The role of nuts in the optimal diet: time for a critical appraisal?

Association of nut consumption with risk of total cancer and 5 specific cancers: evidence from 3 large prospective cohort studies

BACKGROUND

The associations between nut consumption and cancer risk have not been extensively investigated.

OBJECTIVES

We aimed to examine the associations between nut consumption, especially specific types of nuts (peanut, tree nut, walnut, and tree nut other than walnut), and cancer risk.

METHODS

Nut consumption was assessed by FFQ at baseline and updated every 2-4 y in the Nurses' Health Study (1980-2014), the Nurses' Health Study II (1991-2015), and the Health Professionals Follow-up Study (1986-2018). We examined the associations between the intake of total and specific types of nuts and risk of total cancer and common cancers, including lung, colorectal, breast, bladder, and aggressive prostate cancer. Cox proportional-hazards models were used to obtain the HRs and 95% CIs in each cohort as well as pooled.

RESULTS

During 5,873,671 person-years of follow-up in 180,832 women and 45,560 men, we documented 44,561 incident cancer cases. As compared with nonconsumers, the pooled multivariable HRs of total nut consumption for ≥5 times/wk were 0.99 (95% CI: 0.94, 1.04; P-trend = 0.54) for total cancer, 0.88 (95% CI: 0.74, 1.04; P-trend = 0.18) for lung cancer, 1.07 (95% CI: 0.92, 1.26; P-trend = 0.89) for colorectal cancer, 0.90 (95% CI: 0.71, 1.14; P-trend = 0.65) for bladder cancer, 0.96 (95% CI: 0.85, 1.08; P-trend = 0.36) for breast cancer, and 1.18 (95% CI: 0.92, 1.51; P-trend = 0.52) for aggressive prostate cancer.

CONCLUSIONS

In 3 large prospective cohorts, frequent nut consumption was not associated with risk of total cancer and common individual cancers.

Nut consumption and risk of colorectal cancer in women

BACKGROUND/OBJECTIVES

Increasing nut consumption has been associated with reduced risk of obesity and type II diabetes, the risk factors for colorectal cancer. However, the association between nut consumption and colorectal cancer risk is unclear. We aimed to examine the association of long-term nut consumption with risk of colorectal cancer.

SUBJECTS/METHODS

We prospectively followed 75,680 women who were free of cancer at baseline in the Nurses' Health Study, and examined the association between nut consumption and colorectal cancer risk. Nut consumption was assessed at baseline and updated every 2-4 years. Relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards models.

RESULTS

During 2,103,037 person-years of follow-up, we identified 1503 colorectal cancer cases. After adjustment for other known or suspected risk factors, women who consumed nuts 2 or more times per week (that is, ⩾ 56 g per week) had a 13% lower risk of colorectal cancer compared with those who rarely consumed nuts, but the association was not statistically significant (RR: 0.87; 95% CI: 0.72-1.05; P-trend: 0.06). No association was observed for peanut butter.

CONCLUSIONS

In this large prospective cohort of women, frequent nut consumption was not significantly associated with colorectal cancer risk after adjusting for other risk factors.

A review of the effects of nuts on appetite, food intake, metabolism, and body weight

Tree nuts and peanuts are good sources of many nutrients and antioxidants, but they are also energy dense. The latter often limits intake because of concerns about their possible contribution to positive energy balance. However, evidence to date suggests that nuts are not associated with predicted weight gain. This is largely due to their high satiety value, leading to strong compensatory dietary responses, inefficiency in absorption of the energy they contain, a possible increment in resting energy expenditure, and an augmentation of fat oxidation. Preliminary evidence suggests that these properties are especially evident when they are consumed as snacks.