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A common topic of debate on nutrition is the effect of different cooking methods on vegetables, and which one is the best.
This is important information to know, and I’ll tell you what the pros and cons are of each method as well as my opinion on what’s best.
But it’s equally important to get a variety of types of vegetables in your diet.
Actually, variety is probably even more important than the cooking method.
Sure, you lose vitamins when you boil carrots, but if you’re boiling those carrots with a bunch of different vegetables into a delicious soup, you’re probably going to eat a lot more vegetables than you would if they were just chopped up raw.
And looking at the numbers, the Vitamin C lost in boiling carrots is 40%, which for 100 g worth of carrots is 2.3 mg. If you add 100 g of baked sweet potato to your soup, you get 19.6 mg of Vitamin C.
Adding the sweet potato is much more effective than just sticking with raw carrots, especially when the daily recommended intake of Vitamin C is 75-90 mg for adults. Carrots aren’t going to get you there anyway.
Nutrient Loss
Vitamins and minerals are lost from foods when they’re exposed to heat, water and air. Some nutrients are more resistant or susceptible to one of those paths of loss than others.
Vitamins tend to be destroyed in heat, while minerals aren’t as fragile.
There’s a trade off between temperature and time when you cook foods that’s hard to measure, and depends on the specific temperature, time and nutrient you look at.
I think it gets a bit too detailed in the big scheme of balanced healthy eating, so I don’t worry about the specifics and just focus on using heat for the flavor and texture I want.
Using water when you cook vegetables, like in steaming or boiling, can cause some nutrient loss and dilute the flavor, but it keeps the moisture content of the vegetable.
If you use the water that the vegetable cooked in (like in a soup), you’ll retain all of the minerals and most of the vitamins.
Foods will start to oxidize and lose nutrients once they’re peeled or cut, from being exposed to air.
Keeping foods as whole as possible for as long as possible when storing, cooking and serving will help preserve their nutrients.
Preparing your vegetables immediately before cooking and eating them will minimize that effect.
Keep the big picture in mind, though. It’s not about avoiding every possible thing that will reduce nutrient levels, it’s about being aware of how the loss happens so that you can make good choices overall.
Remember too that variety plays a huge role in making sure you get enough of all the nutrients you need, and can often offset the effects of different cooking methods.
Being optimally healthy is about finding the methods and foods that work best for you, and not sweating the small stuff.
Oil
Another factor that affects the nutritional value of foods is when oil is used in cooking, since it’s prone to breaking down into toxic by-products and is pretty much pure fat without much other nutrients.
That doesn’t mean that you should never use oil.
It just means that if you’re aware of the fact that oil creates some toxins, you shouldn’t use it all the time in cooking and you should make sure the negative impact is minimized by using oil properly.
The reason to use oil in cooking is to protect the food from heat, and to concentrate and infuse flavors.
You can minimize the downsides by using small amounts of high quality unrefined oils, and not heating them too much.
You can avoid using oil by using other liquids or lids to buffer the heat, baking or water-sauteeing to concentrate flavor and using whole food fats to infuse flavor and spices.
Above all else, make sure that you have an overall healthy diet and lifestyle so that your body can handle toxins.
The truth is that there are toxins in everything we eat, they are in the air and in the water, our own bodies create them – toxins are very much unavoidable.
Your body has the ability to neutralize toxins if you’re healthy and if you don’t overload your systems.
Once you find and maintain balance, you’ll be able to handle most things thrown at you without worrying so much.
1. Raw
I spent some time experimenting with a 100% raw diet. I lost a bit of weight and felt great. During the winter, I also felt cold and a bit weak.
I think there are times when a 100% raw diet is a great idea, and I think we should always try to get a lot of raw foods in our diet.
The main benefit of eating raw vegetables is that the full vitamin and mineral content is kept intact.
They also retain more fiber and water than cooked foods, things that are very valuable to many people who aren’t getting enough.
However, the cell wall of the vegetables (cellulose) stays intact so certain nutrients aren’t as available for absorption than in cooked vegetables.
Our digestive system isn’t able to break down cellulose, so cooking can release nutrients that would otherwise pass right through our digestive tract.
Raw vegetables also have the potential for toxins that inhibit our bodies’ ability to digest and absorb the foods we eat, and can be more harmful if they are eaten in huge quantities.
It’s difficult to eat enough toxins to make yourself sick with common foods, but white mushrooms, for example, have mild toxins (hydrazines) in them that are neutralized by cooking.
Seeds have phytic acid, which helps them stay intact through your digestive system and prevent you from fully absorbing certain nutrients.
A good strategy is to eat a balance of both cooked and raw. Get most vegetables raw, especially during the summer, and cook others minimally, more so in the winter to keep you warm.
2. Marinate/Massage
Marinating and massaging foods with salt, herbs, spices and other dressings uses no heat, so most vitamins and minerals are retained, aside from the ones lost through air exposure.
Using salt to marinate or massage vegetables draws moisture out of the plant cells and starts to break down the cellulose.
It’s not broken down to the same level as cooking, but it softens the fiber making digestion a bit easier, and makes certain nutrients more available for absorption.
Marinating with certain acids can neutralize the toxins in raw vegetables, and make proteins more digestible.
Some of the toxins found in certain mushrooms can be neutralized by marinating them with citric acid, from lemons or oranges, for a few hours.
Plus, both of these techniques help bring out the flavors of vegetables and make for a tastier meal.
3. Steam
Steaming is a great option for cooking vegetables since it avoids a lot of the ways in which nutrients are lost, but also breaks down fiber and toxins to optimize absorption.
Water doesn’t contact the vegetable too much, so vitamin and mineral leaching is minimal.
There is some vitamin loss through heat, but the vegetable itself doesn’t get as hot as most of the other cooking methods so there’ll be less vitamin loss.
If the vegetable is peeled and/or cut before cooking, some vitamins and minerals will also be lost due to air contact during the time it cooks and before serving.
4. Boil
The heat loss will be the about same as steaming. It might be a slightly higher temperature, but that means it should also take less time.
Vitamins and minerals leach into the water, but you can still get those that aren’t destroyed by heat if you use the broth.
If the cooking water is thrown away, boiling would slip below baking on the healthy cooking method ladder since it has the most nutrient loss.
You can boil vegetables whole, with their skin intact, so that they don’t lose nutrients from air contact.
As with all cooking methods, boiling softens fiber, breaks down cellulose, and allows for more absorption of the energy and nutrients in the vegetables.
5. Bake (No Oil)
Temperatures for baking are usually higher than steaming or boiling, but can be any temperature.
Dehydrating is a form of lower-heat baking, along with a fan to help the water evaporate.
To bake with no oil, the foods need to be kept whole with skin intact, otherwise they’ll dry out with the heat and not cook on the inside.
Baking doesn’t use any water so minerals are retained and vitamin loss is only due to heat.
When baking is defined as being done with the vegetable and skin intact, this minimizes contact with the air and also reduces nutrient loss when compared with boiling.
If foods are baked with some water in the dish (like putting a whole squash in a roasting pan with some water at the bottom), they’re going to be cooked by a combination of steaming and baking.
6. Roast (With Oil)
Temperatures for roasting are usually at the high end of baking range.
Foods are peeled or cut, and need some oil to protect them from drying out in the heat. Heating oil creates some free radicals, particularly at temperatures above 300 degrees F.
Roasting and frying are a bit of a toss up as to which one is better, and it depends on the time and temperature factors.
Roasting takes a longer time, but it’s usually done at a lower temperature than frying. Both factors create increased potential for free radicals forming in the oil, so the exact numbers could make one better than the other. Overall, I don’t think the difference is worth worrying about.
Roasting doesn’t use any water so minerals are retained and vitamin loss is only due to heat and air contact.
7. Fry
Temperatures used for frying are usually higher than for any of the other cooking methods.
Nutrient loss happens by the same factors as roasting, but the upside of frying is that it takes very little time, so the foods are exposed to heat for a shorter period than baking or roasting.
Like roasting, it also has the downside of usually relying on oil.
Frying with water, sometimes called water sauteing, is technically cooking by steaming so the same nutritional considerations apply.
Summary
These cooking methods are roughly from least to most nutrient loss, and least to most toxins generated in cooking, but other factors come into play. I use all of the methods, and I focus on eating healthy foods and not getting obsessive about the smaller details.
- Raw: I eat most of my vegetables raw, especially in the summer.
- Marinate/Massage: I do this all the time to make vegetables taste better.
- Steam: This is the method I use most often, and I cook more of my food in the winter.
- Boil: I also boil a fair bit, especially when I’m keeping the cooking water, like with soups.
- Bake (No Oil): I bake foods whole when I have the time.
- Roast (With Oil): I occasionally roast root vegetables.
- Fry: I don’t fry much anymore, but once in awhile I’ll make a stir-fry. I usually use water, vegetable broth or wine.