It’s important to read behind recent red meat headlines which again linked it and cancer, causing confusion about how much consumers should be eating.
The study in question was a University of Auckland/UK Biobank study ‘Diet and colorectal cancer’ published in the April edition of the International Journal of Epidemiology looking at the diets of nearly half a million British women and men, aged 40 to 69 when the research began, over a period of more than five years. During this time, 2,609 of them developed bowel cancer.
The results are relevant for the New Zealand population as both countries have similar diets and high rates of bowel cancer, believes lead author Dr Kathryn Bradbury, a senior research fellow in the school of Population Health at the University of Auckland’s faculty of Medical and Health Sciences. Her co-authors were Professor Tim Key, University of Oxford, and Dr Neil Murphy, International Agency for Research on Cancer (IARC). Dr Bradbury’s work was funded by a Worshipful Company of Girdler’s fellowship she received from the Health Research Council.
“Aotearoa New Zealand has one of the highest bowel cancer rates in the world,” she explains. “This study shows we could prevent some of these cancers by changing our diets, consuming less red and processed meat and more wholegrains.”
The link between meat and bowel cancer remains unclear
While the association between cancer risk and red meat is not new news, says Beef + Lamb NZ Inc’s head of nutrition Fiona Windle, the link between meat and bowel cancer remains unclear.
“Particularly as there were inconsistencies observed in associations in men and women and differences in statistical significance when you separate processed meat and red meat consumption,” she comments.
In addition, it’s important to consider the relative versus the absolute risk, “as the former is often quoted but not defined, over-stating the actual risk, which is very frustrating,” she explains.
“So, the headlines infer a strong relationship between meat and colorectal cancer risk when in fact the association is weak. Relative risk is reported as 20 percent increased risk for every 50g of red or processed meat eaten, equating to less than one percent absolute risk.
“To put this in context, as Cancer UK explained, for every 10,000 people on the study who ate 21 grams of red and processed meat a day, 40 were diagnosed with bowel cancer. Eating 76 grams of processed or red meat a day caused eight extra cases of bowel cancer per 10,000 people.”
Windle thinks some needs to be work done on ensuring this risk is better explained and understood to demonstrate red meat is not off the plate.
“This weak evidence does not prove meat causes cancer. The benefits of eating red meat need to be weighed up against a very small risk that is shown through a correlation relationship. Correlation does not equal causation. Further, the risk is exacerbated by other lifestyle factors such as being sedentary or less active, eating less fibre, fruit and vegetables higher alcohol intake and having a higher body mass index, which the authors present in their data, but was not overtly reported in press” she says.
Shift to a holistic lifestyle approach
“In fact, the shift to a holistic lifestyle approach, when it comes to reducing cancer risk, is emphasised by the global authority on cancer recommendations, the World Cancer Research Fund (WCRF) report, which itself downgraded the evidence on red meat from convincing to probable, which highlights there are other factors at play for cancer risk.
“Further the global authority recognises red meat does have a place in the diet, hence its current recommendation of up to 500g cooked per week, which is mirrored in New Zealand’s current Ministry of Health guidelines and equates to 71.4 g per day – equivalent to about 100g raw weight per day”, says Windle.
She points to the third WCRF/American Institute for Cancer Research expert report, Diet, Nutrition, Physical Activity and Cancer: A Global Perspective released last year. ”This highlighted that overall dietary and exercise patterns are more important than individual foods or the components that make up those foods, which are favourable to reducing your cancer risk”, she says.
Other limitations in the UoA/Biobank study for Windle are its reliance on 24-hour recall of food intake.
“This has its limitations as it isn’t an accurate reflection of regular food intake, nor were all participants measured regularly over the six-year period and eating patterns can change over that timeframe.”
Evidence is strengthening for fibre and wholegrains
Windle does say what is emerging is that the evidence supporting the importance of fibre and wholegrains in reducing bowel cancer is strengthening, highlighting the importance of combining nutrient-dense red meat with cancer-protective wholegrains and vegetables.
“It’s the company red meat keeps, looking at the whole plate and the proportions that make up that plate: half vegetables, a quarter quality, wholegrain carbohydrate and a quarter quality protein such grass-fed beef and lamb.”
Based on the last New Zealand adult national nutrition survey published in 2009, the average New Zealand adult consumes 50.4g of red meat a day – comprising 9.3g/day lamb and 41.1g/day beef. Current industry data from the B+LNZ Ltd Economic Service indicates a downward trend of red meat consumption in New Zealand over the last 10 years. While quality has lifted, the quantity of beef eaten is down 38 percent, lamb down 45 percent and mutton down 72 percent.
“Current working figures show New Zealanders are eating 17.2kg beef, five kg lamb and 0.7kg mutton per capita per year,” notes Windle.
Red meat is an important source of essential nutrients required for growth, brain development and general wellbeing and the amount consumed should meet dietary goals as well as nutrient requirements, particularly in infants, toddlers and women of child-bearing age who are at risk of iron and zinc deficiency, she says. The most recent statistics indicate New Zealand has concerning rates of iron deficiency including eight out of 10 toddlers don’t meet the recommended daily intake or iron, 14 percent of children under two years with iron deficiency, one in 14 women are low in iron and over a third of teenage girls don’t achieve their daily iron requirements.
“Just last month, the iron status of female New Zealand Army recruits was published highlighting a decline during basic combat training.
“With red meat being one of the richest sources of dietary iron, consideration needs to be given to how the reduction or removal of red meat from the diet will have implications on the health status of New Zealanders, particularly for those who are most at risk. The time is ripe to further showcase the nutritional power of New Zealand grass-fed beef and lamb to fulfil nutrient gaps in the diets of New Zealanders” says Windle.
The Diet and Colorectal Cancer study findings were that:
- People eating around 76g of cooked red and processed meat a day on average had a 20 percent higher chance of developing bowel cancer than those who only ate about 21g per day.
- The risk rose 19 percent with every 25g of processed meat (roughly equivalent to a rasher of bacon or slice of ham) people ate per day and 18 percent with every 50g of red meat consumed.
- Each bottle of beer or small glass of wine raised bowel cancer risk by eight percent.
- People in the highest fifth for fibre intake from bread and breakfast cereals had a 14 percent lower risk of bowel cancer
- No link was found between bowel cancer risk and fish, poultry, cheese, fruit, vegetables, tea and coffee.
The researchers say this is one of the largest single studies in the field and one of the few to measure meat quantities and associated risks so precisely and it also gives a contemporary insight into today’s diet.
By reducing the quantity and frequency of red and processed meat, the risk of bowel cancer could be lowered, they suggest.
“You don’t have to cut out red and processed meat altogether, but this study shows that reducing how often and how much you eat meat, you can lower your risk of bowel cancer,” says Bradbury. “You can try having meat free lunches, or days, and swapping red meat for chicken, fish or legumes.”