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NHS Choices: Behind the headlines   + / -  
last updated: Sat, 20 Dec 2014 23:42:07 GMT

 Fri, 19 Dec 2014 10:29:00 GMT GI diet 'debunked' claims are misleading

Today, the Mail Online says, “The GI diet debunked: Glycaemic index is irrelevant for most healthy people”, explaining how “it doesn't matter if you eat white or wholewheat bread”.

This is overgeneralised and misleading, so the diet certainly hasn't been "debunked".

Glycaemic index (GI) measures how quickly foods containing carbohydrates raise blood sugar levels in the bloodstream. It’s used in some diets on the basis that foods that raise blood sugar slowly (low-GI) are considered better for you.

This small US study tried mainly obese people on different high- and low-carbohydrate versions of the GI diet for five weeks at a time.

It found that low-GI diets were no better than high-GI diets at reducing certain risk factors for cardiovascular disease and diabetes.

However, the results came from mainly obese adults, a quarter of whom had high blood pressure – so may not necessarily represent “most healthy people”. The very select group involved in this research makes it difficult to generalise the findings to the wider population.

What this trial tells us is that selecting low-GI foods as a way to reduce risk of diabetes and cardiovascular disease might not be any more beneficial than choosing high-GI foods.

This is food for thought for those aiming to reduce disease risk through dietary modifications, and for health professionals advising them.


Where did the story come from?

The study was carried out by researchers from Harvard Medical School and collaborators. It was funded by the (US) National Heart, Lung and Blood Institute; National Institute of Diabetes and Digestive and Kidney Diseases; the Harvard Clinical and Translational Science Center; the National Center for Advancing Translational Science; and the general clinical research center at Brigham and Women’s Hospital.

The study was published on an open -access basis in JAMA, a peer-reviewed medical journal.

The Mail Online got its headline a bit wrong when saying that the results applied to “most healthy people”, as the study had specific eligibility criteria to include people with a BMI over 25, some of whom had high blood pressure. It was also not correct to say that GI diets have been “debunked”, as the results may not be generalisable to the wider population.


What kind of research was this?

This was a randomised crossover trial (RCT) looking at the effect of different diets on cardiovascular disease and diabetes risk factors. The dietary elements of interest were carbohydrate content and GI.

GI is a measure of how quickly foods containing carbohydrates raise blood sugar levels in the bloodstream. High-GI foods cause a short-term spike in blood sugar level, while low-GI foods cause a more prolonged and smaller rise in blood sugar.

Some popular diets advocate the consumption of low-GI foods, based on the assumption that low-GI is healthier than high-GI. However, the researchers point out that the independent benefits of GI on health are uncertain.

An RCT is one of the best methods to isolate the effects of a dietary intervention such as this. Common issues reducing the reliability of RCTs are a lack of compliance to the diet, high levels of people dropping out of the study, or only recruiting small or highly specific numbers of people. Anything less than a couple of hundred is generally considered small. In this RCT, participants were assigned to trial at least two of the different diets, with a wash-out period in between.


What did the research involve?

Researchers recruited 189 overweight people (all had a body mass index (BMI) of 25 or above) and randomly allocated them to follow one of four strictly controlled diets for five weeks.

After this first phase, they were allowed a break to eat what they wanted for two weeks – called a wash-out period. After the wash-out period, they were randomly allocated a second time to a different diet for a further five weeks. 

To be eligible, people had to have a systolic (upper figure) blood pressure of 120 and 159mmHg and diastolic (lower figure) of 70 to 99mmHg. On this basis, some of the people could have had normal blood pressure, some borderline/pre-hypertension, and some high blood pressure (hypertension).

Other eligibility criteria included being aged 30 or above, and being free from diabetes or cardiovascular disease, and not taking medication related to these conditions.

The researchers aimed to ensure that everyone included in the trial went on two different strictly controlled diets for five weeks, with a two-week gap in the middle.

The background diets from which GI was manipulated were healthy dietary patterns established in the Dietary Approaches to Stop Hypertension (DASH) and Optimal Macronutrient Intake to Prevent Heart Disease (OmniHeart). These are diets that, the authors state, are being recommended in dietary guidelines to prevent cardiovascular disease (CVD).

Participants were randomised to one of four different diets:

  • high-GI, high-carbohydrate
  • low-GI, high-carbohydrate
  • high-GI, low-carbohydrate
  • low-GI, low-carbohydrate

All food and drink was provided and controlled by the researchers. The researchers directly monitored how people stuck to each diet through food diaries and the participants making daily visits to a centre, where the researchers directly observed them eating their main meal of the day. 

The main health measurements of interest were risk factors for diabetes and cardiovascular disease, including:

  • Insulin sensitivity. Taken via an oral glucose tolerance test, this shows how the body metabolises carbohydrates – specifically, how sensitive your body is to the effect of insulin. A tendency towards glucose intolerance can be a sign of higher risk of developing diabetes in the future.
  • LDL cholesterol – so-called “bad cholesterol”.
  • HDL cholesterol – so-called “good cholesterol”.
  • Blood fat levels.
  • Systolic blood pressure – the top number in a standard blood pressure measurement representing blood pressure as the heart contracts.

The analysis was restricted to people who had successfully completed the two diets, one after another, with the two-week gap in the middle.


What were the basic results?

Of the 189 randomised to start the trial, 163 completed enough of the study to be included in the final analysis. Compliance to the diets was high. The average BMI was 32 (BMI above 30 is classed as “obese”) – 92% of participants were obese or heavier. Around a quarter of people (26%) were defined as having high blood pressure. The main findings fell into three groups, summarised below.

Low-GI, high-carbohydrate diet, compared with high-GI, high-carbohydrate diet

  • insulin sensitivity worsened by 20%
  • bad cholesterol increased by 6%
  • good cholesterol, blood fat levels and systolic blood pressure were not any different between the groups

Low-GI, low-carbohydrate diet, compared with high-GI, low-carbohydrate diet

  • blood fat levels reduced by 5%
  • all other measures were not different between the groups

Low-GI, low-carbohydrate diet, compared with high-GI, high-carbohydrate diet

  • blood fat levels reduced by 23%
  • all other measures were not different between the groups

The researchers’ main conclusion was that: “In the context of an overall DASH-type diet [a diet to prevent or help people with high blood pressure], using GI to select specific foods may not improve cardiovascular risk factors or insulin resistance.”



This RCT showed that low-GI diets might not reduce risk factors for diabetes and cardiovascular disease in a group of mainly obese adults. All of these adults were free from diabetes or current cardiovascular disease, although a quarter of them had high blood pressure, and some may have had borderline high blood pressure.

As such, the trial’s participants were a specific group. This means that the results may not be relevant to the general population or other subgroups – for example, those who are a healthy weight or have an existing medical condition, such as diabetes.

However, compliance to the dietary interventions was high and the statistics seemed sound, thereby increasing our confidence in the results. If the findings were replicated in other studies, or if this trial had included more participants and/or been longer in duration, we could have some confidence in saying that for this group, the GI diet did not have the expected benefits. However, for example, if any of the effects of GI took longer than five weeks to occur, this study will not have picked them up. 

The authors themselves make the points that GI is only one attribute of carbohydrate-containing foods. They said: “Further, nutrients often cluster. Hence, the effects of GI, if any, might actually result from other nutrients, such as fibre, potassium and polyphenols, which favourably affect health.”

The study achieved a high compliance to the diets, through food diaries and observation. If this was attempted in real life, compliance would be much less. This would mean that any GI effects would probably be even smaller than was found in this study.

For this group of overweight people, the evidence of the GI diet reducing certain risk factors for cardiovascular disease and diabetes is lacking. The diet certainly haven’t been “debunked” for “most healthy people”, as the Mail Online claimed.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

The GI diet debunked: Glycaemic index is irrelevant for most healthy people - so it doesn't matter if you eat white or wholewheat bread, scientists claim. Mail Online, December 17 2014

Links To Science

Sacks FM, et al. Effects of High vs Low Glycemic Index of Dietary Carbohydrate on Cardiovascular Disease Risk Factors and Insulin Sensitivity. The OmniCarb Randomized Clinical Trial. JAMA. Published December 17 2014

 Fri, 19 Dec 2014 09:54:00 GMT Ibuprofen unlikely to extend life

The Daily Mirror today reports that, “taking ibuprofen every day could extend your life by up to 12 YEARS”. The Daily Express also has a similar front page headline, while the Mail Online suggests that these extra years would be of “good quality life”.

If you read these headlines and felt sceptical, you’d be right to do so.

The news has been extrapolated to humans, based on research in yeast, microscopic worms and fruit flies. These organisms are often used in longevity research due to their naturally short lifespans – even the longest-lived among them is measured in days, not decades. 

However, if a chemical does extend lifespan in these relatively simple organisms, this is not a guarantee that it will do the same in more complex organisms, such as mammals. We also have no idea whether any extension of life would be of “good quality”.

Even in the fruit flies, the effect was more complicated than in yeast or worms. Ibuprofen increased the flies’ average lifespan, but actually reduced the maximum lifespan in male flies.

We’re definitely not at a stage where taking ibuprofen every day could be recommended as a way to extend your lifespan. While some people might think “what harm can it do?" and "it might do some good”, ibuprofen is not risk-free. As with most drugs, ibuprofen can cause side effects, including gastrointestinal bleeding.


Where did the story come from?

The study was carried out by researchers from the Buck Institute for Research on Aging, and universities in the US and Russia. It was funded by the US National Institutes of Health and National Science Foundation.

The study was published in the peer-reviewed, open access journal PLOS Genetics.

The newspapers’ headlines are unwarranted over-extrapolations of this animal and laboratory research. Most later clarified that the research was in yeast, worms and flies – but read in isolation, the headlines are misleading.

This seems an irresponsible approach, given the potential harm that could result from people taking a cheap and readily-available drug unnecessarily.


What kind of research was this?

This was an animal and laboratory study looking at whether ibuprofen increases lifespan in flies, worms and yeast.

The researchers say that ibuprofen has been associated with a reduction in the risk of some age-related problems such as Alzheimer’s disease and Parkinson’s disease. However, whether it also has an effect on lifespan is unknown.

The organisms used in this study are often used in studies of lifespan, as their lives are short. This means that researchers can quickly find out if a chemical affects lifespan. If they find the same effect on lifespan in the multiple organisms tested, this suggests that the chemical is affecting a system that has been evolutionarily “conserved” across different organisms. This makes it more likely that the effect may also apply to other, untested, organisms.

However, flies, worms and yeast are relatively simple organisms, and things that affect their lifespans may not have the same impact on more complex organisms such as mammals. For example, while a chemical might double lifespan in a yeast, even if it also has an effect on lifespan in mice, it would be unlikely to have as dramatic an effect.

The researchers say that getting from chemicals that show promise in yeast and other organisms to drugs that are effective and safe in humans is a “significant hurdle”. For this reason, they wanted to look at a drug that was already used in humans, as they are already known to be safe enough for human use.


What did the research involve?

The researchers tested the effects of ibuprofen on one type of yeast, one type of microscopic worm, and fruit flies. In each case they exposed one group of yeast/worms/flies to ibuprofen and another group was not exposed (controls). They measured how long each group lived to see if it differed.

For yeast and worms, exposing them to ibuprofen involved growing them in a solution containing the drug. For yeast, the study looked at how long they were able to keep dividing to produce new yeast cells – a standard measure of their “active” lifespan. For flies, this involved feeding them with a solution that included ibuprofen. The organisms were grown in standard conditions, to make sure that the only thing that differed between them was whether or not they received ibuprofen.

The researchers then carried out a wide range of detailed experiments to determine how ibuprofen was having an effect.


What were the basic results?

The researchers found that yeast exposed to ibuprofen lived 17% longer on average than they did without it. Worms exposed to ibuprofen throughout their lives lived about 20 days, compared to about 18 days on average without ibuprofen. The researchers said that the levels of ibuprofen that extended the lifespan of worms and yeast were in the range of levels reached in people taking ibuprofen at typical doses.

In female fruit flies, ibuprofen extended the average lifespan and also the maximum lifespan. In male fruit flies, ibuprofen extended the average lifespan but, oddly, reduced the maximum lifespan. This meant that the shorter-lived flies were living longer with ibuprofen, but the longest-lived flies were not living as long.

The researchers found that ibuprofen seemed to be having its effect by reducing uptake of the amino acid tryptophan by cells.


How did the researchers interpret the results?

The researchers concluded that their results “identify a largely safe drug that extends lifespan across different kingdoms of life” and “implicate [tryptophan] import in aging”.



The current study has found that ibuprofen can extend lifespan in yeast, worms and flies.

This does not guarantee that it will extend the lives of humans – or indeed other animals more complex than flies. Even if a chemical was to have an effect on mammals, it would be unlikely to be as great an effect as in the simpler organisms that have been tested.

The results of the study themselves point to a more complicated story as organisms get more complex. While average lifespan was extended in all of the organisms, in male fruit flies (but not females) maximum lifespan was actually reduced with ibuprofen.

Doubtless these findings will lead to more research, as ways to fight the ravages of ageing are among the “holy grails” of drug development. The researchers point out in the news that there is probably already data available from observational studies in humans that could be used to assess whether ibuprofen use is associated with increased lifespan.

If you’re tempted to take a daily ibuprofen to extend your life because they’re cheap and readily available – don’t!

Ibuprofen, while safe enough for human consumption, is not risk-free. As with most drugs it can cause side effects, including gastrointestinal bleeding. While the benefits are likely to outweigh the harms for people taking the drug in the short term for its intended uses (such as pain relief), this is not the case when taking the drug on a daily basis for an unproven, and potentially non-existent, benefit.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

Is Ibuprofen the key to a longer life? Study finds it may provide 12 extra years of good health. Mail Online, December 18 2014

Taking ibuprofen every day could extend your life by up to 12 YEARS. Daily Mirror, December 18 2014

Ibuprofen adds 12 years to life! Cheap painkillers can slow ageing and fight disease. Daily Express, December 19 2014

Could ibuprofen be key to anti-ageing? Study finds painkiller extends life of flies and worms by equivalent of 12 human years. The Independent, December 19 2014

Hangover cure may aid a longer life. The Daily Telegraph, December 19 2014

Links To Science

He C, et al. Enhanced Longevity by Ibuprofen, Conserved in Multiple Species, Occurs in Yeast through Inhibition of Tryptophan Import. PLOS Genetics. Published December 18 2014

 Thu, 18 Dec 2014 11:30:00 GMT Shift workers more likely to report poor health

"Higher rates of obesity and ill-health have been found in shift workers than the general population," BBC News reports.

These are the key findings of a survey into health trends among shift workers; defined as any working pattern outside of the normal fixed eight-hour working day (though start and finish times may vary).

According to the survey (The Health Survey for England 2013), shift workers were more likely to report general ill-health, have a higher body mass index (BMI) and increased incidence of chronic diseases such as diabetes.

The Health Survey for England 2013 also monitored other trends in the nation’s health, including people’s weight, smoking habits, fruit and vegetable consumption, and prescribing patterns for drugs (a story we covered earlier this month). 

Who produced the data?

The report was produced by the Health & Social Care Information Centre (HSCIC), the official provider of national health and social care statistics. The HSCIC was set up by the government in April 2013. Its role is to provide information on a range of issues concerning health for use by commissioners, analysts and clinicians in driving patient services.

In the interests of transparency we should point out that the Behind the Headlines team, along with all NHS Choices staff, is employed by the HSCIC.

The HSCIC produces an annual Health Survey for England that monitors important aspects of the population’s health.


How was the data collected?

The data comes from interviews with a representative sample of the population. Participants aged 16 years and over who were in employment were asked whether they worked in shifts either "most of the time", "occasionally" or "never". Those who answered either "most of the time" or "occasionally" were then asked which type of shift work they were doing. Shift work was defined in the question as "work outside the hours of 7am to 7pm in your (main) job".

Participants were then grouped into shift workers (who reported that they did shift work "most of the time" or "occasionally") and non-shift workers.

Comparisons between shift workers and non-shift workers across a range of health and lifestyle factors were age-standardised, so that any differences in age profile are taken into account in the comparisons.

What were the key findings?

  • Men were more likely than women to report that they did shift work (33% of men and 22% of women).
  • Shift working was most prevalent in the 16-24 age group, and declined with age for both men and women. Almost half of men and over a third of women aged 16-24 did shift work compared with fewer than a third of men and a fifth of women aged 55 and over.
  • The prevalence of shift work varied significantly by household income, being highest in the lowest two income quintiles (42-43% among men, 27-28% among women, compared with 21% and 19% respectively in the highest income quintile). Similarly, the proportion of men and women in shift work was highest in the most deprived quintile compared with the least deprived.
  • Both men and women in shift work were more likely than non-shift workers to report fair or bad health.
  • Shift workers were more likely than non-shift workers to have a limiting longstanding illness; they were also more likely to have more than one longstanding illness.
  • Shift workers were more likely than non-shift workers to be obese. This is reflected in higher mean body mass index (BMI) measurements, higher proportions classified as obese, and greater proportions with a very high waist circumference.
  • Men and women in shift work were more likely than non shift workers to have diabetes (10% of both men and women in shift work, compared with 9% and 7% respectively of those not working shifts).
  • Current cigarette smoking prevalence was higher among shift workers than non-shift workers, with a larger difference among women than men. 28% of men in shift work currently smoked compared with 23% of men who did not do shift work. The equivalent figures for women were 26% and 15% respectively.
  • The proportion of both men and women who drank alcohol in the last year was slightly smaller among shift workers (84% of men, 81% of women) than among those who did not work shifts (88% and 83% respectively).
  • Daily fruit and vegetable consumption was lower among shift workers than non-shift workers. Men in shift work ate an average of 3.3 portions compared with 3.6 for non-shift workers. Among women the equivalent means were 3.6 and 3.8 respectively. Shift workers were also slightly less likely than non-shift workers to meet government recommendations of eating five or more portions per day.


Why do shift workers tend to be less healthy?

There are a number of potential underlying factors that may impact on health and wellbeing.

Firstly, shift working can disrupt what are known as circadian rhythms, the internal "body clock". This can disrupt the normal workings of a hormone called melatonin. This disruption can lead to poor sleep and chronic fatigue.

Persistent lack of good quality sleep has been linked to a range of chronic conditions such as obesity, depression, diabetes and heart disease.

While the body can slowly adapt to the changes in working patterns, many shift workers are on rotating shifts and suddenly switching from a night to day shift leads to further disruptions.

Rotating shift work can also disrupt the production of insulin, which may increase the risk of someone developing type 2 diabetes.

There is also the fact that shift workers tend to be on the lower end of the socioeconomic scale. And there is evidence that people on lower incomes have an increased tendency to smoke, drink excessive amounts of alcohol and eat a poor diet. There is also the stress and worry associated with trying to make ends meet.


What has previous research found?

There has a been a range of studies linking shift work to a number of different adverse outcomes; which we have looked at previously in Behind the Headlines. These include claims that:

The issue with all the studies is that due to the complex play of personal, environmental and socioeconomic factors, researchers were unable to prove a direct cause and effect link between shift work and the outcomes listed above; only an association.

Still, there seems to be a consensus that while shift work may not be actively dangerous, it is certainly not an ideal arrangement for healthy living.


So what can shift workers do?

Well, ideally, find another job. But that is often easier said than done. Most of us don’t have the luxury of quitting a job if the hours don’t suit us unless we have another job lined up.

That said, if you are unhappy with your current situation, it is worth spending a few hours every week signing up to job search sites. Along with commercial sites, the government also provides a service known as Universal Jobmatch.

The Health and Safety Executive also offers some useful and practical advice for people working shift work. This includes:

  • take extra care if you drive to and from work as your concentration may be impaired; if possible it may be a better idea to use public transport
  • identify a suitable sleep schedule of at least seven hours a day, you may find it useful to keep a diary to assess what sleep times suit you best
  • try to create an environment that promotes good sleep, for example heavy curtains or an eye mask may help you sleep during the day
  • making changes to your diet to improve both alertness and digestion; smaller healthy snacks during your shift may be a better idea than one big meal
  • limit your use of stimulants such as caffeine or energy drinks as well as sedatives such as alcohol; while they may bring short-term benefit they are unlikely to be of help in the long term
  • try to get regular exercise – at least 30 minutes per day

Read more Hints and tips for shift workers


Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To Science

Shift workers 'sicker and fatter'. BBC News, December 15 2014

Shift workers more likely to suffer from poor health, including diabetes and obesity. The Independent, December 15 2014


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