📈 Should you get a continuous glucose monitor if not diabetic?

Continuous glucose monitors (CGM) are increasingly being used to assess blood sugar responses to foods in people without diabetes.

Their popularity in the UK has been driven by the greater focus on controlling ‘sugar spikes’ and by ‘personalised nutrition’ companies, like ZOE.

But, is it worth to track your blood sugar levels using a CGM if not diabetic?

A new study compared the blood sugar responses to different types of fruits obtained from CGM versus blood samples.

Overall, using CGMs to track blood sugar levels in non diabetics can give misleading results and create unnecessary stress.

In detail, tracking blood sugar with a CGM:

• Overestimated the glycaemic index of a smoothie by 30% compared with the gold standard finger prick method

• Misclassified whole fruit as medium or high glycaemic index when it was actually low glycaemic index

• Overestimated how long blood sugar levels were above the healthy limit of 7.8mmol/L by a whopping 400%, causing unnecessary worry about 'sugar spikes'.

🥊 Punchline

CGM overestimated blood sugar responses in numerous contexts and can mischaracterise the glycaemic index of foods.

🍝 Is pasta better than bread at preventing sugar spikes?

Previous research discovered that eating pasta led to a similar blood sugar response as eating bread, despite pasta has a lower glycaemic index.

So, is the argument of slow vs fast acting carbs a fad?

In a follow-up study, people were randomly allocated to eat pasta or bread together with ‘chemically-labelled’ sugar to be able to track and understand what happens to sugar once ingested.

They found that eating pasta led to:

• A slower sugar absorption from the gut (as expected because of the lower glycaemic index of pasta versus bread)

• A lower rate of sugar clearance from the blood into the cells

• A lower concentration of insulin in the blood

This means that eating a food with slow acting carbs doesn’t necessarily translate into a lower ‘sugar spike’ because slow absorption of sugar means slower insulin concentration, and therefore a slower rate of sugar clearance from the blood.

However, pasta and bread are similar starchy foods. Both are processed to strip out most of the fibre and other nutrients. Future studies should focus on comparing bread or pasta with unprocessed wholegrains, like pearl barley.

🥊 Punchline

Eating pasta rather than bread to lower blood ‘sugar spikes’ is not an effective strategy because both foods caused the same response in blood sugar level given the slower rate of sugar clearance from the blood after eating pasta.

🩸Is the HbA1c a more reliable indicator of blood sugar levels?

You may have seen HbA1c in your blood report. But what does it mean?

HbA1c is not just a number. Think of it as a timeline of how much sugar has been sticking to red blood cells for months. This process - called glycation - makes blood cells “sticky” and therefore more likely to damage arteries and other tissues.

The higher the HbA1c, the faster the body is ageing from the inside out.

The optimal HbA1c range is 4.5-5.3% (as a percentage of red blood cells being glycated).

However, emerging evidence is slowly revealing that HbA1c is not a bulletproof marker for those on low-carb high-fat diets, such as ketogenic diets and carnivore diet.

This is because red blood cells tend to live longer than expected when on a low carb diet, thereby collecting more glycation damage over longer time, often leading to a higher HbA1c.

Furthermore, the HbA1c can also vary based on red blood cell count and mean corpuscular volume. RBC and MCV. If a person has higher red blood cell count than expected or larger mean corpuscular volume (and vice versa), the HbA1c value is less likely to be accurate.

And lastly, someone can totally trick their HbA1c levels by donating blood before the blood test.

🥊 Punchline

HbA1c is a good indicator of how well controlled is your blood sugar because it measures your average blood sugar levels over the past 2-3 months. However, this may not be an accurate estimation of blood sugar levels in those on low-carb, high-fat diets.