The glycemic index: debunked!

Apples have a very low glycemic index (GI) of 35, whereas a gluten free white bread has a GI of 95.

Therefore, white bread is more likely to raise blood sugar than an apple. Apples are awesome and white bread is an absolute no go, right?

WRONG. At least partially.

Science/media/whoever fooled us again. (And another great opportunity for a diet concept that can be marketed and made money with.)

High blood sugar and insulin are linked to diabetes, obesity and metabolic syndrome, which are skyrocketing in the western world. So it is true that we should minimize foods that cause high blood sugar.

GIs are determined by giving several people a certain food and measuring their blood sugar (response) after a certain time. Then, the average is taken, converted into a GI number and then declared as the GI of the food tested.

However, the blood sugar responses that people experience are highly individual and therefore, the average taken does not have any significance!

Furthermore, it is very difficult to exactly determine "THE ONE TRUE" GI of a certain food, even in a certain person. Because the person is "not always the same". Maybe has not slept enough, is stressed, has just eaten something else, or (quite likely) did not have the food in isolation, just to name a few.

There are soooooo many factors that influence blood sugar response that the exact GI can vary from time to time, even in the same person.

However, it is true that some foods cause a higher blood sugar response, i.e. have a higher GI than others. But this GI cannot be generalized! It is in fact highly individual. This is very, very important.

A study called the Personalized Nutrition Project (www.personalnutrition.org) revealed exactly what I just described. Dr. Segal, a major conductor of the study, said: "We chose to focus on blood sugar because elevated levels are a major risk factor for diabetes, obesity and metabolic syndrome. The huge differences that we found in the rise of blood sugar levels among different people who consumed identical meals highlights why personalized eating choices are more likely to help people stay healthy than universal dietary advice."

The study was very well done. It followed 800 (!) people for one week. The participants had to record everything they ate as well as lifestyle factors such as sleep and physical activity. In total, about 46 000 different meals were assessed for their responses.

The scientists collected all the blood sugar data and developed an algorithm that predicts the individualized response to a food/meal. In a follow up study, this algorithm was successfully applied! 

Also cool is that the scientists were able to show that lifestyle does indeed have an impact on ones' blood sugar response. The same food affected blood sugar levels differently in the same person, depending, for example, on the sleep they got.

The picture below is an example taken from the study.

The brown line shows the blood sugar response caused by a banana, the blue one the response a cookie evoked. As you can see, the response of participant 445 was almost the opposite of  the one of participant 644! The cookie had basically NO impact at all on the blood sugar of 445! But the banana, OMG, see this hill it created in the graph? Crazy!!!

I hope I am like participant 445 ;P

First take away: The general GI numbers are useless! Don't spend too much money on GI books.

I don't want you to totally throw the principle of the GI overboard though!!! Keep in mind that certain foods do cause higher blood sugar responses and when you constantly eat too much of such foods, it is probably not very good for you in the long term. In the short term, you might get sleepy or be hungry again soon. These are indicators that the meal you just consumed spiked your blood sugar, which then fell very low after approximately 1.5h to 2h (you can see this very well in the two diagrams above), and that's what makes you sleepy or hungry.

Your body tells you which foods have a high GI for YOU! Listen to your body, it is pretty intelligent^^

Whenever someone tells you to not eat this cookie because of its high GI, ignore them, enlighten them, slap them in the face, whatever... They are wrong, or they don't know better, respectively.

YOU must know YOUR own blood sugar responses in order to tell it's GI true for YOU! The generalized numbers might be wrong for your body. A banana might cause a higher response than a cookie, as we saw!

You only find out by testing it, preferably with a continuous blood glucose monitor. Or you listen to your body for hints ;P Also, with the developed algorithm it is now possible to literally calculate  and predict your response and therefore determine your "bad" and "good" foods!!! So cool!

Second take away: Your lifestyle matters! Get your sleep, relax, move, be happy J Because even though a cookie might be the better choice for you regarding its personalized GI effect, when you don't have your shit together you can worsen the response.

As I find this very fascinating, I plan to test myself and my responses to certain meals. When you know your GI numbers, you can improve on energy levels, cravings, inflammation, metabolic syndrome prevention, mood swings, longevity, simply a lot of things. Sadly, a continuous blood glucose monitor is very expensive, so I don't know when I will do it. But I will definitely do it!

Personalized food will emerge more and more, and I'm very excited about what the future will bring! Blood sugar responses will for sure play a big role in personalizing food, and you now know why :)