Tree nuts include almonds, walnuts, hazelnuts, cashews and pecans. Peanuts are legumes.
The study followed 826 participants in a clinical trial for six-and-a-half years after they were treated with surgery and chemotherapy.
Those who regularly consumed at least two one-ounce servings of nuts each week showed a 42 per cent improvement in disease-free survival and a 57 per cent improvement in overall survival.
Senior author Professor Charles Fuchs, director of Yale Cancer Centre in the US, said: “Further analysis revealed that disease-free survival increased by 46 per cent among the sub-group of nut consumers who ate tree nuts rather than peanuts.”
Healthy Lead author Dr Temidayo Fadelu, a postdoctoral fellow at Dana-Farber Cancer Institute in the US, said: “These findings are in keeping with several other observational studies that indicate that a slew of healthy behaviours, including increased physical activity, keeping a healthy weight, and lower intake of sugar and sweetened beverages – improve colon cancer outcomes.
“The results highlight the importance of emphasising dietary and lifestyle factors in colon cancer survival.”
The researchers said the study also highlighted connections between biological mechanisms that worsen disease – not just in colon cancer, but in certain chronic illnesses such as Type 2 diabetes.
Many previous studies have reported that nuts, among other health benefits, may help to reduce insulin resistance, a condition in which the body has difficulty processing the hormone.
Insulin resistance leads to unhealthy levels of sugar in the blood and is often a predecessor to Type 2 diabetes and related illnesses.
Earlier research among patients with colon cancer has revealed worse outcomes among those with lifestyle factors that heighten insulin resistance, such as obesity, lack of exercise, and a diet with high levels of carbohydrates that quickly raise levels of blood sugar.
Prof Fuchs said: “These studies support the hypothesis that behaviours that make you less insulin resistant – including eating nuts – seem to improve outcomes in colon cancer.
“However, we don’t know yet what exactly about nuts is beneficial.”
He said nuts also might play a positive role by satisfying hunger with less intake of carbohydrates or other foods associated with poor outcomes.
Dr Fuchs acknowledged patients may not be eating nuts owing to concerns about high fat content.
For example, a one-ounce serving of 24 almonds holds about 200 calories, including half a ounce of fat.
But he said: “People ask me if increasing nut consumption will lead to obesity. But what’s really interesting is that in our studies, and across scientific literature in general, regular consumers of nuts tend to be leaner.”
The study findings were published in the Journal of Clinical Oncology.