Sunday, 19 June 2016

Coffee's cancer risk downgraded (as long as you don't drink it hot)

reposted from:
crabsallover highlightskey pointscomments / links.

A review by the International Agency for Research on Cancer (IARC) concluded that only beverages consumed at higher than 65C posed a possible cancer risk.

Thursday June 16 2016
Letting drinks cool is a good idea
Coffee's cancer risk has now been degraded
"Very hot drinks may cause cancer, but coffee does not, says WHO," The Guardian reports.
A review by the International Agency for Research on Cancer (IARC) concluded that only beverages consumed at higher than 65C posed a possible cancer risk.
The working group's report re-evaluated the cancer-causing properties of drinking coffee, maté (a South American drink), and very hot beverages.
Coffee was classified as a possible cause of cancer in 1991, but the group has cleared the previous classification and suggested any suspected link was because of the hot temperature of the drink.
The researchers concluded there was limited evidence that drinking coffee and maté causes cancer, but say the risk of cancer of the oesophagus – the gullet – may increase with the temperature of the drink above 65C (149F).
Both the Daily Mirror and Daily Mail covered the story. The Mirror reports that leaving your cup of tea for around five minutes should cool it to a safe level.
The Mail reports that, not entirely surprisingly, store-bought black coffee is hot, at between 66 and 81C. So again, it is best left to cool for a while.
As it stands, smoking or alcohol consumption pose a bigger – and better documented – risk for oesophageal cancer.

So what's the matter with maté?

Maté is probably best described as the South American version of "builder's tea".
It is a caffeine-rich concoction served in very hot water and drunk through a metal straw. 

Who produced the report?

The report was published by an international collaboration of researchers (working group) of the IARC, a specialised cancer agency of the World Health Organization (WHO).
The group came together in France as part of the IARC Monographs Programme, which seeks to evaluate and identify environmental factors that can increase the risk of human cancer.
The researchers reviewed epidemiological studies of exposure to carcinogens in human populations, and used the evidence to classify potential hazards as:
  • group 1 – carcinogenic to humans
  • group 2A – probably carcinogenic
  • group 2B – possibly carcinogenic
  • group 3 – not classifiable (no evidence to make a reliable judgement)
  • group 4 – probably not carcinogenic
However, the classification does not indicate what level of risk is associated with the exposure to a classified hazard.
For example, smoking cigarettes and using a sunbed are both group 1 hazards. But the risk of cancer associated with smoking cigarettes is far higher than using a sunbed.
Overall, the exact method of how the authors identified and selected the research is unclear. As such, it's not possible to say that this was a systematic review.
The monographs are published so they can be used by national health agencies to support their actions in preventing exposure to potential carcinogens.

What did the report find?

As part of their re-evaluation, the group assessed more than 1,000 observational and experimental studies.
They concluded:
  • coffee drinking was "not classifiable as to its carcinogenicity to humans" (group 3)
  • maté was "not classifiable as to its carcinogenicity to humans" (group 3)
  • hot drinks above 65C were "probably carcinogenic to humans" (group 2A)


Coffee drinking was evaluated by the IARC in 1991, and at the time was classified as "possibly carcinogenic to humans" (group 2B).
However, this was based on "limited evidence" – defined on the basis that a positive association between hazard and outcome was observed, but bias could not be ruled out.
The current evaluation has been conducted on a much stronger and larger body of evidence, with nearly 500 relevant epidemiological studies identifying more than 20 different cancers.
The group assessed a collection of epidemiological evidence, and gave the greatest weight to prospective cohort and population-based case control studies that had controlled for other exposures, such as tobacco and alcohol consumption.
The studies followed cohorts of people who self-reported their coffee drinking habits to see how many individuals developed cancer and how it was related to their consumption of coffee.
During this re-evaluation, the majority of epidemiological studies showed no association between coffee drinking and cancers of the pancreas, female breast, and prostate. Reduced risks were observed for liver and endometrial cancers.
On judging the various studies, the group concluded the evidence for "coffee drinking causing cancer" was inadequate. Reasons included insufficient data, inconsistency of findings, inadequate control of potential confounders, and bias.


Maté is a hot drink consumed in South America, and is also the national drink of Argentina.
It's a caffeine-rich infusion made from dried leaves of the yerba maté plant. In 1991 the IARC classified it as "probably carcinogenic to humans" (group 2A).
Since then, several epidemiological studies have been conducted evaluating the risk of oesophageal cancer and the consumption of hot maté.
With this new data, the IARC wanted to better understand whether the associations from previous studies were the result of maté itself or the hot temperatures at which it is usually consumed.
The studies found cancer of the oesophagus was associated with drinking hot maté, rather than maté at warm or cold temperatures.

Hot drinks

The findings from the evaluations of maté led the researchers to assess the association between oesophageal cancer and other hot drinks.
Previous research from China, Iran, Japan and Turkey also found the risk of cancer may increase with the temperature of the drink.
The IARC conducted a combined analysis on several epidemiological studies that had assessed the effect of both temperature and the amount of maté consumed on 1,400 patients with oesophageal cancer.
The results showed that regardless of the amount consumed, the risk of cancer increased with an increase in temperature.
There were significant differences in the results from drinking very hot maté, but not with warm maté.
The studies suggested the carcinogenic effects occur when drinking at temperatures above 65C.

What are the implications?

The IARC monographs seek to identify potential cancer hazards to raise awareness that a certain exposure can cause cancer in exposed people. However, they don't issue recommendations.
Their assessment of scientific evidence is produced so the World Health Organization, health agencies and governments can take it into consideration when developing health policies and guidelines. Whatever actions are taken as a result remain in the hands of the authorities concerned.
Professor Tim Underwood, associate professor in surgery at the University of Southampton, said: "The bottom line here is that drinking very hot liquids is a cause of squamous cell cancer of the oesophagus, but the IARC classification can't tell us anything about the size of the risk – so we shouldn't take from this that there's a high risk of developing oesophageal cancer after drinking very hot drinks."
Professor Sir David Spiegelhalter, Winton professor of the public understanding of risk at the University of Cambridge, said: "Last year the IARC said that bacon is carcinogenic, but it became clear that when eaten in moderation it is not very risky.
"In the case of very hot drinks, the IARC conclude they are probably hazardous, but can't say how big the risk might be. This may be interesting science, but makes it difficult to construct a sensible response."
Arguably, a commonsense approach would be to not drink anything hot enough to give you a serious burn if you spilt it on yourself, whether it's maté, coffee or tea.
Analysis by Bazian. Edited by NHS ChoicesFollow NHS Choices on TwitterJoin the Healthy Evidence forum.
Analysis by Bazian
Edited by NHS Choices

Links to the headlines

Cancer risk from coffee downgraded. BBC News, June 15 2016

Links to the science

The International Agency for Research on Cancer Monograph Working Group. Carcinogenicity of drinking coffee, maté, and very hot beverages. The Lancet Oncology. Published online June 15 2016

Further reading

International Agency for Research on Cancer. Q&A on Monographs Volume 116: Coffee, maté, and very hot beverages (PDF, 65kb). June 2016

News analysis: Does the 5:2 fast diet work? (May 2013 update)

reposted without editing from:
crabsallover highlightskey pointscomments / links.

This is an update of a January 2013 NHS Choices article - see here.

Monday January 14 2013

Is intermittent fasting right for you?
Note – this article, originally written in January 2013, was updated in May 2013.
The 5:2 diet is an increasingly popular diet plan with a flurry of newspaper articles and books being published on it in the run up to Christmas 2012 and in January 2013.
The diet first reached the mainstream via a BBC Horizon documentary called Eat, Fast and Live Longer, broadcast in August 2012.
The 5:2 diet is based on a principle known as intermittent fasting (IF) – where you eat normally at certain times and then fast during other times.
The 5:2 diet is relatively straightforward – you eat normally five days a week, and fast on the other two days.

What does a daily 600-calorie diet look like?

A 600-calorie diet could consist of a slice of ham and two scrambled eggs for breakfast and then some grilled fish and vegetables for your evening meal. And of course nothing but water, black coffee and/or green tea to drink.
Champions of the 5:2 diet claim that other than helping people lose weight, 5:2 diet can bring other significant health benefits, including:
  • increased lifespan
  • improved cognitive function and protection against conditions such as dementia and Alzheimer’s disease
  • protection from disease
However the body of evidence about 5:2 diet and intermittent fasting is limited when compared to other types of weight loss techniques. 

What we don’t know about intermittent fasting

Despite its increasing popularity, there is a great deal of uncertainty about IF with significant gaps in the evidence.
For example, it is unclear:
  • what pattern of IF is the most effective in improving health outcomes – 5:2, alternative day fasting, or something else entirely different
  • what is the optimal calorie consumption during the fasting days – the 5:2 diet recommends 500 calories for women and 600 for men, but these recommendations seem arbitrary without clear evidence to support them
  • how sustainable is IF in the long-term – would most people be willing to stick with the plan for the rest of their lives?

Are there any side effects from intermittent fasting?

Little is known about possible side effects as no systematic attempt has been made to study this issue. Anecdotal reports of effects include:
  • difficulties sleeping
  • bad breath (a known problem with low carbohydrate diets)
  • irritability
  • anxiety
  • dehydration
  • daytime sleepiness
However, more research would be needed to confirm these side effects and their severity.
If you are fasting, you may want to think about how fasting will impact on your life during your fasting days. You are likely to be very hungry and have less energy and this could affect your ability to function (such as at work), in particular it may affect your ability to exercise which is an important part of maintaining a healthy weight.
Also, IF may not be suitable for pregnant women and people with specific health conditions, such as diabetes, or a history of eating disorders.
Because it is a fairly radical approach to weight loss, if you are considering trying IF for yourself, it is wise to speak to your GP first to see if it is safe to do so.

Evidence about the 5:2 diet

Despite its popularity evidence directly assessing the 5:2 model of intermittent fasting is limited.
But since this article was originally written in January 2013 we have been alerted to research, led by Dr Michelle Harvie, which did look at the 5:2 model.
In one study carried out in 2010 the researchers did find that women placed on a 5:2 diet achieved similar levels of weight loss as women placed on a calorie-controlled diet.
They also experienced reductions in a number of biological indicators (biomarkers) that suggest a reduction in the risk of developing chronic diseases such as type 2 diabetes.
further study in 2012 suggested that the 5:2 model may help lower the risk of certain obesity-related cancers, such as breast cancer.
The increasing popularity of the 5:2 diet should lead to further research of this kind.

Evidence about other forms of IF

There is some degree of evidence about the potential benefits of other forms of IF – albeit with some limitations.
It should be stressed that our assessment of the evidence was confined to entering a number of keywords into Google Scholar and then looking at a small number of studies which we felt would be useful to explore further.
We did not carry out a systematic review (though arguably, it would be useful for researchers to do so). So the information provided below should be taken in the spirit of us trying to provide an introduction to some of the evidence and science of IF – not an exhaustive "last word" on the topic.
Is there any evidence that intermittent fasting aids weight loss?
One of the most recent pieces of research on intermittent fasting is a2012 study (PDF, 291kb) that recruited 30 obese women known to have pre-existing risk factors for heart disease.
After an initial two-week period they were then given a combination diet of low-calorie liquid meals for six days of a week (similar to Slim Fast diet products) and then asked to fast for one day a week (comsuming no more than 120 calories).
After eight weeks, on average, the women lost around 4kg (8.8lb) in weight and around 6cm (2.3 inches) off their waist circumference.
However, there are a number of limitations to consider when looking at this as evidence that it might be a generally beneficial thing to do for most ordinary people, including that:
  • These women may have had increased motivation to stick with the diet because they knew their weight would be monitored (this is a psychological effect that slimming clubs make use of).
  • The women had been told that they were at risk of heart disease. It is uncertain how well most of us would cope with such an extreme diet.
  • The follow-up period was short – just two months. It is not clear whether this diet would be sustainable in the long term or whether it could cause any side effects.
  • 30 people is quite a small sample size. A much larger sample – including men – is required to see if intermittent fasting would be effective in most overweight or obese people.
Is there any evidence intermittent fasting increases lifespan?
There is quite a wide range of work on the effects of IF on combating the effects of ageing, but almost all of these studies involved either rats, mice or monkeys. One big problem with studies in animals – particularly rodents – is that they are only expected to live for a few years. While this makes them ideal subjects for longevity studies, carrying out similar, more useful experiments in humans, requires decades-long research to gain credible results.
In an unsystematic look at the evidence, we find only one study involving humans: a 2006 review (PDF, 65kb) of an experiment actually carried out in 1957 in Spain.
In this 1957 study, 120 residents of an old people’s home were split into two groups (it is unclear from the study whether this was done at random). The first group (the control group) ate a normal diet. The second group (the IF group) ate a normal diet one day and then a restricted diet (estimated to be around 900 calories) the next.
After three years there were 13 deaths in the control group and only six deaths in the IF group.
This study is again limited by the small sample size meaning that the differences in death are more likely to be the results of a statistical fluke. Also, many experts would feel uneasy about issuing dietary guidelines based on a study over half a century old with unclear methods. It is unlikely that this experiment could be repeated today – denying food to elderly people in residential care is unlikely to be looked at kindly by an ethics committee.
Is there any evidence intermittent fasting prevents cognitive decline?
It seems that all of the studies on the supposed protective effects of IF against conditions that can cause a decline in cognitive function (such as dementia or Alzheimer’s disease) involve animals.
For example, a 2006 study (PDF, 843kb) involved mice that had been genetically engineered to develop changes in brain tissue similar to those seen in people with Alzheimer’s disease.
Mice on an IF diet appeared to experience a slower rate of cognitive decline than mice on a normal diet (cognitive function was assessed using a water maze test).
While the results of these animals tests are certainly intriguing, animal studies have inherent limitations. We can never be sure that the results will be applicable in humans.
Is there any evidence that intermittent fasting prevent diseases?
Much of the published research into the potential preventative effects of IF involve measuring biological markers associated with chronic disease, such as insulin-like growth factor-I (IGF-I) – known to be associated with cancer.
Using these kinds of biological surrogates is a legitimate way to carry out research, but they do not guarantee successful real-world outcomes.
For example, some medications that were found to lower blood pressure readings taken in laboratory conditions failed to prevent strokes once they had been introduced for use in the healthcare of patients in the world.
2007 clinical review (PDF, 119kb) looking at the effects of IF in humans in terms of real-world health outcomes concluded that IF (specifically, alternative day fasting) may have a protective effect against heart disease, type 2 diabetes and cancer. However, it concluded "more research is required to establish definitively the consequences of ADF (alternative day fasting)".


Compared to other types of weight loss programmes the evidence base of the safety and effectiveness of the 5:2 diet is limited.
If you are considering it then you should first talk to your GP to see if it is suitable for you. Not everyone can safely fast.
Other methods of weight loss include:
Find recommended, simple, low cost ways to lose weight in the Live Well: lose weight pages.
Edited by NHS Choices

Links to the headlines

The power of intermittent fasting. BBC News, August 5 2012

Links to the science

Harvie M, Howell A. Energy restriction and the prevention of breast cancer. Proceedings of the Nutrition Society. Published online March 12 2012
Harvie M, Pegington M, Mattson MP, et al. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomised trial in young overweight women. International Journal of Obesity. Published online October 5 2010
Varady KA, Hellerstein MK, et al. Alternate-day fasting and chronic disease prevention: a review of human and animal trials (PDF, 118.6KB). American Journal of Clinical Nutrition. Published online 2007