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Does heating food cause nutrient loss?

Clients: Does heating food cause nutrient loss?

Dietitian: When we talk about heating food, there are actually several type of cooking method used to heat foods. We will go through all the cooking method. Is it true heating food caused nutrient loss?

Well. First and foremost, It’s true that cooking methods alter the nutritional composition of fruits and vegetables and other food sources like protein but that’s not always a bad thing because  several studies have shown that while cooking can degrade some nutrients, it can also enhance the availability of others. As a result, no single cooking or preparation method is best, and that includes eating vegetables raw. So heating food does not contribute to 100% of nutrient loss. But there are certain nutrients preserved!

So it is actually depends on cooking method, type of food and also nutrients content, usually most of the nutrients that often reduced (not loss) during cooking are:

  • water-soluble vitamins: vitamin C and the B vitamins — thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), folic acid (B9), and cobalamin (B12)
  • fat-soluble vitamins: vitamins A, D, E, and K
  • minerals: primarily potassium, magnesium, sodium, and calcium


For example, in terms of vegetables, most of people believed that raw vegetables are filled with more nutrients than cooked vegetables BUT it actually depends on the type of nutrient.

There are study of 200 people in Germany who ate raw food diet found that they had higher levels of beta carotene, but their plasma lycopene (one type of carotenoid, act as antioxidant that gives red colour of tomatoes) levels were well below average. That is because fresh and uncooked tomatoes actually have lower lycopene content than cooked or processed tomatoes. Study showed that cooking will break down the thick cell walls of many plants, releasing the nutrients stored in them.

Hence, it depends on type of of foods like fruits, vegetables , or protein. Not depends on cooking method entirely. However, there are certain vitamins easier to be degraded during processing and cooking.

As I mentioned above, water soluble nutrients like vitamin C and vitamin B and a group of nutrients called polyphenolics seem to be most vulnerable to degradation in cooking. Apart from that, canned peas and carrots lose 85% to 95% of their natural vitamin C. There are study showed that frozen cherries lost as much as 50% of anthocyanins, (nutrients found in the dark pigments of fruits and vegetables).

There are also based on Journal of Agriculture and Food Chemistry, stated that over all boiling method better for carrots, zucchini and broccoli than steaming, frying or raw. However, frying vegetables was by far the worst method to preserve nutrients..


Client: How about microwave? Is it bad for food?

Dietitian: Many people think that microwaving method is bad for food, however there are study on march 2007 looked at the effects of boiling, steaming, microwaving and pressure cooking on the nutrients in broccoli. It showed that steaming and boiling caused 22% to 34% loss of vitamin C while microwave and pressure-cooked vegetables retained 90% of their vitamin C. Other than that In 2003, study in India also showed that among the three cooking methods, steaming emerged as the most suitable method followed by microwave cooking in terms of retention of phytochemicals and antioxidants activities.  

So microwave food? Is it bad for food? It is actually safe and can retain some nutrients in certain sources of foods. But!! Do not cooked  for too long!! If you over heat the food, then the nutrient might be degraded as well! So! Watch out time to heat your food, do not let your food too dry and overcooked! Temperature and time also plays role to retain the nutrient! The correct combination of time and temperature can help preserve most nutrients while also improving the foods’ taste, texture and colour.

The time and temperature required depends on the type of food. High risk foods such as meat, fish and eggs need to be heated to at least 60℃ to be safe.

Client: So, does it mean there are certain vitamins and mineral preserved if we heat or cook the food? And there are also certain nutrients might be break down if we cook or heat it?

Dietitian: Yes! I think you got what I mean. So it is very important for you to have variety of foods include fruits, vegetables, protein or carbohydrate sources okey! So that you can get nutrients needed from various of food sources from different type of cooking method.

In conclusion, there is no cooking or heating or preparation method which is superior existed in this world for preserving 100 percent of the nutrients in a vegetables, fruits and other source of food.

 The best way to get most of our nutrients from food is to enjoy them in a variety of ways whether raw, steamed, boiled, baked and grilled.

If you concern whether you get adequate vitamins or minerals from fruits and vegetables, then it is advisable for you to eat a variety of fruits and vegetables on a regular basis. Recommended 2-3 servings of vegetables per day, 1-2 servings of fruits per day. Easiest way is to practice “Quarter-Quarter Half” method. Make sure half of your plate is full of colour of vegetables and fruits!!

However here, I would like to share with you type of cooking method that prone to reduce nutrients in certain foods and how to cater the nutrient loss in cooking. Please click the link stated to go to type of cooking method and nutrient loss.


  • Study on Effect of different cooking methods on health promoting compound of broccoli, 2009
  • U.S Department of Agriculture (Table of Nutrient Retention Factors) 2007
  • The Journal of Agriculture and Food Chemistry
  • Study on Effect of steaming, boiling and microwave on the total phenolics, flavonoids, and antioxidant properties of different vegetables of in North Eastern India, 2013; Saikia & Mahanta