Christmas myths dismissed

Behind the Headlines

Thursday December 18 2008

“The idea you can cure a hangover is a medical myth,” reports The Times today. It says that an article in the British Medical Journal shows that this and five other common Christmas beliefs are false.

These beliefs include the ideas that sugar makes children hyperactive, midnight feasts make you fat, and that you should wear a hat in cold weather because we lose almost half our body heat through our heads.

The authors of this article looked for scientific research relating to these six common health beliefs, and judged whether there was evidence supporting the claims or not. The authors acknowledge that this was not a full systematic review, but it does illustrate that there is often little evidence to support even widely held medical beliefs.

This research highlights the importance of looking objectively at the evidence behind any medical claims before deciding whether they are accurate or not.

Where did the story come from?

This article was written by Drs Rachel C. Vreeman and Aaron E Carroll. No sources of funding were reported. The study was published in the peer-reviewed British Medical Journal (BMJ).

What kind of scientific study was this?

This was a review of evidence of common medical myths relating to winter and the holiday season. It was published as part of the light-hearted Christmas edition of the BMJ.

The authors generated a list of six commonly held beliefs: that sugar causes hyperactivity in children; suicides increase over the holidays; most of our heat is lost through our heads; eating at night makes you fat; you can cure a hangover, and poinsettia plants (used as Christmas decorations) are poisonous.

The researchers then searched Medline, an online database of medical and scientific literature, for studies that address these questions. If they could not find any such studies, they then used Google to search the internet for related information.

The researchers then summarised the evidence they found, and determined whether it supported or refuted the myths.

What were the results of the study?

Myth 1: Sugar causes hyperactivity in children

The researchers found at least 12 randomised controlled trials which assessed the effects that diets with differing levels of sugar had on children’s behaviour. None of these studies found differences between the high- and low-sugar diets, even in children with attention deficit hyperactivity disorder (ADHD) or those thought to be “sensitive” to sugar.

The researchers also identified a study which showed that parents perceived their children to be more hyperactive after having what they thought to be a sugary drink, even if the drink was actually sugar-free. This suggests that the myth is being perpetuated by parents’ beliefs rather than genuine differences in the children’s behaviour.

Myth 2: Suicide increases over the holidays

The researchers reported that there was “no good scientific evidence to suggest a holiday peak in suicides”. They describe nine studies from around the world that refute this idea, including studies from Finland, Hungary, India and the US. These studies suggest that suicides are actually most common in warmer months, and at their lowest in the winter.

Myth 3: Poinsettia plants are poisonous

The researchers describe a study on 22,793 reported cases of people being exposed to or eating poinsettia plants. Using data from the American Association of Poison Control Centres, the study found that none of these people died, and 96% did not need medical treatment. This included 92 cases of children eating poinsettias, none of whom required medical treatment.

The researchers found a study in rats that tried to identify how much exposure to poinsettia would be toxic. It found that even exposure to amounts equivalent to 500-600 poinsettia leaves were not toxic. The researchers also state that public health officials and toxicologists have concluded that poinsettias are safe and “exposures and ingestions can be treated without referral to a healthcare facility”.

Myth 4: Most body heat is lost through the head

The researchers noted that if this myth were true, you might expect a person to be just as cold when not wearing trousers as when not wearing a hat. This is not the case, however. They suggest that this myth comes from an old study in which people wore arctic survival suits but not hats, and were exposed to extremely cold temperatures.

Unsurprisingly, the volunteers lost most of their heat through their heads, but only because this part of the body was exposed. The researchers report that if most of the body were exposed, only about 10% of body heat would be lost from the head, according to experts.

They conclude that once you have protected your body from cold, whether you wear a hat is a matter of personal preference.

Myth 5: Eating at night makes you fat

The researchers describe a study of 83 obese and 94 non-obese women in Sweden, which “at first glance” seems to support this myth. The study found that the obese women ate more meals and tended to eat meals later in the day.
However, the researchers point out that an association between two factors does not necessarily mean that one causes the other. The obese women consumed more meals and more calories than the non-obese women, and this would have made them gain more weight regardless of what time of day they ate.

The researchers also describe studies that found no association between weight gain and eating at night. The four studies they describe (the largest featuring 2,500 people) did not provide evidence of a link between night-time eating and weight gain.

Myth 6: Hangovers can be cured

The researchers identified a myriad of internet suggestions for preventing or treating hangovers, including eating bananas or Vegemite, taking aspirin or drinking water.
However, a systematic review of randomised controlled trials of traditional and complementary medicines found no effective interventions for either preventing or treating hangovers. The treatments assessed included medication (propranolol, tropisetron, tolfenamic acid), fructose, glucose, Vegemite, and supplements including borage, artichoke, or prickly pear.

The review found that some small studies, using unproven methods of measuring symptoms, showed some minor improvements. However, it concluded that none of the treatments assessed “cured” hangovers. The researchers note that although some studies in rats have shown that some treatments may alter biological mechanisms associated with hangovers, some of these treatments may also carry health risks for humans.

Using alternative “common sense” methodology, the researchers conclude that the best way to avoid a hangover is to drink alcohol in moderation or not at all.

What interpretations did the researchers draw from these results?

The researchers concluded that “examining common medical myths remind us to be aware of when evidence supports our advice, and when we operate based on unexamined beliefs”. They also say that “only by investigation, discussion and debate can we reveal the existence of such myths and move the field of medicine forward”.

What does the NHS Knowledge Service make of this study?

This article addresses some widely held medical beliefs, and shows that they may not be supported by evidence. Although the authors acknowledge that this was not a full systematic review, they did search for appropriate medical literature.

The review illustrates that there is often little evidence to support even widely held medical beliefs. It highlights the importance of looking objectively at the research evidence behind any medical claims before deciding whether they are accurate or not.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Christmas hangover? There's no cure. The Times, December 18 2008

Losing heat through your head? Discover the barefaced truth about hats and other myths. Daily Mail, December 18 2008

Medical myths that come with a health warning. The Independent, December 18 2008

Hangover cures, sugar causes hyperactivity and poinsettias are poisonous: medical myths debunked. The Daily Telegraph, December 18 2008

Links to the science

Vreeman RC, Carroll AE. Festive medical myths. BMJ 2008; 337:a2769

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