A diet containing only processed foods can lead to serious health consequences. Shutterstock

A 17-year-old UK resident went blind after eating nothing but french fries, chips, white bread, processed ham, and sausage since elementary school, a medical case study reported.

"Nutritional optic neuropathy" is rare in developed countries and reversible if caught early.

A diet packed with processed foods is a lot more likely to lead to health complications like heart problems and diabetes than blindness.

Parents of picky eaters can make sure their kids get enough nutrients by offering a wide variety of healthy options to create balanced meals and snacks.

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Eating junk food day in and out can seriously damage your body - even if you never gain weight.

A UK teenager's story is a case in point. The boy went blind after eating nothing but highly processed snacks for years, according to a case study published Monday in Annals of Internal Medicine.

The teen was first taken to his family doctor at age 14, complaining of tiredness, and received a diagnosis of anemia and B vitamin deficiency. A year later, he developed hearing loss and shortly after started having trouble seeing, the researchers at the Bristol Eye Hospital and University Hospitals Bristol NHS Foundation Trust reported.

By age 17, the patient had lost his vision to the point of being blind, and doctors said the damage was permanent. He had extremely low levels of vitamins B, vitamin D, and other nutrients, doctors found.

The boy, who was a normal weight, told doctors he was an extremely picky eater. He had consumed nothing but french fries, chips, white bread, processed ham, and sausage since elementary school, the study reported.

Nutritional optic neuropathy is rare and reversible, if caught early

The teen's blindness was caused by a condition known as nutritional optic neuropathy, which is usually rare in developed countries. It can be caused by drugs, severe alcohol and tobacco use, and poor diet, according to the research.

Read more: A woman went blind after showering with contacts in, and an eye doctor says it's because a contact lens is a 'sponge' for fungi and amoebas

Specifically, the optic nerve is damaged by a lack of nutrients like folic acid and B vitamins, which help with healthy cell maintenance. Without them, toxic metabolic byproducts can build up within the cells, damaging and eventually killing the nerves, according to research. It can be treated early by providing patients with the right nutrients, but once the nerves are damaged, they can't be repaired.

For the teenager in the study, whose refusal to eat anything other than junk food was so severe doctors categorized it as an eating disorder, treatment included vitamins to balance his nutritional deficiencies and mental-health counseling for the disorder. Still, they couldn't reverse the damage already done to his eyes.

Eating only junk food can leave you malnourished and lead to a host of problems

Though they're full of calories, foods like chips, french fries, and processed meats have few nutrients. In addition to lacking B vitamins, they're also missing essential nutrients like vitamin D, calcium, selenium, and copper. Doctors found the patient in this case was lacking all of the above.

While blindness from a junk-food-only diet is unusual, the eating pattern can lead to plenty of other problems. Excessive junk food can increase the risk of heart disease and diabetes in people of all ages and crowd out healthier options like vegetables, fruits, and whole grains in your daily diet. Limiting junk food is especially important in children because filling up on it can lead them to miss out on nutrients they need to fuel growing brains and bodies.

If you have a young picky eater in your life, you can encourage more balanced food choices by following these tips from the American Academy of Pediatrics:

Offer a choice between two healthy options - kids are more excited about eating something they've picked for themselves.

Find healthy foods they do like and keep them on hand, so they'll always have something to rely on.

Talk to your children about where food comes from and let them help with meal prep - being engaged will make them more interested in healthy food.

Provide balanced meals and eat together as a family.

Read more:

Blue light emitted by smartphones and laptops accelerates blindness by making a molecule in our eyes toxic, according to a new study

The scary ingredients hiding in your junk food - and what they mean for you and your health

How to know if you're not getting enough vitamin B

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