Dr Beas Bhattacharya, a consultant in diabetes and endocrinology based in Bath, is keen to point out that rapid blood sugar spikes after eating a meal, especially one with a higher carbohydrate content, are normal. In healthy people, the pancreas responds by producing insulin to return blood sugar levels to normal.

It is frequent or large blood sugar spikes that we need to be concerned about, as registered dietitian Misbah Ameen-Khan explains: “Over time, this adds stress to the pancreas, which can lead to insulin resistance, where the cells become less responsive to insulin and do not absorb the excess blood glucose as efficiently. This increases the risk of type 2 diabetes.”

Prolonged sugar spikes also signal to the body to start storing sugar as fat, ultimately leading to weight gain. At the same time, excess fat, particularly around the belly, can worsen insulin resistance because it stops the body from using insulin efficiently, so it becomes a negative loop of increasing insulin and further weight gain.

Which foods cause blood sugar spikes?

Because we refer to blood sugar, it is easy to think these spikes are just caused by sugary foods, but Bhattacharya explains that it is carbohydrates more generally that are the culprit.

“Most sweet things are carbohydrates (except certain artificial sweeteners), but not all carbohydrates are sweet. For example, bread, rice, noodles and pasta are not sweet, but they are carbohydrate-rich and therefore cause significant blood glucose increases after being eaten.”

How can you eat to minimise blood sugar spikes?

There are two food strategies that help keep blood sugar levels on an even keel: selection and combination.

Selection means choosing foods with a lower glycaemic index (GI). The GI is a measure of how quickly a food raises blood sugar levels on a scale of 1 to 100. Anything ranked 55 or less is considered low, and anything above 70 is considered high. Bhattacharya advises that carbohydrates with a low GI take longer to digest, resulting in a flatter sugar release and fewer spikes. Low-GI carbohydrates include whole grains, legumes such as beans and lentils, and most fruits and vegetables.

Combination involves eating different food groups together so that the effect of higher GI foods is mitigated. Ameen-Khan suggests pairing carbohydrates with protein, fibre or healthy fats, as this lowers the overall glycaemic load and slows digestion, which keeps energy levels steady and sustains us for longer. For example, avocado on wholegrain toast with an egg on top.

Six savoury foods that spike your sugar levels and what to eat instead

It is not just sugary foods that can cause blood sugar spikes. Here are six savoury foods that have a relatively high GI, and what to eat instead.

Swap white rice (GI 73) for quinoa (GI 35)

Quinoa is heavily associated with the now discredited ‘clean-eating’ movement, but the truth is, it’s significantly more nutrient-dense than white rice, boasting higher levels of protein, fibre, and essential minerals like magnesium and iron. It also contains all nine essential amino acids (the compounds that make up protein), making it one of the few plant foods that are a complete protein. It’s especially good when added to soups.

Swap white bread (GI 75) for sourdough bread (GI 54)

We all love our doughy farmhouse loaf, but it is one of the highest GI foods around. Sourdough bread, on the other hand, is low-GI, thanks to the fermentation process, which changes the structure of the carbohydrates, making digestion slower. Another tip is to slice and freeze your sourdough, which creates resistant starch in the bread, further lowering the GI. You can pop it straight in the toaster from frozen.

Swap rice noodles (GI 65) for soba noodles (GI 45)

Soba noodles are made from buckwheat, and their higher fibre content results in a lower GI. As with the sourdough bread, if you cook and cool your noodles before using them in a cold soba noodle salad, the resistant starch will further reduce potential blood sugar spikes.

Swap potatoes (GI 78) for cauliflower (GI 15)

Potatoes are a stalwart of the British kitchen, but if you’re keen to get your blood sugar under control, then cauliflower could be the smart swap. Cauliflower has a minuscule GI and can be baked, roasted, mashed and boiled in the same way as potatoes. To spice things up a bit, toss the florets in a mix of paprika and cayenne, then drizzle with olive oil, season and roast until golden.

Swap sweetcorn (GI 60) for edamame (GI 16)

As with quinoa, edamame are a complete protein and also have more fibre and fat than sweetcorn, which explains their very low GI. While sweetcorn does contain some fibre, its higher carbohydrate content and more rapid digestion mean it can cause greater blood sugar spikes, especially when consumed in larger portions. Frozen, podded edamame are now widely available and can be used in salads, stir-fries, or even blended in a dip.

Swap pumpkin (GI 64) for carrots (GI 39)

While pumpkin has a relatively high GI, it does contain some fibre and eaten in moderate amounts, won’t affect blood sugar too adversely. Even better are carrots, which are equally rich in beta-carotene (a powerful antioxidant that the body converts to vitamin A, which supports good vision, a strong immune system, and healthy skin), but have a lower carbohydrate content per serving, making them a safer daily choice for stable blood sugar levels.

FAQs

Do portions make a difference when it comes to blood sugar control?

We know that carbohydrates cause blood sugar spikes, but is quantity also a factor? According to Bhattacharya, portion size has a huge impact on blood sugar control. “Larger portions, especially those of carbohydrates, cause greater blood glucose spikes, and blood sugar levels stay elevated for longer.”

She advises following the diabetes healthy plate, a visual guide for creating balanced meals by filling half the plate with non-starchy vegetables, one quarter with protein, and one quarter with high-fibre carbohydrates such as whole grains.

Can better blood sugar control help with weight loss?

Better blood sugar control is crucial for effective weight management. Bhattacharya clarifies that glucose spikes trigger insulin production, which sends signals to the body to store fat rather than burn it for energy. Conversely, by controlling blood sugar you can lower insulin, allowing your body to become more efficient at burning fat. Additionally, when blood sugar levels crash, we feel hungry, and there is a tendency to overindulge – that ravenous feeling that often hits in the afternoon and has us reaching for the biscuit tin.

Can alcohol impact our blood sugar levels?

“Drinking alcohol initially causes blood sugar to rise, depending on the quantity of carbohydrates in the drink, and can lead to blood sugar spikes,” says Ameen-Khan.

“However, the liver then prioritises breaking down the alcohol instead of managing blood sugar levels. This can cause drops or ‘crashes’ in blood sugar levels, which can be particularly unsafe for people with diabetes.”

This is because the brain and body need a continuous supply of glucose to function, and a severe and sustained drop in blood sugar, or hypoglycaemia, can lead to confusion, loss of consciousness and even death if not treated promptly.

Of course, the other downside to a night on the booze is a heavy head the next day, and it is low blood sugar that is also to blame for those hangover munchies. Ameen-Khan explains, “After drinking alcohol, blood sugar levels are often low. This triggers the urge for foods that are absorbed quickly, such as sugary foods and refined carbohydrates, for a quick energy boost.”