In the news: Folic acid & Glaucoma, Overall Diet & AMD

Pseudoexfoliation, a Form of Glaucoma

Open angle glaucoma can develop in some patients with a condition called exfoliation syndrome. In this condition, there is an abnormal build-up of protein and exfoliation material that can clog the eye’s drainage system. Some people with exfoliation syndrome have higher eye pressures and faster disease progression than patients with classic open angle glaucoma.

EG, Homocysteine & Folic Acid: A Connection?

One possible risk factor for exfoliation glaucoma (EG) that has received a good deal of research attention is homocysteine. Homocysteine is a naturally occurring amino acid that can build up in blood due to dietary influences, genetics, and other causes.

High blood levels of homocysteine seem to enhance the formation of exfoliation material by contributing to vascular damage and oxidative stress. Researchers, in fact, have fairly consistently found elevated homo-cysteine levels in the blood, aqueous humor (fluid inside the front of the eye), and tears of people with exfoliation syndrome or EG.

Blood levels of homocysteine tend to be higher in people who eat a lot of animal protein and consume few fruits and leafy vegetables – sources of folic acid and other B vitamins that help keep homocysteine levels in the normal range.

Folic Acid & Risk for EG

Harvard researchers have conducted the first prospective study evaluating long-term B vitamin intake and risk for EG and suspected EG (cases of exfoliative syndrome who met criteria for other signs of glaucoma) in over 119,000 men and women followed for 20 years (1).

The participants were free of glaucoma to begin with, and their intake of the B-vitamins was updated over time. The researchers previously reported that higher intakes of folate and vitamins B6 and B12 are linked to lower levels of homocysteine. The authors now report that higher intake of total folate is associated with a lower risk for EG. The association was strongest for supplemental folic acid, which is more bioavailable than natural folate. (Folate is the generic term for both naturally occurring folate in foods, and for folic acid, the vitamin form used in dietary supplements and fortified foods.)

According to the authors, their results support the idea that homocysteine plays a role in EG and that folate may be protective. They also stress the need for more research before firm conclusions can be drawn.

Does Overall Diet Affect the Risk for AMD?

The results of two new studies suggest that how we eat may well be a factor in staving off age-related macular degeneration (AMD). In the first US study (2), people who most closely followed a dietary pattern identified by higher intake of produce, whole grains and seafood (dietary pattern A) had a significantly lower risk of developing early AMD. A greater risk for early AMD was seen for those adhering most closely to a diet higher in red meat, processed meat, high fat dairy and refined grains (pattern B).

The risks associated with advanced AMD were even more pronounced: A 62% lower risk was seen for diets most closely matching pattern A compared to diets that matched up the least. People whose diets lined up the best with pattern B were about 3.7 times more likely to develop advanced AMD compared to those whose diets were the least well aligned.

The findings from the second study (3) conducted in Australia were fairly similar in terms of broad food consumption and risk of advanced disease. Diets high in fruits, vegetables, chicken, and nuts and diets low in red meat appeared to be associated with lower prevalence of advanced AMD.

References

1. Kang, JH, et al. A prospective study of folate, vitamin B6, and vitamin B12 intake in relation to exfoliation glaucoma or suspected exfoliation glaucoma. JAMA Ophthalmol 132:549-59, 2014.
2. Chiu C, et al. The relationship of major American dietary patterns to age-related macular degeneration. Am J Ophthalmol [Epub ahead of print, Apr 29, 2014].
3. Amirul I, et al. Dietary patterns and their associations with age-related macular degeneration: The Melbourne Collaborative Cohort Study. Ophthalmol [Epub ahead of print Feb 20, 2013].