How does lutein filter blue light? - Little Étoile
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How does lutein filter blue light?


What is lutein?

Lutein is a member of the carotenoid family, a group of colored substances that is found in carrots (where the name comes from); green leafy vegetables and coloured fruites and vegetables, including tomatoes, capsicums, lemons, squashes, banana, sweet potato, corn and eggs.

The word lutein comes from the old latin word, meaning “yellow”, which relates to the color of the substance. It is also called a natural pigment. Its role in plants is to control the amount of sunlight that penetrates into the leaves.


What does light filtering mean?

When we look at a colored object, the color we see is what is reflected back to us, but the ones we don’t see are the ones that are absorbed. The same applies to lutein – the yellow color is the one that can be seen, but the others (especially blues and greens) are absorbed.

Filtering of the damaging parts of daylight and artificial light means that they are absorbed, so they don’t cause problems. Parts of light including the blue light and UV light (similar to blue light) are known for their ability to cause damage to living cells and DNA [1] . This happens when oxidative stress and free radicals are not under control.


How does this relate to the eye and vision?

The retina is found in the back part of the eye. It is a delicate part of the eye that is sensitive to light, and it allows us to see objects, what color they are, and how bright they are. Light enters the eye through the pupil at the front and is focused on the retina by the lens, to make images.

Lutein is concentrated in the macula, where is acts as an antioxidant and controls free radicals by blue light. This prevents damage to the light sensitive parts. The macula is responsible for detailed, close-up vision. So, the lutein does a similar job of absorbing light as it does in plants.


Where does blue light come from and how does it affect vision?

Natural sunlight contains a lot of blue and UV light. Other sources include artificial light and electronic devices that use LED or plasma flats screens, for example, PC’s, laptops, smart phones, tablets, video games and virtual reality glasses.

Because children are increasingly using electronic devices, there is a increasing concern this could be causing subtle eye damage, which leads to problems like short sightedness. In one study, exposure of eyes to more blue light than red light caused a slight size change in eye size, similar to what happens when eyes become short-sighted [2].

The eye is also used to more blue light during daylight hours, and less at night. The day/night cycle in the body is tuned in to how much blue daylight the eyes get [3]. So, exposing the eyes to more blue light at the end of the day tricks the body into thinking the day is longer. This can lead to sleep problems, which in children causes delays in cognitive development and the ability of the eyes to repair. And as we know, children sleep longer than adults.


Lutein increases in children with age

As children get older, their macula increases in size, and so the protective effects of lutein against blue light damage become increasingly important. One study has shown a direct relationship between macular content of pigments, and the amount of lutein in their systems, from infancy to childhood [4].

As a result of this evidence, FSANZ recognizes the blue-light filtering ability of lutein as having a protective nutrient effect on growing eyes, and suggests that it can make a valuable contribution to children’s formulas and dietary intake [5].

References

  1. Kielbassa et al. 1997 Apr;18(4):811-6 https://pubmed.ncbi.nlm.nih.gov/9111219/
  2. Thakur et al. Invest Ophthalmol Vis Sci. 2021 Dec 1;62(15):22. https://pubmed.ncbi.nlm.nih.gov/34935883/
  3. Wahl. J Biophotonics. 2019 Dec;12(12):e201900102. https://pubmed.ncbi.nlm.nih.gov/31433569/
  4. Bernstein et al. Invest Ophthalmol Vis Sci. 2013 Jun 10;54(6):4034-40. https://pubmed.ncbi.nlm.nih.gov/23652486/
  5. https://www.foodstandards.gov.au/code/applications/pages/applicationa597lutei3491.aspx