Lutein and zeaxanthin for eyes and brain

Screen Shot 2016-08-19 at 12.34.34 PMI love when nutrition research intersects with actionable food recommendations to promote health.  A recent talk on the relationship of lutein and zeaxanthin to cognitive function is the perfect example of that concept.

Lutein?  Zeaxanthin? I hope I haven’t lost your attention already.  These are carotenoid molecules found in egg yolk and many plant foods.  Unlike some other large antioxidant molecules, they can cross the blood-retina barrier*, where the accumulate in the macula and form macular pigment.  Together they act as antioxidants, protecting retinal tissue.  People with lower concentrations of these molecules have a higher risk for eye diseases like macular degeneration.  In studies where people with age-related macular degeneration are supplemented with lutein and zeaxanthin, macular pigment increases and vision improves.

What does this have to do with cognition?  Lutein and zeaxanthin also cross the blood-brain barrier*, and research in animals shows that these molecules accumulate in brain tissue.  Their function in brain is not well understood, but the thought is that, since they are antioxidants, they may protect and benefit brain tissue.  However, it’s not so easy to examine brain tissue from human subjects.  One study solved that problem by examining brain tissue from elderly people enrolled in a study of cognitive performance.  These subjects had agreed to donate their brains after death.  The researchers measured the subjects’ macular pigmentation and cognitive function (while still alive), and compared that to brain tissue lutein and zeaxanthin concentrations after death.  Concentrations of these two antioxidants were significantly related to several measures of cognitive performance.  Which explains why other studies have shown that plasma levels of carotenoids are linked to risk for cognitive impairment and Alzheimer’s disease.

Where the antioxidant rubber hits the road

So, assuming you’d like to protect your eyes and brain, what do you eat to increase your lutein and zeaxanthin intake?  Vegetables and eggs.  That’s the conclusion of other studies about lutein intake.  But there’s a catch.  These molecules are fat soluble, meaning better absorbed in the presence of fat.  You might not absorb much lutein by chowing down on non-fat kale or spinach, even though both have high lutein content.  One study showed that lutein from eggs was much better absorbed and raised blood levels of lutein more compared to spinach or 2 different lutein supplements. Why?  Lutein in egg yolk is associated with fat, which may account for better absorption.  Spinach and supplements have no fat.  Interestingly, despite lack of fat, the lutein from spinach was better absorbed than from the supplements.  another study I saw shows that avocado was another excellent and well-absorbed source, increasing blood and macular pigment levels even more than egg.  Avocado is even higher in fat than egg, which may explain that effect.  Hmmm.  Makes you wonder about the effect of our decades-long fear of egg yolks on eye and brain health.

Food Is Best!

Which foods are best for lutein and zeaxanthin?  Based strictly on the concentration of these in food, you’d go for

  • kale
  • spinach
  • chard
  • collards
  • kiwi
  • peas
  • zucchini
  • beet greens
  • corn and cornmeal
  • broccoli
  • winter squashes
  • grapes
  • peppers
  • egg yolk
  • avocado

But based on bioavailability (absorption) you’d go for egg yolk and avocado.  What are some practical food ideas to use this information?

  1. An omelet with spinach or kale.
  2. A salad with chunks of avocado
  3. Egg salad sandwich with avocado slices
  4. Guacamole dipped with pieces of broccoli or pepper
  5. Tacos made with yellow corn tortillas, topped with avocado

How do you know it’s working?  Researchers use a special machine that measures macular pigment in the eye.  Perhaps someday that measurement will become commonplace when you visit the eye doctor, as a way to alert people to get more of these important antioxidants in their diet.  Why wait though?  I’ll be focusing on high lutein foods every day anyway.

*The blood-brain and blood-retina barriers are specialized membranes surrounding those tissues that selectively allow certain molecules in while keeping others out.  Think of the barrier as a biological security system.

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