Most of us think blood sugar/glucose measurement is only for those that have diabetes. But there can be real value in measuring how our body deals with different foods. You can gain a lot of information by a simple finger prick blood test. Let’s look at what we can learn.
My own blood glucose monitoring began last year after the publication of a fascinating paper from Israel, entitled Personalized Nutrition by Prediction of Glycemic Responses. This graphical abstract summarizes the study.
The study included 800 people, who all ate identical meals for a week, with continuous monitoring of their glucose levels. The data came from 46, 898 meals!
What the study found was that there was a high variability in responses to identical meals. This goes against what we are led to believe – that certain foods will raise blood glucose levels in us all. All that glycemic index and glycemic load stuff…all the universal dietary recommendations that one size fits all…this study blew that apart.
The study researchers went on to examine all this data and devised a machine learning algorithm that could predict how individuals would respond to specific meals. The parameters they used to create this algorithm were blood parameters, dietary habits, anthropometrics (body size measurements), physical activity, and gut microbiota. All these played a role in the response to food and affected postprandial (after meal) glucose response (PPGR).
A sub-study checked this algorithm for accuracy on a further 100 people and found it worked well. Finally, they ran a blinded randomized controlled dietary intervention using the algorithm. Individual parameters were entered into the algorithm for each participant in order to determine personalized meals that would lower the PPGR. These meals were then tested on the participants to see their PPGR.
The results suggest that personalized diets can successfully be created that prevent high elevations in postprandial blood glucose and its metabolic consequences. They also show that many factors are involved in how our body deals with glucose in our diet – not just the food itself.
Overall, this was a very detailed, well-designed study. Let’s look at some of the findings more closely.
Study findings in more detail
The subjects, aged 18-70, in the study did NOT have a diagnosis of type II diabetes. Their blood glucose was measured every five minutes for a week through a continuous glucose monitor (phew, they didn’t have to prick their finger every five minutes!). 54% of the subjects were overweight (BMI>25kg/m2 ) and 22% were obese (BMI > 30 kg/m2). (Body mass index (BMI) is a measure of body fat based on weight and height.)
Here are some of the postprandial (after meal) glucose levels after specific meals:
Postprandial response to bread
The first graph shows the variation between the PPGR in four different participants after eating the same amount of bread. You can see that one participant had very little rise in blood glucose levels – max around 100 mg/dl, 40 minutes after eating. Compare that to the participant whose blood glucose rose to about 220mg/dl, at 80 minutes after eating.
The AUC is a measurement for the “area under the curve” so is a calculation of just how much rise in glucose levels happened over the whole time period. It’s amazing to see the variation that one participant had an AUC of only 15 after bread, while another had an AUC of 139 after the same food!
Postprandial response to glucose and bread
The second graph compares two participants who ate glucose alone and then bread alone to see which item caused the greater PPGR. In the top participant (468), glucose (red line) has a much greater effect. But in the bottom participant (663), the opposite is true.
Postprandial response to bananas and cookies
This third graph looks at the effect of a banana vs. a cookie on the PPGR of two participants. Like the glucose and bread graph, opposite effects are seen in these participants. For each of them, one of the foods hardly changed their blood glucose levels, while the other food led to large increases.
We’ve been led to believe that both bananas and cookies would cause blood sugar spikes if we ate them – but here we see that it is a very personal effect. Just like with the bread and glucose.
Why is this important?
In the US, it is estimated that 37% of the adult population have pre-diabetes and impaired glucose tolerance. Beyond the US, it seems that all over the world, our blood glucose levels just keep on increasing. This is leading to more diabetes and other diseases linked to poor glucose control, including:
- metabolic syndrome
- non-alcoholic fatty liver disease (NAFLD)
- cardiovascular disease
Unless we monitor our levels, we don’t know what they are and how they change with what we eat. We don’t know if we are increasing our risk of these diseases with our same breakfast every day. We don’t know if we are the person who can eat a banana and not get a glucose spike. Or if eating bread messes with our system. Fasting blood glucose levels and HbA1C results give us a snap shot picture. But they don’t tell us what effect our dietary intake is having on our levels throughout the day, nor what food choices prevent blood sugar spikes.
What should we be looking for?
It appears that a far more important number than both fasting blood glucose and HbA1c is the number of hours a day our blood sugar is elevated over the level known to cause complications.
The ADA (American Dietetic Association) states this level is 140mg/dL US units/ 7.7mmol/L UK units). Prolonged exposure to blood sugars above 140 mg/dL causes damage to the cells that produce insulin (beta cells), can cause nerve damage, and when levels rise above 160mg/dL, cancer rates increase.
However, while 140mg/dL is the upper level quoted for “normal”, this is based on the ‘average’ of the population. An optimal upper level is actually 120mg/dL for health and longevity.
We can’t continuously monitor our levels, but measuring them after meals gives us a lot of information. By monitoring our PPGR we can look at which foods tip us over this level, and then we can make appropriate changes. It personalizes the whole picture. One size does not fit all.
Next week we’ll look at how you can measure your blood glucose levels and what our goals are. We’ll also cover finding out which foods suit you and which lead to blood sugar/glucose spikes.