Experts are warning about the risks of extreme fussy eating after a teenager developed permanent sight loss after living on a diet of chips and crisps.
Eye doctors in Bristol cared for the 17-year-old after his vision had deteriorated to the point of blindness.
Since leaving primary school, the teen had been eating only French fries, Pringles and white bread, as well as an occasional slice of ham or a sausage.
Tests revealed he had severe vitamin deficiencies and malnutrition damage.
The adolescent, who cannot be named, had seen his GP at the age of 14 because he had been feeling tired and unwell. At that time he was diagnosed with vitamin B12 deficiency and put on supplements, but he did not stick with the treatment or improve his poor diet.
Three years later, he was taken to the Bristol Eye Hospital because of progressive sight loss,?Annals of Internal Medicine?journal reports.
Dr Denize Atan, who treated him at the hospital, said: "His diet was essentially a portion of chips from the local fish and chip shop every day. He also used to snack on crisps - Pringles - and sometimes slices of white bread and occasional slices of ham, and not really any fruit and vegetables.
"Nutritional yeast is a way of adding B12 to your diet," she said.
Sources of vitamin B12 for vegans include:
breakfast cereals fortified with B12
unsweetened soya drinks fortified with vitamin B12
yeast extract, such as Marmite, which is fortified with vitamin B12
Rebecca McManamon, consultant dietitian and spokesperson for the British Dietetic Association, said restricted diets might happen for a range of reasons, including eating disorders, allergies and autism, and need specialist assessment.
"It's also worth noting that since 2016 the UK government has recommended daily Vitamin D supplementation (10 microgrammes/400 International Units) for everyone between October and March as we are not likely to get enough from fortified foods.