Summary

• Lutein and zeaxanthin are xanthophylls, types of carotenoids, which are pigments present in many foods. Leafy green vegetables and herbs are especially rich sources.
• Lutein and zeaxanthin are antioxidants that preferentially accumulate in the macula of the retina at the back of the eye, where they filter short-wavelength light, protecting the retina from damage due to oxidative stress. Through this, they protect against age-related macular degeneration.
• Xanthophylls can accumulate in other tissues too, and lutein can improve several cognitive functions in both young and older people, including memory and attention. In the skin, xanthophylls help guard against damage from the sun.
• Because they are fat-soluble, lutein and zeaxanthin are in the gel capsules of Coastline at doses shown to enhance eye health, cognition, and skin health.
• Lutein and zeaxanthin are perfectly safe, even at daily many times higher than the ones in Coastline

What are lutein and zeaxanthin?

Lutein is a xanthophyll, a type of carotenoid that animals cannot synthesise by themselves. Zeaxanthin is an isomer of lutein, meaning that they're chemically very similar. The difference is that zeaxanthin has 11 double bonds in its xanthophyll chain whereas lutein has 10, giving zeaxanthin a slightly higher antioxidant rate. Lutein and zeaxanthin accumulate in the back of the eye, protecting cells against damage from UV radiation. They also sharpen cognitive function and protect the skin from UV radiation.

Lutein and zeaxanthin are present in small amounts in the diet, and the richest sources are green leafy vegetables such as kale and spinach.

Effects of lutein and zeaxanthin on lifespan and healthspan 

Unlike most ingredients in Coastline, lutein and zeaxanthin aren’t included for their effects on lifespan per se. (Their effects haven’t really been studied, other than tentative evidence from fruit flies that lutein extends lifespan). Instead, we included lutein and zeaxanthin for their effects on the function of two body systems, the central nervous system and the integumentary system (the skin, specifically).

Positive effects of lutein and zeaxanthin on human health and performance

Lutein and zeaxanthin are best known for their effects on eye health and their protective effects against age-related macular degeneration (AMD). However, as more research on them unfolds, we’re finding that lutein and zeaxanthin have other benefits too. Let’s explore these positive effects, starting with eye health.

Lutein and zeaxanthin protect the eye and ward of macular degeneration

True to its name, AMD is degradation of the macula in the retina, the layer of cells that line the wall at the back of each eye. There are two types of AMD. “Dry” AMD is due to thinning of the retina. “Wet” AMD, by contrast, involves growth and leakage of blood vessels behind the retina. AMD generally starts dry and then progresses slowly to wet in about a fifth of cases. Both forms can impede vision, but wet AMD is the leading cause of blindness in older adults in economically-developed countries. And there's no cure for late-stage AMD. 

To understand how lutein and zeaxanthin help counter AMD, it might be helpful to have a quick primer on a few structures on your eyes. The retina contains several types of light-sensitive (“photoreceptive”) cells. “Rods” are involved in vision in low light levels. “Cones”, of which there are three types, are key to color vision. Then there are other cells that send information about light exposure to several parts of your brain that help coordinate your body’s clockwork and other processes. The macula is the central portion of the retina and is particularly important to being able to see details. 

When cells in the retina absorb light they produce free radicals. This oxidative stress then damages lipid structures, including cell membranes made fragile by their polyunsaturated fatty acids. The damage needs to be cleaned up, and this role is fulfilled by retinal pigment epithelial cells, which gobble up (“phagocytose”) and digest the mess. The problem is that as the damage is digested, lipofuscin, a tangled mess of fat and metals, can start to accumulate, doing further damage that compromises local function and vision. This isn’t the only process at play, but it does matter.

Importantly, the amount of damage light can instigate in the eye depends heavily on the light’s parameters, including its wavelength, which gives light its color. Wavelength has a tremendous effect on how damaging light can be: Light with a wavelength of 440 nm, which appears blue, needs about 100 times less energy to damage retinal cells than light with a wavelength of 590 nm, which appears orange. 

Here’s where lutein and zeaxanthin come in: Lutein and zeaxanthin are antioxidants that get taken up into the eye and concentrated in the eye’s lens and macula lutea. The macular pigment acts as a blue-light filter, absorbing some short-wavelength light and hence shielding other cells from damage. Lutein and zeaxanthin are the only carotenoids that preferentially accumulate in the macula, and roughly twice as much lutein accumulates as zeaxanthin. However, lutein and zeaxanthin aren’t distributed evenly. Instead, zeaxanthin dominates the fovea, an area with a high density of cones that is exposed to very bright light, whereas lutein dominates the peripheral retina. Fundamentally, this is why they’re like Batman and Robin, Thelma and Louise, or whatever your favourite duo is — they’re best together!

The AREDS2 study was one of the first to show that lutein and zeaxanthin help halt AMD, finding that adding 10 mg lutein and 2 mg zeaxanthin (the same doses as in Coastline) to a multi-ingredient nutraceutical product reduced progression of AMD to the advanced form. Since then, however, there have been many more related studies, and it’s now clear that combined lutein and zeaxanthin supplements increase macular pigment density, including in people with healthy eyes, provided the total dose is 5 mg per day or higher. While this affords people with healthy eyes some protection against the kind of damage that drives AMD, in people with eye disease it also translates into sharper vision too.

Lutein and zeaxanthin improve cognitive function

The potential for xanthophyll supplementation to enhance cognitive function as well as vision has come into focus (sorry, couldn’t resist the lame pun), and experiments have consistently found that lutein and zeaxanthin enhance cognition. For example, a study of older adults found that supplementing the same doses of lutein and zeaxanthin as in Coastline for a year helped preserve performance in a word-learning task. The scientists also measured blood flow in the brain, finding improved blood flow in some brain regions. The pro-cognitive effects of lutein and zeaxanthin are apparent even in healthy young adults and children. As just one example (there have been several similar studies), healthy young adults who supplemented 10 mg lutein and 2 mg zeaxanthin (again, the same doses as in Coastline) for a year improved multiple cognitive functions compared to the placebo group, including attention, memory, and reasoning ability. 

Some of these improvements are probably due to improved fidelity of the visual system enhancing related cognitive functions, such as quickly processing seen information and remembering the locations of viewed objects. This is congruent with several studies that have reported that the degree to which the density of macula pigment increases correlates with how much cognition improves by. Lutein doesn’t only accumulate in the eye, it also accumulates in other parts of the brain, including the hippocampus, which is key to short-term (“working”) memory, and frontal cortex, which is a bit like the brain’s CEO and is involved in reasoning and planning (“executive functions”). Notably, the concentrations of xanthophylls in some brain regions mirror the concentrations in the macula, and higher concentrations are associated with better cognitive functions. In the brain, lutein probably serves several functions, including protecting against oxidative stress. Some research has also found that lutein and zeaxanthin increase blood levels of brain-derived neurotrophic factor, a protein that helps remodel the brain in response to changing demands.

Lutein and zeaxanthin protect the skin against sun damage and aging

Finally, like several other carotenoids, such as lycopene, lutein and zeaxanthin might improve skin health in a way somewhat similar to how they protect the eye. Specifically, xanthophylls can boost skin carotenoid levels and thereby protect the skin against photodamage. While more clinical research is needed, there is preliminary evidence both lutein and zeaxanthin improve skin function and are likely to protect against skin aging. For example, an experiment compared the effects of four groups of products over 12 weeks in 25- to 50-year-old women: 1) 10 mg lutein and 0.6 mg zeaxanthin per day plus a placebo cream, 2) a topical skin cream containing lutein and zeaxanthin plus a placebo supplement, 3) both the lutein and zeaxanthin supplement and cream, and 4) a placebo supplement and a placebo cream. Focusing on group 1) only, it found that the supplement protected the skin against damage from UV radiation, both reducing skin reddening and decreasing peroxidation damage to lipids in the skin. The supplement also increased skin elasticity (wrinkling is driven by loss of skin elasticity) and hydration. Other research on the effects of 12 weeks’ supplementation with 10 mg lutein on skin responses to UV radiation found that some of lutein’s photo-protective actions are likely due to changes in the expression of genes in the skin implicated in photoaging and oxidative stress.

Our use of lutein and zeaxanthin

Regarding the doses of lutein and zeaxanthin we use, as mentioned above, we use doses that have proven effective in improving macular pigment density, vision in people with certain eye diseases, and several cognitive functions, and the dose of lutein matches that shown to protect skin against damage from UV radiation.

Regarding timing, lutein and zeaxanthin are in the Coastline SoftGels. Honestly, we don’t think the timing of when you take these matters significantly. Some of our team members take these in the morning based on a speculative rationale related to roles of the ingredients in the gel capsules on mitochondrial function and oxidative stress. Other team members, however, take them in the evening for convenience because they prefer to take all their capsules at once. The choice is yours! 

Regarding the forms of lutein and zeaxanthin we use, both are extracted from marigold flowers, consistent with research on these supplements. Since both are lipid soluble, the lutein and zeaxanthin we use are suspended in oil to improve their bioavailability.

Lutein and zeaxanthin typical dietary intakes and safety

Our bodies cannot make lutein or zeaxanthin by themselves, and most of us consume inadequate amounts for maximal benefits. Most US adults have been estimated to consume about 1 to 2 mg per day, for instance. The best dietary sources of lutein and zeaxanthin are leafy green vegetables and herbs, especially parsley (about 85 mg lutein and zeaxanthin per 100 g), kale (about 81 mg lutein and zeaxanthin per 100 g), basil (about 71 mg lutein and zeaxanthin per 100g), and spinach (about 69 mg lutein and zeaxanthin per 100 g).

Being parts of the normal human diet, both lutein and zeaxanthin are very safe at reasonable doses. For example, the European Food Safety Authority (EFSA) has suggested an Acceptable Daily Intake for lutein of 1 mg per kg bodyweight, 75 mg for a 75-kg person. Similarly, the EFSA deems the safe intake of synthetic zeaxanthin to be 0.75 mg/kg body weight per day, 56 mg for a 75-kg person. These levels are many times higher than the doses in Coastline.