Can Science Help You Stay Warm?

The seasonably cold weather motivated this second entry in my series of Infographic Analyses. I’m originally from Michigan (the photo is me with my dad in a slightly snowier-than-normal Michigan winter) and spent a few years in Ontario, Canada, so I don’t need any help handling the relatively mild Scottish winters, but Jones Oil has produced a infographic on The Science of Staying Warm to help those with less experience with the cold. So let’s have a look at the evidence behind their claims.

Does cold kill?

The most egregious error on this infographic is right at the top. Flu, pneumonia and the common cold are caused by viruses, not the cold. The relationship between cold weather and infection rates is complicated, but there is little evidence for a strong link between cold temperatures and decreased immune function.

The NHS Choices webpage on the common cold is very clear on the issue:

The only thing that can cause a cold or flu is a cold or flu virus. Getting cold or wet won’t give you a cold. However, if you are already carrying the virus in your nose, it might allow symptoms to develop.

Researchers at Cardiff Common Cold Research shed some light on why colds are more common in the winter. They dismiss outdated ideas about increased indoor crowding in the winter and cite a new theory that cooling the nose lowers resistance to infection, suggesting that covering your nose with a scarf might reduce your susceptibility to infection.

The infographic is absolutely correct that cold is a leading cause of hypothermia, though.

Are 180 pensioners killed by the cold every day?

This is an accurate estimate of excess winter mortality in England and Wales, which is a complicated concept comparing death rates from December to March to the previous August to November and the subsequent April to July.

However, there are several problems with the reporting of these numbers. Infographic writers love to feature big, round numbers, but often leave out important context. For example, is this excess mortality worldwide, or within a specific country like the US or UK? Actually, it is the statistic for England and Wales. This context-less number also doesn’t allow for any perspective. Do you know how many pensioners die each day in England and Wales each day in the summer? I had to look this up from data tables available from the Office for National Statistics: 255,778 people age 65+ died between April and November 2010, which is 1044 pensioners each day. A 17% increase in mortality rate is nothing to dismiss, and fuel poverty is a serious issue, but sensationalised statistics with no context don’t help to communicate the actual scope of these problems.

The characterisation of these 180 pensioners each day as having been “killed by the cold” is also a bit sensationalised. Most of the excess winter mortality (EWM) is not directly due to the cold. Indeed, the Office for National Statistics includes this warning about interpreting EWM statistics:

Previous research has shown that although mortality does increase as it gets colder, temperature only explains a small amount of the variance in winter mortality, and high levels of excess winter mortality can occur during relatively mild winters (Brown et al, 2010). Curwen and Devis (1988) showed that both temperature and levels of influenza were important predictors of excess winter mortality. Thus, the relationship between temperature, influenza and winter mortality is complex.

Can food and hot drinks make you warmer?

Holding a hot drink can make your judgements of others ‘warmer’, but I found no evidence that simply holding a hot drink can make a significant difference to body temperature. In fact, Cambridge neuroscientist Peter McNaughton suggests the opposite; hot drinks can actually cool you down by inducing sweating.

While I don’t want to spoil the comfort that comes from a hot cuppa, I must take serious exception to the next statement, “Perspiration induced by drinking hot drinks can flush toxins from the body, helping to purify the bloodstream.” This is an unreferenced claim from a ‘blog‘ that seems to be an advert for Aquasana water filters. They suggest that, “Additionally, drinking hot water helps remove deposits in the nervous system. These deposits are believed to have a negative effect on thoughts and emotional responses.” I don’t have the space to explain everything that is wrong with these statements, but Ben Goldacre’s excellent Bad Science website has a whole section on this detox codswallop.

I couldn’t find much information in the scientific literature about the warming properties of complex carbohydrates, but this advice was echoed in an interview of Washington State University food scientist Barry Swanson.

Do spices “boost your metabolism”? A quick Google search showed that bloggers certainly seem convinced of the metabolism-boosting properties of spicy food, but what does the scientific research conclude? A well-referenced article on the benefits of spices suggests that capsinoids (non-spicy compounds in some sweet chilis) can increase thermogenesis, but that these effects require very large doses, have very small effects, last a very short time, and the effects are only present in those who do not eat spices regularly. However, there is evidence that ginger may really warm you up.

So does drinking water make you warmer, as claimed in the infographic? First of all, the word hydration has nothing to do with ions. It comes from the Greek hydr- meaning water and the noun-forming suffix -ion. I ran the next sentence, “Our bodies are full of ions, and when ions dissolve in water, the stabilising reactions release heat. This is known as the heat of hydration.” past our resident chemical expert, Ross Forgan, who confirmed that the infographic’s statement is “an incorrect interpretation of a fundamental physical property of ionic compounds.”  Our bodies really are full of ions, such as sodium and calcium, which are important for many biological processes, and the heat of hydration really is the change in energy when ions dissolve in water, but the ions in your body are already in solution unless you’re dehydrated to the point of mummification. While drinking plenty of water can have real health benefits, the heat of hydration is just a sciency-sounding justification for baseless pseudo-medical advice on staying warm.

So how can I stay warm?

You can usually rely on government health organisations to provide sensible, non-sensationalised advice based on science or common sense. Age UK and the BBC have sensible, concrete advice on making your self and your home winter-proof. Also see an excellent and well-referenced article on Huffpost, Everything you know about getting warm is wrong.