World renowned neuropathologist Dr Bennet Omalu is urging parents to stop their children under the age of 18 from playing contact sports or risk them suffering permanent brain damage - with rugby considered one of the worst sports of all.
Dr Omalu has today released a new book, Truth Doesn't Have a Side, which paints an even more dire picture of the damage of constant head knocks from contact sport and its link to brain disease.
But with the book came a message to parents to stop their children playing contact sports until they were at least 18.
"The big six are rugby, (American) football, boxing, ice hockey, mixed martial arts and wrestling," he told TVNZ1's Breakfast this morning.
"If your child plays any of these games, even for one season, there is a 100 per cent risk of exposure to permanent brain damage."
Dr Omalu was portrayed by actor Will Smith in the 2015 film Concussion which detailed his struggle against the NFL to have his scientific discovery of chronic traumatic encephalopathy (CTE) in American football players accepted as fact.
But now the Nigerian physician says it's not just professional athletes that can suffer from permanent brain damage.
"The big question is in 2017, knowing what we know today, why would we continue to intentionally damage the brains of our children?
"We would not let a child smoke a cigarette but we would rather send a child to the field of rugby or football to suffer a concussion of the brain.
"What's more dangerous? A cigarette or a concussion of the brain?"
Dr Omalu says parents should instead be enrolling their children in non-contact sports such as athletics, volleyball and tennis.
"Each and every parent must ask themselves, 'do I love rugby more than I love my child?'
"Pull your child out. Let your child play non-contact, non-collision sports - there are so many of them.
"Non-contact sports would provide everything rugby provides to your child but even more, these non-contact sports would preserve your child's intelligence and your child's mind and enable your child to attain every goal he or she was born to attain."