Nearly every food preparation process reduces the amount of nutrients in food. In order to get most nutritional value from your vegetables, it is important to choose cooking methods that help preserve nutrients and vitamins.1

Some vitamins dissolve in water, so you lose your vitamins to the cooking water if you prefer to boil your vegetables. If you consume the water, say in a soup, then you may be able to get the nutrients back. Other cooking methods such as grilling, roasting, steaming, stir-frying or microwaving generally preserve a greater amount of vitamins and other nutrients.1 Although there are many benefits to eating raw vegetables, cooking can help make some vegetables taste better, break them down to be more digestible, and kill bacteria.

One question that we get from many people taking warfarin is: does cooking foods affect the vitamin K amounts?

Vitamin K is an essential vitamin found in many foods, beverages, and some cooking oils. Known to help with normal blood clotting, this fat-soluble vitamin is also important for bone strength. Some vitamins are more stable (less affected by processing) than others. Water-soluble vitamins (B-group and C) are more unstable than fat-soluble vitamins (K, A, D and E) during food processing and storage.2

According to Sarah L. Booth, PhD, Senior Scientist and Director of the Vitamin K Laboratory at HNRCA, in her presentation “Vitamin K-Rich Foods for the Warfarin Patient: To eat, or not to eat?”, fat-soluble vitamin K content is not affected by cooking nor freezing foods.3 Water-soluble vitamins are the ones more likely to be lost in most cooking methods.

But, what about the differences in vitamin K content found in the Vitamin K Finder?

Vitamin K is a fairly stable nutrient to most types of processing. If you look at a couple of vegetables in the Vitamin K Guide, you may notice a difference in the amount of vitamin K in 1 cup of frozen spinach or broccoli versus 1 cup of raw broccoli. The biggest difference is that you may be consuming more spinach when frozen or cooked because in wilts and condenses down greatly when frozen or cooked.

Since the best vegetables are the ones you will actually eat, taste should also be factored in when deciding on a cooking method. The best way to get the most out of your vegetables is to enjoy them in a variety of ways.


  1. 1. M. Jiménez-Monreal, L. García-Diz, M. Martínez-Tomé, M. Mariscal, M. A. Murcia. Influence of Cooking Methods on Antioxidant Activity of Vegetables. Journal of Food Science. Volume 74, Issue 3, pages H97–H103, April 2009.
  2. 2. Russell, L. Faye. Water-soluble vitamins. Food Analysis by HPLC 100 (2012): 325.
  3. 3. Sarah L. Booth, PhD. “Vitamin K-Rich Foods for the Warfarin Patient: To eat, or not to eat?” HNRCA. September 2013. Alere Webinar.
  4. 4. USDA, National Nutrient Database for Standard Reference, Release 22, 2009.



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