Macular degeneration is the leading cause of blindness in the US in those over 65. Twenty-five to thirty million people are afflicted worldwide and currently there are no effective treatments for the disease. The disease has two forms known as dry and wet AMD.
Ninety percent of the AMD cases diagnosed are the dry form. In dry AMD, also referred to as early AMD, debris deposits under the center of the retina (known as the macula) interfering with its normal function. Parts of the macula atrophy, causing the central vision to slowly become dimmer or more blurry. Wet age-related macular degeneration, also known as late AMD, often develops in areas where dry AMD exist. Abnormal blood vessels grow and leak blood and fluid under the macula, causing scarring, which leads to a rapid loss of central vision.
Dr. Joanna Seddon published one of the first studies demonstrating a link between lutein intake and AMD risk in 1994 (1). This epidemiological study compared the risk of developing AMD to nutrient intake and showed a significant reduction in risk for developing AMD as lutein intake reached 6 mg per day (57% reduction in risk). Since the Seddon study, researchers have shown that increasing dietary lutien intake raises blood levels of lutein as well as levels of lutein in the eye (2). Bone et al. demonstrated that eyes with higher levels of lutein were less likely to be afflicted with AMD (3).
The latest clinical trial that investigated lutein's role in AMD is known as the Lutein Antioxidant Supplementation Trial (L.A.S.T.) (4). This study evaluated the effect of lutein supplementation for one year in 90 veterans diagnosed with dry AMD. Supplementation with lutein in these subjects significantly increased the concentration of lutein in the macula. Improvements in visual function were also detected with lutein supplementation. Glare recovery, visual acuity, and contrast sensitivity were all improved. This study continues to build on clinical evidence that the dry for of AMD may be responsive to changes in nutrition.
A cataract is a natural clouding of the lens, the area of the eye responsible for focusing light and producing clear, sharp images. For most people, cataracts are a natural result of aging. Currently in the US, cataracts are the second leading cause of blindness in the elderly behind AMD.
Lutein is the major carotenoid that has been identified in the human lens and is thought to provide similar benefits to the lens that are seen in the retina. Two large epidemiological studies consisting of >70,000 women (age 45-71) and >30,000 men (age 45-75) compared the risk of cataract extraction to nutrient intake (5,6). Similar to AMD, a significant reduction in risk of cataract extraction was associated with lutein intakes of 6 mg per day (20% reduction in risk). Besides catarct extraction, higher levels of lutein consumption have been associated with a decrease risk of cataract development and improvements in visual acuity and glare sensitivity in people with age-related cataracts.
The richest sources of free lutein in the typical US diet are dark green leafy vegetables, with the highest concentration found in kale follwed by spinach.
The average daily lutein intake is low, averaging between 1-2 mg/day. Currently there is no recommended intake for lutein. However, if you were to eat according to the recommendation of the Dietary Guidelines for Americans 2005 ( 9 servings of fruits and vegetables every day) you would consume between 4 and 8 mg of lutein a day (7). Epidemiological evidence, animal models, and clinical data have indicated levels of 6-10 mg a day may be necessary to realize the health benefits associated with lutein consumption. By continuing to increase our intake of lutein, we begin to ensure the optimal health of our eyes.
Seddon et al. (1994) Dietary carotenoids, vitamins A, C, and E, and advanced age-related macular degeneration. Eye Disease Case-Control Study Group. JAMA. 272: 1413-20.
Bone et al. (2000) Lutein and zeaxanthin in the eyes, serum and diet of human subjects. Exp. Eye Res. 71: 239-45.
Bone et al. (2001) Macular pigment in donor eyes with and without AMD: a case-control study. Invest. Ophthalmol. Vis. Sci. 42: 235-40.
Richer et al. (2004) Double-masked, placebo-controlled, randomized trial of lutein and antioxidant supplementation in the intervention of athrophic age-related macular degeneration: the Veterans LAST study (Lutien Antioxidant Supplementation Trial). Optometry. 75: 216-30.
Brown et al. (1999) A prospective study of carotenoid intake and risk of cataract extraction in US men. Am. J. Clin. Nutr. 70: 517-24.
Chasen-Taber et al. (1999) A prospective study of carotenoid and vitamin A intakes and risk of cataract extraction in US women. Am. J. Clin. Nutr. 70:509-16.
HHS?USDA> Dietary Guidelines for Americans 2005. http://www.healthierus.gov/dietaryguidelines/CDC. National Health and Nutrition Examination Survey Data 2001-2002. http://www.cdc.gov/nchs/about/major/nhanes01-02.htm