Oh no. Jasmine rice has a high glycemic index? I’m going to get diabetes! Ahh!!
This is a typical conversation by the confused. My mission is to de-confuse myself first and foremost, and share the knowledge with you, for a better world, so here we go.
Long story short, the glycemic index is useless and misunderstood.
Since most people think weight loss is universally healthy, and most of our discussions even in academic circles and institutions fallaciously partners weight loss with greater health, we have learned to think that lower GIs are better. Foods with lower GIs will spike your blood sugar less!
This type of black-and-white thinking persists despite the fact that so many people have already debunked this issue and attempted to de-confuse the world about this. Glycemic load matters too. The total amount of food you eat matters, and the quality of carbohydrate matters. Let’s break this post down to better understand the value of glycemic index, it’s limitations, and how we can best move forward with this information.
1. What is the Glycemic Index?
The glycemic index is a ratio between how much a particular food (the test food) increases your blood sugar compared to pure glucose (the reference food). The increase in blood glucose after eating something is termed the glycemic response. After eating say, bread, we’d expect blood glucose to go up for about 2 hours before coming back down to where it was. The total elevation in glucose over the two-hour period is the glycemic response. The same person’s response to pure glucose is measured on a separate day, and the ratio between the test food and pure glucose, the reference, is calculated.
2. How is it Measured?
The glycemic index is measured in the form of a small clinical trial, where about ten participants show up to the lab on multiple occasions, in a fasted state, and eat enough of the reference food to supply 50 grams of carbohydrate from that food alone. Their blood glucose is measured at these intervals: 15, 30, 45, 60, 90, and 120 minutes. This data is plotted on a graph, like the one I drew below. On a separate day, they show up to the lab again and drink 50g of a glucose solution, and their blood is sampled at the same intervals. Each person’s response to the test food and reference food is calculated as an area under the curve (second photo) and the ratio between the two is the glycemic index for that individual person.
The glycemic indices for all ten-ish people are averaged and the value is now dubbed the glycemic index of that food. That’s what you see in the graphs above, hence the error bars on the graph. The error bars represent the variation in responses to the foods.
Limitations of the Glycemic Index
There are many problems with relying on the glycemic index to understand what’s healthy. Although whoever first thought of it didn’t anticipate these problems, most of these problems are due to the pitfalls of the human mind.
Reductionism is something I talk about a lot because from my near-decade of experience in nutrition and health now I’ve seen it lead so many people astray. Although academics are less prone to this, the general public, when focusing on a measure like glycemic index, may get the wrong idea about a food. The glycemic index has a very specific purpose, and it is to determine the extent at which a food increases blood glucose. From this measurement is has been speculated that eating foods with a high glycemic index is bad for us. But the amount you eat makes a huge difference.
2. We eat mixed meals
We don’t often just eat single foods by themselves. We eat them with other things, and this will lower the glycemic response, as fat and protein will tend to do that.
Thinking too much about glycemic index promotes a fear of insulin, a very important hormone in the body. If you are diabetic, sure, you need to address this issue. If you are not, stop being afraid of insulin. There are many health leaders promoting fear over insulin lately, and the fact is that eating carbohydrates does not lead to chronically elevated insulin levels, as seen in metabolic syndrome. That is caused by weight gain and inflammation. Thus, you can be on a zero carb diet and get diabetes.
4. Glycemic Load
Glycemic load is calculated by multiplying the amount of carbohydrate eaten by the glycemic index of the food. This gets complicated when you factor in single meals. But say for example, when you compare brown basmati rice, which is estimated to have a GI of 75, to white basmati rice, which has a GI around 50, it seems like brown basmati rice is worse for diabetics. But from personal experience, I know that I can’t eat much brown rice because it’s bland and chewy. White rice picks up more flavors from the curry gravy so I eat more of it. Implications? I get more nutrition into my body, which is especially useful for exercise recovery. But if I was overweight and diabetic for several years, I’d choose brown rice because I’d eat less of it than white rice.
Since most nutrition science is published in journals based out of Western countries, spices aren’t talked about a lot. In fact there are zero retrospective cohort studies attempting to tease out the effect of spice consumption on health. There is just one on chili consumption but let’s not be confused here; chilis and spices are different things. Spices aren’t always spicy. Cardamom for example is not spicy, but it is a spice, and it is used along with several other spices in Asian cooking. Asians eat a lot of white rice, but they also eat a lot of spices with it, and this type of complex interaction is rarely considered in nutrition science. Which is why I talk about why we should stop relying on it to determine what’s on our plate, in my upcoming book (which you can get for free by giving me your email–don’t worry I won’t sell it to anyone).
6. The term itself is misleading
The fact is there is no glycemic index for a food, because the response of an individual to food depends on many factors, like ethnicity, microbiome, and other aspects of their health. It’s crazy in retrospect to think that I used to look up the glycemic index of a food, and think it was a fixed number, when in fact it varies in individuals. It’s an estimate at the end of the day, based on a small trial with just ten people usually. Just consider the implications of that. Although ten people is enough to approximate how it will affect your health, many of us have been mislead thinking that a tool that was designed for research purposes could actually inform our eating decisions.
To conclude, I will say that the glycemic index is a useful tool in determining how a food increases your blood glucose. If we get too fascinated with it however, we will make wrong decisions regarding our health. Dates and watermelon for instance have high glycemic indices. Should we avoid eating them for that reason alone? There are so many other nutrients in those fruits that can help improve our health in other ways.
And perhaps, foods with high glycemic indices have a benefit: they can help us use glucose when we really need it, like when we’re famished. And that’s why white rice, not brown rice, has helped our species survive through famines in the past: it’s a palatable form of starch that gives us energy. Simple.
- Brouns F, Bjorck I, Frayn KN, et al. Glycaemic index methodology. Nutr Res Rev. 2005;18(1):145. doi:10.1079/NRR2005100.
- Osman NMH, Mohd-Yusof B-N, Ismail A. Estimating Glycemic Index of Rice-Based Mixed Meals by Using Predicted and Adjusted Formulae. Rice Sci. 2017;24(5):274-282. doi:10.1016/J.RSCI.2017.06.001.