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In the news: Better Nutrient Intake & Lower Cataract Risk; Tackling Dry Eye and Depression

Vitamins, Carotenoids & Lower Cataract Risk

Over the years, a number of studies have linked a better intake of certain nutrients with a lower chance of having age-related cataract. As a follow-up, university researchers in China conducted a meta-analysis of many of these studies, both observational (population-health) investigations and randomized trials (1).

Most of the nutrients evaluated in the observational studies were associated with a reduced risk for age-related cataract including: Lutein / zeaxanthin (19% lower risk), vitamin A (19%), vitamin C (20%), and vitamin E and beta-carotene (each 10%). In the intervention trials, neither vitamin E nor beta-carotene reduced risk vs. placebo.

Looking further at the observational studies, the researchers performed a dose-response analysis. They found that the risk of age-related cataract decreased by 26% for every 10-mg/day increase in lutein or zeaxanthin intake and decreased by 18% for each 500-mg/day increase in vitamin C intake.

The authors point out that slowing down the develop-ment of age-related cataract by 10 years, would reduce the number of people needing cataract surgery. We do have to keep in mind that while observational studies identify associations, they don’t prove cause and effect. Yet, we can’t go wrong by eating more citrus fruit, tomatoes and dark green vegetables – sources of lutein, vitamin C and other health-supporting antioxidant nutrients.

Dry Eye Disease & Depression Often Overlap

Many studies have found that people with dry eye disease (DED) frequently are dealing with depression too. A newly published study adds to those findings2. In short, the study found that depression is more common among patients with DED than without DED.

The researchers noted that out of 1600 consecutively enrolled participants, 30% were diagnosed with DED. And of those with DED, nearly 27% had depression, as measured by the Geriatric Depression Scale.

It may be that the chronic, painful symptoms of DED can lead to depression. Additionally, anti-depression medications often taken for depressive symptoms are considered to be a risk factor for DED and may cause or at least contribute to dry eye.

But whether depression or DED strikes first, depression may worsen DED. Research has shown that longer-term depression increases the production of pro-inflammatory molecules called cytokines, and inflammation is an important underlying factor in DED.

Tackling Depressive Symptoms: Mood & Food

DED should, of course, be treated by a health care professional, and that in and of itself could have a beneficial effect on mood for some. Improving what we eat can also have a positive impact on depression (although not major depression) and anxiety.

A newly published meta-analysis (2), for example, looked at 16 controlled trials involving over 45,000 participants most of which investigated patients with mild or non-clinical depression. Many of the trials focused on improving the diet in general, reducing unhealthy pro-inflammatory foods, limiting fat intake or weight loss. One study – the SMILES trial – found significant improvement of depressive symptoms with the Mediterranean (Med) diet. Another trial (not included in this meta-analysis) found benefit from a Med diet plus fish oil supplementation.

The meta-analysis authors conclude that dietary interventions significantly reduce depressive symptoms, with women benefiting more than men for both depressive and anxiety symptoms. Dietary changes might be acting through pathways related to oxidative stress, inflammation and dysfunction of the energy producing mitochondria in cells – pathways which can be disrupted in people with depressive disorders. Fruits and veggies also contain polyphenols that have been linked to reduced rates of depression in some observational studies.

References

1. Hong Jiang, et al. Dietary vitamin and carotenoid intake and risk of age-related cataract. Am J Clin Nutr. 109: 43,54, 2019.
2. Firth J et al. The effects of dietary improvement on symptoms of depression and anxiety: A Meta-analysis of Randomized Controlled Trials. Psychosom Med. Feb. 5, 2019.