Client: Hi, Dietitian! I have heard about eating food raw is better as heating food can cause nutrient loss? Could you please explain more about it?
Dietitian: I would partially agree with the statement. When we talk about heating food, there are actually several types of cooking method used to heat foods. We will go through all of the cooking methods. Is it true heating food caused nutrient loss?
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, there is no single cooking or preparation method is the best, and that includes eating vegetables raw. So heating food does not contribute to 100% of nutrient loss. But there are certain nutrients preserved!
It actually depends on the cooking method, types of food and nutrients content. Generally, 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
Most of the people believed that raw vegetables are packed with more nutrients than cooked vegetables BUT it actually depends on the types of nutrient.
There was a study of 200 people in Germany who ate raw food diet found that they had higher levels of beta-carotene, however their plasma lycopene (one type of carotenoid, act as antioxidant that gives red colour of tomatoes) levels were well below average. This is because fresh and uncooked tomatoes actually have lower lycopene content than cooked or processed tomatoes. Cooking increases the certain nutrient bioavailability by breaking down the thick cell walls of many plants, releasing the nutrients stored in them.
Hence, types of of foods is also one of the factor that may affect the nutrient loss, for example fruits, vegetables , or protein. It does not entirely depends on cooking method.
There are certain vitamins easier to be degraded during processing and cooking. As I mentioned above, water soluble nutrients like vitamin C, B vitamins and polyphenolics seem to be more vulnerable to degradation in cooking. Furthermore, canned peas and carrots lose 85% to 95% of their natural vitamin C. Another study showed that frozen cherries lost as much as 50% of anthocyanins (nutrients found in the dark pigments of fruits and vegetables).
Therefore, a study published by the Journal of Agriculture and Food Chemistry, stated that boiling method is better for carrots, zucchini and broccoli as compared to other cooking methods such as steaming, frying or raw in preserving nutrients.
Client: How about microwaving? Is it bad for food?
Dietitian: Many people think that microwaving method is bad for food, however a study in year 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, another study in year 2003 in India demonstrated that microwave cooking was the second suitable method in terms of retention of phytochemicals and antioxidants activities among three cooking methods.
Microwaving is actually safe and can retain some nutrients in certain sources of foods. However, do not cook food for too long! If you happened to overheat the food, then the nutrient might be degraded as well! Do watch out time to heat your food and make sure your food is not too dry and overcooked Temperature and time also play important role in retaining 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 for consumption.
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 broken down if we cook or heat it?
Dietitian: Yes! You are right. So it is very important for you to have variety of foods include fruits, vegetables, protein or carbohydrate sources by using different types of cooking method.
Take Home Message
Last but not least, there is no cooking 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. The recommendation is take 3 servings of vegetables and 2 servings of fruits per day. The easiest way is to practice “Quarter-Quarter Half” Healthy Plate method. Make sure half of your plate is covered with diferrent colour of vegetables and fruits.
Conclusion:
We provide healthy balanced meals that is cooked with various cooking method that retains most nutrients for each ingredients used. Get nutribalanced meals by using promo code “HOMEYBLOG” to enjoy 5% discount!
References:
Miglio, C., Chiavaro, E., Visconti, A., Fogliano, V., & Pellegrini, N. Effects of Different Cooking Methods on Nutritional and Physicochemical Characteristics of Selected Vegetables. Journal of Agricultural and Food Chemistry. 56(1): 139-147. https://doi.org/10.1021/jf072304b
Saikia, S. & Mahanta, C. (2013). Study on effect of steaming, boiling and microwave on the total phenolics, flavonoids, and antioxidant properties of different vegetables of Assam, India. International Journal of Food and Nutritional Sciences. 2(2): 1-9.
U.S Department of Agriculture. (2007). Table of Nutrient Retention Factors.
Yuan, G., Sun, B., Yuan, J. & Wang, Q. (2009). Effects of different cooking methods on health-promoting compounds of broccoli. Journal of Zhejiang University SCIENCE B. 10, 580. https://doi.org/10.1631/jzus.B0920051