They were the bright yellow in the calendula flowers, the ocher streaks in the tomato skins, the yellow-green of the sorrel and kale, and the topaz of the turning maple leaves. They were the darker green of the delicate lamb’s quarters and serrated dandelion greens. And because nature is thrifty and likes to make the most of any useful substance, they were also the burnt umber in the wings of a passing butterfly. And yes, they are in us as well.
Xanthophylls are antioxidants in the carotenoid family, and lutein and zeaxanthin (or L/Z, as they are often denoted) are the main xanthophylls found in food. We can’t synthesize xanthophylls, or any carotenoids for that matter, so we get them by eating plants that make them or animals — such as chicken and fish — that also eat plants. Despite their availability in nature, I am seeing lutein and zeaxanthin supplements sold everywhere.
It appears that L/Z are the nutrition boost du jour; their market share is growing and is expected to reach $396 million in 2024. An entire shelf in my local drugstore is dedicated to lutein-containing supplements, and I’m now spotting L/Z on eyedrops and in face creams, dairy products, sports drinks, fruit juices and baby formula. Some egg producers, whose products already have lutein naturally, are fortifying their eggs with the stuff.
Why such hunger for L/Z, particularly lutein? After all, they are just two of the 30-plus carotenoids that are found in the human body, with other notable ones being lycopene and beta carotene, an antioxidant we convert to vitamin A.
“Lutein is a major workhorse molecule,” said Billy Hammond, a neuroscientist at the University of Georgia who studies the role of these compounds in eye and brain health. Other carotenoids are found in our kidneys, livers skin, immune system, fat cells and so on, but lutein and zeaxanthin are the main carotenoids in our macula (the vision center of the eye) and brain.
Without these colorful compounds, we would be stumbling in the dark, blinded by light, and terrible drivers. We would also be missing every fly we tried to swat (or baseball, for that matter) and our balance would be shaky. There is also strong evidence that lutein and zeaxanthin protect against age-related macular degeneration, the leading cause of blindness in the United States and most industrialized countries. Neuroscientists are discovering that we need an adequate stockpile of xanthophylls to reason, learn new things and ward off dementia. Two newly published studies suggest that low blood levels of L/Z can be a harbinger of frailty — the inability to bounce back from an illness — in older adults.
Perhaps one of the reasons that we are hearing so much about L/Z is because there is a noninvasive way to measure them. While most nutrients from foods or supplements are challenging to trace once they enter the cavern of the human body, lutein and zeaxanthin are 100 times more concentrated in the macula than elsewhere, and their density can be studied using a fancy desktop ophthalmoscope. This measurement, called Macular Pigment Ocular Density (MPOD) correlates well with blood levels of the compounds and with the amount we ingest. Conveniently, MPOD also correlates with objective tests of eye and brain function such as how fast we process visual stimuli.
“We have found that most people are in a deficiency state and would get a big benefit from just getting to normal,” Hammond said. His research shows that even young, healthy athletes can improve their eye and brain performance when they boost their levels of L/Z, and he estimates that this benefit only increases as we age.
John Erdman, a nutrition scientist at the University of Illinois who has spent much of his career studying carotenoids, agrees with Hammond. In a recent article in the European Journal of Nutrition, he and his colleagues argue that the sum of the evidence in favor of lutein is so strong that the Institute of Medicine, the group that sets the Daily Recommended Intake of other nutrients, should include lutein on the list. “Establishing dietary guidance for lutein would encourage people to eat lutein-containing foods and raise public awareness about the potential health benefits,” he said, adding that other compounds with much less evidence of benefit, such as fluoride, have made the list.
So, ideally how much L/Z do we need? Do we really need to shop the nutraceutical aisles or buy fortified eggs to get it?
Both Hammond and Erdman estimate, based on the available research, that we need about 12 mg of lutein and 2 mg of zeaxanthin a day, and yet the average American adult gets about one-tenth that amount. As for how to increase our lutein intake, “Food is always the better choice,” Hammond said. Supplements, on the other hand, are better for research, he said, because study subjects can’t differentiate them from placebos and the researchers know exactly how much of a given substance they are administering. (Hammond’s research is partially funded by nutraceutical companies.)
Though food’s complexity makes it tougher to measure any effect on our health, that complexity makes food a better choice for adding lutein to your diet. Consider spinach, a lutein-packed food. Roughly three cups of raw leaves gives you your daily dose of lutein, but because carotenoids are fat soluble, mixing that spinach with an olive oil dressing will greatly increase your absorption of the compound.
Cooking also makes the carotenoid more bioavailable. Many traditional recipes from around the globe are lutein and zeaxanthin bombs, including saag, a tasty North Indian dish of simmered spinach mixed with yogurt; the Middle Eastern side dish of roast carrots tossed in za’atar spices and olive oil; and the Mesoamerican classic combo of tomato salsa, cilantro, avocado, and corn tortillas or tortilla chips. To check out how much lutein and zeaxanthin is in your dinner, you can use a calculator when you search “food composition database” on the Agriculture Department website.
In the quest for xanthophyll-rich meal, the cultivar (or specific genetic traits) of any fruit or vegetable can add yet another level of complexity. Take your classic supermarket Cavendish banana. It has negligible amounts of lutein, but researchers have found that the Hung Tu, a lesser-known banana indigenous to Papua New Guinea, has 30 times as much of this carotenoid. Eggs are generally a good source of lutein and zeaxanthin, but the amounts of these compounds vary depending on the breed of hen, what she gets in her diet (marigolds are good) and how she spends her day. One study suggests that pastured hens deposit more lutein and zeaxanthin into their egg yolks. Note to the egg-whites-only crowd: You will be missing out on these bioactive compounds.
There are some instances when supplemental lutein and zeaxanthin is in order. The Age-Related Eye Disease studies, two large multicenter trials, make a convincing case for taking L/Z early if you are diagnosed with macular degeneration, because they might prevent progression to more serious disease. Older people might also need a supplement boost because they are less likely to absorb L/Z through the intestinal lining. Some studies show that people who are inactive, overweight or have diabetes generally have lower blood levels of lutein and zeaxanthin. Of course, these are observational studies, so it’s not clear which is the chicken and which is the lutein-enriched egg.
“The bottom line,” Hammond said, “is that most people just don’t eat enough fruits and vegetables.”
I told him about the xanthophyll inventory I had made in my own garden — how it seemed to be everywhere. “Yes,” he said, “my work is always reminding me that we are one with nature, that we integrate plants into our own biology. Sadly, we are making parking lots of our bodies, just like we are doing with the forests.”