The Wellness Industry Wants You to Fear Glucose. Science Says Otherwise
Blood sugar spikes are a normal response to eating, yet wellness influencers have turned them into a source of anxiety. Here is what the evidence actually shows.
Over the past few years, two curious trends have taken hold. Healthy people have begun wearing devices that track their blood sugar throughout the day, while others have cut out refined carbohydrates such as white bread and pasta altogether. Authors, podcasters and wellness influencers have fuelled the idea that we must all monitor our blood sugar and avoid spikes at any cost. According to this extreme view, allowing significant amounts of glucose into the bloodstream invites hormonal imbalances, acne, mood swings and worse, even in those with no metabolic disease. Experts are now pushing back.
When we eat and digest sugary foods, such as refined sugar, fruit and carbohydrate-rich fare, our blood sugar naturally rises. Carbohydrates and sugars are broken down into glucose, which is absorbed into the bloodstream, temporarily lifting blood sugar levels. The pancreas then secretes insulin, the hormone that moves glucose out of the blood and into the body's cells to provide energy. Food is not the only trigger. During high-intensity exercise, hormones such as adrenaline signal the liver to release more glucose, providing extra fuel for working muscles, says Jennifer Sherr, a paediatric endocrinologist at Yale School of Medicine in Connecticut. In people with diabetes, the body does not produce enough insulin, or no longer responds to it properly. Their blood sugar can therefore become dangerously high after eating, which is why careful dietary management, exercise and monitoring are essential, with some requiring 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 at University College London. Blood sugar typically peaks about an hour after eating and returns to baseline within two hours. If the spike is brief and occurs in someone with a normal metabolism, there is little cause for concern, Brown says. It is when glucose remains elevated for longer than expected that the body may not be regulating it properly, says Sherr. This can signal insulin resistance, which develops when the body is exposed to high blood sugar over a long period and can eventually lead to prediabetes and type 2 diabetes. The persistently high glucose experienced by some diabetics can then cause nerve and eye damage, heart disease and stroke.
Some experts, however, argue there is insufficient evidence that excessive glucose directly causes insulin resistance. Nicola Guess, a dietician and senior research fellow at the University of Oxford, suggests the explanation may instead lie in excess calories being converted to fat, with the resulting weight gain acting as a risk factor for type 2 diabetes. People with diabetes already monitor their blood sugar regularly, often using continuous glucose monitors that measure levels throughout the day. A growing commercial market now sells these devices to otherwise healthy people, though some experts warn they are unnecessary for those without diabetes. One study of non-diabetic participants found their blood sugar remained in the healthy range 96% of the time. Others caution that the devices can prompt harmful dietary changes and distort perceptions of health, particularly as they may overestimate blood sugar levels. In a recent review, Brown and colleagues found a lack of consistent, high-quality evidence that the monitors improve health outcomes in people without diabetes. The exception may be those at risk of type 2 diabetes, though more evidence is needed.
While blood sugar rises are normal and unlikely to cause dire consequences in healthy people, there are benefits to keeping levels steadier. A rapid dip after a meal can increase hunger and lead to greater energy intake overall. Different meals affect blood sugar in different ways. Foods that keep levels steady, such as wholegrains and protein-based foods, keep us fuller for longer. Simple carbohydrates, like white bread and white rice, are absorbed more quickly. The order in which you eat can also help. Eating protein and vegetables before carbohydrates has been found to reduce the subsequent rise in blood sugar. Aiming for balanced meals containing protein, fibre-rich plant foods and healthy fats can slow digestion and provide steadier energy, while helping to maintain a healthy weight. It is worth noting that we all respond differently to the food we eat. Brown points to considerable variation between individuals, with the same person showing different responses depending on sleep, stress, activity levels and the type of meal consumed.
Avoiding carbohydrates altogether, as some diets suggest, could backfire. When we eat a carbohydrate-rich meal after a period of restriction, it can cause blood sugar to rise more than usual. Carbohydrates are considered an essential part of a balanced diet, and Guess notes in a recent review that restricting certain food groups can mean unnecessarily avoiding foods that are good for you. While the jury remains out on the benefits of glucose monitoring for the healthy, it helps to remember that most of us already eat too much added sugar. Reducing that is a far more sensible place to start.