Zeaxanthin

 

Zeaxanthin Introduction

Zeaxanthin is a member of a group of nutrients referred to as carotenoids. Carotenoids are pigments found in plants, which give them their rich color. Zeaxanthin is often discussed in combination with lutein, another carotenoid. Both Zeaxanthin and lutein cannot be converted to vitamin A, like other carotenoids (e.g. beta-carotene); their structure is more polar due to hydroxyl groups attached to the cyclic ring structure. [1]

Zeaxanthin, lutein, and meso-zeaxanthin are referred to as the macular pigment. The macula is an area of the retina responsible for focusing images. Zeaxanthin specifically accumulates in the fovea region. [2] Interestingly, when zeaxanthin and lutein are consumed, they are deposited into the macula at a rate of 5 times more than the rest of the retina. [3]

A review of zeaxanthin and lutein for macular degeneration summarized the mechanisms of action for protecting ocular tissue against photooxidative damage as filters for damaging blue light, antioxidants quenching excited triplet state molecules or singlet molecular oxygen, and scavenging further reactive oxygen species like lipid peroxides or the superoxide radical anion. [1, 2, 4]

Zeaxanthin Food Sources

Most supplements are made from an extract of the Marigold flower. Good food sources include orange colored fruits and vegetables (e.g. orange bell peppers, yellow sweet corn, nectarines, squash) and dark green leafy vegetables like kale, spinach and collard greens, and egg yolks. The metabolites of zeaxanthin are also found in milk.

Zeaxanthin Uses

Zeaxanthin has been primarily studied for macular degeneration. However, some emerging research indicates that zeaxanthin may also play a role in cardiovascular disease, stroke, and breast cancer. [5- 10] One interesting epidemiological study was conducted on 19 countries, ranging from Central, Eastern, and Western Europe (including Russia), to countries located in the Mediterranean, Asia, and also the United States. [11] Mortality rates from coronary artery disease and dietary information were examined. Results showed that diets low in foods containing folate and carotenoids (i.e. beta-carotene, lutein, zeaxanthin) may be a major contributing factor to increased coronary risk observed in the countries of Central and Eastern Europe.

A recent review stated that research suggests that higher levels of macular pigment are correlated with reduced risk of age-related macular degeneration. Oral supplementation with lutein and zeaxanthin increases levels of these macular pigments in the retina and plasma. [12] Another review examined zeaxanthin and lutein for age-related macular degeneration (AMD) and summarized epidemiologic and clinical studies. [13] There have yet to be any controlled clinical trials of zeaxanthin for age-related macular degeneration, however, basic animal research does exist with epidemiological and clinical evidence (autopsy donors with AMD have lower concentrations of zeaxanthin in the maculas region) indicating the potential benefit of zeaxanthin. [14] To definitively answer whether zeaxanthin supplementation is effective in treating AMD, double-blind randomized, placebo-controlled trials are necessary.

Other conditions that may be influenced by zeaxanthin status include cognitive impairment and preeclampsia. Low plasma levels of zeaxanthin and other carotenoid antioxidants have been observed in both patients with mild cognitive impairment (MCI) and Alzheimer's disease, suggesting that an increased intake of these antioxidants in patients with MCI can be helpful in lowering the risk of conversion to dementia. [15] A controlled study of 173 pregnant women with preeclampsia and 186 case controls showed that preeclampsia risk was decreased when increasing concentrations of certain carotenoids (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, and zeaxanthin) were administered. [16]

Zeaxanthin Dosages

Oral supplementation with zeaxanthin ranges in dosage level and is largely dependant upon the condition being addressed. For prevention of AMD, a dosage level of 3 milligrams per day is likely sufficient, while treatment of AMD requires up to 10 milligrams of zeaxanthin daily. Generally, zeaxanthin should be taken in combination with lutein and other carotenoids to maximize effect.

Zeaxanthin Toxicities and Deficiencies

Zeaxanthin Toxicities

Zeaxanthin is well tolerated and is generally considered a safe therapeutic substance when taken in recommended doses. [19] However, long-term safety studies are lacking.

Zeaxanthin Deficiencies

Zeaxanthin is a phytochemical that has not yet been established as an essential nutrient; however data suggests that it should be considered a conditionally essential nutrient. [17] Low levels of zeaxanthin have been associated with macular degeneration, coronary heart disease, and breast and lung cancers. [18] Interestingly, the deprivation of zeaxanthin and lutein in primates has produced pathological changes in the macula. [17] As well, obesity may lead to increased destruction and decreased circulatory delivery of zeaxanthin and lutein to the macula of the eye, which could explain the correlation between obesity and age-related macular degeneration. [18]

References

1. Khachik F et al. Identification of lutein and zeaxanthin oxidation products in human and monkey retinas. Invest Ophthamol Via Sci 1997;38:1802-1811.

2. Handelman GJ et al. Carotenoid sint eh human macula and whole retina. Invest Ophthamol Via Sci 1988;29:850-855.

3. Bone RA et al. Analysis of the macular pigment by HPLC: retinal distribution and age study. Invest Ophthamol Via Sci 1988;29:843-849.

4. Stahl W. Macular carotenoids: lutein and zeaxanthin. Dev Ophthalmol. 2005;38:70-88.

5. Ribaya-Mercado JD, Blumberg JB. Lutein and zeaxanthin and their potential roles in disease prevention. J Am Coll Nutr. 2004;23(6 Suppl):567S-587S.

6. Freudenheimm JL et al. Premenopausal breast cancer risk and intake of vegetables, fruits and related nutrients. J Natl Cancer Instit 1996;88:340-348.

7. Dorgan JF et al. Relationships of serum carotenoids, retinol, alpha-tocopherol and selenium with breast cancer risk: results from a prospective study in Columbia, Missouri (United States). Cancer Causes Control 1998;9:89-97.

8. Zhang S et al. Dietary carotenoids and Vitamin A, C and E and risk of breast cancer. J Natl Cancer Instit 1999;91:547-556.

9. Dwyer JH et al. Oxygenated carotenoid lutein and progression of early atherosclerosis: the Los Angeles atherosclerosis study. Circulation 2001;103(24):2922-2927.

10. Iribarren C et al. Associations of serum vitamin levels, LDL susceptibility to oxidation, and autoantibodies against MDA-LDL with carotid atherosclerosis. Arterioscler Thromb Vasc Biol 1997;17:1171-1177.

11. Connor SL et al. Diets lower in folic acid and carotenoids are associated with the coronary disease epidemic in Central and Eastern Europe. J Am Diet Assoc. 2004;104(12):1793-9.

12. Ahmed SS, Lott MN, Marcus DM. The macular xanthophylls. Surv Ophthalmol. 2005;50(2):183-93.

13. Mozaffarieh M et al. The role of carotenoids, lutein and zeaxanthin, in protecting against age-related macular degeneration: A review based on controversial evidence. Nutr J 2003;2(1):20-28.

14. Bone RA et al. Macular pigment in donor eyes with and without AMD: a case contolled study.Invest Ophthalmol Vis Sci 2001;42:235-240.

15. Rinaldi P et al. Plasma antioxidants are similarly depleted in mild cognitive impairment and in Alzheimer’s disease. Neurobiol Aging. 2003;24(7):915-9.

16. Williams MA et al. Plasma carotenoids, retinol, tocopherols, and lipoproteins in preeclamptic and normotensive pregnant Zimbabwean women. Am J Hypertens. 2003 Aug;16(8):665-72.

17. Semba RD, Dagnelie G. Are lutein and zeaxanthin conditionally essential nutrients for eye health? Med Hypotheses. 2003;61(4):465-72.

18. Johnson EJ. Obesity, lutein metabolism, and age-related macular degeneration: a web of connections. Nutr Rev. 2005;63(1):9-15.

19. Hartmann D et al. Plasma kinetics of zeaxanthin and 3’-dehydro-lutein after multiple oral doses of synthetic zeaxanthin. Am J Clin Nutr. 2004;79(3):410-7.