According to TikTok, freezing your bread makes it healthier. I’m told by various creators on the platform that “something great happens when you freeze your bread,” that “diabetics should freeze their bread,” and even that freezing your bread makes it “keto friendly.” There’s a grain of truth to the idea, but the people promoting it are missing some big caveats.
What the TikToks say
According to several health-focused TikTokers:
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Freezing your bread changes the structure of the starch in the bread (true) .
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This in turn reduces the glycemic index of the bread by 31%, or 39% if you also toast it (true for homemade bread but not store-bought, according to one study).
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A lower glycemic index is considered to be better for people with diabetes (true but not the whole picture).
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Therefore, freezing bread lowers your risk of metabolic disorders (potentially sort of true but not really supported by existing literature) or prevents you from gaining fat (not supported at all).
Different TikTokers each have their own take on why freezing bread is good for you: some focus on blood sugar management for diabetes, some on weight loss, and so on. The guy claiming that freezing bread makes it “keto friendly” made me chuckle, because it’s still bread and still mostly made of starch, whether you freeze it or not.
What is resistant starch, anyway?
The main macronutrients in our diet are carbohydrates (carbs), fats, and protein. The category of carbs includes sugars, starches, and fiber. Starch is the main component in the foods you think of as carbs. White bread, potatoes, and white rice, to name a few, are mostly made of starch.
Starch is made up of chains of glucose, and glucose is a sugar. It breaks down pretty quickly into glucose when we eat it. But there isn’t just one type of starch: there are many. And some of those starches are called “resistant starches” because they take a little longer for our body to digest. We can’t always break them down in our stomach or small intestine. Instead, we have to wait for the bacteria in our large intestine to break them down and produce nutrients we can absorb. (This also arguably makes resistant starch a type of fiber, and a prebiotic.)
So where does freezing come in? Well, when starch is cooked in the presence of water, it changes shape and becomes gelatinized. After cooling, it can become retrograded. This retrograded starch doesn’t have the same structure as the original starch, and it’s considered to be resistant to digestion (making it, specifically, resistant starch type 3).
Frozen bread isn’t the only food that contains resistant starch. Cooking and cooling rice or potatoes can produce it as well; many starch-containing foods also have some resistant starch naturally.
What is the glycemic index?
The TikTokers often focus on the effect that resistant starch can have on your blood sugar, and they’ll point to studies that measure the glycemic index.
The glycemic index is a number that scientists can give a food based on how much it spikes people’s blood sugar when they eat a small portion of just that food. To be clear, this isn’t a test of people eating sandwiches or dinners or breakfasts. Instead, they’ll eat (for example) 50 grams of bread, and their blood glucose measurements will be compared to the blood glucose measurements when someone was given 50 grams of a reference material (either pure glucose, or sometimes they’ll use white bread as the reference food).
If you’re interested in keeping your blood sugar at a more even level, as many people are if they have diabetes or other blood sugar issues, you may want to avoid big spikes of blood glucose. That’s where knowing the glycemic index of different foods can help. Brown rice has a lower glycemic index than white rice, for example.
There are, indeed, studies showing that resistant starch can reduce the glycemic index of a food, and there are studies showing that freezing bread can increase the level of resistant starch in the bread. So what are the TikTokers missing? A couple big things, it turns out.
This may not even happen in store-bought bread
The biggest caveat on the advice in the TikToks is that the study they all quote, the one that found freezing bread reduces its glycemic index by 31%, only found that reduction in homemade bread.
The researchers also tested store-bought bread, and found that freezing it didn’t significantly change its glycemic index. Toasting it did reduce the glycemic index by about 18%, though.
Those researchers speculate that the lack of an effect for store-bought bread is due to dough conditioners and improvers, additives that are used in factory-produced bread to help them mix better and keep from going stale. Those additives might be preventing the formation of resistant starch as a side effect. That said, they only tested one homemade recipe and one type of store-bought bread, so there could be other differences due to the type of flour or other factors.
The TikTokers promoting this hack aren’t specifying that it’s for homemade bread. Often they talking about freezing while they point to a loaf of bread that looks store-bought.
The difference is still very small
Sometimes freezing your bread is recommended as a way of reducing the calories in the bread. If you can’t fully digest it, you’re getting fewer calories out of it, right? That’s technically true, but it’s not likely to make much of a difference.
In this study, for example, resistant starch made up 1.1% of the dry weight of fresh rolls, and 1.3 to 1.6% of the dry weight of frozen rolls. In a typical slice of white bread, that would correspond to a difference of 0.1 gram of carbohydrate. Carbs are generally understood to contain 4 calories per gram. So you’re saving less than one calorie if these numbers are representative.
There are better ways to manipulate glycemic index
Remember when I mentioned, above, that the glycemic index is calculated in a lab scenario, not in actual meals? If your goal is to cause less of a blood sugar spike, you’re better off thinking about what you’re having your bread with than whether the bread itself was frozen or not.
For example, here’s an international table of glycemic index values. Relative to pure glucose, a French baguette has a glycemic index of 95. But a French baguette with chocolate spread has a glycemic index of 72. In other words, you can reduce the glycemic index of bread by 25% just by adding chocolate spread!
I say this not to seriously argue that chocolate spread makes bread healthier, but to point out that lowering the glycemic index doesn’t automatically make a thing healthier or better for you. And if your goal is, specifically, to lower the glycemic index of a food, then you can do that by adding other foods to the meal. Bread with butter, for example, would be expected to spike your blood glucose less than bread alone or bread with jam.
To take an even bigger-picture perspective on this, I’ve often said that when you’re comparing two very similar things (like which vegetables are healthiest) you owe it to yourself to step back and ask if there’s a bigger choice worth paying attention to. Are you eating that bread as part of a PB&J, or a grilled chicken sandwich with vegetables? That’s a much bigger difference than a few granules of resistant starch.
