How does the heat treatment of vegetables affect the vitamin content?
Recently, one of my readers asked a question about how much baked bell pepper is rich in vitamin C or is it completely resolved by heat treatment. This question prompted me to prepare a more detailed answer to the question of the preservation of vitamins and other nutrients during the heat treatment of vegetables in the form of this article.
Indeed, different cooking methods change the nutrient composition of fruits and vegetables, but this is not always a bad thing. Some studies show that, although heat treatment of products may lead to degradation of some nutrients, the availability of others may increase.
Therefore, it is impossible to say that there is the "best" form of using plants, for example, raw.
Many people believe that raw vegetables contain more nutrients than cooked ones, but again, it depends on the type of nutrients. In one study conducted in Germany with 200 people who followed a diet based on raw foods, it was found that the levels of beta-carotene in their body were elevated, but the levels of lycopene in plasma were significantly lower than average. Probably due to the fact that fresh, raw tomatoes are indeed characterized by a lower content of lycopene than cooked or processed tomatoes. Heat treatment destroys the thick cell walls of many plants, releasing the nutrients stored in them.
Water-soluble vitamins such as vitamin C and B vitamins, as well as a group of nutrients called polyphenols, are most vulnerable when processing and cooking food. Canned peas and carrots lose 85 to 95 percent of their natural vitamin C. Another study showed that frozen cherries lose up to 50 percent of anthocyanins — nutrients contained in the dark pigment of fruits and vegetables. During the cooking process, about two-thirds of vitamin C is removed from fresh spinach.
Depending on the cooking method used, the loss of vitamin C in home cooking can range from 15 to 55 percent, according to a review by researchers from the University of California, Davis. Interestingly, vitamin C levels are often higher in frozen foods compared to fresh foods — this is probably because vitamin C dies during storage and transportation of fresh foods.
Fat-soluble vitamins such as A, D, E, and K, and antioxidant compounds called carotenoids, become more readily available after cooking and processing. An article in The Journal of Agriculture and Food Chemistry concluded that carrots, zucchini and broccoli are better cooked than steamed, fried or served raw. Least of all nutrients are preserved during frying.
But when it comes to cooking vegetables, you always need to look for compromises. It is possible to increase the availability of one nutrient while destroying another. For example, boiled carrots contain significantly more carotenoids compared to raw carrots. However, raw carrots contain much more polyphenols, which disappear as soon as you start cooking them.
Summarizing all this, it is fashionable to say that no cooking method is ideal in terms of preserving 100% of the nutrients in vegetables. And since the best vegetables are the ones you will actually eat, taste should also be taken into account when deciding on the cooking method.
The best way to get the most out of your vegetables is to enjoy them in different ways — raw, steamed, boiled, baked and fried. If you regularly eat a variety of fruits and vegetables, you don't need to worry about the way they are cooked.
