In the news: Flavonoids Lower Mortality Risks; Air Pollution May Increase AMD Risk

Flavonoids May Lower Risk of Cancer & CVD Death

A study published in Nature Communications reports that a diet moderate and consistent in plant-based flavonoids may lower the risk of all cause, cancer and cardiovascular mortality (1).

Short-term clinical trials have shown that flavonoid compounds and flavonoid-rich foods improve markers of CVD risk, while results from preclinical studies suggest that flavonoids may also lessen the risk of cancer. Last year, an independent and protective association between higher flavonoid intake and the likelihood of having AMD was also reported.

In the present study, Danish and Australian researchers aimed to learn more about flavonoid intake and mortality – especially cancer mortality, where observational data is scarce.

The researchers assessed the diets of over 56,000 Danes and followed their health and diet prospectively for 23 years, during which 14,083 deaths occurred.

After controlling for relevant factors (smoking, high blood pressure, and numerous other potential dietary and lifestyle confounders), they found that those with the highest flavonoid intake (top 20% of intake) had a 17% lower risk for all-cause mortality and a 15% lower risk for death from CVD compared to those with the lowest intake. Cancer mortality risk was reduced by 20% in the highest vs. lowest flavonoid groups.

The inverse associations between total flavonoid intake and mortality outcomes were strong and plateaued at daily intakes of about 500 mg for non-smokers and low-moderate alcohol drinkers.

For smokers and heavy alcohol consumers, the associations were even stronger and more linear.
According to the authors, emerging evidence suggests that flavonoids may afford greater protection to those with these lifestyle habits. Flavonoids may be protective against some detrimental effects these lifestyle factors have on nitric oxide bio-availability, endothelial function, blood pressure, inflammation, blood lipids, platelet function, and/or thrombosis.

The authors point out that meeting the threshold level of 500 mg flavonoids/day is readily achievable. One cup of tea, 1 apple, 1 orange, about 3 ½ ounces each of blue-berries and broccoli would provide most of the 6 sub- classes of flavonoids and over 500 mg total flavonoids. Tea, chocolate, wine, apples, and pears were the main flavonoid sources in the present study population.

Air Pollution May Up the Risk of AMD

In the first study of its kind, Taiwanese researchers report in BMJ’s Journal of Investigative Medicine that long term exposure to vehicle exhaust-related air pollution is associated with a nearly two-fold increase in AMD risk (2). While the effects of air pollutants on the risk of respiratory and cardiovascular disease are well acknowledged, not much evidence has been generated suggesting that air pollution impacts ocular disorders.

Analyzing air-quality data (1998-2010) and health insurance data for nearly 40,000 AMD-free urban dwellers (aged 50+), the researchers explored whether long term exposure to the common pollutants nitrogen dioxide (NO2) and carbon monoxide (CO) is associated with AMD risk. Over the 11-year follow-up, 1442 participants developed AMD 

Compared with the lowest exposures, those with the highest NO2 exposures were 91% more likely to develop the disease while the highest CO exposure increased the risk by 84%.

Interestingly, exposure to moderate levels of the pollutants did not significantly raise AMD risk, raising the possibility of a threshold effect. More research to confirm these findings remains to be done.

According to the lead author, these macula-harmful pollutants are more likely to be entering the blood stream after being inhaled rather than entering the eye directly. NO2 and CO damage cells by creating reactive molecules (free radicals), which underscores the importance of the eye’s antioxidant defense system.

References

1. Bondonno NP, et al. Flavonoid intake is associated with lower mortality in the Danish Diet Cancer and Health Cohort. Nature Comm. 10:3651, 2019.
2. Kuang-Hsi C, et al. Traffic-related air pollutants increase the risk for age-related macular degeneration. J Invest Med. Epub August 19, 2019.