A new study out of Australia suggests that eating at least one serving of oranges per day can reduce one’s likelihood of developing age-related macular degeneration (AMD) – an incurable, progressively blinding disease – thanks to the fruit’s high content of chemicals called flavonoids.
So, should you go out and buy an entire crate of citrus? Probably, but it’s a bit complicated.
There are two forms of AMD, referred to as wet and dry, that both slowly destroy the eye’s light-sensitive retina via different mechanisms. Mild cases of dry AMD are quite common in people more than 50 years old and typically have little impact. More severe cases of both types are the leading cause of visual impairment in adults, impacting upwards of 196 million people worldwide. Given that there are currently no effective treatments to restore the vision loss it causes, finding out what lifestyle factors help protect against the disease is a high priority for ophthalmologists.
Many past investigations have shown that consuming a diet rich in antioxidants and anti-inflammatory substances reduces the chance of AMD, and several particularly beneficial molecules have been identified: vitamin A, vitamin C, zeaxanthin, and lutein.
The authors of the current paper, published in The American Journal of Clinical Nutrition, sought to examine the poorly understood potential of flavonoids because this class of plant-produced compounds also appears to have potent free-radical scavenging and inflammation-reversing properties.
To do so, they turned to a previously collected dataset of health and lifestyle information for 2,037 Australian adults, aged 49 or above, who were followed for 15 years. Subjects had been examined for signs of AMD at the study onset, year five, year 10, and year 15, and every year they completed questionnaires about how often they consumed different types of food.
After adjusting their statistical analysis for subjects’ consumption of other antioxidants, similarly protective omega fatty acids, and the presence of genetic variations associated with increased risk of AMD, the authors found that risk of any form of AMD went down significantly as overall flavanoid intake went up, a finding that could further explain the established link between general fruit and vegetable consumption and AMD protection.
But the effect was particularly notable in those who consumed foods rich in two types of flavanoid – flavonol and flavanone. When subsequently investigating what flavonol and flavanone-rich foods the AMD-free subjects were consuming, one stood out dramatically.
Compared with participants who did not consume any oranges, those who reported consuming at least one serving of oranges per week were 58 percent less likely to develop AMD, they wrote.
“The data shows that flavonoids found in oranges appear to help protect against the disease,” lead author Bamini Gopinath said in a statement.
“Significantly, the data did not show a relationship between other food sources protecting the eyes against the disease.”
However, as is bound to happen with this type of study, there are several key limitations that must make us consider the results with a bit of skepticism. To begin with, subjects reported each years-worth of food consumption in just one annual survey – a data collection method that is pretty inaccurate given the inconsistency of most people’s diets. Furthermore, their calculations of flavonoid intake from dietary sources were drawn from standardized values reported for American foods, a reference that does not take into account inherent natural variation or differences in US and Australian produce.
In conclusion, are oranges and other citrus fruits going to help save your eyesight? Considering these results and the fact that they also contain tons of vitamin C, the evidence looks good. But consuming any variety of antioxidant-packed fruits and vegetables will most likely do the trick too.
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