Can what we eat really influence our eyes?
When was the last time you thought about your eyes? You have to admit it; you wake up and they just start working. There is no warming up period, no lag time between opening your eye-lids and receiving images and, unlike you telephone or internet connection, there are no problems with intermittent connections. You eyes just work, day in and day out. In fact you eyes can process around 36,000 bits of information per hour and contribute towards 85% of your total knowledge. Being composed of over two million working parts you eyes use around 65% of all the pathways within the brain. Eyes are truly miraculous structures yet we just expect them to work and never question their existence until something goes wrong. It is with this in mind may be its about time to consider the special nutritional requirements the eyes have. After all, we have discussed heart health in the past and the importance of nutrition and the brain. The eyes have their own specific needs and being aware of this could help offset some of the slow to develop degenerative conditions that afflict a growing number of people. Feeding your eyes may be one of the best dietary and lifestyle changes you could make to help protect such a vital pair of structures.
It is a sad reality that in some of the poorest countries in the world a simple supplement of vitamin A could prevent the estimated 250 million cases of deficiency that I turn leads on to night blindness and more seriously a drying of the eyes called xerophthalmia. This type of dry eye is not just an irritating symptom it’s a sight threatening condition. In Africa, if you can’t see you will probably not survive very long! Vitamin A is one of those vitamins that acts as a bit of a double edges sword. Too much can cause toxic reactions that may, rather ironically, include dry eyes, along with other serious issues including headache, drowsiness, abdominal pains and vomiting to name a few. Luckily, this is a rare situation since supplements containing vitamin A tend to deliver it in the form of the non-toxic, water soluble form known as beta carotene. True vitamin A (retinol) is a fat soluble vitamin that over time can accumulate in the body to the point where toxicity symptoms may ensue. Beta carotene, on the other hand, is only converted into retinol within the body if the body is deficient in retinol. Unless there is an overt deficiency of vitamin A in its retinol form the water soluble version is always preferable for this reason if you are taking supplements. Simply check the label where you will probably see the vitamin A ingredient described as being in the beta carotene form. Excessive intake of beta carotene can occur especially if supplements containing it are taken at the same time as a regular serving of carrot juice because carrots are also high in beta carotene. Over time the skin can turn a yellow-orange colour, most noticeable on the palms of the hands and soles of the feet. This situation is known as carotenemia and is not in itself hazardous but is a strong indication that you need to cut back on the carrots and beta carotene supplements! In general, it is recommended that people do not take vitamin A (retinol) for extended periods and that pregnant and lactating women avoid it altogether (it can sneak into the diet via fish liver oils and organ meat such as liver) because of the increased risk of damage to the foetus and breast fed newborn. Keeping you intake of water-soluble vitamin A foods up though. These include the bright coloured fruits such as papayas and oranges and the coloured vegetables like sweet peppers, squash and pumpkin. These foods not only deliver water soluble vitamin A but a complex array of other compounds that are being shown to be of great importance in the fight against nutritional related eye problems and offsetting degenerative eye disease. What needs to be remembered here is the fact that the need for vitamin A in African children is quite different from the requirements of vitamin A in the UK population so boosting the vitamin A (retinol form) intake is probably unnecessary and could be hazardous. On the other hand, maintaining vitamin A levels can be achieved by using beta carotene containing supplements if the diet is very low in the foods mentioned above. However, keep the intake to sensible levels to avoid carotenemia!
The antioxidant connection
There does not appear to be a week that passes without some news on the benefits of antioxidants, but what are they and why are they important in maintaining eye health? Antioxidants are naturally occurring compounds that help slow or prevent oxidative changes in the body and oxidative changes are associated with accelerated degenerative disease. We all live in an oxygen rich environment but this comes at a price. As we breathe our cells utilise the oxygen and produce by-products known as free radicals. These are a group of compounds that if left unchecked or are generated at an accelerated rate cause the oxidative damage we all read about. Antioxidants are the key to keeping this process in check since they neutralize and make safe the free radicals. So, the less free radicals there are buzzing around the less damaging oxidative changes occur and, in turn, the rate of tissue damage and degeneration takes place. Hence, diets high in antioxidants have been advocated for a range of degenerative problems ranging from heart disease and diabetes through to arthritis, cancer and eye problems such as macular degeneration. No one would be as bold as to suggest that such diets can reverse these situations but a change in diet and lifestyle can definitely benefit these problems and could slow their progression.
The key antioxidant nutrients are vitamin A (in the carotenoid form), vitamin E and C along with the mineral selenium. All these important nutrients can be found in a balanced diet but you can top up a diet with a well formulated food supplement. This may be important in those with food intolerances or for those with specific eye related problems where a guaranteed daily intake of antioxidant nutrients would be desirable.
Key antioxidant foods
Carrots, squashes, broccoli, sweet potatoes, tomatoes, kale, peaches, apricots and all bright coloured fruits and vegetables
Citrus fruits such as oranges, limes, coloured berries such as blue berries, strawberries, sweet peppers, green leafy vegetables, broccoli
Nuts, seeds, whole grains, green leafy vegetables, vegetable oils
Fish, shellfish, grains, eggs, chicken and garlic
The carotenoid connection
Within the group of antioxidant compounds the carotenoids appear to have specific influence on the health of the eye. One of these, known as lutein, has come to the attention of scientists and had been the centre of intense investigation when it as noted that in may help off set the effects of macular degeneration. Lutein is found in egg yolks and in the dark green leafy vegetables. It appears to act, like all antioxidants, as a free radical neutraliser but because it accumulates in the tissues that are exposed to the outside environment (the eyes and skin) it exerts this effect to great effect in these tissues over other antioxidants that are distributed to all body tissues. In regards to eye health lutein filters out the high energy blue wavelengths common to sunlight and artificial light. By doing this it is thought that lutein could reduce the damaging effects of these wavelengths on light exposed tissues such as the eye and skin. Getting enough lutein (research suggests around 6-10 mg per day) may be difficult from diet alone since you would need to eat a large bowl of fresh spinach every day to get around 6mg. This could be a case where a food supplement is a good idea. Another up and coming eye specific antioxidant is known as zeaxanthin. Again, it belongs to the carotenoid group of compounds.
Just as a word of caution, some research has shown that taking high doses of beta-carotene (20 to 30 milligrams per day) from supplements could increase the risk of lung cancer in people who smoke. It might also increase the risk in people who used to smoke. Speak to your doctor or pharmacist if you smoke, or used to smoke, and are considering starting a high dose beta-carotene supplement.
There is no good evidence that beta-carotene supplements increase the risk of any other type of cancer.
Foods high in key carotenoids
High lutein foods
Yellow peppers, spinach, mango, bilberries, green leafy vegetables, broccoli, eggs
High zeaxanthin foods
Orange peppers, corn, lettuce (not iceberg), tangerines, spinach, broccoli, oranges and eggs
Pulling it all together
It is clear that good food promotes all aspects of health but certain foods do appear to be associated with specific eye related nutritional needs.
When looking to the UK population, the Royal National Institute for the Blind comments that research has shown that many people do not get enough vitamins and minerals from their diet and suggest the use of food supplements. These must not be taken, however, as a substitute for a balanced diet!
When to consider a eye specific supplement
When intake of fresh fruit and vegetables are low
When the absorption of vitamins and minerals poor
When its hard to obtain and prepare fresh produce
When food intolerances prohibit eating key foods
Eye specific supplements: balanced all-in-one eye specific nutrition