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.

Monday, 14 November 2016

Can a garlic soup conquer colds and flu?

I was fascinated to see a post on Facebook relaying a claim that a soup made with 52 cloves of garlic can 'defeat colds, flu and even norovirus.' Leaving aside the possibility that this is because anyone consuming that much garlic will never get close enough to anyone else to catch anything, it seemed a claim that was worth putting under the Science for Life spotlight.

The claim is from a two-year-old article on a website called Complete Health and Happiness, which as a source, I admit, did rather get my dubiousness sensors tingling. However, I decided to take it at face value and see what the claim was based on.

The website gives as its source a 'recent and significant finding from Washington State University' and helpfully provides a link - but this takes the reader to another so-so looking site called PreventDisease. However, this at least appears to have a link to the research - but it turns out the link just goes to the home page of the respectable Journal of Microbial Chemotherapy. While I struggled to find the precise article, a search on Washington and garlic did throw up a number of papers such as this one which reports the impact of an active chemical from garlic on Scedosporium prolificans in vitro. Most of the work on garlic seems to be in vitro - effectively in a test tube - which makes it impossible to draw any conclusions from it for consuming garlic soup. Lots of substances destroy disease-causing microbes in a test tube (washing up liquid, for example), but that doesn't mean that they will help if you swallow them.

Other papers did cover experiments with mice and humans, though as yet these were very limited and not providing sufficient information to be practical. However, what all the papers have in common is that (like the antibiotics the original website refers to) they are dealing with bacteria. There is nothing whatever in them about viruses. And so, I'm afraid, that there is no evidence that this soup will defeat colds, flu and even norovirus.

Don't get me wrong - garlic is good for you and almost all of us could do to have more vegetables in our diet. But don't think that eating a soup will protect you from infection.

Thursday, 22 September 2016

Sugary science

Sucrose - image from Wikipedia
It is well known that the cigarette companies were aware of the dangers of smoking long before the general public, yet spent large amounts of money on attempting to counter the science. Similarly, many of the oil companies have actively sponsored attacks on global warming. Now it appears there is a new bad guy on the block - the sugar industry.

It is only in the last few years that we have displaced some of our concern about fat in the diet to take on sugar as a dangerous substance to over-consume. And it's easy to assume that this awareness also took the sugar industry by surprise. But research undertaken by the University of California, San Francisco suggests that the US sugar giants were aware of the risks of sugar consumption as far back as the 1950s.

To make matters even worse, the paper tells us
Together with other recent analyses of sugar industry documents, our findings suggest the industry sponsored a research program in the 1960s and 1970s that successfully cast doubt about the hazards of sucrose while promoting fat as the dietary culprit in [coronary heart disease].
This is astounding if true. Not only was the risk from sugar played down, but it appears that the sugar industry used a distraction technique by overplaying the role of fat.

There's the possibility here of tobacco-style mass law suits. But what interests me more is whether or not US big business (Europeans do it as well, but not on the same scale) is still playing this kind of bait and switch game with our health. We know that the oil companies are still trying to play down climate change - but what about the food industry? Or pharmaceuticals?

I'm no enthusiast for conspiracy theories, but this kind of behaviour defies belief. Don't these people have children?

Sunday, 5 June 2016

Is Manuka Honey great for the immune system?

We are constantly being bombarded with the latest celebrity fad, so I'm grateful to an email from Chelsea asking if Manuka honey is great for the immune system.

The quick answer - no.

This is a honey produced by bees exposed to pollen from the Manuka tree, mostly in New Zealand and Australia. It sold at incredibly high prices for honey - as much as £50 or more for a small jar.

Unfortunately, this is a classic case of assuming something that has a topical benefit - if you use it externally - will have a benefit if consumed. And as is usually the case, there is no link.

Honey in general has a mild anti-bacterial action (as do many substances - washing up liquid, for instance) - and there is reasonable evidence that Manuka honey is amongst the best at this. So applied appropriately to a wound (and I'm not recommending just slapping honey on), it can in principle have a positive effect (though there are many other, cheaper and more effective anti-bacterial agents).

When you eat it, though, it has no impact on your immune system. As discussed in Science for Life:
Your immune system is not a single part of your body but rather a vast network comprising physical barriers like your skin, white blood cells, various different organs and a whole range of complex chemicals with literally thousands of different roles. ‘Boosting’ it by simply eating something is a bit like hoping to redecorate your house by throwing a capsule of paint at the wall.
And in this case there is no evidence that the honey will be anything more than an incredibly expensive sweetener, adding unnecessary sugar to your diet. See the Cochrane report for details on use of honey in treating wounds.