Consumption of certain tree nuts has been linked to a dramatically lower risk of colon cancer recurrence, according to researchers from the Dana-Farber Cancer Institute.

The study, to be presented in the American Society of Clinical Oncology next month in Chicago, has reconfirmed findings of how living healthily would actually benefit patients with advanced cancer.

However, what is more surprising is that the team suggests eating a daily handful or two of commonly known nuts could work as well as standard chemotherapy at keeping colon cancer from recurring after surgery – and even keeping patients from dying.

If the benefit is true, this could be exaggeratedly translated to mean chemotherapy can be replaced by eating tree nuts.

Keyword: "if".

Finding comes from an observational study

The study comes from a respected clinical trial in 1999, but this finding was not from the original research. Rather, it is an add-on instead. The original trial randomly assigned stage 3 colon cancer patients to either of two drug treatments.

Patients answered questionnaires that looked at their diet and lifestyle, once while receiving chemotherapy and again six months after the treatment ended. Other researchers then data-mined and looked for associations such as an increased rate of recurrence of colon cancer is linked to smoking early in life and consumption of sugary beverages.

Dr Temidayo Fadelu of Dana-Farber Cancer Institute and his colleagues looked at nut consumption as other studies have been associated with lower mortality and a reduced risk of cardiovascular disease. They analysed whether eating nuts was associated with better outcomes – making it an observational study.

Therefore, it was not possible to say whether a given behaviour caused an outcome, or was instead simply associated with the true cause.

"This is the challenge with observational studies," said Dr. Richard Schilsky, chief medical officer of the American Society of Clinical Oncology. He added "All you can say is that these patients [who ate nuts] had better outcomes. But is eating nuts a proxy for other things that have an effect, including generally healthy behaviours?"

Results only apply to consumption of certain tree nuts

The study found that among the stage 3 colon cancer patients in the study, those who ate 2 ounces or more nuts or more per week – about 19% of the 826 patients – were revealed to have 46% lower chance of cancer recurrence than among participants who ate fewer than 2 ounces of nuts per week. They also had a 53% lower chance of death compared to those who did not consume the same amount of nuts.

This only applied to those who ate "nuts" such as almonds, walnuts, hazelnuts, cashews and pecans. There was no effect in those who ate peanuts. "This is the first study to show an association between nut consumption and cancer outcomes," remarked Fadelu.

Other experts raise red flags of the study

The team was confident that "something is going on" with tree nuts providing a biological benefit; for instance, they decrease insulin resistance, a "potential mechanism" which might keep colon cancer from recurring.

However, Fadelu added that "When you see an association that is more dramatic than you expect, you have to repeat [the study] in another [group of patients]. ... There could be underlying confounders that we didn't control for."

One confounder could be that patients, who consume tree nuts, might be different from patients who do not, something called "healthy patient bias". They "might be more health-conscious" or wealthier, better connected to the healthcare system or have healthier habits in general, Dr Manish Shah, director of gastrointestinal oncology at Weill Cornell Medicine and New York-Presbyterian Hospital, who was not involved in the study, suggests.

Others suggest that what people remember and what they report about their diets are unreliable, or that those who are more health conscious are pressured to simply say they ate lots of tree nuts, regardless of their true diets.

"There's nothing I know that could be a clear causal mechanism," ASCO's Schilsky said. MIMS

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