A lot of people are starting to worry about how glucose spikes might impact their health, as this has been a popular topic on social media. Let’s take an evidence-based look at this.

What are glucose spikes?

A glucose or blood sugar spike occurs when there is a fast temporary rise in blood glucose levels after eating.

When we eat foods containing carbohydrates, such as bread, pasta, rice or potatoes, our body breaks down the carbs into sugar molecules called glucose. These glucose molecules are then released into the bloodstream, causing our blood sugar levels to rise. This triggers the pancreas to release insulin, a hormone that helps the body use and store glucose for energy.

This is a completely normal physiological response that can happen for a number of other reasons too, such as (1, 2, 3, 4):  

• Consuming fat, protein or caffeine (so not just carbs!)

• Stress 

• Dehydratration

• Illness, injury or sunburn

• Certain types of high intensity exercise 

• Hormonal changes across the menstrual cycle 

• As a side effect of certain medication like steroids

Which foods cause glucose spikes?

Although foods that contain protein, fat or carbs can all contribute to glucose spikes, it’s carbs that have the biggest impact.

Glycemic index (GI) is a measure of how quickly foods containing carbohydrates raise our blood sugar levels. Foods with a high GI score (70 or above) are digested quickly and cause a rapid increase in blood sugar levels, while foods with a low GI score (55 or below) are digested more slowly and cause a more gradual increase in blood sugar levels.

Examples of high GI foods: 

• Sugary food and drinks

• White bread

• White rice

• Potatoes

Examples of low and medium GI foods:

• Meat, chicken, fish and eggs

• Dairy (unflavoured/unsweetened) 

• Non-starchy vegetables like broccoli, spinach, cauliflower, aubergine (etc.)

• Most fruit 

• Oats

• Pasta (white or wholemeal)

• Basmati rice

• Beans, peas and lentils

But focusing on GI alone isn’t recommended, as this doesn’t tell us how nutritious a food is  and blood glucose response is influenced by so many factors (3, 5, 6):   

• Cooking methods

• How ripe a food is

• The amount and combination of food consumed 

• Individual genes and physiology — two different people can respond very differently to the same meal or situation

• The time of day — tends to be most efficient in the morning 

• Health conditions like diabetes and PCOS

• Meal pattern e.g. skipping breakfast may increase glucose spikes later in the day

• How well rested your are

Food choices can also help with lowering glucose spikes. For examples, adding foods that contain fibre, fat and protein to those containing higher GI carbs, slows down absorption of carbs which leads to less of a glucose spike (5). This is also a nutritious and balanced way of putting meals and snacks together.

Should you worry about glucose spikes?

As already highlighted in this article, an increase in blood glucose levels is an entirely normal physiological response. This means that your body is functioning and digesting carbs to be used as energy, and can happen for a number of other reasons as well.

However, if glucose spikes are very frequent or remain high for long periods of time this can damage blood vessels and other tissues, increasing the risk of complications to the eyes, heart, kidneys and nerves (7).

But this is most likely to occur in those who have conditions like diabetes or insulin resistance, when glucose spikes can occur more frequently and be more severe. Symptoms of chronically high blood glucose levels would also be present — like peeing a lot, extreme thirst and fatigue, blurry vision or losing weight.

It’s important to mention that the opposite extreme, low blood glucose levels, is also a problem as this can lead to issues such as confusion, drowsiness, blurred vision, slurred speech and in more extreme cases, seizures, coma or even death (8). Again, this is most likely to occur where there is a medical issue with controlling blood glucose levels such as diabetes.

So it’s clear that monitoring and managing blood glucose levels is important when it comes to diabetes, but what about those who don’t have this medical condition?

Although this is becoming more popular, there is currently very little evidence to back this up and it isn’t routinely advised by health care professionals at the moment (9). The pros and cons need to be weighed up on an individual level, as although it may be useful for some people to learn how their blood glucose levels respond to certain foods or situations, or for spotting issues with insulin responses early, for others this could do more harm than good if it becomes obsessive and damaging to their relationship with food.

Overall, having some awareness of how food and lifestyle choices can help with keeping blood glucose levels stable can be helpful for health and maintaining stable energy levels. But unless you have a medical reason to do so, the recent trend of obsessing over managing glucose spikes may do more harm than good.

Top tips for supporting stable blood glucose levels:

• Eat regularly without big gaps in the day i.e. every 2-4 hours

• Consume balanced meals most of the time that contain: carbs, protein, fibre and fat (it’s normal and healthy to stray from this at times of course)

• Adding protein, fibre or fat to a high GI snack will reduce the glucose spike e.g. adding peanut butter to white toast

• Movement, stress management and sleep all help with maintaining healthy glucose levels

• Attend medical appointments and check-ups and speak with your doctor if you are worried about possible high or low blood glucose levels