Many processes impact the nutrient content of vegetables. People often wonder if sticking to raw vegetables is the best way to go. The following information will provide you with some more clarity on how to prepare your vegetables in order to make the most of their nutritional content. There is also a great table that directly compares nutrient losses between different preparation methods.
Cooking Your Vegetables
Cooking vegetables will always result in some nutrient losses, no matter what the method. This is because some vitamins and minerals are heat sensitive – namely vitamin C, thiamine and folate. Exposing vegetables to heat for periods longer than 5 minutes will therefore result in lower levels of these vitamins [1]. Fortunately, fibre and minerals are not heat sensitive and will therefore remain present in the vegetables [1].
There are, however, cooking methods that are preferable to others in terms of nutrient retention. Those cooking methods that don’t require vegetables to be immersed in liquid will result in far fewer losses (in addition to the losses from heat). This is because some vitamins are also water soluble (B vitamins and vitamin C) and will leach out in to the cooking substrate. If the cooking liquid is to be consumed as part of the meal then the leached vitamins will not be wasted e.g. casseroles, stews.
Raw
Eating your vegetables raw will provide you with a good dose of those vitamins that are diminished when you cook them. Don’t think just of salad vegetables, some vegetables that are typically cooked can also be eaten raw e.g. broccoli, cauliflower.
The verdict – Cooked VS Raw
Raw vegetables may sound like they have the edge over cooked vegetables in this battle however this is not necessarily the case. Cooking vegetables also helps to release some vitamins that are not as biologically available and hence well absorbed from raw vegetables. As an example, the antioxidant lycopene and beta-carotene (present in tomatoes) are both released when they are cooked and therefore absorbed more effectively than when eaten raw [1].
Interesting fact: Adding some fat to the cooking process (e.g. a small amount of extra virgin olive oil) will further increase the absorption of lycopene and beta-carotene [1].
So it is best to get a mixture of both raw and cooked vegetables in your day e.g. salad vegetables on your sandwich and as snacks and cooked vegetables for dinner or breakfast. That way you can ensure you’re getting nutritional bang for your buck! Make sure all vegetables to be eaten raw are washed well!
Specific examples of including raw and cooked vegetables in to your daily diet include:
- An omelette with lightly stir-fried spinach, tomato, mushrooms and onion
- Toast and eggs with grilled tomato and mushrooms
- Vegetable sticks e.g. capsicum, carrot, cucumber, celery
- Salad sandwich
- Salad with raw broccoli, cauliflower, mushrooms etc
- Stir fries
- Baked/ roast vegetables for lunch or dinner
Frozen vegetables
I often get asked if frozen vegetables are as nutritious as fresh. Fortunately – they are! Vitamins and minerals are only very slightly impacted by this process [2]. However, frozen vegetable have already been part cooked so when you are ready to use them, quickly cook in little to no water. Ideally frozen vegetables should be used within 6 months [1,2].
Fresh vegetables
Even fresh vegetables will have lost some nutrients. Most “fresh” vegetables have gone a reasonable time between harvesting and being put on your plate. During this time, the nutrient content will somewhat deteriorate. They are still a great option, however.
The figures
The table below is a great summary of how different cooking/ preservation processes will affect the nutrient content of vegetables. Of course the precise figures will depend on specifics like cooking duration, temperature and type of food but this is a fantastic guide.
Summary points
- Frozen vegetables are still a very nutritious option and very convenient!
- Cook vegetables as quick as possible and in as little liquid as possible – unless the cooking substrate is to be consumed.
- Aim to get a mixture of cooked and raw vegetables in your day
Contact us for results focused nutritional advice
This article was written by our dietitian Belinda Elwin who is a Dietitians Association of Australia member and Accredited Practising Dietitian and Nutritionist. If you have questions about healthy eating, make an appointment. We‘ll provide you with a simple and effective routine targeted to your concerns.
Contact us today.
References
For more detailed information, see the ‘USDA Table of Nutrient Retention Factors’ from: www.ars.usda.gov
