Being healthy has never been so simple: Eat vegetables in their natural, whole form to get the most nutrients you can out of your food. Studies show that vegetables and fruit have the most available nutrients and vitamins in their raw form, and when they are cooked, most of these benefits go up in smoke – one reason raw food diets have become so popular.

But not everyone wants to eat food raw or is willing to completely step away from the stove, microwave, and air fryer, so we investigated the healthiest cooking methods for each type of food so that you don't get rid of all the antioxidants and fiber as you prepare your meal. (Hint: Don't sautée all the good stuff away). Here's everything you need to know about how to cook fresh food to get the most health benefits, and the optimal methods and timing, for when you want to turn up the heat.

Here's why raw foods have more nutrients than cooked foods

Heat kills nutrients, bottom line. Some nutrients simply become "deactivated" when they're cooked and vitamins can get "lost," according to one study that looked at the world's cuisines and compared how foods are cooked. Heat breaks down the fiber and membranes in vegetables and fruit, releasing the water within and along with it, the food loses its water-soluble vitamins, an extremely important part of a healthy diet.

The vitamins include Vitamin C and an array of B vitamins, and other vital nutrients, according to another study. Vitamin C and B vitamins are crucial nutrients because they help boost your immune system, provide energy, help create healthy new cells, maintain healthy skin, and promote strong, healthy tissues in the body – helping to protect against diseases.

Cooking foods like leafy greens and sweet potatoes at high temperatures also destroys their enzymes, which can lead to the loss of Vitamin E. Vitamin E is a fat-soluble nutrient that protects cells from damage caused by free radicals and also helps to protect your eye health. However, this doesn't mean you should never cook your food. A raw diet allows cooking foods between 104–118°F because enzymes are still active at these "critical temperatures." Anything higher, and certain enzymes are deactivated and vitamin E can become lost.

Cutting vegetables can start the process of losing nutrients to the air

Even the act of cutting up or mixing certain vegetables can cause plant tissue damage and the loss of enzymes due to the "collapse of cell compartments," and oxidization, according to researchers in one study that looked at the effects of different cooking methods on vitamins in vegetables from broccoli and chard to sweet potatoes and spinach.

When you cut up broccoli, it releases a gas called Sulforaphane Glucosinolate, which is known as a disease-fighting agent that boosts immunity even as it helps take the stress off your other organs. (In the garden this gas kills any bugs that try to munch on the leaves.) The more you cook broccoli the more it loses this nutrient, which gets released and dissipated. But that is not the only nutrient lost in cooking broccoli or other vegetables. Vitamin C is heat-sensitive, and in the cooking study, boiling destroyed vitamin C in almost all the vegetables, with nutrient retention ranging from 0 to 73.86 percent.

Here is the study's chart on what happened when the vegetables were cooked by the researchers:

How vitamin C and K reacted when cooked: Microwaving wins

SampleCooking treatmentVitamin CVitamin K
CWa (mg/kg)TRb (%)CWa (mg/kg)TRb (%)
Blanched32.15 cd72.71b0.03b71.86b
Steamed262.78 cd44.75c3.61ab87.70b
Sweet potatoRaw131.35b100.00aNDND

For other nutrients like vitamin E and β-carotene raw was the clear winner, with microwaving coming in a close second, this study found.

Different cooking methods are better than others, research tells us

If you are set on cooking your foods, be aware that some cooking styles have less of an impact on different nutrients than others, but generally, the less you heat up your vegetables the better, and the most nutrients get lost with either extended times, such as baking or high heat such as frying and roasting. The healthiest cooking methods are either pressure cooking and steaming, according to yet another study.

A third study found that steaming foods for a short time (so they are easier to chew but the vegetables don't lose all their tensile strength which means they retain most of the fiber) is your best bet. Researchers investigated the effects of nutrients with five cooking methods: Steaming, microwaving, boiling, stir-frying, and stir-frying followed by boiling (stir-frying/boiling) on broccoli. Researchers concluded: "The results show that all cooking treatments, except steaming, caused significant losses of chlorophyll and vitamin C and significant decreases of total soluble proteins and soluble sugars." Steaming foods for three minutes is the ideal time, but less is always preferred.

The worst way to cook food for nutrient retention is deep-frying and stir-frying

The researchers also found that stir-frying and stir-fry boiling had killed off the most glucosinolates in broccoli, a plant compound found in cruciferous vegetables that have an antibiotic effect on infection, bacteria, and viruses. The cooking style that had the lowest loss of glucosinolates was steaming.

One style of cooking to avoid – the studies agree – is frying food. A new study published in the Journal of the American Heart Association and reported by Perri O. Blumberg for The Beet found a  link between the southern diet and sudden cardiac death.

I tried a raw vegan diet for a week, to hit reset on my diet, and loved it

On a personal note, I recently tested eating a mostly raw plant-based diet for a week to reset my eating habits that weren't so healthy during the past year. I chose to eat mostly raw after feeling inspired by my friend who visited not too long ago and raved about her low-pressure raw diet that helped her lose 60 pounds and find the motivation to feel more active and train for her first marathon.

Raw always sounded like a good idea, since I've spoken to more than a handful of incredible everyday people who saved their lives or beat some kind of illness by eating a raw vegan diet. For example, Eric Sanchez treated his alopecia and depression, Elissa Goodman swears she treated her cancer, and Lexi Tavares overcame severe depression, quit smoking, and created a new life for herself.

So after my first week of eating mostly raw, not only did I learn a lot more than I expected but I also curbed my sweet cravings, cleared my skin, felt more energized and motivated, and overall felt lighter, more nourished, and satiated. Without giving too many details, I wrote about my mostly raw vegan journey in a separate article and now I am a strong believer in eating this way to feel your healthiest.

Bottom Line: High heat can kill or minimize nutrients like Vitamin C

If the goal is to retain the most nutrients in your food, the best way to ensure optimal health is to eat minimally processed and cooked foods. If raw isn't for you, try eating your vegetable pressure cooked or steamed to keep essential nutrients, vitamins, and enzymes.

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