Can eating your vegies really help to fight cancer and other chronic conditions such as cardiovascular disease and type 2 diabetes?
New research has found that dozens of plant-based compounds can slow the spread of many common cancers – including breast, skin, lung, prostate, colorectal and others – by turning on cancer-fighting, metastasis suppressor genes.
A study by Gary Meadows, a Washington State University professor and an associate dean at the college of pharmacy, published in the journal Cancer and Metastasis Reviews, has identified more than 40 plant-based compounds that help slow the progression of cancer. They include glucosinolates – found in cruciferous vegetables such as broccoli, cabbage, cauliflower and kale; lycopene – the bright-red carotenoid found in tomatoes, watermelon, papaya and pink grapefruit; lupulone – a flavonoid found in hops; curcumin – found in turmeric; and pomegranate juice.
Professor Meadows used existing cancer studies to survey information on metastasis-suppressor genes, which was often buried in reports focused on other areas of cancer research.
He said most cancer studies concentrated either on preventing cancer or treating the initial tumour but little work had been done to understand how cancer spreads to other organs – that is, when it metastasised.
Professor Meadows said he was “very surprised that there had been little specific research in this area and very little to specifically look at the interaction between diet and lifestyle and their effects on these genes”.
Metastasis was responsible for up to 90 per cent of cancer deaths, he said.
The chief executive of Cancer Council Australia, Ian Olver, agrees that diet has a crucial role in fighting cancer but warned against “over-interpreting” Professor Meadows’ study.
Professor Olver, who is a member of the federal government’s advisory council for Cancer Australia, said foods such as fresh fruit, vegetables and fish products were known to be rich in chemicals that could turn on tumour-suppressor genes, which might stop a cancer spreading.
“The discovery of the ability of chemicals in these foods to influence the development of cancer by turning on or off genes gives us a mechanism to explain the observations that people on ‘healthy diets’ are less prone to developing cancer,’’ he said.
“But we have to be careful about not over-interpreting the research to construct very specific diets of particular fruits or vegetables.
“The evidence has not reached that level of detail but we can confidently recommend that fresh fruit and vegetables and foods such as fish should be eaten regularly.
“A diet which contains these foods is not only less likely to contribute to obesity but more likely to decrease the chance of developing cancer,” he said.
A cancer expert at the University of Sydney, Qihan Dong, said that “as most of these results are from isolated cancer cells grown under non-physiological conditions, it is important to verify the findings in animals and ideally in humans.
“The amount of nutrients required to achieve these effects also needs to be carefully examined, as some levels of nutrients may not be achievable in humans.”
But the research adds yet more strength to age-old advice to eat your five a day.
Researchers at the Western Australian Institute for Medical Research last year found that eating vegetables and fruit reduced the risk of two types of colon cancer.
The lead researcher, Lin Fritschi, said the study, published in the Journal of the American Dietetic Association, found that eating vegetables, including brussels sprouts, cabbage, cauliflower and broccoli, reduced the risk of proximal colon cancer, while total fruit and vegetable intake cut the risk of distal colon cancer.
Patients who eat plant-based diets can reverse severe coronary artery disease and significantly lower the chronic inflammation that causes heart disease, according to Dean Ornish, a clinical professor of medicine at the University of California and founder of the Preventive Medicine Research Institute.
“In 35 years of medical research,” Professor Ornish wrote in The New York Times, “we have seen that patients who ate mostly plant-based meals, with dishes like black bean vegetarian chilli and whole-wheat penne pasta with roasted vegetables, achieved reversal of even severe coronary artery disease.”
“The program [which included moderate exercise and stress-management techniques] also led to improved blood flow and significantly less inflammation, which matters because chronic inflammation is an underlying cause of heart disease and many forms of cancer,” said Professor Ornish, who reshaped the White House menu in 1993 at the request of Hillary Clinton and later encouraged Bill Clinton to switch to a mostly plant-based diet after he had quadruple bypass surgery.
“We found that this [plant-based] program may also slow, stop or reverse the progression of early-stage prostate cancer, as well as reverse the progression of type 2 diabetes.
“Also, we found that it changed gene expression in over 500 genes in just three months, ‘turning on’ genes that protect against disease and ‘turning off’ genes that promote breast cancer, prostate cancer, inflammation and oxidative stress.
“Your diet needs to be high in healthful carbs like fruits, vegetables, whole grains, legumes, soy products in natural, unrefined forms and some fish, like salmon,” said Professor Ornish. “But never underestimate the power of telling people what they want to hear – like cheeseburgers and bacon are good for you
“Consumption of both processed and unprocessed meat is associated with an increased risk of premature death as well as greater incidence of cardiovascular disease, cancer and type 2 diabetes.
“About 75 per cent of the $US2.8trillion [$2.7trillion] in annual healthcare costs in the United States is from chronic diseases that can often be reversed or prevented altogether by a healthy lifestyle,” he said.
Another large-scale study, published in the American Journal of Epidemiology, has found that eating carrots and cruciferous vegetables can reduce the risk of breast cancer.
Boston University researchers tracked more than 50,000 African-American women for 12 years, in which time 1300 of them developed breast cancer – and 35 per cent of those were aggressive oestrogen receptor-negative (ER-negative) breast cancers.
But women who ate at least two servings of vegetables each day were 43 per cent less likely to develop ER-negative breast cancer than those who ate less than four servings of vegetables a week.
Researchers also identified certain types of vegetables – including broccoli, cabbage, carrots and collard greens – that appeared to cut the risk of all types of breast cancer.
The lead researcher, Deborah Boggs, told Reuters: “It is clear that, in addition to potential protective effects against breast cancer, higher vegetable consumption can lead to many health benefits, including lower risk of cardiovascular disease.”