Winter Kale and Citrus Salad for Ocular Health
What is lutein? What is a carotenoid?
Lutein is a type of dietary carotenoid that is found in many different dark green leafy vegetables as well as orange and yellow fruits and vegetables. A carotenoid is a type of fat-soluble pigment that is responsible for giving the fluorescent yellow, orange, or red pigments to various fruits and vegetables like bell peppers, carrots, and of course, kale. Not only are carotenoids produced by these vegetable plants, but they are also produced by algae and certain bacteria. In the human body, lutein is found in the retina. Dietary intake and supplementation of lutein has been shown to have positive effects on ocular health by improving the pigment density of the macula, and it is also speculated to have antioxidant benefits. Some randomized controlled trials have even drawn conclusions towards lutein having a positive effect on cognitive function and possibly preventing against certain neurodegenerative diseases like Alzheimer's (4).
Possible Benefits of Lutein on Ocular Health
Many studies have proposed the inverse relationship between an intake of foods rich in lutein and the risk of acute macular degeneration (AMD). AMD is the leading cause of vision impairment in developed countries (2). It is characterized by the blur and loss of central vision that is needed to details straight ahead. Rarely, the diagnosis can progress to blindness. AMD normally rears its head between the ages of 55 and 65. Factors that usually influence its onset include genetics and race, but most often it is environmental/behavioral phenomena that sway AMD's progression. Things like smoking, obesity, cardiovascular disease, and excessive exposure to certain light wavelengths (X-rays, gamma rays, and ultraviolet light) have an effect on macular health. Specifically, the degeneration of the macula is caused by anything that produces oxidative stress or damage in the retina. Oxidative damage can happen anywhere in the body where there is an excessive accumulation of "free radicals", which are highly volatile molecules that can disrupt/interfere with the normal molecular processes of different systems throughout the body. Oxidative damage is caused by any of the risk factors mentioned above, as well as other things like excessive fatty food intake or other toxin exposure. Many studies have suggested the beneficial impact that lutein (and xeanthin, another carotenoid found in many of the same foods as lutein) has on AMD because if its antioxidant properties. Ophthamologists and other biomedical experts have noted the ability of certain carotenoids (including lutein) to "quench" the singlet oxygens and scavenge the free radicals created from oxidative stress (2). Therefore, researchers have drawn a possible relationship between lutein consumption and/or supplementation and the reduction in risk of AMD and other age-related diseases, however the exact dosage has not been fully illustrated (2, 1).
Potential Benefits of Lutein as an Anti-Inflammatory
Inflammation is a broad umbrella term that is used to describe the reasoning behind many chronic conditions and illnesses. Chronic, low-grade inflammation is the usual culprit behind things like atherosclerosis, neural degenerative diseases, liver disease, many cancers, and more. Risk factors and behaviors that lead to low-grade inflammation include smoking, a poor diet, excessive alcohol consumption, lack of exercise, stress, and excessive weight gain. Physiologically, inflammation occurs when toxins and damage accumulate in various areas in the body, which calls for molecules called "inflammatory cytokines" to flock to the threat. Inflammatory cytokines have a main purpose of promoting cell growth, activation, and differentiation, and they play a large role in marking areas of damage or infection to signal to immune cells where repair is needed. This is a normal bodily response to internal damage and it can prove to be very beneficial when put in the correct context. However, when one engages in certain behaviors like those mentioned above, toxins and damage are constantly being introduced, which places the body in a perpetual state of inflammation. Many studies have noted the ability of lutein to interfere with the pro-inflammatory cytokine cascade, and others have gone as far as to say that lutein supplementation was a associated with a decreased risk of some diseases caused by chronic inflammation, most notably atherosclerosis (a disease of the arteries caused by fatty buildup and leads to cardiovascular disease). The premise of this research comes from the population observation that those with higher serum levels of carotenoids and those with a higher dietary intake of carotenoid-rich foods were seen to be at lower risk for atherosclerosis. In a study published in the journal Atherosclerosis in 2017 on the anti-inflammatory effects of lutein in patients with coronary artery disease (CAD), researchers took blood serum samples of patients with CAD before and after intervention with various carotenoids (lutein, xeanthin, β-cryptoxanthin, lycopene, α-carotene, β-carotene). They found that lutein was the only carotenoid associated with a significant inverse relationship to interleukin-6 (IL-6) levels, which is an important inflammatory cytokine that is often used as a biomarker for chronic inflammation. The more lutein a patient had in their blood after intervention, the less IL-6 was present, which leads scientists to believe that lutein may have a role in reducing chronic inflammation in CAD patients. However, the exact physiology behind this is not yet known (3).
Benefits of Lutein on Cognitive Health
New research is now drawing conclusions on the association between cognitive health and lutein content in the brain. It is known that the pediatric brain has twice the amount of lutein than the adult brain, which insinuates that lutein plays a role in cognitive development in early age. Further, lutein is also the predominant carotenoid in the brain in late life. Lutein is the only carotenoid that is seen to significantly (meaning scientifically irrefutably) improve executive function, language, learning, and memory, as seen by Johnson et. al. in 2013. Additionally, biomedical researchers have begun to suggest lutein's possible effect on the onset of Alzheimer's disease. Alzheimer's disease is one that is caused by oxidative stress to the brain that leads to the accumulation of singlet oxygen species and free radicals (like mentioned in the antioxidant section above). Seeing as lutein has been shown to have antioxidant effects in such areas of the brain involved in memory, learning and higher brain function, it may be possible that a higher consumption of this carotenoid may effectively prevent the onset of such oxidative stress-related cognitive diseases (5). However, the question of how lutein helps cognitive function is still unknown.
Where else can I find lutein?
The most efficient way to intake the carotenoid is through dark leafy vegetables, seeing has they have higher levels per unit of measurement. Vegetables such as kale, spinach, broccoli, peas, and lettuce are great sources of lutein. Fruits such as kiwi, grapes, oranges, and squashes other than pumpkin also contain lutein. But in general, choose fruits and vegetables that are most vibrant in color and you should be well on your way!
Winter Citrus and Kale Salad
Yields 4 servings
For the dressing:
- 1/2 cup olive oil
- 3 tablespoons balsamic vinegar
- 2 teaspoons honey
- 2 teaspoons dijon mustard
- 1 teaspoon minced garlic
- salt and pepper to taste
For the salad:
- 1 bundle kale
- 3/4 cup shaved parmesan
- 2 grapefruit, skinned
- 1 white or red onion
- Not pictured: add in some pistachios for a nice crunch. Pistachios also have a substantial lutein content!
Add a source of protein to make this a more balanced meal! I added some roast pork tenderloin to eat on the side.
Resources
1. Abdel-Aal, e., Akhtar, H., Zaheer, K., & Ali, R. (2013). Dietary sources of lutein and zeaxanthin carotenoids and their role in eye health. Nutrients, 5(4), 1169–1185. https://doi.org/10.3390/nu5041169 2. Buscemi, S., Corleo, D., Di Pace, F., Petroni, M. L., Satriano, A., & Marchesini, G. (2018). The Effect of Lutein on Eye and Extra-Eye Health. Nutrients, 10(9), 1321. https://doi.org/10.3390/nu10091321 3. Chung RWS, Leanderson P, Lundberg AK, Jonasson L. Lutein exerts anti-inflammatory effects in patients with coronary artery disease. Atherosclerosis. 2017 Jul;262:87-93. doi: 10.1016/j.atherosclerosis.2017.05.008. Epub 2017 May 6. PMID: 28527371. 4. Jia, Y. P., Sun, L., Yu, H. S., Liang, L. P., Li, W., Ding, H., Song, X. B., & Zhang, L. J. (2017). The Pharmacological Effects of Lutein and Zeaxanthin on Visual Disorders and Cognition Diseases. Molecules (Basel, Switzerland), 22(4), 610. https://doi.org/10.3390/molecules22040610 5. Johnson EJ, Vishwanathan R, Johnson MA, Hausman DB, Davey A, Scott TM, Green RC, Miller LS, Gearing M, Woodard J, Nelson PT, Chung HY, Schalch W, Wittwer J, Poon LW. Relationship between Serum and Brain Carotenoids, α-Tocopherol, and Retinol Concentrations and Cognitive Performance in the Oldest Old from the Georgia Centenarian Study. J Aging Res. 2013;2013:951786. doi: 10.1155/2013/951786. Epub 2013 Jun 9. PMID: 23840953; PMCID: PMC3690640.