DR MICHAEL MOSLEY: Why you should AVOID coffee first thing… and eat last night’s pasta

I love self-testing: I regularly test my blood pressure and cholesterol. And, as many of you will know by now, I was once diagnosed with type 2 diabetes, and while I reversed it, I also still check my blood sugar levels.

It’s something more of us should do — millions of Brits have an abnormally high blood sugar level but many are blissfully unaware of the damage this is doing to their arteries and nerves.

An estimated seven million people in the UK have prediabetes (i.e. raised blood sugar levels that can be a precursor to full-blown type 2 diabetes) — but a good proportion won’t know it.

And even if you don’t go on to develop type 2 diabetes, simply having prediabetes increases your risk of premature death by more than 60 per cent.

You can check your blood sugar levels using a standard DIY fingerprick test (for around £20) from the High Street or online. These kits are reliable; if the result suggests you have a problem then do talk to your GP.

Many people with diabetes now use a continuous glucose monitor (CGM) — the coin-sized device, which sticks to your arm and has a tiny needle that measures your blood sugar levels: you then link it to your smartphone, and within an hour it will start giving readings, updated every 15 minutes. Theresa May, who has type 1 diabetes, wears one.

But while these devices are intended for people with diabetes, anyone can buy one (they cost around £60 and last for two weeks), and they’re increasingly being used by people — including TV presenter Davina McCall — who want to see what foods (and activities) push their blood sugar levels up.

The idea being the fewer the big glucose spikes, the better.

I decided to try this out myself, not least to put some popular social media ‘hacks’ to the test.

So two weeks ago I bought myself a type of CGM called Freestyle Libre. So what did I learn?

Well, first, that the device takes a while to settle down — for the initial couple of days it suggested my blood sugar levels were far higher than the readings from my fingerprick monitor (which is more reliable). If I hadn’t known this, I might have been very worried.

After that — and not surprisingly — I found that anything sweet or carb-heavy (such as cake or breakfast cereal) soon pumped my blood sugar very high, followed by a crash which left me hungry — and irritable. Sadly this was also true of one of my favourite treats, dark chocolate, which contains a fair amount of sugar, around 4g (one teaspoon) per square.

More tragically, I discovered that coffee — even black and without sugar — led to big blood sugar spikes, particularly consumed first thing in the morning.

This is because a couple of hours before you wake up, your body releases a big shot of the stress hormone cortisol to get you ready for the day ahead.

If you introduce caffeine while your cortisol is high, you get a big blood sugar spike.

The advice I got from James Betts, a professor of metabolic physiology at the University of Bath, is to delay having coffee until at least an hour after waking, when your cortisol levels are falling. And that trick certainly seems to help control my blood sugar response. I also found that a brisk walk soon after eating was a good way to bring my blood sugar levels down — this is because my muscles were using up some of the surplus sugar.

Recent research by the University of Limerick showed that a brisk walk 60 to 90 minutes after eating is best, as that’s when your blood sugar levels will be peaking.

Ideally you should walk for at least 15 minutes, but even something is better than nothing.

Oddly, more vigorous exercise had the opposite effect: after a lengthy bike ride I was horrified to see my blood sugars go up.

This was probably because more vigorous cycling led to the release of adrenaline, which made my body release sugar into my blood to cope with the extra workout.

Of course, this doesn’t mean vigorous exercise is bad, but it can be disconcerting if you are looking at your monitor and see blood sugar going up, rather than down.

So what about those internet hacks for avoiding blood sugar spikes?

One of the most popular is to drink a tablespoon of apple cider vinegar in water before having a sugary snack or carb-heavy meal.

This is based on the idea that the acetic acid in the vinegar slows down the breakdown of the carbs into sugar. It seemed to work for me, but it didn’t taste great.

Another hack I tested was the claim that cooking, cooling and reheating carb-heavy foods such as rice, pasta or potatoes changes their structure, so they become ‘resistant’ to gut enzymes that break them down, causing a smaller blood sugar surge.

On two consecutive days I ate pasta for lunch, but on the second day, I used leftover pasta that had been in the fridge, and then reheated. This time my blood sugar spike was half what it had been.

This, too, has been confirmed in studies, including one in 2021 by the University of Surrey which found that cooking, cooling and reheating pasta made a significant difference to the blood sugar spike.

Despite these positives, there are serious limitations to bear in mind if you’re using a CGM and don’t have diabetes.

Looking at what foods cause my blood sugar to spike was interesting, but I became a bit obsessed, even checking my readings in the middle of the night, which is clearly not healthy.

And it’s important to note that blood sugar levels don’t tell the full story.

Lentils and a bar of chocolate both made mine soar, but that doesn’t make them equivalent nutritionally — lentils have significant benefits, including the fact that they’re prebiotics, so nourish the ‘good’ bacteria in your gut.

A recent study by the National Institutes of Health in the U.S. also showed that you can get very different results to eating the same meal on two consecutive days, for all sorts of reasons, including how stressed you are and how well you slept.

So don’t rely on a CGM as a way of shaping your future diet.

And if all you really want to know is whether you have prediabetes or not, then a trip to your GP, or a fingerprick test, is a cheaper and simpler way to find out.

At last, a clampdown on the lip filler cowboys 

An awful lot of young — and not so young — people these days seem to have large, pouty lips, thanks to fillers.

While many people are delighted with the results, thousands are left every year traumatised by botched procedures.

If you are having injections into your face, it is clearly a good idea to have it done by someone who knows something about the underlying anatomy.

That’s because underneath the skin there’s a complex network of arteries and veins, and if you inject filler into one of these, it could obstruct blood flow and cause permanent tissue damage.

Amazingly, this industry is almost entirely unregulated, so pretty much anyone can pick up a needle and start advertising — there’s no guarantee that the person at the other end of the needle knows what they are doing. A couple of years ago I made a TV series about tweakments and was horrified by some of the stories I heard, including people who’d been blinded by fillers inserted too close to arteries that feed the eye.

In light of these disasters, the Department of Health and Social Care has recently announced a consultation on tweakments, to make them safer and curb the cowboys (and cowgirls). About time.

Autumn is on the horizon but pesky mosquitoes and other flying insects are still out looking for me — I seem to be a magnet for them.

But the good news is that scientists at the University of California may have found a solution. They’ve isolated a species of bacteria, found on some people’s skin, that is good at keeping mosquitoes at bay. These bacteria produce a range of chemicals, including butyric acid, which mosquitoes find repulsive.

The researchers hope to test this effect by spraying animals with the bacteria, before moving on to human trials.

We know that people in their 60s or 70s who develop new skills (such as painting) experience big improvements in memory and other cognitive abilities.

Now a major study of ageing Brits has found that adult education classes can significantly lower your risk of dementia. One theory is that being mentally active boosts your brain’s ability to cope with damage or decline in later life — or it may be that learning something forges new neural pathways. The bottom line is that the benefits of learning continue well into old age.