Lutein, zeaxanthin and meso-zeaxanthin accumulate in the retina of the eye via a dedicated transportation pathway. Like other antioxidant substances that are found in the diet that have dedicated transport mechanisms, such as l-ergothioneine, the transport mechanism is not fully understood. But in the case of the macular carotenoids, the effect of these compounds is clear, and evidence is mounting.
James Stringham, PhD, is an experimental psychologist by training who has concentrated on the effects of visual performance as a factor in cognitive performance. Stringham, who is now a research scientist at the University of Georgia, has in the past studied visual performance and the role carotenoids play in other career stops including a stint as senior vision scientist at the Air Force Research Laboratory (AFRL).
“I started studying visual perception which of course involves the brain,” Stringham told NutraIngredients-USA. “Along the way I have become something of a neuroscientist.”
Concentration of carotenoids
Many researchers in the field of dietary ingredients start out with the compounds themselves, looking at traditional uses and trying to build up a picture that conforms to Western scientific methods of their modes of action and activities in the body. Stringham worked the other way, so to speak, starting with the obvious and profound concentration of these carotenoids in the eye and working backward to fill in the blanks as to why there are there.
“That led me into nutrition as well,” Stringham said. Studying these xanthophyll carotenoids led Stringham to a revelation; of all the well-researched dietary ingredients, such as omega-3s and vitamin D3, lutein, zeaxanthin and meso-zeaxanthin stand alone in terms of the concentration at one site. Like those other dietary ingredients these carotenoids, especially lutein, can be found in many tissues, too, but their prevalence in the retina really stands apart.
“It is the highest concentration of any nutrient that the body takes in in any tissue in the body,” Stringham said.
Stringham has studied these ingredients in connection with a variety of visual parameters. Last year he published a paper showing that they can help improve recovery from so-called ‘disability glare.’ Also last year, a group led by Stringham studied how macular carotenoids can improve visual performance by enhancing contrast sensitivity. Another paper on contrast sensitivity is in the final stages of publication, Stringham said.
Dual purpose ingredients
These carotenoids have both a physical and metabolic function, Stringham said. From a purely physical, mechanical point of view, they help to filter blue light that can damage sensitive tissues in the macula, setting the eye up for macular degeneration, the leading cause of vision loss in people over the age of 50. From a metabolic standpoint, they are effective antioxidants and help squelch tissue-damaging free radicals in the macular tissue.
Blue light damage is of course of most concern when strong sunlight enters the eye. But modern life has led to an insidious pathway for blue light to enter the eye, through the constant soft glow of LED screens, Stringham said.
“It’s little known that iPads, iPhones, computer screens, they all incorporate LEDs which emit a combination of blue and yellow light. If you mix blue light and yellow light you get a perfect white. I’m getting a fair amount of blue light exposure just by looking at my phone,” Stringham said.
“It’s not like being out in sunlight but it’s enough blue light to affect the retina and it causes a very subtle squinting to occur. Over time that squinting adds up to produce eye strain, eye fatigue and headaches. Researchers have labeled it ‘computer vision syndrome,’” he said. Stringham said another paper is in the review process looking at macular carotenoids in connection with CVS.
“After six months of supplementation it lessens these negative symptons and it actually improves sleep quality. Sleep disturbance is another effect of CVS,” Stringham said.
Green light on blue light
One brand that is taking advantage of Stringham’s work on blue light is Twinlab, which recently relaunched products in the eye health category under the Blutein brand name. The products are built around OminActive’s Lutemax 2020 ingredient, which Stringham has used in some of his research.
According to Twinlab, the average American adult spends 11 hours a day in front of an electronic screen, cell phone, tablet, computer and TV, while children are exposed 6.5 hours, and even toddlers receive an average of 2.5 hours of damaging blue light every day.
“Only two hours of using a digital device can lead to eye strain, fatigue and dry eyes. Do the math and you can see the impact of all the hours we spend with non-stop screen exposure,” Twinlab CEO Naomi Whittel said. The launch of the four new Bluetein products within the Ocugard family of offerings is part of Whittel’s plan to reinvigorate the legacy Twinlab brand. Whittel was named CEO a little more than a year ago after Twinlab’s parent company acquired Reserveage, the brand she founded.