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How Does Cooking Food Affect Nutrient Content?

How Does Cooking Food Affect Nutrient Content?

If you’ve been keeping up with our blog, you’ll have seen our recent post on the potential benefits of eating more raw foods. With the vast majority of fruits, vegetables and wholefoods in general, nutrient content is at its highest when there’s no cooking or preparation involved.

Hence, the more raw foods you manage to incorporate into your diet, the better.

Every vegetable has two very different forms - raw and cooked. Some people can’t get enough of crisp and crunchy carrots, but cannot stand the thought of them boiled. The same is also true in reverse, as some just can’t bring themselves to eat bowls of raw veggies.

All well and good, but this undoubtedly raises questions as to what actually happens when you cook your food. With the popularity of raw food diets on the rise, there’s growing speculation as to the extent to which cooking vegetables ‘destroys’ their nutrient content.

It’s a logical argument given the nature of the cooking process, but is it actually true?

Does cooking food have a devastating impact on its nutrient content, or has the whole thing had been blown completely out of proportion?

The Short Answer: Sometimes 

Truth is, you can’t claim outright that cooking or preparing vegetables annihilates all the good stuff they contain in their raw form. This is due to the fact that cooking is by no means a binary process.

Vegetables can be cooked in infinite different ways and for infinite different lengths of time. In addition, the different nutrients in different vegetables respond in different ways to different cooking methods.

Quite a lot of ‘differences’ to take into account, so it’s not quite as simple as cooking vs raw. 

Getting to Grips with Nutrients

There are two main classifications of nutrients present in the foods we eat - macronutrients and micronutrients. Fats, carbs, and proteins are the macronutrients in food, which are the primary building blocks of the human body and provide us with the energy we need to do our thing.

Meanwhile, macronutrients are present in much smaller quantities in everyday staples. They’re just as important for the human body, but we do not need quite as much of them as the macronutrients listed above. Micronutrients include things like minerals, vitamins and phytonutrients. All of which play essential roles in bolstering the immune system and basically taking care of the body on a cellular level.

When examining the extent to which cooking affects nutrient content, research tends to concentrate on micronutrients. Vitamin content is the main point of focus with most studies, which examine how cooking has an impact on fat soluble vitamins (A, D, E, and K) and water soluble vitamins (C and the B vitamins). 

As the name suggests, one of these groups of vitamins dissolves in water, whereas the other dissolves in fat. Something that should be taken into account when considering how cooking methods affect nutrient content.

Whether a vitamin is soluble in water or fat provides a good indication of how it will be affected by any given cooking method. For example, if a vegetable contains high quantities of vitamin C and vitamin B, boiling it for several minutes will reduce its vitamin content. The same applies if you were to fry vegetables with a high content of fat soluble vitamins.

There’s more to it than solubility alone, but it nonetheless gives you a good indicator of how your chosen cooking method could affect what’s in your veggies. 

Which Cooking Methods Are Better or Worse?

There’s no outright answer to this question, due to the way different nutrients react very differently to various cooking methods. Some vegetables even benefit from an increased nutrient content, depending on how they are cooked.

For example, some of the vitamin C in a Brussels sprout will be lost as it is boiled. By contrast, the beta-carotene content of chard can actually increase as it is cooked.

In this instance, it’s all down to the cellular structure of the veggies you are cooking. In accordance with where the cell of a nutrient is stored in a vegetable, different things can happen when it is cooked - including:

  • The nutrient becomes easier to absorb as cooking softens the cell wall
  • The nutrient is broken down and largely neutralised by the cooking process
  • The quality of the nutrient is improved as oxidizing agents are killed off

If this is the case, then the argument regarding cooking vegetables always reducing their nutrient content to some extent is invalid. Depending on the type of vegetable you’re preparing, cooking in the right way could actually boost its nutritional value and vitamin-richness.

Understandably, this makes the whole thing quite complicated for the average person looking to maximise the nutrient content of their meals. Though it can be as simple as getting to grips with which cooking methods have the most dramatic impact on key micronutrients. 

Vitamin C

Citrus fruits are renowned for their vitamin C content, and have become a staple for those looking to get more of this essential micronutrient into their diet. As citrus fruits are almost always consumed raw, they pack the maximum vitamin C punch. 

Meanwhile, certain vegetables are also noted for their huge vitamin C content, including spinach, Brussels sprouts and broccoli. With the latter two, boiling is by far the most common preparation method. Unfortunately, the fact that vitamin C is water-soluble means that much of it is lost during the cooking process. In fact, it is estimated that up to 50% of the entire vitamin C content in the raw veggies could be lost by boiling them.

Worse still, vitamin C is also heat sensitive. This means that the higher the temperature and the longer it is exposed to heat, the less potent it becomes. In which case, opting for a gentler cooking method (or removing the water from the equation entirely) is the way to go.

Or better yet, find creative ways of enjoying them in their raw form.

Vitamin K

An essential nutrient for healthy bones and blood, vitamin K is fat-soluble. It’s most prevalent in leafy greens like kale, chard and spinach - all of which can be prepared in a variety of ways. As touched upon above, it’s actually possible to increase the amount of vitamin K in chard by cooking it. And that applies to most cooking methods.

If getting more vitamin K in your diet is your priority, you can’t really go wrong with this group of veggies and almost any cooking method. Absorption is key with fat-soluble vitamins, so consider preparing or serving these veggies with olive oil (or an equivalent healthy fat) to help your body absorb the vitamin K.

Beta-Carotene (Vitamin A)

This is the stuff responsible for giving carrots their orange colour. Beta-carotene levels are higher in carrots than any comparable vegetable, and are not adversely affected by gentle cooking. In fact, if you lightly steam or carefully boil your carrots, it becomes easier for the body to absorb much higher quantities of beta-carotene. 

It’s similar to an extent with chard and spinach, though both contain slightly less vitamin A than carrots. As touched on earlier, it’s all to do with the way in which the cooking process makes the cell walls softer, ensuring more of the good stuff is absorbed by the body when eaten.

Vitamin E

As for vitamin E, there’s a fair amount of this essential antioxidant in most leafy greens and root vegetables. A powerful nutrient that crops up the immune system, vitamin E is something most people could do with more of in their diets. 

Unfortunately, there’s no realistic way of cooking root vegetables that doesn’t result in lower levels of vitamin E.  By contrast, gently cooking leafy greens can (as above) increase the nutrient value of the vegetable. With root vegetables, it’s therefore a case of cooking with care, avoiding the tendency to cook them to death and wreck their nutrient content.

Baking vs Boiling 

Last up, the debate as to whether it is better to boil or bake vegetables continues to rage. What should be evident by now is that neither is strictly ‘better’ than the other. It all depends on what it is you are cooking, how long you’re cooking it for and what kinds of nutrients it contains.

Likewise, it’s also not true to say that eating raw vegetables is always better for your health than cooking them. Again, depending on the nutrient content of the ingredients, its nutritional benefit could actually be boosted with careful cooking.

Something to think about, next time you’re shopping for vitamin-rich veggies!  

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