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Dry macular degeneration stopped with low glycemic index diet in mouse study

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A low glycemic index diet might halt or prevent dry macular degeneration, according to a study conducted in mouse models. This form of macular degeneration is by far the most common kind.

Moreover, switching the diet from high- to low-glycemic, even late in the lifespan of the mice, stopped disease progression, the study found. This means that if humans respond the same way, changing to a low-glycemic index diet could reduce the incidence of dry AMD.

“The GI appears to be an attractive dietary intervention target, because simple replacement of small amounts of high-index foods (such as white bread) with lower-index foods (such as whole grain bread) can significantly reduce glycemic peaks without requiring a change in overall dietary patterns,” the study stated.

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Moreover, the study said its findings in mice correlated with human observational studies that find consuming lower GI diets is associated with delayed progression of early-stage AMD.

The study, appearing in Proceedings of the National Academy of Sciences, is available online at j.mp/maculard. Allen Taylor was the senior author; Sheldon Rowan the first author. Both are of Tufts University in Boston.

Located on the opposite side of the lens, the macula includes the region of sharpest vision, the fovea. Dry AMD is a breakdown or thinning of retinal pigment epithelial cells, which support the light-sensitive cells. Those with the disease progressively lose central vision, preserving sight on the periphery.

While mice don’t have a macula, when fed a Western-style diet they do exhibit age-related features characteristic of dry AMD, the study stated. This type of diet includes easily absorbed sugars that raise blood sugar levels, prompting a release of insulin. It has been linked to insulin resistance and type 2 diabetes, among other conditions.

The low glycemic diet was the same in composition and calories as the high glycemic one, except that they differed in the ratio of amylose to amylopectin in the starch they consumed. More amylose content raises the glycemic index of the starch.

To find out what was going on inside the mice, the researchers examined their metabolism and gut microbes.

“These studies revealed changes in the gut microbiota that altered the production of metabolites that protected against AMD, including serotonin,” the study stated. “Changing the diet to a low-glycemic-index diet, even late in life, arrested the development of AMD, offering dietary interventions for AMD.”

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