Carotenoids are natural pigments found in leaves, fruits, vegetables and flowers with yellow, orange or some reddish colours as well as several aromas in plants .
There are more than 500 carotenoids known in nature, but only 20 of them are present in the human body. They are derived from food and supplements and cannot be synthezied in the body.
Among the carotenoids present in the body are two dietary xantophylls, lutein and zeaxanthin, and another xanthophyll, meso-zeaxanthin (which is presumably formed from lutein or zeaxanthin) are deposited in that portion of the eye which is responsible for focusing the light (macula lutea) [2,3].
Many studies have been shown that lutein and zeaxanthin provide significant protection against potential damage caused by the light in the macula lutea.
These carotenoids act like a filter of high-energy blue light also shown antioxidants properties which protect against the formation of reactive oxygen species (ROS) and free radicals .
Evidence suggests the lutein and zeaxanthin consumption is linked with age-related macular degeneration, cataracts, retinitis pigmentosa, night vision acuity and computer display light exposure.
A Retinitis pigmentosa is an inherited, degenerative eye disease that causes severe vision impairment due to the progressive degeneration of the rodphotoreceptor cells in retina.
There is no generally accepted medical or surgical treatment to stop the progressive course of renitis pigmentosa however there is evidence of lutein supplementation as a potential tratment which can improve macular pigment density.
The study conducted by Bahrami H. et al (2006) suggest that lutein supplementation improves visual field and may improve visual acuity slightly .
Another study undertaken by Berson E.L et al in 2010 has shown that lutein supplementation (12 mg/d) alongside with vitamin A slowed loss of midpheral visual field on average among nonsmoking adulds with retinis pigmentosa .
Age-related Macula Degeneration
An Age-related macula degeneration (AMD) is a disease which may result in blurred or no vision in the center of the visual field.
Over the time, some people may experience a gradual worsening of vision that may affect both eyes.
In the study performed by Yang-Mu et al (2014), investigated 112 people and checked whether lutein and zeaxanthin supplementation can promotes functional and macular pigment (MP) changes in patients with early related macular degeneration.
Study showed supplementating with the above carotenoids increases macular pigment optical density (MPOD) and retinal sensitivity .
Richer S. et al have also shown visual function in atrophic age-reated macula degenration is improved once lutein or lutein together with other nutrients is taken .
However a bigger study consisting of both gender’s over a longer period of time is required to assess long term effects of lutein together with a broad spectrum of antioxidants.
A cataract is a clouding of the lens in the eye leading to a decrease in vision. It can affect both eyes and develop slowly.
Symptoms may include faded colors, blurry vision, halos around the light, trouble with bright lights and trouble seeing at night .
Long term study undertaken by Olmedilla B. et al (2003) suggested that lutein supplements may improve visual function in patients with age-related cataracts .
Another study performed by Moeller S.M et al (2008) showed diet rich in lutein and zeaxanthin are moderately associated with decreased prevalence of nuclear cataract in older women.
A randomised, double-blind, placebo-controlled study from China, performed on 120 healthy drivers, showed benefits of using lutein supplementation with better night vision performance.
Assessment included visual acuity, serum lutein concentration, macular pigment optical density (MPOD), and visual performance .
Comparing to the placebo group, who received 20mg of lutein daily, noticed serum lutein and MPOD had increased, along with significant increases in contrast and glare sensitivity .
Computer display light exposure
The study undertaken by Le M. et al in 2009 on 37 healthy subjects with long-term (12 weeks) computer display light exposure.
Different doses of lutein supplementation were used (none – placebo, 6mg group and 12 mg group) .
There was a trend toward increased visual acuity in group which had taken 12mg of lutein.
No statisitcal change was observed in glare sensitivity over the time.
Visual function had improved in subjects who receive lutein supplemention, especially in contrast to sensitivity, suggesting higher intake of lutein may have beneficial effects on visual performance .
Lutein and zeaxanthin absorbtion
Xanthophylls, similarily like carotens are fat-soluble nutrients.
There are number of factors which affects bioavailability to tissues i.e. nutrient source (whole food vs supplement), state of the food (raw, cooked, or processed), extent of disruption of the cellular matrix via mastification and digestive enzymes, and absorbtion by the enterocytes of intestinal mucosa (primarily the duodenum).
Cooking and adding vegetables oils to lutein/zeaxanthin-containing foods may increase bioavailabity .
Lutein absorption from a purified crystalline lutein supplement is almost twice that from spinach or other vegetable sources .
High dose dietary supplementation of a single carotenoids can alter the assimilation of other carotenoids.
The retina has the capacity to store the lutein and zeaxanthin however the capacity is diminished when intake of beta-carotene is high (once they compete for the absorbtion) .
Food sources of lutein and zeaxanthin
Foods highest in concentrations are dark green, leafy vegetables (spinach, kale, collard greens, and others), corn, and egg yolks.
Zeaxanthin is the major carotenoid found in corn, orange peppers, oranges, and tangerines .
Side effects and toxicity
No toxicities or adverse reactions have been reported in the scientific literature for lutein/zeaxanthin at doses of up to 40 mg daily for two months .
Average daily intake for lutein and zeaxanthin in the United States is 2.0-2.3 mg daily for men and 1.7-2.0 mg daily for women , although dietary intakes of approximately 6-20 mg lutein daily appear to be necessary to decrease risk of macular degeneration and notice any benefits with other disorders.
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