How Cooking Affects Nutrients

From texture to flavor, cooking methods have a major effect on how your food comes out. But what about nutrition?  Let’s look at how cooking can affect nutrients and calories in our food.


While many foods can be eaten raw, such as fruit, cooking has many important functions:

  • Destroying potentially harmful bacteria
  • Improving palatability
  • Making foods easier to digest
  • Improving absorption of nutrients by the body upon digestion


The exact effects can vary by cooking method, which we’ll get to later in this post.

First, let’s answer these two questions:  How does cooking food affect the calorie content of foods? And, how does cooking affect the volume?


Calories in Raw vs. Cooked Foods


Most people may be more interested in how cooking affects the calorie content of food.  So, if you were to take a raw sweet potato and then bake it, does that potato now have more calories cooked than it did when it was raw?  Yes and no.


Putting all other variables aside, that sweet potato contains about the same amount of calories cooked as it did when it was raw.  However, now that it’s been cooked we can digest the sweet potato easier and the body is able to absorb more of the nutrients.


Cooking can also add energy (calories) through oil, butter and marinades. And depending upon the cooking method, you may end up using more or less added fat to cook your food (think frying vs. steaming).


Changes in Volume

Before we move onto different cooking methods, one important thing to note is that the volume of food changes when cooked, which can affect your calorie estimates.


Some foods, like meats and vegetables, lose water when cooked.  What started out as a 4 oz patty is now a 3 oz patty (a 25% reduction).  On the opposite side of the spectrum, a 1/2 c of dry quinoa is 100 calories; a 1/2 cup cooked quinoa is 200 calories, a difference of 100 calories!


How Various Cooking Methods Affect Nutrients


While protein and antioxidants are more easily absorbed thanks to cooking, other nutrients may be reduced.  Water soluble nutrients (B-vitamins and vitamin C) and some minerals are particularly prone to being lost from food during cooking.


Let’s review some of the popular cooking methods and their benefits and drawbacks when it comes to preserving nutrients.


Baking and Roasting



  • High heat, slower cooking can bring out the sweetness in vegetables
  • Can be a low-fat way to cook
  • Minimal loss of nutrients



  • Due to high heat, some B-vitamins may be reduced by as much as 60%





  • Low calorie, low fat way to cook
  • May improve availability of antioxidants
  • May make omega-3’s in fish easier to absorb


  • High heat and large amounts of water can wash away up to 50% of the vitamin C in some vegetables. Tip: if boiling potatoes, save the boiling liquid and use to make a soup, thus saving all of nutrients lost to the water.
  • B-vitamins and thiamine are also significantly reduced





  • Short, high-heat cooking can be a great way to cook tender pieces of meat. Use for blanching vegetables to kill bacteria for food safety requirements



  • For vegetables, the very high temperatures used in prolonged broiling can degrade enzymes, resulting in the loss of B-vitamins and possibly some minerals


Deep Frying



  • Preserves the B-vitamins and vitamin C found in vegetables better than many other cooking methods



  • Increases the amount of calories and saturated fats due to using a large amount of oil
  • The high temperature of cooking oil can degrade healthy Omega-3’s found in fish.
  • Toxic compounds (aldehydes) form when oil is heated to high temperatures for a prolonged period of time. This is a concern since aldehydes have been associated with an increased risk of chronic diseases, including cancer.



  • Depending upon the marinade, grilling strikes the perfect balance between flavor and nutrient quality
  • Similar to baking, very little nutrients are lost during grilling



  • Grilling can result in the formation of potentially carcinogenic compounds. Luckily, these can be significantly decreased by marinating your meats and veggies and using leaner cuts of meat.





  • Due to short cooking times, microwaving is the method that best preserves nutrients in foods
  • A lean way to cook as you don’t need to add extra fat



  • Doesn’t do much in terms of enhancing flavor





  • The short cook time is beneficial for preserving nutrients
  • The use of a small amount of oil can help with the absorption of fat soluble vitamins
  • Studies have shown when cooked in olive oil, sautéed vegetables have increased antioxidant capacity



  • Stir-Frying may decrease the amount of vitamin C in broccoli and red cabbage.
  • If too much oil is used, it can result in excess fat and calories





  • Foods soften thanks to the steam and their own juices rather than relying on fat
  • Brings out the existing flavor within vegetables, thus best to use the freshest vegetables for steaming.
  • Very minimal nutrient, color and pure flavors are lost in steaming



  • Does not add any additional flavors


Other Considerations:


Frozen Foods


To get the most nutrition from your fruits and vegetables-regardless of how you are going to cook them- you want to be sure you are buying the freshest possible produce.  Generally, that means buying what’s local and in season.  And when nothing is in season, don’t forget about the frozen fruits and vegetables. Freezing is very kind to nutrients-and frozen fruits and vegetables are usually picked at their nutritional peak and processed within days if not hours, locking in those nutrients.


Fruit and Vegetable Prep


Last but not least, peeling foods like potatoes, carrots, cucumbers, apples, pears, etc. will have an impact on the amount of nutrients.  The reason is that a lot of nutrients are located directly underneath the skin. Thus, by scrubbing your fruits and vegetables clean instead of peeling the skin off, you will gain a lot of good nutrients.



In summary, cooking helps to improve the digestibility of food, and as a result makes many nutrients and calories easier to absorb.  As we have discussed, however, some cooking methods can easily lead to a loss of nutrients, so it is important to be aware of the trade-offs with these different methods depending on the food you’re cooking.

Author: Michelle Hanson

Michelle Hanson, MA, RD, LD is Fresh & Natural Food’s Registered Dietitian. She received a Bachelor of Science degree in Nutrition and Clinical Dietetics with a minor in Community Health from the University of Minnesota – Twin Cities. She is a registered dietitian and current member of the Academy of Nutrition and Dietetics. Michelle has been a nutrition consultant for numerous years as well as a nutrition research director at the University of Minnesota – Twin Cities.

Michelle is passionate about food and nutrition and believes in helping people find simple, realistic ways to make healthy eating a part of their everyday lifestyle.
If you are interested in meeting Michelle or have questions for her, you can email her at: She will look forward to meeting you!