Diets with higher nut consumption appeared to be associated with reduced risk for disease recurrence and mortality among patients with stage III colon cancer, according to results from the prospective, observational CALGB 89803 study.
Observational studies have suggested diet and lifestyle factors — such as type 2 diabetes, obesity, sedentary lifestyle, Western-pattern diet, increased dietary glycemic load and high intake of sugar-sweetened beverages — are associated with risk for colon cancer recurrence and death. Although nut intake is associated with lower risk for type 2 diabetes, metabolic syndrome and insulin resistance, whether nut consumption had an effect of colon cancer recurrence and survival had not been known.
“These studies support the hypothesis that behaviors that make you less insulin resistant, including eating nuts, seem to improve outcomes in colon cancer,” Charles S. Fuchs, MD, MPH, director of the Yale Cancer Center, said in a press release. “However, we don’t know yet what exactly about nuts is beneficial.”
Fuchs and colleagues evaluated data from 826 patients with stage III colon cancer who reported dietary intake on a food frequency questionnaire while enrolled in a randomized trial of adjuvant chemotherapy.
During a median 6.5 years of follow-up, 199 patients experienced recurrence or developed new primary tumors and 177 patients died, 39 of whom died without documented cancer recurrence.
Researchers considered nut consumption levels as never (n = 145; median age, 64 years), less than one serving per month (n = 98; median age, 60 years), one to three servings per month (n = 211; median age, 58 years), one serving per week (n = 214; median age, 59 years), or two or more servings per week (n = 158; median age, 62 years).
Compared with patients who did not eat nuts, those in the highest category of consumption demonstrated improved DFS (HR = 0.58; 95% CI, 0.37-0.92) and OS (HR = 0.43; 95% CI, 0.25-0.74), with a trend toward improved RFS (HR = 0.7; 95% CI, 0.42-1.16).
Subgroup analyses showed the improvement was confined to consumption of tree nuts — which include almonds, walnuts, hazelnuts, cashews and pecans — for DFS (HR = 0.54; 95% CI, 0.34-0.85) and OS (HR = 0.47; 95% CI, 0.27-0.82).
Researchers found no association between the consumption of peanut butter and improved outcomes.
The association of total nut intake on improved outcomes persisted in analyses that considered other known colon cancer recurrence risk factors.
Patients may be wary of nut consumption due to their greater fat content, according to the researchers.
“People ask me if increasing nut consumption will lead to obesity, which leads to worse outcomes,” Fuchs said. “But, what’s really interesting is that in our studies, and across the scientific literature in general, regular consumers of nuts tend to be leaner.”
Researchers noted the study may be limited by the self-reported nut intake and measurement error. Also, although the findings further support the role of diet and lifestyle as modifiable risk factors for colon cancer, the observation study does not support causality.
“Overall, we are working to apply the same rigorous science to the understanding of diet and lifestyles in the colon cancer patient population that we apply to defining new drugs,” Fuchs said. – by Alexandra Todak