Low-fat diets significantly reduce lung cancer risk in older adults, study finds

In a recent study published in The Journal of Nutrition, Health and Aging, researchers investigated the associations between dietary patterns and lung cancer risk in a large cohort of older adults (> 55 years) American cohort. Specifically, they evaluated the change in lung cancer hazard ratios given the long-term (~8.8 years) consumption of different fat components (saturated, unsaturated [mono and poly]). For increased specificity, the associations between fat consumption and both small cell lung cancer (SCLC) and non-small lung cancer (NSCLC) were further investigated.

Study findings reveal that adherence to low-fat dietary regimes significantly reduced lung cancer risk across cancer subtypes. These findings and the observed beneficial outcomes were most substantial for participants currently engaged in smoking practices. In contrast, the consumption of high saturated fatty acids was observed to increase lung cancer risk in the studied cohort.

Study: Adherence to the low-fat diet pattern reduces the risk of lung cancer in American adults aged 55 years and above: a prospective cohort study. Image Credit: Tatjana Baibakova / Shutterstock

The relationship between health behaviors and lung cancer

Lung cancer represents one of the leading non-communicable contributors to human mortality, with the Global Cancer Observatory (GLOBOCAN) estimating 2.2 million novel incidences and 1.8 million deaths due to the disease for 2020 alone. Lung cancer regularly finds itself among the two most prevalent cancer subgroups globally, with its alarming impacts on human health and public well-being primarily attributed to the habit of smoking. A growing body of scientific evidence, however, is discovering the role of health behaviors, particularly sleep and dietary patterns, in lung cancer development and progression.

Research investigating the associations between dietary elements and lung cancer is currently in the spotlight of oncology, with studies from European cohorts highlighting the role of retinol, beer/cider, and offal with an increase in cancer risk. At the same time, fiber, fruits, and vitamin C were observed to reduce this risk. Dietary fat intake has been hypothesized to play a profound role in lung cancer pathology, with low-fat diets (LFDs) suggested to reduce lung cancer risk substantially.

Unfortunately, conventional definitions of LFDs – less than 30% of calories derived from total fat consumption – fail to account for real-world eating habits and are thus not ideal representations of typical dietary regimes. Furthermore, most previous studies either used small cohort sizes or employed insufficient follow-up periods, confounding their results.

About the study

In the present study, researchers investigate the long-term, large cohort outcomes of differing fat intakes (including a modified LFD score) on lung cancer and its subtypes (SCLC and NSCLC). This novel LFD score is derived from the percentage of calories derived from fats compared to those from proteins and carbohydrates.

The study cohort was obtained from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), a long-term randomized, controlled cohort trial conducted by the United States (USA) National Cancer Institute (NCI). Participants were included if they did not have a history of cancer at baseline and provided completed demographic and medical reports. Data collection comprised baseline health evaluations and follow-up annual questionaries, specifically the Dietary History Questionnaire (DHQ) and a study-tailored Supplemental Questionnaire (SQX).

“…the participants were divided into 11 strata based on the percent of the energy gained from macronutrients like fat, carbohydrates, and protein consumption (Supplementary Table S1). For fat, 10 points were assigned to the participants in the lowest stratum and 0 points to participants in the highest stratum. The order of the strata was reversed for macronutrients like protein and carbohydrates. Subsequently, we summarized the points for the three macronutrients for calculating LFD scores for all participants, ranging from 0–30. Thus, a higher LFD score indicated better adherence by the participants to the LFD pattern.”

Medical health records confirmed cancer diagnoses during the study’s course annually. The records included diagnostic procedures, the stage, grade, and histopathology of the identified cancer, and any ongoing clinical interventions against the disease. Cox proportional hazard ratios (HRs) were computed for each stratum of included participants and were adjusted based on participants’ demographics and medical records.

“We conducted a subgroup analysis to investigate the relationship between LFD score and overall lung cancer risk, taking into account potential confounders such as participant age, sex, BMI, drinking or smoking status, and history of emphysema or diabetes. The P-values for interaction were calculated to determine the significance of these potential confounders.”

Study findings

Of the more than 155,000 participants enrolled in the PLCO trial, 98,459 met the study inclusion criteria and were included in the current work. Of these, 47.96% were found to be male, and 92.65% were found to belong to the “White” ethnicity. LFD strata assessments reveal that the highest low-fat diet adherence was observed in older, female, and non-white participants, with educational status playing a significant role in LFD adherence (direct relationship).

Over the course of the 8.83-year-long follow-up period, 1,642 patients contracted lung cancer (1,408 with NSCLC and 234 with SCLC).

“In the fully multivariable-adjusted model, the participants in the highest quartile had a reduced risk of lung cancer compared to the lowest quartile (HR _{Q4 vs. Q1} = 0.76, 95% CI: 0.66−0.89, P < 0.001 for trend). Additionally, an inverse association was observed between the LFD scores and the risk of NSCLC (HR _{Q4 vs. Q1} = 0.79, 95% CI: 0.67−0.93, P = 0.001 for trend) as well as SCLC (HR _{Q4 vs. Q1} = 0.59, 95% CI: 0.38−0.92, P = 0.013 for trend).”

Study results suggest that saturated fatty acids (SFAs) might present the poorest cancer outcomes, with their consumption substantially increasing lung cancer risk. In contrast, no such associations were observed for monounsaturated (MUFA) or polyunsaturated fatty acids (PUFA). Encouragingly, while the highest incidence of lung cancer contraction was found in subgroups with a current or prior history of smoking, the benefits of PFA were also most pronounced in this subgroup.

Conclusions

The present study investigated the long-term associations between dietary fat consumption (LFD score) and lung cancer risk. Study findings within a sizeable American cohort reveal a direct correlation between increased LFD score and cancer risk, highlighting that low-fat diets may confer a protective effect against the disease. Notably, while SFAs were strongly associated with increasing cancer risk, MUFAs and PUFAs did not reveal similar patterns. Encouragingly, while smokers were found to be at the highest risk of contracting cancer, the protective effect of LFD adherence was found to be strongest in this cohort.

“Regards to dietary fatty acids, high consumption of SFA may contribute to an increased risk of lung cancer, with a higher risk observed for SCLC in particular. Therefore, our findings support the potential benefits of adhering to LFD and reducing SFA intake as a strategy for preventing lung cancer.”