Nutrition and Eye Health
Lutein and Zeaxanthin intake & Age-Related Macular Degeneration Protection
The objectives of our recent work were to examine the literature and evaluate the link between L/Z intake and AMD risk and describe food sources and factors that increase the bioavailability of L/Z, to inform dietary models.
Eyes & carotenoids: importance of lutein and zeaxanthin
Among thirty carotenoids identified in human blood and tissues, only lutein and zeaxanthin (L/Z) are found in the eye. L/Z are the major constituents of macular pigment, a compound concentrated in the macula region of the retina that is responsible for fine-feature vision. Age-Related Macular Degeneration (AMD) is one of the leading causes of blindness in older adults in the developed world. US research has forecast that the number of patients with AMD is likely to double between 2010 and 2050, and this disease is becoming a crucial public health issue1.
Cohort studies and clinical trials showed that L/Z may prevent and/or slow the progression of this disease. A 2012 systematic review and metaanalysis of six longitudinal cohort studies found a 32% risk reduction of neovascular AMD among those people who consumed the highest category of L/Z compared to those who consumed the lowest2.
Recommended intake for Lutein and Zeaxanthin
Nowadays, there are no official recommended dietary intake levels for L/Z. A study published in 1994 showed that an intake of 6 mg/d of L/Z could reduce the risk of AMD3. However, 2 recent studies (AREDS2 and the BMES) consider that a level of L/Z intake less than 6 mg/d is associated with a decreased likelihood of AMD4.
Data on population L/Z intake is limited and varies depending on countries:
- In Europe, the average daily intake of major carotenoids (including retinol, alpha-tocopherol, beta-carotene, alpha-carotene, betacryptoxanthin, lutein, zeaxanthin, and lycopene) ranges from 3.5 mg/d in the Spanish population to 5.33 mg/d in the German population5.
- In an American study of older adults, L/Z consumption was 2.7 mg/d for men and 3.09 mg/d for women6. Another study estimated that American adults consume approximately 1−2 mg/d of lutein7.
- In an Australian study of older adults, the average L/Z intake was 0.9 mg (slightly higher for women)8.
In US and Autralia, we have also seen that the national intakes of lutein may be declining due to the decrease of fruit and vegetable
Dark green leafy vegetables, eggs and fruits: source of lutein and zeaxanthin
Dark green leafy vegetables, like kale and spinach, are the most important source of lutein and zeaxanthin. It’s important to note that the cooking method may change the content of lutein and zeaxanthin: for example, raw spinach contains 12 197 μg/100g of lutein and zeaxanthin while cooked spinach contains 11 308 μg/100g11.
Eggs are also an important source of lutein and zeaxanthin. Nevertheless, the amount is more important in the raw egg yolk (1094 μg/100g), and when the whole egg is raw (504 μg/100g) 11.
Avocado and orange are the fruits that contain the most lutein and zeaxanthin, with amounts of 270 μg/100g and 129 μg/100g, respectively11.
The original article presents two examples of menus providing a certain amount of lutein and zeaxanthin, proving that effective levels of L/Z can be achieved through diet alone, with values of 5 mg or 10 mg per day. These diet models show the availability of L/Z from different types of foods: dark green leafy vegetables, pistachio nuts and eggs, and must be adapted according to the country.
Factors affecting absorption and bioavailability of dietary carotenoids
The absorption of certain carotenoids is shown to be increased effectively by the addition of fat to the meal containing carotenoid; for example, we can add olive oil to the salad, or cooking oil like extra virgin olive oil, or even a whole egg.
However, when consumed within the same meal, there’s a competition for absorption between carotenoids. This competition may decrease the bioavailability of carotenoids.
Moreover, it has been shown that carotenoid absorption is reduced by dietary fiber from plant sources (e.g. pectin and guar gum), and carotenoids bioavailability may be deceased if they are located within the chloroplasts and chromoplasts of plants.
Despite the fact that eggs contain a lower amount of L/Z than most containing vegetables, the bioavailability of these compounds from eggs is higher, most likely due to the fat content.
Current evidence suggests that we can be protected against AMD by consuming foods that contain high amounts of lutein and zeaxanthin. In order to achieve adequate dietary levels of L/Z, it’s important to have a diet high in a variety of foods, including plenty of leafy green vegetables.
Based on: Eisenhauer, B.; Natoli, S.; Liew, G.; Flood, V.M. Lutein and zeaxanthin-food sources, bioavailability and dietary variety in age-related macular degeneration protection.
Nutrients 2017, 9, 120.
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