Running bad for your kidneys?

I am sat here looking at my running shoes. I have that guilty feeling since I haven’t gone out for a jog for a few weeks. Instead, I have an Easter egg in my hand. And then there are the headlines. ‘Marathons are bad for your health, scientists warn runners’ screamed the headline in the Daily Telegraph. The article came in response to research published in the American Journal of Kidney Disease and studied 22 runners completing the Hartford Marathon.

It isn’t new news though. There was a similar study published in 2011. Both had the same message. Acute kidney injury stage 1 is common in marathon runners, resolves quickly and we don’t know the impact of repetitive ‘marathon’ running on the kidneys.

I could replace kidney with heart. Same newspaper and ‘Marathon running can ‘scar’ the heart, researchers warn.’ Now I belong to a running club, and after that one I had a load of emails and social media comments from club members – was I worried? For the record, I have run 8 marathons in my life to date but didn’t start running until I was 46. My fastest time is 3 hours 56 minutes, set in Venice one lovely November day. For a front row forward I am pretty happy with that.

But I know running long distances can do awful things to our physiology. People are always encouraged to drink plenty to ward off the risk of dehydration. Yet hyponatraemia (low sodium levels in your blood) is a far greater risk to your wellbeing. A combination of overdrinking, the way your hormones work and the possible additional use of anti-inflammatories (ibuprofen) all contribute. For a good read, look at this article in Runners World. 

For those not in the know, you need a qualifying time to get into Boston – something I will never achieve – so the study on which this is based looked at the best of the best. And I like the message in that article – ‘Drink to minimize weight loss, but don’t overdrink. And favour a good sports drink over water’.

But am I worried about the research? Despite all the newspaper headlines, I believe that running overall is good for you (like all exercise). It helps our heart, keeps our weight down, lowers our blood pressure and helps us mentally. It is also cheap. But long distance running itself is not a fun run. Be sensible, know your body, learn to drink when thirsty and in your training, weigh yourself before and after a long run, aiming to be at the same weight when you finish. Look at the colour of your urine after a long run and use our chart. If it is absolutely clear you have drunk too much, dark and it’s too little. And avoid those NSAIDs.

What about those papers? Well, for me it is a reminder that tests need to be interpreted in the context of the situation. The AKI warning test score that the labs across England and Wales produce is not a diagnosis of AKI – it is a warning that the person needs evaluating. Many will have AKI, some will not. It reminds us that serum creatinine is not a perfect biomarker for kidney disease although it serves us well. And it wouldn’t stop me running. One, because the balance of benefit is way in favour of being fit and second, I want to run 10 marathons in total by the time I am 60 – under 4 hours again would be a dream but I will take any time.

For those of you running your spring marathons, such as Manchester, Brighton that have run or Edinburgh, London or Paris or indeed anywhere else, enjoy it, look after your kidneys and have a safe trip around the course. In the meantime, I am lacing up my shoes.

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