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A search on the internet reveals varied and sometimes inaccurate information about glaucoma and diet. Various substances are claimed to lower IOP when they are not the subject of rigourous randomised trials - and when they are not prescribed as a routine by the majority of glaucoma specialists in the world. For example, some websites claim that Vitamin C "relieves eye pressure". Claims like this can be misinterpreted. Yes, vitamins are generally thought to be beneficial to the eye in a number of ways, and some evidence exists that they are helpful in preventing age-related macula changes in particular; however vitamin C supplementation has no immediate measurable effect on eye pressure - potentially it might help glaucoma in some way in the long term but this is open for debate - and its use very much should not replace eye drop medications which might be an unintended insinuation from vitamin marketeers.
General information about diet and glaucoma
1. What about Vitamin E supplementation and glaucoma? Vitamin E is toxic at high levels and doses at 400 IU or greater increase cardiovascular risk. The use of Vitamin E supplementation for glaucoma is not supported by large trials.
2. Is a normal salt intake appropriate for glaucoma patients? Some patients might be advised to take a higher salt diet, for example patients with normal pressure glaucoma and very low blood pressure might first however discuss with their physician / GP to see if they are taking the correct blood pressure tablet dose. Otherwise, some doctors recommend 1 gram of salt of bedtime, for specific patients with this problem of low blood pressure not amenable to changes in other medication.
3. Should fluid intake be restricted? Normal intake is advised. Generally, 6-8 cups of water a day is advised - be careful about consuming more than 3 cups an hour (unless dehydrated) - this could potentially increase eye pressure for a short period. A water drinking test where that patient would drink a large volume of fluid was previously used as a test for glaucoma.
4. Should I take ginkgo biloba if I have glaucoma? Generally, no. Evidence is limited here. Ginkgo can have side effects including increasing blood pressure, which might be harmful. Discuss with your doctor. [Very high doses of this medication can be purchased overseas over the counter eg Hong Kong.] Research into Ginkgo is limited. One randomised trial published just does not have enough patients in it to draw meaningful conclusions. 5. Is lutein safe? Lutein is available in a healthy diet and it is found in many vegetables. It is a safe nutrient found in many vegetables. Lutein is thought to be helpful in protecting the macula, as it is a pigment that lies infront of the photoreceptors in the central macula region. Lutein and other pigments are found - for example - in:
Green peppers, raw, 1 cup - 559 ug lutein/xeaxanthin (0.5 mg); 309 ug beta-carotene (Vit A derivative)
Red peppers, raw, 1 cup - 76 ug lutein/xeaxanthin; 2419 ug beta-carotene (Vit A derivative)
Broccoli, raw, 1/2 cup - 1183 ug lutein/xeaxanthin (1 mg)
Tomatoes, red, raw 1 cup - approx 500ug lutein/xeaxanthin (0.5 mg)
Kale, 1 cup, cooked, boiled - approx 23719 lutein/xeaxanthin (23 mg); beta carotene (10 mg)
Spinach, 1 cup, cooked - approx 3mg Lutein / xeaxanthin
In a balanced diet, therefore, eat a varied selection of leafy greens, red and green peppers, as beta carotene and lutein are both felt to beneficial for eye health. Leafy green vegetables are generally exceptionally high in lutein, eg spinach, Kale. Age related macula problems (ARMD) is a common condition, as is glaucoma (relatively speaking, in older patients); and as it is best not to develop macula problems if you have glaucoma; therefore as lutein is believed to be protective in ARMD, eating foods in your diet that contain lutein seems rational. The "AREDS2" study may confirm the benefit of taking lutein. Meantime, it would seem appropriate to take a healthy mix of fruit and vegetables (5 to 10 a day, every day). The evidence is mounting that diet plays a significant role in preventing various eye diseases. 6. Does caffeine affect eye pressure? Yes, caffeine temporarily increases eye pressure. Is this effect important? A prospective study looked at over 120,000 people, and concluded that: "Overall caffeine intake was not associated with increased risk of POAG (glaucoma)". The study however did notice in secondary analyses, that caffeine appeared to elevate risk of high-tension POAG among those with a family history of glaucoma. (Kang et al Invest Ophthalmol Vis Sci. 2008 May;49(5):1924-31). In view of this, a sensible recommendation would be to limit caffeine intake to less than the equivalent of 5 cups of coffee a day, and for patients with established progressive glaucoma with field defects, that caffeine intake should be ideally restricted. Green tea is a fine alternative as it contains less caffeine than ordinary tea, and it also contains various antioxidants. [Incidentally, green tea is associated with a reduced risk of lung cancer - Tang N, Wu Y, Zhou B, Wang B, Yu R. Lung Cancer. 2009 Jan 5; also a recent study in China indicates that green tea antioxidants are neuroprotective i.e. they slow cell death (Biol Pharm Bull. 2009 Jan;32(1):55-60). Green tea contains various substances: Epigallocatechin gallate, polyphenols, thearubigins, epicatechins, and catechins. A study that directly evaluates the effect of green tea and glaucoma is awaited.
7. Should I eat fish? In some studies, eating fish regularly, twice a week, reduces the risk of macula problems. No clear data is available for reducing the risk of glaucoma.
8. Smoking and glaucoma. Beta carotene intake that protects against ARMD further increases lung cancer risk in smokers. Avoid supplements of beta carotene if you smoke.
9. The good news! Dark chocolate and red wine contains anti-oxidants and might be beneficial! (Surv Ophthalmol. 2008 Sep-Oct;53(5):479-505. The potential value of natural antioxidative treatment in glaucoma. Mozaffarieh M, Grieshaber MC, Orgül S, Flammer J.). Please note however that migraine sufferers should try to avoid trigger factors for migraine, this might include red wine or various cheeses.
Glaucoma dietary leaflet v1.2
P.G. 11/01/2009 |
