How chopping your veg changes its nutritional content

If you’re trying to eat healthily, vegetables are a no brainer. But did you know that how you prepare your veg could affect the nutrients you get from them?

Cook first, then cut

Most of us peel, chop, slice, dice, and even julienne our vegetables without a second thought about to how it affects them beyond how they look and taste. But vegetables are made up of cells just like any other plant, and cutting can open up those cells and disturb what lies inside.

Carrots, for example, contain a group of chemicals known as polyacetylenes. One of those chemicals is called falcarinol, and, in a study on rats, has been linked with a reduction in cancer risk. It’s too early to say whether falcarinol has any benefit to humans.¹

To see how polyacetylenes like falcarinol were affected by different preparation methods, researchers cut carrots into disks, batons, or left them whole during cooking. They found that carrots left whole, retained the most polyacetylenes.² This is likely because the surface area of the chopped veg is larger, allowing more nutrients to leach out during the cooking process.

So, if falcarinol and related chemicals do have an anti-cancer effect in humans, cooking your carrots before cutting them would be the way to make the most of that.

Cutting vs shredding: boosting antioxidant properties

Cutting some vegetables can increase their levels of a group of potentially beneficial chemicals known as polyphenols. Polyphenols aren’t nutrients in the same way that vitamins are, but they are abundant in most plant-based foods, including things like coffee, red wine, and tea.³

Polyphenols may have beneficial health effects through their antioxidant properties, meaning they can protect your cells from damage by stopping reactions with oxygen— although the science on that is not yet settled.⁴

To investigate how cutting food affects polyphenols, researchers looked at what happens to different vegetables – courgettes, white and red cabbage, iceberg lettuce, celery, carrot, parsnips, radish, sweet potatoes and potatoes – when they were “wounded” by cutting them with a knife, then shredding them in a food processor. Parsnips, lettuce, and celery all saw boosted polyphenol levels when they were shredded.⁵

So maybe next time you’re thinking about a nice recipe, think of how to include these shredded veggies to get the most polyphenol out of them!

Chopping & why your food goes brown

Another thing to bear in mind is that cutting fruit and veg open exposes the insides to oxygen. Have you ever noticed that cut apples go brown quickly? That’s because of a process called enzymatic browning.⁶

Enzymes in the apples react with oxygen and compounds known as tannins, a type of polyphenol. This chain of events leads to the production of melanin – the same pigment that colours our skin and hair – making the exposed inside of the apple brown. At the same time, oxidisation causes the loss of some Vitamin C from the apples, too.⁶

It’s not just apples that suffer this fate. Other fruits like pears, grapes, and avocados, and vegetables like potatoes and lettuce, undergo enzymatic browning.⁷

Chop then refrigerate

Polyphenols from all kinds of fruit and veg are lost through oxidisation after they’re chopped. Storing your vegetables in the fridge will slow down the process (though not stop it entirely).

On the other hand, you might not want those polyphenols in the first place. Polyphenols actually have a slightly bitter taste, which can be detected by some people even in small quantities.⁸

In that case, tearing rather than chopping might be a good tactic. Recipes will often call for you to tear herbs like basil, for example. Why? Because it’s been widely considered by chefs that tearing the leaves damages the cells less than cutting through them with a knife does. This might seem counterintuitive but tearing causes less damage because it runs down the edges of the plant’s cells rather than across or through them.

Use a ceramic knife instead

Speaking of knives, there is one-way food tech that might be able to help in the fight against browning fruits and vegetables: the ceramic knife.

Lots of metal knives contain iron or copper, which can speed up the enzymatic browning reaction. So, if you switch to a chemically unreactive ceramic or plastic knife you can actually slow down the process of browning slightly. Having a sharp knife also helps reduce the damage to the vegetable’s tissues by cutting through fewer cells.⁹
 

The main thing, though, is to make sure you eat enough vegetables in the first place. If that means dicing and slicing them, even with a metal knife, to make them palatable, go for it.

All of the changes that come about from different preparation methods pale in comparison to the extra vitamins, minerals, and other nutrients you get when you add an extra vegetable or two to your dinner.