- The relationship between obesity and cancer is clear, and researchers have also been interested in investigating whether there is a similar link between diet and cancer risk
- The role of smoking in causing lung cancer has been firmly established for decades but other lifestyle factors have received less attention.
- A large observational study of older adults in the United States has shown that a low-fat diet is associated with a lower risk of lung cancer, and a high-fat diet is associated with a higher risk of lung cancer in smokers.
A low-fat diet has been associated with a lower risk of lung cancer in a cohort of people in the United States.
Researchers from China analyzed data from a cohort of over 98,000 people taking part in a U.S.-based cancer study, and found a 24% lower risk of lung cancer in people who had the lowest amount of fat in their diets.
This reduction was even more pronounced, standing at a 29% reduced risk in smokers who had the lowest-fat diets.
These results were reported in the The Journal of Nutrition, Health and Aging. Overall, they suggest that diets high in saturated fats were associated with a 35% increased risk of lung cancer, in general, and double the risk of small-cell lung cancer.
Researchers analyzed data from The Prostate, Lung, Colorectal and Ovarian Cancer Survey cohort as part of this observational study.
Participants were recruited between November 1993–July 2001, and data on cancer incidence and mortality was collected 2009 and 2018.
Participants’ medical histories were collected, including information on their diet provided via a dietary questionnaire that asked about calorie consumption, macronutrients, and the amount of food they ate from different parts of the food pyramid, such as fruits and vegetables, lean meat, dairy, and added sugars.
The participants’ average age was 65 at follow-up, the cohort was predominantly white, with 47.96% of participants being male.
Researchers cross-referenced these data with data collected on cancer incidence, staging and type. They adjusted the data for confounding factors, including activity levels, age, education, height, race, weight, whether or not the participants smoked, whether they had diabetes, and used aspirin.
After calculating low-fat diet scores, the researchers discovered that participants in the highest quartile were older, female, and typically not white, with a higher level of educational attainment, when compared to those in the lowest quartile, that is, the people who had the highest-fat diets.
People with a family history of lung cancer were also more likely to be more physically active, and have a lower body mass index (BMI). People in the highest quartile for low fat diets also consumed less sodium and cholesterol.
Results showed an inverse relationship between low-fat diets and risk of lung cancer, in a linear, dose-dependent manner. This was more pronounced for smokers and high fat diets were associated with a higher risk of small cell lung cancer.
The authors of the current study said their findings were supported by other research, similarly showing that low-fat diets can be associated with lower risk of some other cancers. They pointed to a UK Biobank study, which showed that diets high in red and processed meats are associated with lung cancer.
However, theirs was the first study looking at the impact of low-fat diets on lung cancer risk, they said.
Nilesh Vora, MD, a board-certified hematologist, medical oncologist and medical director of the MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA, not involved in this research, told Medical News Today that he found the study interesting:
“It is a surprising finding specific to lung cancer. In breast cancer there is a known association between high fat diets, obesity and cancer recurrence. I had not seen similar data in lung cancer.”
The study did not propose a reason why the trend observed was more pronounced for people who smoked.
Vora said that “[l]ots of hypotheses can be made with regards to the mutations and inflammation that smoking can cause to normal cells, and this study mentioned the additional harm that fats may do.”
Lung disease and cancer have historically been stigmatized due to their link to smoking, and their perceived avoidable nature, but this is the first study to look at the role of fat in the diet on risk of developing lung cancer.
The authors of the study proposed that their findings could support recommending low-fat diets to smokers, highlighting that saturated fats were particularly associated with increased lung cancer risk, but not polyunsaturated fats or monounsaturated fats.
Catherine Rall, RDN, a registered dietitian based in Denver, CO, not involved in this study, hypothesized that:
“The key here is saturated fatty acids. These produce an inflammatory response in the body, and chronic inflammation is one of the key underlying causes of cancers of all types. It makes sense that reducing fat intake, including saturated fat, would lead to a lower risk of cancer, including lung cancer. It also makes sense that, if we’re comparing smokers to other smokers, factors like diet would be the deciding factor in whether or not they develop lung cancer.”
Rachelle Caves, RDN, a registered dietitian and fitness trainer based in Massachusetts, also not involved in this study, concurred, saying: “I’m not surprised that saturated fat was associated with increased cancer risk because most foods containing high levels of saturated fat carry a pro-inflammatory burden with them. Foods low in saturated fat tend be healthful foods such as lentils, beans, peas, fruits and vegetables – the types of food that may help prevent cancer.”
Vora highlighted the limitations of the study, saying that: ”[The] next step is to see if a randomized control trial is feasible to be done to definitely prove this point. This was a prospective observational study with lots of potential flaws in collecting the data. I found it very interesting, nevertheless.”
