Last time we looked at what phytonutrients are. Now let’s start digging into some specific phytonutrients and how they improve our health.
Carotenoids
Carotenoids are the yellow, orange, and red colorings made by plants. There are more then 750 naturally occurring carotenoids. The most common carotenoids in the North American diet are alpha carotene, beta carotene, lycopene, lutein, beta cryptoxanthin, and zeaxanthin. Most of these are found in fruits and vegetables. Alpha carotene, beta carotene, and beta cryptoxanthin are considered “provitamin A” carotenoids as our bodies can convert them to vitamin A.
Eating fruits and vegetables rich in carotenoids is associated with a reduced risk of heart disease and some cancers.[1] Carotenoids are absorbed in a much higher concentration when you eat them with fat in the meal. Three to 5 grams of fat is enough to optimize absorption. Chopping and cooking carotenoids also increases their bioavailability.[2]
Lutein and Zeaxanthin
Lutein and zeaxanthin (and meso-zeaxanthin which is made by the body from lutein) are found in high concentrations in the macula of the eye and are known as the macular pigments. They are the only carotenoids that cross the blood-retina barrier and are therefore the only carotenoids found in the eye. Lutein and zeaxanthin protect the eye by filtering out blue light and acting as antioxidants. They may improve visual acuity and slow the progression of age-related macular degeneration (AMD). AMD is the leading cause of blindness in older adults in the developed world. Consumption of about 6 mg/day of lutein and zeaxanthin from fruits and vegetables may decrease the risk of AMD.[3] A 2019 study found that high adherence to a Mediterranean diet rich in fruits, vegetables, legumes, and fish was associated with a 41% reduced risk of advanced AMD.[4]
A typical US diet only has 1-3 mg/day of lutein and zeaxanthin.[5] Ten to 20 mg of lutein/zeaxanthin per day may be ideal for reducing the risk of AMD.[6] In the AREDS2 study, 10 mg of lutein and 2 mg of zeaxanthin lowered the progression to advanced AMD in those with the lowest dietary intakes of lutein and zeaxanthin.[7]
Cataracts are another major cause of blindness among people over the age of 40. Observational studies find those eating a diet high in lutein and zeaxanthin containing foods are less likely to require cataract extraction or develop cataracts.[8] A 2019 meta-analysis found the risk of age-related cataract decreased by 26% for each additional 10 mg of lutein or zeaxanthin eaten per day.[9]
Until recently, testing technologies did not allow for lutein and zeaxanthin to be measured separately. Because of this most tables report their content as a single figure.[10] By far, the greatest sources of lutein and zeaxanthin, by weight or calorie, are dark green leafy vegetables.
Image: Lutein and Zeaxanthin-Food Sources, Bioavailability and Dietary Variety in Age-Related Macular Degeneration Protection. Nutrients. 2017 Feb 9;9(2):120.
Just 100 grams of cooked kale (about 1 cup) would provide 18 mg of lutein and zeaxanthin. Like the other carotenoids, fat greatly increases the absorption of lutein and zeaxanthin. Make sure you have at least 5 grams of fat with your leafy greens or other foods high in lutein and zeaxanthin. A teaspoon of olive oil, 3 ounces of salmon, or about 5 walnut halves would have you covered. Although lutein and zeaxanthin in eggs may be better absorbed compared to vegetable sources, you would need to consume about 72 eggs to equal the amount of lutein and zeaxanthin in 100 grams of kale.[11] Taking into account the increased bioavailability of eggs, you might be able to decrease that to 44 eggs/day to equal the amount of lutein and zeaxanthin you would absorb from 100 grams of cooked kale. Those 44 eggs would cost you 4,500 calories, but the 100 grams of kale is only 60 calories for the same of amount lutein and zeaxanthin.
Lutein and zeaxanthin are not only associated with eye health. Eating foods high in these carotenoids is linked to a reduced risk of many diseases,[12] including Alzheimer’s Disease.[13] This shouldn’t be a surprise if you read my article on brain health.[14] Leafy greens, which are highest in lutein and zeaxanthin, may be the most important food for reducing the risk of cognitive decline, dementia, and Alzheimer’s Disease.
I try to eat some leafy greens every day. How many days in a row do you think you can eat a salad without missing a day?
About the Author: Keith Herman is an estate planning attorney who is also passionate about nutrition and helping others live their healthiest lives.
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Keith Herman is a certified nutrition coach, personal trainer, and estate planning attorney. He is an elected Fellow of the American College of Trust and Estate Counsel, a former adjunct professor at Washington University in St. Louis School of Law, and winner of the Excellence in Writing Award from the American Bar Association.
Keith is the creator of the Health & Well-Being JournalTM, a daily accountability planner for optimizing your mind, body, and spirit, and tracking healthy behaviors.
He is also the author of Eat Like an Expert: How to Start Eating Healthy (and Stick to It), which combines the best of plant-based, Mediterranean, low-carb, and anti-inflammatory diets to create a customizable plan that delivers transformational results.
You can find more information about Keith at KeithAHerman.com
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