Monday 17 July 2017

Coffee again

Image from Wikipedia
Yet again we've seen newspapers flooded with stories on diet and health - specifically that drinking coffee can reduce mortality rates by a small but significant amount.

The good news is that the two studies referenced are high quality, large scale studies. Admittedly one of them does not specify the dosage of coffee involved (for the other, 3-4 250ml cups a day seems to be it), and that same first study did not seem to control for many other lifestyle contributors - could the coffee drinkers have been more health-conscious in other aspects of their life, for example.

You can read an excellent summary of the details of the studies and find links to read the original studies if you wish at the Skeptical Raptor website.

Thursday 13 July 2017

Sugar, sugar

We all know these days that sugar is a problem in our diet, but there is huge confusion over what sensible limits are. Practically everyone seems to be confused by this - and I'm afraid this included me, when I wrote about sugar in Science for Life, because I didn't realise just how stupid the regulations and recommendations are (thanks to reader Clare Kendall for pointing out an error in the book, and Phil Langton from Bristol University for useful guidance).

Our food packaging in the UK is generally labelled with the quantity of sugar in the product. In 2015, the UK's Science Advisory Committee came up with a report recommending we reduce consumption to 5% of total dietary energy, which led to the figures of no more than 35g for a man and 25g for a woman. Now, it would only be sensible to make such a recommendation if, as I assumed, it matched the labelling - but it doesn't, making it practically meaningless. This is a recommendation for 'free sugar', where the labelling is the amount of total sugar. Free sugar is defined as 'all monosaccharides and disaccharides added to foods by the manufacturer, cook or consumer, plus sugars naturally present in honey, syrups and unsweetened fruit juices. Under this definition lactose (the sugar in milk) when naturally present in milk and milk products and the sugars contained within the cellular structure of foods (particularly fruits and vegetables) are excluded.' Got it?

There are two problems here. One (the one that confused me) is that it doesn't make any sense for your labelling legislation to require a different definition of sugar content to your recommendation for consumption. But the other is that limiting restrictions entirely to free sugars makes very little sense. For example, they treat all the sugar in orange juice as free sugar, but none of the sugar in an orange (say) as free sugar. However, when you eat an orange, you release a lot of the fruit juice in your mouth, assuming you don't swallow the segments whole. Why isn’t that free sugar? Clearly it is.

There is also a problem with lactose, the sugar in milk. Again, it’s not clear how much this should be counted, but it seems wildly illogical to simply ignore it. And downright weird to count it when it's added, but not when it's already there, as milk has no structural protection to prevent absorption, as there is in fruit.

As far as I can see from the document, there is not good evidence of the involvement of non-free sugars in diabetes, but equally there is not good evidence they are not involved (and nothing either way on heart conditions etc.) My suspicion is they didn't want to scare people off eating fruit and drinking milk because there are other nutrients in them that are good - but the result is a very confusing message.

I suspect the best thing is to cut down on all sugar, but of the sugar you do have, to make sure that it is accompanied by other beneficial nutrients. By all means drink milk (assuming no lactose intolerance) and eat fruit - they are good for you because of those nutrients - but don't consume too much. As mentioned in the book, it's sensible if more of your 5 (or 7 or 10) a day are vegetables rather than fruit. And I'd definitely stay away from smoothies and other very high sugar content drinks (Frappacinos, for instance) and foods mentioned in the book, except as occasional treats.

Thursday 16 February 2017

Will Vitamin D supplements protect me against colds and flu?

Vitamin D supplements are often combined with
calcium as a treatment for osteoporosis
No one likes getting respiratory tract infections such as colds. There is interesting news that a wide-ranging study shows that vitamin D supplements can reduce the risk of getting colds and flu, particularly in those with severe vitamin D deficiency.

This is encouraging, especially as it isn't based on a single small trial. However, it is worth repeating once piece of the report: '... 33 people would need to take vitamin D supplements to prevent one acute respiratory tract infection.' That's for ordinary folk - for those with severe deficiencies, it's only four people taking the supplement to get one prevention.

So there does seem to be an effect, particularly if you are in that deficient group. As we get most of our vitamin D from sunlight, that's most likely to be people who avoid exposure to the sun, or who live in countries with low levels of sunlight in winter.

Even so, it's best not to get too excited. Assuming your vitamin D levels are average, rather than extremely low, bear in mind that the chances are high that taking the supplement would not prevent you getting an acute infection. (The study doesn't not cover non-acute infections.) But this is one of the few examples suggesting that people who are generally healthy might benefit from vitamin supplements.

The study is published in the BMJ.

Monday 23 January 2017

Crispy roasties and burnt toast

There's been an outbreak of news stories about cancer risk from over-cooked starchy foods because of the production of substances called acrylamides. If your roasties, chips and toast, for instance, are too dark, we are told that they could increase your risk of cancer. This is not news - it's an idea that has been around for a long time and was covered in Science for Life. All that's new is that the Foods Standards Agency (FSA) has launched a campaign called Go for Gold encouraging us not to cook these starchy products too harshly and to leave them golden coloured. Bizarrely they are using that well known food science expert, Olympic medallist Denise Lewis to publicise the campaign (see what they've done - go for gold?), and the FSA wants us to cut back.

As mentioned in Science for Life, some studies do show a small potential increased risk of a handful of cancers, so there's no harm in avoiding really dark fried or grilled starchy foods, which is what I recommended. However, these studies are not definitive - in fact at the moment the general view is that there is no strong evidence of risk from acrylamides - and even if the risk does exist, it is small enough to happily still enjoy the crunchy bits of roast potatoes.

To put it into context, lots of things we eat may well produce a very small increase in risk of cancer. Things like, for instance, those killer foods orange juice and celery. We know for certain that alcohol has the biggest influence on cancer risk of anything we eat or drink, and coffee certainly has some small risk attached. But it the grand scheme of things, worrying about these small risks is like worrying about being struck by lightning or being in a fatal train crash. It can happen. It will happen to some people. And you don't want to stand on a high hill holding a metal pole in the air when there's thunder nearby. But life's too short to worry excessively.

You can read more on the statistical aspect here.