There’s a lot written about the wonder of nuts. They have shown to be effective at lowering risk factors for heart health and boosting your metabolic health.

But they’re also rich in mega-3 fatty acids and vitamin E – helping protect the eyes from age-related damage and diseases, such as cataracts, macular degeneration and dry eye syndrome.

Hazelnuts and almonds in particular are talked up as good for eye protection.

In the meanwhile, you don’t hear so much about the pistachio, except they’re easy to peel.

Pistachios are packed with nutrients, but with less calories and fat than other nuts. They also boost your immunity.

Uniquely, though, they contain a pigment that serves as the eyes’ ‘internal sunglasses’.

How boosting this pigment helps the eyes

A new study by researchers from Tufts University has found that consuming pistachios daily may significantly improve eye health by increasing macular pigment optical density (MPOD).

The researchers describe MPOD as “an important indicator of eye health, as it protects the retina and is linked to a reduced risk of age-related macular degeneration (AMD), a leading cause of blindness in older adults”.

Found in the fovea, or the centre of the macula, the macular pigment is comprised of two dietary carotenoids, zeaxanthin and lutein, a powerful antioxidant.

Optometrists say that these pigments, when healthy, function like “internal sunglasses”, screening photoreceptors from oxidation and potential harm.

Pistachios are the only nut that provides a measurable source of lutein.

The study found that pistachio consumption “nearly doubled participants’ daily intake of lutein, which is typically very low in most American diets, and significantly raised plasma levels of lutein”.

The randomised controlled trial showed that compared to eating a usual diet alone, eating 57 grams of pistachios per day for 12 weeks resulted in a significant increase in MPOD in otherwise healthy middle-aged and older adults.

Dr Tammy Scott is a research assistant professor and clinical neuropsychologist at the Friedman School of Nutrition Science and Policy at Tufts. She is the lead author of the study.

She said that in the study, participants were selected to have low habitual baseline lutein intakes in their diet. Just 57 grams per day rapidly increased lutein levels in the blood in only six weeks.

“By simply incorporating a handful of pistachios into your diet, you can improve your intake of lutein, which is crucial for protecting your eyes,” she said.

Scott noted that “pistachios provide a source of healthy fat, potentially making the lutein from pistachios better taken up into the body”.

Other health benefits of lutein

A 2008 study showed that taking a lutein supplement may help improve your cognitive function, such as learning, thinking, reasoning and remembering.

This finding is supported by other studies that suggest higher lutein levels are associated with better cognitive performance, including memory and processing speed.

This suggests that lutein has potential in supporting overall healthy ageing.

“Lutein crosses the blood-brain barrier, where it may help reduce oxidative stress and inflammation,” said Dr Elizabeth Johnson, a co-investigator on the new study.

As with the eye, “lutein selectively accumulates in the brain and may play a role in reducing cognitive decline”.

The study was supported financially by American Pistachio Growers.