Burger lovers could be at a higher risk of cancer than vegetarians because of the damaging impact junk food has on blood cells, say scientists.
Researchers from Swansea University in Wales found that people who don't eat enough antioxidants - which are found in fresh foods - produce red blood cells that are damaged.
These cells are a vital part of human wellbeing as they carry oxygen from the lungs of the body's tissues, and remove waste carbon dioxide.
Examining red blood cells is a useful way to judge someone's health, The Sunday Times reported.
Dr Hasan Haboubi, a gastroenterologist and cancer researcher said: "We have found that lifestyle, and especially diet, is intimately linked to the health of our tiniest cells.
"If we have a bad diet it is rapidly reflected in the state of those cells."
Dr Haboubi studied red blood cells, which are created by stem cells in the bone marrow.
As they move around the body, stem cells are affected by many lifestyle factors including diet, exercise and exposure to radiation.
The findings, which came to light when Dr Haboubi was attempting to develop a blood test for cancer, showed that if stem cells become mutated, faulty blood cells are created.
Per million cells, a healthy person should have no more than three to five cells that have mutated.
But Dr Haboubi found people who eat low levels of fruit and vegetables had more than double the mutation frequency.