Blood sugar spikes are not necessarily bad for you

It's trendy to be concerned about blood sugar spikes, but these can be a normal response to eating. Here's when you don't need to worry.

Over the last few years, two surprising things have started happening.

Normal, otherwise healthy people have started wearing devices that allow them to check their blood sugar levels throughout the day. Others have been cutting out refined carbohydrates such as white bread and pasta entirely.

In fact, authors, podcasters and wellness influencers have been selling the idea that we all need to check for blood sugar spikes and avoid them. According to this extreme view, we allow significant amounts of glucose in the bloodstream at our peril. Even in healthy people with no metabolic diseases, to risk a blood sugar spike is, they say, to welcome hormonal imbalances, acne, mood swings, and worse.

But now experts are pushing back. Here's when to worry, and when that carbohydrate-heavy meal is unlikely to do any lasting damage.

When we eat and digest sugary foods, such as refined sugar, fruit and carbohydrate-rich food, our blood sugar naturally inclines.

That's because as we digest carbohydrates and sugars, they are broken down into glucose, which is then absorbed into the bloodstream, temporarily leading our blood sugar levels to rise. As it does so, the pancreas responds by secreting the hormone insulin, which helps move the glucose out of our bloodstream and into the body's cells to provide energy.

It's not only food that can raise our blood glucose levels. During high-intensity exercise, hormones such as adrenaline signal the liver to release more glucose into the bloodstream, providing extra fuel for working muscles. As a result, blood glucose can temporarily rise, says Jennifer Sherr, a paediatric endocrinologist from Yale School of Medicine, Connecticut in the US.

In people with diabetes the body does not produce enough insulin, or it no longer works as it should (insulin resistance). This means that after eating, their blood sugar can become dangerously high. In this case, it's essential that people carefully manage their diet, exercise, and monitor their blood sugar levels to avoid spikes. Some people also need to take medications such as insulin or metformin.

Among healthy individuals, a rise in blood glucose after eating is a normal physiological response. "The biggest misconception is that every glucose spike is harmful," says Adrian Brown, associate professor in nutrition and dietetics from University College London in the UK.

Recently I experimented with giving up added sugar for six weeks (read more from the BBC on what I learned). Since then, I've been especially attuned to the fact that when I eat sugary foods, my blood sugar is bound to rise.

Experts say it's a misconception that every glucose spike is harmful (Credit: BBC/ Serenity Strull/ Getty Images)

Our blood sugar level typically peaks around one hour after eating and tends to return to baseline within the next two hours. If a spike is brief and occurs in someone with a normal metabolism, we should not be concerned, says Brown.

It's when blood glucose remains elevated for longer than expected that it could indicate that the body is not regulating glucose normally, says Sherr. This could be a sign of insulin resistance, where the body doesn't respond to glucose normally. Insulin resistance can happen if the body is exposed to high blood sugar levels over a long period of time. Eventually it can lead to prediabetes and type 2 diabetes. The persistently high blood glucose experienced by some diabetics can then lead to complications including nerve and eye damage, heart disease and stroke.

However some experts argue that there is not enough evidence to say that excessive blood glucose leads to insulin resistance directly. Instead, the explanation could be that when we eat more than our body needs these excess calories tend to be converted to fat, says Nicola Guess, a dietician and senior research fellow at the University of Oxford in the UK. The resulting weight gain is a risk factor for type 2 diabetes, she adds.

People with diabetes already monitor their blood sugar regularly. One way they do this is with continuous blood sugar monitors (CGMs), which measure blood sugar levels throughout the day.

There's now a growing commercial market for these devices in otherwise healthy people. However, some experts warn that they are unnecessary for those without diabetes. One study of non-diabetic participants found that their blood sugar levels were in the healthy range 96% of the time, for instance.

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Others urge caution that they can "prompt harmful dietary changes and distort perception of health", especially as they can overestimate blood sugar levels. In a recent review, Brown and colleagues found "a lack of consistent, high-quality evidence showing that CGMs improve health outcomes in people who do not have diabetes.

The exception may be those at risk of type 2 diabetes. Emerging research suggests that trackers monitoring blood glucose could help predict those at greater risk, says Sherr, but more evidence is needed to determine if CGMs are beneficial to this group.

While blood sugar rises are normal and unlikely to lead to dire consequences in healthy people, there are some benefits to helping your body keep sugar levels steadier. For example, a rapid post meal glucose dip can increase our hunger and lead to a greater energy intake overall.

Different types of meals will also affect how much our blood sugar changes. Foods that keep our blood sugar steady can keep us fuller for longer. These include wholegrains and protein-based foods. Simple carbohydrates, like white bread and white rice, are absorbed into the bloodstream more quickly.

Considering the order in which you eat certain foods can also help. For instance, eating protein and vegetables before carbohydrates has been found to reduce the subsequent rise in blood sugar that normally follows a carbohydrate-rich meal.

Another tip is to aim for balanced meals containing protein, fibre-rich plant foods and healthy fats. This can help slow digestion and provide a steadier supply of energy, as well as helping you to maintain a healthy weight.

It's also worth noting that we all respond slightly differently to the food we eat. "There is considerable variation between individuals, and the same person may show different responses depending on factors such as sleep, stress, activity levels and the type of meal consumed," says Brown.

In addition, avoiding carbohydrates, which certain diets suggest, could backfire, says Guess. When we eat a carbohydrate-rich meal after a period of restriction, it can actually cause our blood sugar to rise more than usual. Crucially, carbohydrates are considered an essential part of a balanced diet. As Guess notes in a recent review, restricting certain food groups can mean unnecessarily avoiding foods that are good for you.

So while the jury might be out on the benefits of glucose monitoring, in the meantime, it helps to remember that the majority of us already eat too much added sugar. We can certainly work on reducing that instead.

*All content within this article is provided for general information only, and should not be treated as a substitute for the medical advice of health care professionals.

Melissa Hogenboom is a senior health correspondent at the BBC and author of Breadwinners and The Motherhood Complex. She is melissa_hogenboom on Instagram.

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