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(CNN) - Eating a diet of French fries, Pringles and white bread was enough for a teenager to lose his sight, according to a case study published in a medical journal.
The scientists at the University of Bristol examined the case of a young patient whose extremely delicate diet led to blindness and warned of the dangers of a poor diet.
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The unidentified patient told doctors that he had only eaten fries from the fish and potato store Pringles, white bread, slices of processed ham and sausages since elementary school, and avoided foods with certain textures. He first visited a doctor at age 14, complaining of fatigue, according to a case report published in the Annals of Internal Medicine on Monday.
He was not taking any medication, had a normal BMI and height and showed no visible signs of malnutrition.
Doctors discovered low levels of vitamin B12 and anemia, and treated the patient with injections of vitamin B12 and gave dietary advice.
A year later there were signs of hearing loss and symptoms of vision problems, but doctors did not find the cause.
His vision had worsened to the point of blindness at 17 years of age, and doctors identified vitamin B12 deficiency, low levels of copper and selenium, a high level of zinc, a reduced level of vitamin D and bone density, according to a statement from the University of Bristol
At this stage, the vision damage was permanent.
Researchers at the Bristol School of Medicine and the Bristol Eye Hospital examined the case and concluded that the patient suffered from nutritional optic neuropathy, an optic nerve dysfunction.
In developed countries, it is mainly due to intestinal problems or medications that interfere with nutrient absorption, and rarely due to a poor diet because food is readily available.
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In some places, malnutrition caused by poverty, war and drought is related to higher rates of nutritional optic neuropathy, according to a statement.
The condition is reversible if treated early, but can lead to blindness if no action is taken.
"Our vision has a great impact on quality of life, education, employment, social interactions and mental health," said lead study author Denize Atan, an ophthalmologist at the Bristol School of Medicine and Bristol Hospital Eye.
"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."
The researchers say that a poor diet and a reduced intake of minerals caused vision loss in this case, and they warn that nutritional optic neuropathy could become more common due to the consumption of junk food.
They also warned vegans to make sure they supplement vitamin B12 to avoid deficiency.
To prevent similar cases, doctors should ask patients about their dietary history as part of routine clinical examinations, the researchers urged.
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Extreme example
Tom Sanders, professor of nutrition and dietetics at King's College London, criticized the case report and said it was based on the patient's memory of his eating habits and did not take into account other possible explanations of the condition, including genetic defects or environmental exposures
"Vitamin B12 deficiency can cause optic neuropathy, but it is very unusual to find a deficiency in the diet when consuming animal products, for example, ham and sausages, which are important sources of vitamin B12," he told the Science Media Center in London. .
Gary Frost, a professor of nutrition and dietetics at Imperial College London, who was not involved in the research, told CNN that it is incredibly rare for someone in the UK to have such a limited diet that results in micronutrient deficiencies.
"Although it is an extreme example, it highlights the importance of having a wide and varied diet to ensure that you get the profile of nutrients and micronutrients necessary for healthy development," said Frost.
These deficiencies become more likely the more limited the food choice is, he added.
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"Fussy eating is very common in young children and in extreme cases it can lead to a very limited food choice," said Frost.
"There is a need to resume eating problems like these as soon as possible to address the problem of textures and limited tastes."
