It's not good news if you're a fan of diets such as the Atkins or Dukan eating plans, which restrict carbs but encourage lots of protein - especially as so many people have found these and other similar high-protein diets have helped them shed lots of weight.
The study, however, is on a very small scale, having involved only 17 people who each followed three short-term diets which allowed 360g, 181g and 22g of carbs per day respectively. After four weeks on the two diets with the lowest amount of carbs allowed, the volunteers were found to have higher levels of substances called N-nitroso compounds, which have been linked to cancer.
The key, say the scientists whose study is published in the American Journal of Clinical Nutrition, is fibre. If you eat lots of protein and very little carbs, it's likely that you won't be getting enough fibre, which is thought to protect against colon cancer.
As a result the experts claim people should be wary about eating too much protein and too little fibre in the long term.
It's thought that most people in the UK already don't eat enough fibre (the official recommendation is 18g per day, but on average we only eat about 12g).
Have you lost weight on a high-protein diet?