. Increased risk for COVID-19 in patients with vitamin D deficiency. Nutr. 81:111106, 2021.