Last week, Dr. Billy R. Hammond from the Department of Psychology at UGA presented a seminar on his carotenoid research. Carotenoids are a group of pigments found in plants that give them yellow, orange, or red color. They are considered phytonutrients, compounds that are naturally found in food and appear to have a health benefit. Dr. Hammond’s research explores the benefits of two specific carotenoids, lutein and zeaxanthin. They are found in high levels in the retina of the eyes and the brain, so his lab has studied the roles of these two compounds within the central nervous system.
The research presented provided compelling arguments for the benefits of lutein and zeaxanthin. One of their primary functions in the body is to serve as antioxidants, compounds that reverse cell damage. Cell damage is a normal part of aging and exposure to things in our environment. For example, exposure to the sun can damage skin cells over time. To demonstrate lutein’s antioxidant ability, they studied its effects on the skin. The group who took a lutein supplement had increased skin hydration, elasticity, and less damage to skin cells compared to those who did not. To translate this to the central nervous system they did a similar study but looked at the retina of the eye, because its cells can be damaged by blue light. Lutein resulted in improvements in vision by reducing glare and stray light. Again, these types of damage in our body cannot be entirely prevented, but these compounds can act as a natural defense.
Lutein and zeaxanthin (LZ) are also beneficial because they improve brain signaling. Signals in the brain are sent through brain cells (neurons), and supplementation with LZ has been shown in their research to improve communication between these cells. For example, when one group took LZ and the other did not, they found that the LZ group had faster visual processing and reaction time. To confirm these results, similar studies were done in different age groups (pre-adolescents, undergraduates, and older adults) looking at brain function outcomes. Again, groups with LZ had increased academic performance (pre-adolescents), visual and reasoning ability (undergraduates), and brain activation (older adults). These studies point to the importance of lutein and zeaxanthin for brain activity and processing throughout the lifespan.
These results are desirable and dramatic, but should everyone take LZ supplements? Right now, a conclusion has not been made for recommended intake. Although they have health benefits, they are not considered essential nutrients. The best recommendation is to include adequate food sources of lutein and zeaxanthin in your diet. Some of the top food sources are dark green leafy vegetables (kale, spinach, turnips, collards), zucchini, summer squash, egg yolk, and corn.1 It is a good health habit to eat fruits and vegetables in a variety of colors to ensure you are getting different nutrients and phytonutrients. Make sure to include some bright red, yellow, and dark green vegetables to boost lutein and zeaxanthin in your diet.
Source:
- United States Department of Agriculture. Food Composition Database version 3.8.6.1. Nutrient List: Lutein + zeaxanthin (micrograms). (2017, July 28). Retrieved August 30, 2017, from https://ndb.nal.usda.gov/ndb/nutrients/report?nutrient1=338&nutrient2=&nutrient3=&fg=1&fg=9&fg=11&max=25&subset=0&offset=50&sort=c&totCount=1002&measureby=g.
Emily, I really enjoyed reading this discussion. However, there are a few areas of concern that I noticed while reading. First, is the ability of the LZ to reverse cell damage. The study mentioned was conducted on epithelial skin cells. However, the cells being targeted in relation to reversing cell damage are brain and nerve cells. This is significant, because skins cells and central nervous system (CNS) cells are vastly different from one another. In most cases, CNS cells such as brain cells and spinal cord cells do not heal from damage. That would mean that the effects of the antioxidants in the LZ would not be noticed in brain and spinal cord cells. Therefore, does LZ actually have any effect on cell damage in the CNS? In addition to this, another question I have is how much does a person need to consume, before your body does not need anymore for a day? Most nutrients have a threshold, that once met, does not have a difference on the effects in the body. So how much is needed to reach that threshold? Is it met during a normal diet for the majority of Americans? Or is it something that most people are deficient in? I believe that there are some benefits that could be associated with LZ, but it is most likely not in the CNS, and much more research needs to be done to find the best uses for LZ supplementation.
Hello Anthony,
Thank you for your comments and questions! You make some good points. From what I could gather, Dr. Hammond has not conducted any research on repairing cell damage with LZ supplementation. I apologize if I did not clearly indicate the purpose of his research. Rather, he has looked at how increasing the concentration of LZ in tissues like the retina and brain can enhance vision and cognitive function. First, he conducted the experiment looking at skin cell damage to see if lutein alone is an effective antioxidant. When supplementation resulted in improvements to skin lipids, hydration, and elasticity, he concluded that the lutein decreased peroxidation. Because both the brain and retina are tissues that use a lot of oxygen, he wanted to see if increasing LZ could be beneficial to these parts of the CNS as well. The summary of his many research studies indicated that supplementation does improve the amount of LZ in the retina and brain and can improve visual processing speed, visual reaction time, and cognitive function. My take-away from his presentation was that LZ may be more beneficial to these neural processes by maintaining cell integrity and preventing oxidation, perhaps the preventing the damage in the first place. It should also be noted that lutein is concentrated in the retina and certain parts of the brain, so it could be that supplementation is simply creating appropriate stores of the compounds that should have already been present for adequate function.
In regard to a threshold, lutein and zeaxanthin are not essential nutrients at this time, so they do not have recommended dietary allowances (RDAs). Technically they are not nutrients but phytochemicals. Dr. Hammond made the point that one reason lutein and zeaxanthin are not essential nutrients is that a deficiency in them cannot be linked to any disease or condition. Therefore, you could not diagnose someone with a deficiency of these nutrients. Just as a reference point, though, one of his placebo-controlled supplementation trial that had positive results used 20 mg of zeaxanthin per day or 26 mg of zeaxanthin with 8 mg of lutein per day (Bovier, 2014). He did not comment on a dose-response effect or if he has found a threshold of supplementation. The largest dietary sources of LZ come from dark green leafy vegetables, a food group that is commonly under consumed in the American diet, so it could be likely that many Americans do not consume adequate amounts of these phytonutrients. Personally, I wonder if the reason Dr. Hammond saw such great improvements with LZ supplementation is that many of the participants did not have enough LZ in these tissues in the first place. It seems that often in supplementation research the biggest improvements are seen in those that do not have adequate stores in the first place. Going above and beyond the recommended intake does not always provide more benefit. Again, that is simply my personal thoughts on it.
I hope that this helps to clarify my blog post and answer your questions!
References
Bovier ER, Renzi LM, Hammond BR. A double-blind, placebo-controlled study on the effects of lutein and zeaxanthin on neural processing speed and efficiency. PLoS ONE 2014;9(9):1-6.
Hey Emily! I’d like to ask you two questions that came to mind while reading you post. First, how can we clearly convey to the public the difference between being essential and being helpful when it comes to nutrients? Secondly, eating a variety of colorful fruits and vegetables is already a national dietary recommendation. Does research like this really add something to the body of scientific nutrition knowledge if it does not change recommendations?
Hi Hannah,
Those are great questions. I think for the general public, it would be best to promote overall variety and balance in the diet to ensure they receive both essential and helpful nutrients. As you mentioned, it is already a recommendation to eat many colors of fruits and vegetables, and that is adequate for most of the public. Nutrition messages can be easily misconstrued, so it seems too complicated to classify every nutrient we can consume as essential or helpful.
I think that Dr. Hammond’s research does add to the body of nutrition science. It points to the fact that we do need variety in our diet to obtain these helpful nutrients. We may can live without an adequate store in the body, i.e. they are not essential, but the body performs better with a sufficient amount. This is fascinating to me and adds more substance and depth to the idea of promoting fruits and vegetables for their “phytonutrients.” Although supplement companies might view this research as contributing to their marketing of lutein and zeaxanthin supplements, I feel that it supports the principle of getting nutrients from foods. If people ate adequate amounts of dark green, leafy vegetables in their diets, they would have optimal lutein and zeaxanthin stores in the macula and retina already.