There are a lot of reasons to eat whole grains. They are a major source of dietary fiber as well as vitamins, minerals, phytonutrients, and other numerous nutrients, which are removed from refined grain products. Consuming whole grains has also been linked to a lower risk of obesity, type 2 diabetes, and nonalcoholic fatty liver disease. But now a new study shows eating diet rich in whole grains can reduce the risk of liver cancer by 37%.
In a large observational study of two health professional cohorts with long follow-up that was published in JAMA Oncology, researchers found that incorporating high levels of whole grains into a daily diet could potentially lower the risk of hepatocellular carcinoma (HCC), the most common type of liver cancer in the United States. The incidence of HCC has been increasing for the past 3 decades and HCC is projected to be among the top 3 causes of cancer death by 2030.
Known risk factors for liver cancer include obesity, type 2 diabetes, chronic infection with hepatitis B or C, heavy drinking, and smoking, but the researchers noted that for a large percentage of liver cancer cases, these factors are absent.
“Dietary factors have been suspected as important, but only excessive alcohol use and aflatoxin-contaminated foods are considered to be established dietary risk factors for HCC,” write the study authors, led by Xuehong Zhang, MD, ScD, Brigham and Women’s Hospital and Harvard Medical School, Boston.
A higher consumption of whole grain and dietary fiber has been associated with lower risk of insulin resistance, hyperinsulinemia, and inflammation, all of which are known predisposing factors for HCC.
The researchers also point out that eating more whole grains and dietary fiber may improve gut integrity and alter gut microbiota composition which in turn may lead to increased production of microbiota-related metabolites, including short-chain fatty acids. This may also play an important role in the development of liver diseases, including HCC. But to date, there haven’t been any epidemiological studies that have investigated the association between the intake of whole grains and the risk of HCC, and only one study which assessed the link between dietary fiber and HCC risk
With these data in mind, they hypothesized that long-term intake of whole grains and dietary fiber may be associated with lower risk of HCC.
A cohort study was conducted using 125,455 participants from the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS) and looked at the intake of whole grains, their subcomponents (bran and germ), and dietary fiber (cereal, fruit, and vegetable). Both of these studies have been ongoing for several decades. The NHS was started in 1976 with an enrollment of 121 700 female registered nurses aged 30 to 55 years, while the HPFS was established in 1986 and enrolled 51,529 male health professionals aged 32 to 87 years. Every 2 years, participants are asked to update their information on medical history, lifestyle, and incidence of chronic diseases using validated questionnaires. A validated food frequency questionnaire was administered in 1980 and 1986, and then almost every 4 years afterwards.
The researchers identified 141 patients with HCC during an average follow-up of 24.2 years. A significant association was seen between increased whole grain intake and lower risk for HCC (highest versus lowest tertile of intake: hazard ratio [HR], 0.63; 95 percent confidence interval [CI], 0.41 to 0.96; P = 0.04 for trend). A nonsignificant association was observed for HCC and total bran (HR, 0.7; 95 percent CI, 0.46 to 1.07; P = 0.11 for trend) but not for the germ subcomponent of whole grain. Additionally, increased intake of cereal fiber (HR, 0.68; P = .07 for trend), but not fruit or vegetable fiber, was associated with a reduced risk of HCC (but it was also nonsignificant).
“If our findings are confirmed, increasing whole grain consumption may serve as a possible strategy for prevention of primary HCC,” they conclude.
Yang W, Ma Y, Liu Y, Smith-Warner SA, Simon TG, Chong DQ, Qi Q, Meyerhardt JA,
Giovannucci EL, Chan AT, Zhang X. Association of Intake of Whole Grains and
Dietary Fiber With Risk of Hepatocellular Carcinoma in US Adults. JAMA Oncol.
2019 Feb 21. doi: 10.1001/jamaoncol.2018.7159.
Last updated on 9/30/19.