How you cook your food changes it's nutrition
By Paris Owen, Nutrition Student
In the last post I talked a bit about how the components in our food can affect the absorption of nutrients like calcium and iron. However, there are other ways you can get the most nutrients from your food-simply by the way you prepare or cook them!
Some nutrients are unstable, which means they can be easily damaged or lost through certain stages of processing. This can be anything from washing, packing, storing or cooking food. It’s a given that some nutrients will be lost through cooking, however there are certain methods that are more gentle than others.
o Leave edible skins on- Most nutrients, particularly fibre and antioxidants are stored in the skin of fruit and vegetables. These nutrients are purposefully located in the skin as they protect the produce from the surrounding climate, especially the sun. You do however need to give them a good rinse beforehand to remove any dirt, bacteria, insects or pesticides (if not organic).
o Chop-up just before meal times- When fresh fruit and veggies are peeled or cut, they’re exposed to oxygen in the air. This is called ‘oxidation’, which damages nutrients within your food. To reduce exposure time to oxygen, prepare food just before cooking. What if you’re really struggling for time? What you could also do is wrap chopped items in glad wrap and place them in the fridge. Alternatively, dip or brush exposed areas with citrus juices like lemon, lime, orange or grapefruit juice. These juices are naturally high in Vitamin C, which acts as an antioxidant to prevent browning!
o Chop-up larger portions- By cooking with larger vegetable portions (instead of lots of smaller ones), it means there’s less surface area for nutrients to escape from. If you like smaller pieces, simply cut them up further on your plate!
o Use minimal water where possible- Water is not our friend when cooking vegetables. This is because beneficial B and C vitamins leach out into the water, which is then evaporated or incorporated in the little that remains after cooking. Basically- the less you use, the less nutrients leach out.
Handy tip alert! Crush fresh garlic cloves to activate its ‘organosulphur compounds’. Studies have shown these are beneficial for inflammation, lowering cholesterol, antioxidation and much more!
Frying involves cooking food in hot fat (oil or butter). Surprisingly, cooking some foods in fat can actually increase their absorption! This is because some nutrients are also fat soluble. These nutrients include vitamins A, D, E & K and a class of antioxidants called carotenoids. Most good sources of fat soluble vitamins are already found in ‘fatty’ foods such as dairy products, meat, fish, nuts and oils and therefore don’t require additional fat during cooking. Vitamin K however is considerably high in spinach, kale, turnip greens and collards and therefore adding a little fat would be beneficial. Carotenoids are high in red, orange, yellow and green vegetables like carrots, oranges and spinach.
Handy tip alert! Bake some sweet potato, carrots and pumpkin with olive oil, garlic, salt and pepper for a simple and nutritious meal!
If you follow a vegetarian or vegan diet, it may a little harder to get enough fat soluble vitamins. To find other alternatives, follow this link.
Microwaves work by emitting ‘electromagnetic waves’. Water molecules in your food absorb these waves, which cause them to vibrate. This vibration between molecules causes heat (like rubbing your hands together). Although microwaves may seem like a ‘harsh’ cooking method, they’re actually up there with the best! This is because they can cook food relatively quickly and therefore nutrients are exposed to heat for a shorter period of time. Make sure however, to heat your food in plastic containers that are microwave-safe or use other containers, like glass or ceramics.
Many people continue to be concerned with radiation exposure from microwaves, however the Australian Radiation Protection and Nuclear Safety Agency ensures you shouldn’t be. They state there’s no evidence to suggest that microwave ovens, when used according to the manufacturer's instructions, will be a radiation hazard or promote cancer. It is however important that they are in good working order and that the door, seals and hinges are intact to prevent any leakage.
STEAMING AND BOILING
Both steaming and boiling use water to heat and cook food. One method however, is much harsher than the other. This is due to the amount of water that is used. The more water available, the more water soluble nutrients that can leach out. Steaming is therefore better than boiling. If done lightly, steaming has very little impact on the nutritional quality of food. To prevent further leaching of water soluble nutrients, It is recommended to steam veggies so they are still a little crunchy and bright in colour. If you need to boil veggies, make sure to use the left over nutrient-rich water to make a soup or sauce.
Although slow cooking may not be as convenient, it is effective at conserving the nutrients in your food. This is because a lower heat is used, yet over a longer period of time. You can also take further measures such as trapping any escaping steam (which may contain nutrients that have leached out), saving the broth and use a lower heat setting.
AND THE WINNER IS…
It’s a close call between steaming and microwaving. Ultimately, it depends on the intensity and duration of heat and the amount of water you use.
Hi fellow food lovers! My name is Paris Owen and I am currently undertaking a Masters in Nutrition and Dietetics at University of Wollongong. I am also a university-qualified Nutritionist, graduating last year with a Bachelor of Science in Nutrition. I work with Body Bloom, a women’s fitness training group, providing specialised sports nutrition advice and meal plans. Bondi Farmers Markets is where you will find me on Saturdays making nutritious goodies with an incredible team at the Inside Out Nutritious Goods stall.
I like to take an evidence-based approach for nutritional recommendations to ensure the best health outcomes for each unique individual. I also like to approach health in a holistic way incorporating physical, mental and spiritual wellbeing. In the future, I will become an Accredited Practicing Dietitian, working in the public health system and eventually, in private practice. I am particularly interested in food allergies and intolerances and sports nutrition, however there are so many other areas I am yet to discover!
Joachim, D & Schloss, A 2012, Fine Cooking, The Taunton Press, Newtown, CT.
Higdon, J 2008, Garlic and Organosulfur Compounds, Linus Pauling Institute, viewed 16 December 2014, < http://lpi.oregonstate.edu/infocenter/phytochemicals/garlic/#intro>.
Novella, S 2014, Microwaves and Nutrition, Science-Based Nutrition, viewed 16 December 2014, <http://www.sciencebasedmedicine.org/microwaves-and-nutrition/>.
ARPNSA 2014, Radiation Emissions from Microwave Ovens, viewed 16 December 2014, <http://www.arpansa.gov.au/radiationprotection/factsheets/is_microwave.cfm>.
Roizen, M & Oz, M 2009, Slow-cooked vegetables can keep their nutrients if prepared correctly: You Docs, Cleveland, viewed 16 December 2014, <http://everydaylife.globalpost.com/slow-cooking-nutrients-out-vegetables-24518.html>.