Dietitian Laura Tilt smiling at the camera while carrying a basket of veg

Fact v Fiction: Glucose Spikes and Gut Health - What You Need to Know

If you follow health trends, you might’ve seen the current fixation with glucose spikes. Maybe you’re wondering what they are and if you should worry about them. Dietitian Laura Tilt breaks it down.

Blood glucose basics

Blood glucose is the amount of glucose in your blood. It’s measured in units called millimoles per litre (mmol/l). Your brain and other tissues use glucose to function normally, so a minimum level is needed in the blood all times. It’s also true that too much glucose in the blood can cause health problems over time. This means that in healthy adults, blood glucose levels are carefully controlled within a narrow range.

What is a glucose spike?

A glucose spike describes a rapid rise in blood glucose (sugar). But you might be surprised to hear there’s no scientific agreement on exactly how much of a rise counts as a spike.

The most common reason for a rise in blood glucose is eating a meal. After eating, blood glucose levels rise as your body breaks down carbohydrates into glucose and the glucose is absorbed into your bloodstream. It’s how your body turns carbs into energy!

How much and how quickly your blood glucose rises after eating depends on a few things. These include:

  • the amount of carbohydrate in the meal or snack.
  • how quickly that carbohydrate is broken down and absorbed. This is influenced by several things including the chemical structure of the carbohydrate and the fibre content. White bread is broken down into glucose more quickly than wholegrain seeded bread.
  • what you’ve eaten alongside the carbohydrate. Eating carbohydrates with protein or fat (like a meal of eggs on toast or tuna pasta) slows the absorption of carbohydrates.
  • What you ate for your last meal - eating wholegrains or beans, peas or lentils can reduce the blood glucose response at the next meal. Equally skipping a meal.

If you’re thinking ‘wow there’s a lot of variables here’, you’re right! Glucose levels can vary from day-to-day even when eating the same foods. Carbohydrate isn’t the only thing that can cause your blood glucose to increase either. Intense exercise, stress and being sick can all cause a ‘spike’ in blood glucose too.

Is a ‘spike’ normal?

A rise in blood glucose after eating is completely normal. As blood glucose rises, your pancreas responds by releasing the hormone insulin, which transports glucose from your bloodstream into your cells where it is used for energy or stored for later use. Under normal circumstances this means glucose levels return to normal within a short time frame of 2 hours or less.

Raised glucose levels are only a problem if they remain raised for a long time. This is what happens in diabetes, because the body either stops making insulin or stops responding to it. This means glucose can’t move out of the bloodstream. As a result blood glucose levels remain high and over time (months or years) this can cause damage to the body’s tissues and cells.

So should I worry about glucose spikes?

Normal increases in blood glucose after a meal shouldn’t worry you. There isn’t any concrete evidence that definitively shows short-term ‘spikes’ or ‘peaks’ in blood glucose in healthy adults without diabetes are a problem.

In fact, the limited data we do have about glucose patterns in healthy, non-diabetic adults show that glucose spikes outside of the ‘normal range’ (4-7.8mmol/l) are quite common.

In one study of 80 adults without diabetes, 93% of participants reached a glucose level above this normal range. Other studies have shown similar findings. This suggests it’s normal for healthy people without diabetes or prediabetes to spend brief periods of the day with glucose levels above 7.8mmol/l.

Has gut health got anything to do with glucose?

Research suggests the gut microbiome plays a role in how your body regulates blood glucose. For example some types of gut microbes have been linked with better insulin sensitivity. This could be because compounds (known as short chain fatty acids or SCFA) produced when some microbes break down dietary fibre can influence how the body responds to insulin.

To keep your gut bugs healthy and happy and churning out SCFA, it's important to eat plenty of fibre rich foods. That means plenty of fruits, veggies, wholegrains, nuts, seeds, beans, peas and lentils. Incidentally, eating plenty of fibre has loads of benefits for your gut health and overall health - promoting a diverse microbiome and reducing the risk of bowel cancer, heart disease and type 2 diabetes. Foods which are high in fibre also slow down the release of glucose.

Given the benefits of a high fibre diet is something we do have strong and consistent evidence for, my advice is to focus on a plant forward diet with plenty of fibre rather than worrying over normal glucose responses. These simple tips or these lovely recipes are a good place to start.

Want to read more from our Fact v Fiction series with Laura Tilt? Dig into Fact v Fiction: The Baking Soda Burp Test


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