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What spikes your blood glucose?

And why knowing about it is important for good health.

Samarth Bansal
5 min read • 
15 October 2022

I love pizza. But I hate how often it’s called “unhealthy”. Huh.

These labels don’t fly with me. It’s all about what’s in there: good food has good ingredients — the central tenet of TBT’s food philosophy.

Take, for example, these two:

Pizza A: whole wheat base, veggies-loaded, homemade sauce (with no added sugar), and fresh, flavourful cheese.

Pizza B: refined flour base, no toppings, store-bought sauce (with hidden sugars?), four types of cheese.

From a nutritional standpoint alone, which one is superior? Pizza A. (You may have guessed it.)

Why exactly, though? What happens when you eat these two pizzas? What’s the difference?

I’ll focus on one basic thing: how the food (especially carbs) we eat affects blood glucose levels. (Also called blood sugar, the same thing.)

It matters. Glucose is our body’s primary energy source and needs tight regulation for metabolism to function efficiently. So keeping glucose levels in a healthy range is crucial for metabolic health. It improves our energy levels, avoids fatigue, and reduces susceptibility to chronic diseases.

And we have the agency to control it. Dietary choices (Pizza A vs Pizza B) is one key factor, among others like physical activity, stress level and sleep.

Let’s start with the basics. Four things you must know.

One, carbs come in three forms: sugar, starches, and fibre. Eating or drinking food with carbs breaks down the first two (sugar and starches) into a simple sugar called glucose. Fibre gets through the body undigested.

Two, glucose is the primary energy source for our body cells: it enters our bloodstream after eating. It can be processed right away to form energy. What remains is stored in muscle and liver as glycogen or triglycerides.

Third, two hormones regulate blood glucose levels: insulin tells cells to absorb glucose (so it goes from the blood into the cell body), and glucagon releases the stored ones in the liver when blood glucose levels are low. The two work in tandem so the body remains fueled.

Fourth, all foods are not the same: the critical difference is how quickly the body digests the food and the speed at which glucose enters the bloodstream.

For example, the whole-wheat base in Pizza A is superior from a nutritional standpoint because the ‘whole’ refers to ‘complex carbs’, the ones with a complex cell structure, so the body needs to do more work to break them down.

The longer it takes for food to digest, the slower it is absorbed in the bloodstream. So blood sugar rises slowly and steadily. It provides sustained energy and helps us feel fuller for longer.

It’s not the same for refined flour or maida. It’s digested quickly, and glucose rushes into the bloodstream. Sugar levels spike instantly. And a crash follows the sugar spikes.

You ideally don’t want this: in the short-term, this cycle of spikes and crashes can leave you feeling lousy and trigger hunger. Felt the mid-afternoon slump after a heavy carb-rich lunch? That’s what it is. In the long run, it can lead to type-2 diabetes.

Let’s sum this up: eat foods that keep glucose levels stable. We don’t want big and frequent spikes and crashes. Avoid refined carbs (like maida, which are anyway stripped of most nutrients, vitamins, minerals and fibre) and eat more complex carbs (whole grains).

Now look, it’s not that one spike will kill you. The problem occurs when our body is taxed with too much glucose over a long period.

Say you eat doughnuts for breakfast, jalebi-rabri for lunch, and carrot cake for dinner. Boom. Sugar bomb. Too much for the day. You will have elevated glucose levels throughout the day. The regulatory balance is disturbed. Do it one day, acceptable.

But say if that’s all you eat daily, then the chances of having chronically elevated blood sugar levels are high. And that can lead to long-term health problems. Three reasons.

One, excess glucose levels lead to higher insulin levels: Remember insulin — the hormone tells our cells to absorb glucose from the bloodstream? It’s a saviour. It saves us from high levels of circulating glucose.

When glucose levels are high, the pancreas secretes more insulin to keep glucose in control. So you don’t just get the sugar spike. You also get the insulin spike. You don’t want that.

Two, insulin resistance: if sugar levels remain high over a long period and the pancreas continuously secretes insulin, it can numb our cells to the hormone’s effect. It becomes less effective, meaning more insulin is needed to do the same amount of work, so more release of insulin to keep glucose in check. This increases the risk of diabetes.

Third, build up to diabetes: If the body has become so insulin resistant that blood sugar remains dangerously high, you need to inject insulin to control glucose levels. That’s type-2 diabetes.

Fourth, excess glucose can affect weight loss: too much glucose in the bloodstream means the body doesn’t break the stored fat for energy. So if you are facing stubborn fat loss issues, insulin may be high and blocking that pathway.

In short, excess glucose leads to more insulin which leads to insulin resistance which leads to diabetes (and other diseases).

This is why Pizza A’s ingredients are better. Not only because of the crust but also because the sauce has no sugar (or hidden sugar, so common in store-bought processed food), and pizza is loaded with veggies, which means more fibre, so more time to digest, and a lower spike.

But how are we supposed to know which food spikes blood sugar and which doesn’t?

We have a way. Look at the glycemic index (GI) chart.

Glycemic Index

GI gives a rough estimate of a food’s predicted glucose impact. It measures how fast a food item raises the average blood sugar levels after eating. It goes from 0 to 100, and a higher GI will lead to higher spikes.

The formula is simple: the higher the GI, the higher your blood sugar, and the higher your insulin. So you want to avoid high GI food, especially if GI replacements are available.

Foods with GI between 0 and 55 are classified as low-level, between 56 and 75 are medium-level and above that are high-level GI foods. Spend some time with the GI table here, here and here.

Two examples from my personal experience:

1) Oats: I swapped instant oats (GI 83) and rolled oats (GI 55) to eating steel-cut oats (GI 42) — whole grain, the least-processed version of oat groats. It works: my morning oatmeal (steel-cut oats with milk mixed with dried cranberries, walnuts and dry chia seeds) is a great breakfast.

I had already abandoned cornflakes long ago — which many may think is a ‘healthy’ breakfast — because its GI value is north of 80. Too high.

2) Whole grains: My kitchen mostly has whole grains. I eat red rice (GI 55) instead of white (GI 70) and whole wheat pasta (GI 40) instead of the regular one (GI 50).

Again, that does not mean you should altogether avoid high-GI foods. The point is that eating more foods with lower GI in your overall diet is better for long-term health as it keeps sugar levels stable.

Related on Truth Be Told:

Should you count calories?

Few things hacks can do to keep sugar levels stable, apart from eating low-GI foods.

One, food pairing: Don’t eat naked carbs. Pair them with protein and fat. It leads to a lower spike. That’s why I eat my mid-morning fruit snack (mostly apple or banana) with peanut butter which has a good amount of fat and protein.

Two, eating protein and fat before a high-carb meal: this is another hack for a lower spike post your meal. For example, say two eggs before your potato sandwich.

Third, look for hidden sugars in processed foods: “Added sugar” is hiding in 74% of packaged foods, but it’s harder to spot given its 60+ alternative names. Some, like maltodextrin, have a higher GI (ranging from 106 to 136) than regular table sugar’s GI value of 65. Yikes. Avoid it.

Fourth, take a short walk after every meal: It works wonders to stabilise blood sugar. Muscles get actively engaged in walking and use excess glucose found in the bloodstream, lowering the spike. Do it.

It took me some time to convert these tips into habits. But now that we know how these simple enough changes can improve long-term health, the switch is worth it. That’s the key point of today’s article: account for blood sugar response as a factor in my dietary choices.

And just to be sure. I am not giving up on Pizza B forever.

As I explained in a previous article: Dieting creates mental conditions that make it hard to diet. Cravings only increase if I deprive myself of the food I enjoy eating. My strategy is balance and moderation.

So I follow the 80-20 rule. That is 80% of calories from more nutritious food and 20% from less nutritious food.

Pizza B is not poison. In most cases, I don’t know — and sometimes, I don’t even want to know — each ingredient when hanging out with friends at, say, at Leo’s Pizzeria in New Delhi. That’s my 20% time. If they give me an option, I choose the whole wheat crust. If not, fine.

Don’t obsess over every meal. It’s all about what you are eating in most of your meals.

Eat what’s right for you

I want to end with one last point that complicates the narrative. Our bodies are not the same. We respond differently to different foods. So the same meal can boost my metabolism and hinder yours.

Remember, GI values are average — and averages hide the variability in the underlying data. It doesn’t capture how different people may respond to the same food. So you can get a big spike from low-GI food. It’s possible. (Life would be much better had our bodies been simple machines.)

That’s the idea behind personalised nutrition: Eat what’s right for you.

And we now have technology that can help us find that out. One way is through a continuous glucose monitor, a topic we will cover in a future article.

That’s it for today. I hope you are enjoying this series on long-term fitness. Next week, we will take a break from the series and publish a story on how to make everyday cooking healthier. It’d be fun.

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