A 14-year-old boy goes to the doctor with complaints of tiredness. He's an extremely picky eater. (Think a daily diet of French fries, plus snacking on Pringles potato chips, white bread and some processed pork.) But overall, he appears OK. He's not overweight and takes no medications.
Tests show he has low levels of vitamin B12 and anemia, so he's given B12 injections and diet advice. But a year later, he has begun to lose his vision. Then, by age 17, he's legally blind.
Turns out, the boy's highly limited daily diet — lacking in healthy foods, vitamins and minerals — had led to optic neuropathy. That's the conclusion of researchers from the University of Bristol in England, who have published a case study in the Annals of Internal Medicine.
"This case highlights the impact of diet on visual and physical health, and the fact that calorie intake and BMI are not reliable indicators of nutritional status," Dr. Denize Atan, the study's lead author and a consultant senior lecturer in Ophthalmology at Bristol Medical School, said in a statement.
Not everyone is convinced by the case study.
"It's intriguing," say Allen Taylor, a professor at the Friedman School of Nutrition Science and Policy at Tufts University who studies vision, aging and nutrition. "But it's important to remember it's a study of only one case, with very limited information in it," Taylor says.
Taylor says he'd like to know more about how the teen ended up with permanent vision loss, given that optic neuropathy is very uncommon and usually temporary.
But he says the case study could serve as a wake-up call to remind people of the importance of good nutrition.
"There is, absolutely, a link between poor diet and vision loss," Taylor explains. But, he says usually, people don't develop symptoms until much later in life.
He points to a study he and his collaborators published back in 2014, which found that poor-quality diets can increase the risk of age-related macular degeneration. This can lead to blurry vision and can make reading more difficult. It usually occurs after age 60.
"Conversely, the more one subscribes to a diet rich in fruits and veggies, whole grains, the less the risk for AMD," Taylor says.
People in Taylor's study who consumed plenty of vegetables, legumes, fruits, whole grains, tomatoes and seafood had a lower risk of developing AMD. On the other hand, people who consumed a diet rich in red meat, processed meat, high-fat dairy products, French fries and refined grains had a higher risk of developing the condition.
Taylor says it's important to note that the quality of the carbohydrates you eat really does seem to matter. (As we've reported, aim for "slow carbs.")
Consuming a lot of refined carbohydrates, including foods such as white bread, chips, crackers and sweets, is linked to a higher risk of developing AMD and some forms of cataracts. Taylor and his collaborators are trying to understand how refined carbohydrates may inflict damage on the cells within our eyes and bodies.
"If you look at the chemistry behind what's going on in the cells, you can actually see the vestiges of the carbohydrates in the cells," Taylor says.
"The carbohydrates end up damaging the proteins within the cells of the eyes," he says, so the proteins are no longer as functional as they might have been.
Taylor's findings are not a huge surprise, given what's known about diet and health overall.
Around the globe, poor diets are a leading contributor to premature death — even more than smoking — and in the U.S., an estimated 1,000 deaths per day from cardiovascular and metabolic diseases are linked to diet. So the idea that diet influences the health of eyes makes sense.
Bottom line: "Be sure to feed yourself and your loved ones a diet that's rich in fruits and vegetables ... and whole grains," Taylor says.