How high-fat diet raises cancer risk
Eating broccoli to protect against liver cirrhosis as small, regular dose of aspirin keeps colorectal tumour at bay
New research on mice suggests that by boosting stem cell production in the gut – and also by inducing other cells to become like stem cells – a high-fat diet could increase the risk of colon cancer.
The study – published in Nature – is the work of researchers from the Whitehead Institute and the Koch Institute for Integrative Cancer Research at the Massachusetts Institute of Technology (MIT), both in Cambridge, MA, United States (U.S.)
Studies published over the last 10 years have shown that being obese and eating a high-fat, high-calorie diet can raise the risk of many types of cancer, including colon cancer.
The new study suggests an underlying mechanism through which this link might operate. It reveals the effect that a high-fat diet has on the biology of stem cells in the lining of the gut of mice and how this might make cancer more likely.
The team discovered that feeding mice on a high-fat diet resulted in a boom in their intestine’s production of stem cells. And it also had an effect on some other cells – it caused them to become more like stem cells and make them more likely to form tumors.
Stem cells are precursor cells that can reproduce indefinitely and have not fully differentiated – they have the potential to become a number of different cells.
Meanwhile, broccoli and other cruciferous vegetables have been hailed for their protective effects against breast, prostate and colon cancer. But now, a new study adds liver cancer to the list.
The study, led by Prof. Elizabeth Jeffery at the University of Illinois, is published in the Journal of Nutrition.
“The normal story about broccoli and health is that it can protect against a number of different cancers,” says Jeffery. “But nobody had looked at liver cancer.”
The typical Western diet consists of high saturated fats and added sugars, both of which are stored in the liver and converted to body fat. But eating such a diet, as well as having excess body fat, is linked to non-alcoholic fatty liver disease (NAFLD).
This disease can also lead to cirrhosis and liver cancer, and the researchers add that without treatment, NAFLD can progress to hepatocellular carcinoma (HCC), a cancer that has a high mortality rate.
Although NAFLD is not typically accompanied by signs or symptoms, sometimes it does, and these include fatigue, pain in the upper right abdomen and weight loss.
She adds that men’s risk of liver cancer increases five-fold if they are obese.
Broccoli decreased number of cancer nodules in mice.
Also, a regular, small dose of aspirin may help prevent cancer in general and colorectal cancers in particular, say findings published in JAMA Oncology.
Long-term aspirin use has been linked with a modest but significantly reduced risk of overall cancer, especially gastrointestinal (GI) tract tumors.
Historically, aspirin has most commonly been taken to treat or prevent headaches, arthritis, musculoskeletal pain and cardiovascular disease (CVD).
The US Preventive Services Task Force recently recommended taking aspirin regularly to stave off CVD and colorectal cancer (CRC).
In previous research, Jeffery and colleagues showed that sulforaphane – broccoli’s cancer-fighting compound – is best acquired by eating the vegetable chopped or lightly steamed.
Broccoli – along with cauliflower or Brussel sprouts – is a brassica vegetable, and previous research has suggested that brassica vegetables could stop the accumulation of fat in the liver, protecting against NAFLD.
As such, the researchers wanted to see what effect broccoli has on mice with a liver cancer-causing carcinogen.
They studied four groups of mice. Some groups were on a control diet, and others were on a “Westernized diet,” which is a model of how many of us eat today. And some groups were given broccoli, while others were not.
Jeffery explains that they wanted to investigate mice who were obese, not through a genetic component, but through eating a high-fat, high-sugar diet, like many people in the West today.
Results showed that mice who were fed the Westernized diet saw an increase in both the number and size of cancer nodules in the liver. When broccoli was added to the diet, however, the number of nodules decreased.
The researchers note that the size of the nodules was not affected by consuming broccoli.Jeffery says prior to their study, there was almost no information about high-fat associated diseases and broccoli.
Dr. Andrew T. Chan, of the Massachusetts General Hospital in Boston, MA, and coauthors examined the effect of aspirin on cancer among 135,965 participants registered in two large cohort studies of health care professionals in the US.
The Nurses’ Health Study ran from 1980 to 2010, and the Health Professionals Follow-up Study ran from 1986 to 2012.The team looked at 20,414 cases of cancers among 88,084 women and 7,571 cancers among 47,881 men over a period of 32 years.
Among people who took 0.5 to1.5 standard aspirin tablets a week, the prevalence of cancers overall was three per cent lower, with a 15 per cent reduced risk of GI tract cancers and a 19 per cent lower risk of developing colorectal cancer.
Results suggest that the effectiveness of aspirin in preventing CRC is dose-dependent.
Regular use of aspirin did not correlate with a lower risk of breast, prostate, lung or other major cancers. What effect, if any, aspirin might have on other types of cancer risk remains unclear.
Findings suggest that aspirin may impact additional mechanisms that contribute to the formation of cancer in the GI tract. This could explain the stronger association of aspirin with a lower risk of gastrointestinal cancers.
Aspirin may prevent CRC whether people undergo screening or not. However, findings indicate that substantially more cases were prevented among people who did not undergo screening.
In the general population, the researchers suggest that regular aspirin use by people aged 50 years or over could prevent CRC in people who do not adhere to screening.
The team estimates that 17 per cent of cases of CRC were prevented among people who did not undergo lower endoscopy and 8.5 per cent of CRC cases among those who underwent the screening.
The authors recommend balancing the benefits of aspirin for CVD and cancer with potential harms, such as GI tract bleeding.
They conclude: “Aspirin may be a potential low-cost alternative to endoscopic CRC [colorectal cancer] screening in resource-limited settings or a complement in settings in which such programs are already implemented, including the general US population, in whom screening adherence remains suboptimal.”
In a linked comment, Dr. Ernest T. Hawk, of the University of Texas MD Anderson Cancer Center in Houston, and coauthors highlight the study’s findings regarding aspirin’s potential impact for the general population, as well as the value that aspirin can add to the screening process.
Aspirin use, they say, could complement colorectal cancer screening and could be beneficial regardless of endoscopy status.
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