In the news: EPA/DHA Intake Linked to Early AMD Risk; Excess Sugar May Impact Mitochondria

Omega-3 Fatty Acids & Risk of AMD

Several established mechanisms may account for the impact of the intake of DHA and EPA on AMD risk. Omega-3 fatty acids have demonstrated beneficial effects on anti-inflammatory and anti-thrombotic processes. Omega-3 PUFAs have shown antioxidant effects on the retinal pigment epithelium and photoreceptors. Additionally, EPA and DHA can generate inflammation-resolving molecules.

It’s also thought that atherosclerosis of the vessels that supply the retina contributes to the risk of AMD in the same way this mechanism underlies coronary heart disease (CHD). According to this theory, dietary fats related to CHD may also be related to AMD. Increased intake of the omega-3 fatty acids EPA and DHA for example have been associated with a reduced risk of CHD and may have a similar association with AMD.

However, population studies on the relationship between dietary fatty acids and the risk of AMD have yielded inconclusive results. To gain further insight into this relationship, researchers recently conducted a dose-response meta-analysis of prospective cohort studies to evaluate the link between specific types of dietary and plasma fatty acid and early and advanced AMD risk(1).

Higher EPA/DHA Lowers Early AMD Risk

Eleven observational cohort studies with over 167,000 participants were included in the meta-analysis. For highest versus lowest comparison and dose-response analyses, the authors analyzed the relative risk estimates with a 95% confidence interval. During the follow-up periods, which ranged from 3 to 28 years,6,318 cases of AMD were recorded.

Dietary intake of EPA and DHA combined (per 1 gram per day increment) were found be associated with a 33% risk reduction of early AMD.

The dose–response analysis revealed that a 1 g/day increase in dietary DHA and EPA intake was significantly associated with a 50% and 60% decrease in the risk of early AMD, respectively.

Plasma DHA and EPA were significantly associated with reduced risk of advanced AMD. However, no clear associations were found between AMD risk and other types of fatty acids – monounsaturated, saturated, and polyunsaturated fatty acids, including alpha linolenic acid.

The authors conclude that the dose-response meta-analysis provides high quality evidence that a higher dietary intake of DHA and EPA was significantly associated with a decreased risk of early AMD. In terms of advanced AMD, insufficient evidence precluded definitive conclusions concerning dietary fatty acids and plasma fatty acids.

Excess Sugar & Mitochondrial Dysfunction

Mitochondria are intracellular organelles necessary for synthesizing cellular energy (ATP) and cell survival – including cells of the retinal pigment epithelium (RPE). Mitochondrial dysfunction induced by environmental toxicants may be an important risk factor in the etiology of dry AMD. Altered morph-ology and dysfunction of RPE mitochondria has been observed in eyes with AMD, and mitochondrial DNA from these eyes show more oxidative damage.

Using a new mouse model to study metabolic disease, researchers report that excess sugar may cause mitochondrial inefficiency(2). Too much glucose in cells, which is directly linked to sugar consumption, reduces PUFAs in mitochondrial membranes. The excess sugar is instead made into a less flexible fatty acid which changes the membrane composition and damages mitochondria. The investigators were able to reverse this effect in mice by feeding them a low-sugar ketogenic diet.

As Americans consume on average roughly 2-3 times the recommended amount of sugar daily, this novel pre-clinical finding might eventually lead to better eye health by cutting back on added sugar.

References

1. Zhong Y, et al. Dietary fatty acid intake, plasma fatty acid levels and the risk of AMD: a dose-response meta-analysis of prospective cohort studies. Eur J Nutr. 60:3013-3027, 2021.
2. Waldhart N, et al. Excess dietary carbohydrate affects mitochondrial integrity as observed in brown adipose tissue. Cell reports 36:109488, 2021.