According to TikTok, freezing your bread makes it healthier.

Theres a grain of truth to the idea, but the people promoting it are missing some big caveats.

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 isnt just one throw in of starch: there are many.

We cant always break them down in our stomach or small intestine.

(This also arguably makes resistant starch a punch in 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 becomesgelatinized.

After cooling, it can becomeretrograded.

Frozen bread isn’t the only food that contains resistant starch.

What is the glycemic index?

To be clear, this isnt a test of people eating sandwiches or dinners or breakfasts.

Thats where knowing the glycemic index of different foods can help.

Brown rice has a lower glycemic index than white rice, for example.

So what are the TikTokers missing?

A couple big things, it turns out.

The researchers also tested store-bought bread, and found that freezing it didnt significantly change its glycemic index.

Toasting it did reduce the glycemic index by about 18%, though.

Those additives might be preventing the formation of resistant starch as a side effect.

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.

If you cant fully digest it, youre getting fewer calories out of it, right?

Thats technically true, but its not likely to make much of a difference.

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 youre saving less than one calorie if these numbers are representative.

For example,heres an international table of glycemic index values.

Relative to pure glucose, a French baguette has a glycemic index of 95.

But a French baguettewith chocolate spreadhas a glycemic index of 72.

Thats a much bigger difference than a few granules of resistant starch.