TL;DR: When cooking choose to bake, sauté and steam and avoid boiling, deep frying, grilling and excessive cutting and peeling of food.
Intro
There are many different techniques when it comes to preparing food. You can throw some nice steak on the grill for a delicious and satisfying meal. You can boil up some frozen veg for a quick fix of your greens. You can bake yourself some tasty potatoes wedges. You can even steam some dumplings to mix things up a little bit.
There are endless methods when it comes to food preparation, yet not all of them are created equal. You can drop tonnes of cash on the best, most nutrient dense, premium ingredients, just to throw it all away during the cooking process. This article will go over the pros and cons of various conventional cooking methods with hopes of giving you, the reader, the knowledge you need to make the best possible choices when preparing your meals.
Cutting and Peeling
Before you even start cooking, your food can be subject to nutrient loss. As soon as you cut into a fruit or vegetable some of the vitamin C is lost [1]. If you wash your cut vegetables, or leave them exposed to air they will continue to lose even more vitamin C. To minimize this, try cutting your veggies into as big of pieces as you can comfortably eat. Avoid cutting them at all, if possible. Cut your food immediately prior to using it and try to eat leftovers containing cut fruit or vegetables within 1 to 2 days. Never buy pre-cut food at the supermarket, as by the time you get around to using it, it will have lost a significant amount of its Vitamin C. Additionally, if your food requires washing, do so before you cut it, rather than after.
The peels of most fruits and vegetables have been found to be the most nutrient dense part. An apple with skin can contain up to 332% more vitamin K, 142% more vitamin A, 115% more vitamin C, 20% more calcium and up to 19% more potassium than a peeled apple and a potato with its peel can contain up to 175% more vitamin C, 115% more potassium, 111% more folate and 110% more magnesium and phosphorus than a peeled one [2].
Avoid peeling your ingredients as much as possible when cooking in order to take advantage of all the nutrients hidden away in the peel.
Boiling
Boiling is one of the easiest cooking methods there is. Simply throw your ingredients into some boiling water, give them a stir every now and again and then boom, 10 to 20 minutes later your food is done. Unfortunately, despite being so easy, boiling is hands down one of the worst ways of cooking food.
Vitamin C and all of the B vitamins are water soluble. So when you throw a bunch of food chocked full of Vitamin B and C into a big boiling pot of water, a lot of those vitamins are going to leave the food and dissolve into the water. Broccoli, spinach and lettuce may lose up to 50% of their Vitamin C when boiled. Similarly, up to 60% of thiamine, niacin, and other B vitamins may be lost when simmering meat [3].
Fortunately, these vitamins aren’t disappearing when you boil food, they are simply just leaching into the water. Therefore, if you consume the water, rather than just dumping it down the drain you can recoup a significant amount of these lost nutrients. Simply drinking the water you used to boil your food will allow you to reclaim some of those lost nutrients. You can make this easier on yourself by minimizing the amount of water you use to boil your food. Enough water to just cover the food is usually sufficient for most foods. If drinking used cooking water isn’t your style you can try making a soup out of the leftover water, or simply select a better cooking method going forward.
Deep Frying
Nothing is more delicious than deep fried food. It seems that you can deep fry just about anything, from veggies to ice-cream, and it will turn out amazing. Unfortunately, as you are probably aware, deep frying is not a great method for cooking.
To start, deep frying your food will cause it to absorb a substantial amount of the oil used. Oil has an extremely high caloric density so if you are looking to lose weight you should definitely stay away from all things deep fried.
Additionally, some oils are absolutely terrible for you as they are high in omega-6 fatty acids. Throughout most of history humans got omega-3s and omega-6s in roughly a 1:1 ratio. However, the western diet has changed significantly over the last 100 years and now the average diet contains a 20:1 ratio of omega-6s to omega-3s. Scientists have hypothesized that this unbalanced ratio of omega-6s to omega-3s causes chronic inflammation, which is strongly linked to the development of serious and widespread health complications, such as heart disease, cancer, diabetes and arthritis [4]. If you must deep fry foods, make sure you use oils that are low in omega-6, such as olive and coconut oils, and stay away from oils high in omega-6 such as soybean, corn, cottonseed, peanut and sesame oils.
Believe it or not, deep frying gets even worse! Keeping oil at a high temperature for long periods of time begins to form a toxic substance called aldehydes, which have been linked to an increased risk of cancer and other diseases [3]. The oil type, temperature, and cooking time will all affect the amount of aldehydes formed, so try to reduce the time as much as possible, keep the temperature low and choose a good oil. Fortunately, as well as being lower in omega-6, coconut oil has been found to still be suitable for cooking after 8 hours of continuous cooking in one study [5]
Furthermore, deep frying subjects food to extremely high temperatures, which can easily damage nutrients, such as the omega-3s found in fish. Deep frying tuna has been found to reduce its omega-3 content by 70-85% [3].
At this point it goes without saying that deep-frying is a cooking method to be avoided!
Sautéing/Stir Frying
Sauteing food is basically like deep frying with most of the bad stuff removed. Lower temperatures means toxic aldehydes aren’t being formed and heat sensitive nutrients are not being damaged as much. Less oil means fewer calories and less intake of omega-6s. Additionally, cooking without water and for shorter periods of time can significantly reduce the amount of lost B vitamins.
There are many health benefits to sauteing as well. Cooking vegetables in fats has been shown to increase the absorption of compounds and antioxidants. One study found that the absorption of beta carotene was 6.5 times greater in stir-fried carrots than in raw ones and another found that blood lycopene levels increased 80% more when people consumed tomatoes sautéed in olive oil rather than without it. [3]
Also, much like how Vitamin B and C are water soluble, Vitamin A, D, E and K are fat soluble [1] meaning that they will leave the food and enter the oil. Fortunately, the oils that have been used for sauteing usually taste amazing (quite unlike water which has been used for boiling) so make sure to scoop it all out of the pan to get those vitamins.
Baking and Roasting
Baking is one of cleanest methods of cooking. No water to wash away your B and C vitamins. No high calorie, high omega-6 oils. No extreme temperatures to damage delicate nutrients and produce toxic aldehydes. Baking really is the king of cooking with minimal nutrient losses.
The only downside is when roasting large pieces of meat, the large amount of time required can begin to break down B-vitamins. One study found that the B-vitamins in roasted meats were reduced by 40% [3]. Try to avoid baking for long periods of time, because of this.
Steaming
Steaming is a vastly superior method of cooking compared to boiling. Less water contact means significantly less loss of water soluble nutrients like Vitamin B and C. The steaming of broccoli, spinach, and lettuce reduces their vitamin C content by only 9–15% [3] which is significantly less than the 50% loss which comes from boiling.
Grilling
It’s hard to beat a nice big juicy steak from the BBQ. Sadly, grilling food has been shown to have negative health implications.
When you grill a piece of meat, two carcinogens are known to commonly form. The first is called heterocyclic amines (HCA) and forms when amino acids, sugars, and creatine react with each other at high temperatures. The second is called polycyclic aromatic hydrocarbons (PAH) and forms when dripping from the meat causes flames and smoke. The smoke contains PAH and can adhere to the meats surface [6]
Thankfully, there are several methods which have been shown to reduce the amount of both HCA and PAH in grilled foods. A 2008 study found that marinating meats in spicy marinades can reduce HCA content by up to 88% [7]. Additionally, the length and temperature in which you cook your meat has been shown to correlate with the HCA content in food [8], so turn down the heat, flip it often and eat your steak the right way i.e. rare. Lastly, keep your grill clean to reduce the amount of flame ups and smoke and thus the amount of PAH getting absorbed into your food.
A Note on Nutrient Loss
One common thing you may have noticed upon reading this article is that every single cooking method will reduce the nutrients in food in one way or another. It may seem logical to then conclude that the best cooking method is simply not to cook at all, and eat your food raw. This couldn’t be further from the truth.
Cooking does so much more than making our food taste good. It allows us to access much more nutrients from our food than we would be able to if we just consumed it raw. For more information on this please check out our article on bioavailability here.
Conclusion
All forms of cooking are going to reduce the nutrients in your food in one way or another, yet some methods will have significant more nutrient losses than others. Choose steaming over boiling and sauteing over grilling. Bake as many things as possible to minimize nutrient loss and stay far, far away from deep frying. Furthermore, reduce cutting and peeling as much as possible to decrease nutrient loss prior to cooking.
References
[1] http://agritech.tnau.ac.in/nutrition/nutri_cookingtips_nutrientloss.html
[2] https://www.healthline.com/nutrition/peeling-fruits-veggies#section1
[3] https://www.healthline.com/nutrition/cooking-nutrient-content#boiling-simmering-and-poaching
[4] https://www.healthline.com/nutrition/are-vegetable-and-seed-oils-bad
[5] https://www.healthline.com/nutrition/healthiest-oil-for-deep-frying#coconut-oil
[6] https://www.cancer.gov/about-cancer/causes-prevention/risk/diet/cooked-meats-fact-sheet
[7] https://www.ncbi.nlm.nih.gov/pubmed/19241593
[8] https://www.naturalmedicinejournal.com/journal/2010-07/marinades-reduce-heterocyclic-amines-primitive-food-preparation-techniques
