A Rise in Blood Sugar After Eating Does Not Always Mean Danger, Experts Say

Many people worry about sudden rises in their blood sugar levels. But experts say a rise in blood sugar after eating can also be the body's normal response — so there is no need to panic over every single increase.

Two surprising trends have emerged in recent years. Healthy people have begun using devices that measure their blood sugar levels throughout the day. Meanwhile, some people have cut refined carbohydrates such as white bread and pasta out of their diets completely.

Writers, podcasters and wellness influencers have promoted the idea that everyone should monitor sudden rises in blood sugar and avoid them. According to this extreme view, allowing significant amounts of glucose into the bloodstream is dangerous; it is claimed that even in healthy people with no metabolic disease, such rises can cause hormonal imbalance, acne and mood swings. Now, however, experts are pushing back against that idea.

When we eat and digest refined sugar, fruit or carbohydrate-rich food, blood sugar levels naturally rise. Carbohydrates and sugar break down during digestion into glucose, which is absorbed into the bloodstream. The pancreas then releases the hormone insulin, which helps move glucose from the blood into the body's cells so it can be used to produce energy.

Food is not the only thing that can raise blood glucose. During high-intensity exercise, hormones such as adrenaline signal the liver to release more glucose into the bloodstream so that working muscles get extra fuel, says Jennifer Sherr, a paediatric endocrinologist at Yale School of Medicine in Connecticut, USA.

For people with diabetes, however, the picture is different. Their bodies do not produce enough insulin, or the insulin does not work properly. As a result, after eating, their blood sugar levels can rise dangerously. In such cases, carefully controlling diet and exercise and monitoring blood sugar levels is extremely important; some people also need medication such as insulin or metformin.

Adrian Brown, an associate professor in nutrition and dietetics at University College London in the UK, says: "The biggest misconception is that every glucose spike is harmful." Blood sugar usually peaks about an hour after eating and returns to normal within the following two hours. If the rise is short-lived and a person's metabolism is normal, there is nothing to worry about, he says.

According to Sherr, problems can arise when blood glucose levels stay high for longer than expected. That can indicate the body is unable to control glucose normally; it may be a sign of insulin resistance. If sugar levels remain very high for a long time, it can lead to prediabetes and type 2 diabetes, and later to complications including nerve and eye damage, heart disease and stroke.

However, according to Nicola Guess, a dietitian and senior research fellow at the University of Oxford in the UK, there is not enough evidence to claim that excess blood sugar directly causes insulin resistance. Rather, when we eat more than the body needs, the extra calories are converted into fat and weight increases — a major risk factor for type 2 diabetes.

People with diabetes regularly monitor their blood sugar; one way is a continuous glucose monitor (CGM), which measures levels throughout the day. Now a growing commercial market for these devices has emerged among healthy people too. But some experts warn that for those without diabetes, they may be unnecessary. One study of participants without diabetes found their blood sugar levels were within the healthy range 96 percent of the time. Others warn the devices can encourage harmful dietary changes and create misconceptions about health.

For people at risk of type 2 diabetes, though, the situation may be different. Jennifer Sherr says new research suggests glucose-monitoring devices could help identify at-risk individuals; but more evidence is needed to determine whether CGMs are truly beneficial in such cases.

Some habits can help keep blood sugar relatively stable. Whole grains and protein-rich foods keep us full for longer; by contrast, simple carbohydrates such as white bread and white rice are absorbed quickly into the bloodstream. The order of eating also matters — eating protein and vegetables before carbohydrates can reduce the post-meal rise in sugar. A balanced meal containing protein, fibre-rich plant foods and healthy fats slows digestion and supplies energy more steadily.

Brown says: "There are significant differences between individuals, and the same person can respond differently depending on sleep, stress, levels of physical activity or the type of food eaten." According to Guess, advice to avoid carbohydrates can also backfire — after a long period of restriction, eating carbohydrate-rich food can raise blood sugar more than usual. Carbohydrates remain an essential part of a balanced diet. One thing is worth remembering, though — most of us already eat more added sugar than we need; attention could instead go to reducing that. It should be noted that such information is provided for general informational purposes only and is not a substitute for a doctor's advice.