Key Nutritional Ingredients for Eye Health
Vitamin A as beta-carotene
Beta-carotene is a precursor for vitamin A and is a red-orange pigment found in many plants and fruit. It is the substance that gives carrots, pumpkins and sweet potatoes their characteristic orange colour.
Beta-carotene is thought to be good for the eye because of its anti-oxidant effects and ability to remove damaging ‘free-radicals’. It has also been approved by the European Food Standards Agency for the claim ‘Vitamin A contributes to the maintenance of normal vision’.
High doses of beta-carotene have been linked to an increased risk of lung cancer in smoker and ex-smokers. This is why AREDS2 was looking for an alternative that would be as effective, but could still be taken by smokers.
Vitamin C cannot be made by the body so must be taken in through the diet and 90% comes from eating fruit and vegetables. It is needed to make collagen which is vital for the health of our skin, eyes, bones, teeth, cartilage, tendons, ligaments and blood vessels.
By strengthening and repairing the walls of the tiny blood vessels at the back of the eye, vitamin C helps to stabilise macular degeneration.
This vitamin has also been shown to reduce the length and severity of colds, although it does not prevent them.
Vitamin E refers to a group of fat soluble compounds found relatively freely in our diet, including various oils, spreads, cereals, nuts and seeds. It has various functions including anti-oxidant functions.
Vitamin E is included in the AREDS2 formula as it protects cell membranes. This is important as it then maintains the structure of the cells at the back of the eye, preventing their degeneration.
Zinc is a trace mineral thought to improve a number of medical conditions including the common cold. Studies have shown it can help with healing wounds such as burns or leg ulcers. Zinc is also believed to be important for vision because it is found at relatively high levels in the macula and enables vitamin A to create the pigment melanin which helps absorb light.
Zinc has also been approved by the European Food Standards Agency for the claim ‘Zinc contributes to the maintenance of normal vision’.
Zinc supplements can cause gastrointestinal effects, including abdominal pain, indigestion, nausea, sickness and diarrhoea. This usually occurs when supplements are taken on an empty stomach but is one of the reasons AREDS2 looked into the effect of lowering the dose.
Long term use of high doses of zinc can result in reduced levels of copper and this is why copper is included in the AREDS2 formula.
Copper is not thought to have a direct effect on macular health. However, zinc supplementation can lead to copper deficiency so its inclusion resolves this issue.
Lutein & Zeaxanthin
Lutein and zeaxanthin are two of over 600 known carotenoids. They are believed to be important for the eye because they are found in high doses at the macula – the central part of our eye responsible for vision and affected by macular degeneration. For this reason they, along with meso-zeaxanthin which is made from lutein in the body, are termed ‘macular pigments’.
Their role in macular heath is not fully known, but they are thought to play an important role by absorbing damaging blue wavelengths of light and acting as anti-oxidants, helping ‘mop-up’ damaging ‘free radicals’.
Lutein and zeaxanthin are not made in the body so have to be consumed in our diets and that is why they are considered the most interesting constituents for use in dietary supplements. They give some food their characteristic colour e.g. sweet peppers, saffron, sweetcorn. They are found in higher quantities in green leafy vegetables like spinach and kale. When they age and start to turn yellow, this is the lutein you are seeing.
Some people have lower macular pigment levels (either naturally or due to diet or weight issues) and this may put them at a greater risk of developing macular degeneration. Most studies use a dose of 10mg lutein to look for a protective effect but most European diets are thought to only contain about 3mg a day.
Omega 3 (EPA & DHA)
Omega 3 essential fatty acids refer to a group of three fats called alpha-linolenic acid (ALA), Eicosapentaenoic acid (EPA), and Docosahexaenoic acid (DHA). ALA is found in plants such as flaxseed and EPA and DHA in fish oils. They are termed essential because they are not made within the body but are needed for vital body functions.
With relation to the eye, Omega 3 is believed to have several beneficial effects including reducing the symptoms of dry eyes and slowing the progression of macular degeneration. It is for this reason that it was included in the AREDS2 study.
Some omega 3 fatty acids have also been approved by the European Food Standards Agency for an eye health claim ‘EPA contributes to the maintenance of normal vision’.