If you follow any health and fitness accounts on social media it can feel like everyone is talking about their blood sugar levels. Thanks to the rapid emergence of continuous glucose monitors (CGMs) – in part thanks to the near non-stop promotion by Dr Tim Spector of his ZOE personalised nutrition app – which give a real-time reading of exactly what you blood sugar level is doing at any given moment, more of us than ever are giving greater (and for some, constant) thought to how the food we eat immediately impacts our body.

But just how important is the management and control of your blood sugar levels to improve your short- and long-term health and wellbeing? Keep reading to discover the science-supported answer to this, and all the other big questions about blood sugar levels, to empower you to start making better decisions to optimise how well you look, feel and perform.

What is blood sugar and why is it important?

Blood sugar, also known as blood glucose, is the concentration of glucose in the bloodstream. Glucose is the primary source of energy for our cells (see below). Maintaining stable blood sugar levels is crucial because imbalances can lead to immediate and chronic health problems. Low blood sugar levels, called hypoglycemia, can lead to sudden issues including dizziness, confusion, and fainting.

Consistently high blood sugar levels, called hyperglycemia, can cause severe conditions such as cardiovascular disease, nerve damage, and kidney failure. Better regulation of blood sugar will keep your energy supplies steady and constant to fuel your mental and physical activities, support metabolic function, and reduces the risk of chronic disease.

What is a blood sugar spike?

A blood sugar spike occurs when glucose levels in the bloodstream rise sharply after consuming carbohydrate-rich foods. This rapid increase triggers the pancreas to release insulin, a hormone that helps cells absorb glucose for energy or storage.

What is glucose?

Glucose is a simple sugar and the primary source of energy for our cells. It is derived from the foods we eat, particularly carbohydrates, and is transported through the bloodstream to be used or stored by the body. The body regulates glucose levels to ensure a consistent supply of energy for cellular functions.

How is food converted to glucose?

It’s a multi-step process involving digestion and metabolism. Digestion begins in the mouth, with saliva enzymes and the process of chewing breaking down carbohydrates. In the stomach, gastric juices further digest the food, particularly protein and fats.

The partially-digested food moves to the small intestine, where enzymes from the pancreas and bile from the liver continue the breakdown. Carbohydrates are converted into simple sugars, mainly glucose, which are absorbed into the bloodstream. Insulin helps cells absorb glucose for energy. Any excess glucose is stored in the liver and muscles as glycogen for later use.

What is insulin?

Insulin is a hormone produced by the pancreas that plays a critical role in regulating blood sugar levels. When we consume food, particularly carbohydrates, glucose enters the bloodstream. In response, the pancreas releases insulin to help transport glucose into cells, where it is used for energy.

Insulin also signals the liver to store excess glucose as glycogen for later use. Proper insulin function is vital for maintaining balanced blood sugar levels and preventing metabolic disorders.

Is a blood sugar spike bad for my health?

A blood sugar spike is a perfectly normal and necessary reaction to eating: you need a rise for insulin to be released to do its thing. Yet even a single mild spike has been labelled dangerous, thanks in no small part to social media influencers – we’re looking at you, Glucose Goddess – who’ve built their name and career pathologising a perfectly normal physiological function in an attempt to convince us of the need to blunt our blood glucose rises or else all hell will break loose. And guess what? They just happen to sell supplements that claim to prevent spikes.

Are frequent and extreme blood sugar spikes bad for my health?

Yes, that’s a different matter altogether. While small post-meal spikes are needed, frequent and extremely high rises on blood sugar levels are a big problem. It can lead to insulin resistance, a condition where cells become less responsive to insulin, increasing the risk of type-2 diabetes and other metabolic disorders, according to the American Diabetes Association.

Chronic blood sugar spikes can also damage blood vessels, leading to cardiovascular diseases, according to a study in “Diabetes Care”. Additionally, persistent high blood sugar levels can cause inflammation and oxidative stress, which are linked to various chronic conditions, including nerve damage and kidney disease.

Which foods cause the biggest blood sugar spikes?

Foods high in simple carbohydrates and sugars can cause significant blood sugar spikes. These include white bread, pastries, sugary drinks, sweets, and processed snacks. A study published in the “American Journal of Clinical Nutrition” found that high Glycaemic Index foods, such as white rice and potatoes, also lead to rapid increases in blood glucose levels. Conversely, foods with a low GI, such as wholegrains, legumes, and non-starchy vegetables, cause a slower, more gradual rise in blood sugar

Should I monitoring my blood sugar level?

Monitoring and managing blood sugar levels is crucial, especially for individuals with diabetes or pre-diabetes. But if you are in good health, exercise regularly and eat a nutritious and balanced diet that is low in added sugar and processed foods you shouldn’t concern yourself too much with it. If you are worried, using tools like continuous glucose monitors (CGMs) can provide real-time data on blood sugar levels, helping to make better dietary choices.

How can I prevent blood sugar spikes?

Preventing blood sugar spikes involves making dietary and lifestyle changes. Here are some strategies:

Choose low-GI foods
Opt for whole grains, legumes, and non-starchy vegetables, which cause slower increases in blood sugar levels.

Eat balanced meals
Include a mix of carbohydrates, proteins, and healthy fats in meals to slow down glucose absorption.

Control portion size
Consuming smaller portions of high-carbohydrate foods can help manage blood sugar levels.

Stay active
Regular physical activity helps improve insulin sensitivity and glucose uptake by cells.

What is the Glycaemic Index?

The Glycaemic Index (GI) is a numerical scale that measures how quickly and significantly a carbohydrate-containing food raises blood glucose levels after consumption. Foods are ranked on a scale from 0 to 100, with pure glucose assigned a GI value of 100. Foods with a high GI (70 and above) cause a rapid increase in blood sugar levels, while those with a low GI (55 and below) result in a slower, more gradual rise. The GI helps people make informed dietary choices, particularly beneficial for managing blood sugar levels in individuals with diabetes.

Choosing low-GI foods can improve blood sugar control and reduce the risk of developing type-2 diabetes and cardiovascular disease, according to the “American Journal of Clinical Nutrition”, and the Harvard TH Chan School of Public Health suggests that low-GI diets can aid in weight management by enhancing satiety and reducing hunger.