To cook or not to cook? Nutrition research scientist Tim Crowe explores the popular claim that raw food is healthier than cooked — and explains why some foods are better with a little heat.
Do you worry that you’re missing out on important nutrients by cooking your food? Fear not. Cooking causes much less nutrient loss than you think, and can even make food more nutritious. Find out why.
The rise of raw diets
Raw food diets move in and out of popularity. ‘Going raw’ is underpinned by the idea that cooking food destroys enzymes and nutrients, so you can see why it seems so appealing.
A big plus for going raw is you eat plenty of plant-based foods — in all their natural and uncooked glory. Compared to a typical meat-heavy Australian diet with too many processed foods, raw food diets are streets ahead in vitamins, minerals, fibre and other plant nutrients.
Does cooking lower the nutritional value of food?
Cooking does result in chemical changes in food and a loss of some nutrients. But it’s just vitamin C, folate and thiamine that stand out as the main nutrients lost, and their levels rarely drop by half. Most other nutrients are unaffected or are altered by a very small amount.
There are plenty of other foods rich in vitamin C, thiamine and folate to make up for any shortfall caused by cooking. Citrus fruits are an excellent source of vitamin C. Leafy green vegetables and avocados are great sources of folate. And whole grains come packed with thiamine, as does bread, due to its fortification.
What about antioxidants?
Looking beyond vitamins and minerals, there are hundreds of antioxidants found in plant foods that have favourable health benefits, and the losses of these through cooking are small.
In fact, cooking increases the amount of some of these antioxidants. Carotenoids (the pigment that gives carrots and other vegetables their rich, vibrant colours) exist inside cell structures, but they are not easily available. Cooking carrots breaks open the cell walls, freeing up the carotenoids so that your body can absorb their goodness. The same goes for tomatoes. Cooked — and canned — tomatoes are much higher in the powerful cancer-fighting antioxidant, lycopene, than raw tomatoes.
Cooking not only maximises the health benefits of some foods, it also improves the foods’ safety by what it takes away. Cooking at 75°C or hotter kills most of the bacteria that cause food poisoning.
Put the heat on
So, what’s the best way to retain the most nutrients from food during cooking? The three keys are water, temperature and time. As temperature, cooking time and water volume increase, so too do nutrient losses. Steam rather than boil, if possible, as this reduces nutrients leaching into the water. In fact, the orange water left after boiling carrots signals the loss of nutrients.
Cook at lower temperatures where possible, or at a higher temperature for a shorter time, as when quickly stir-frying. Keep the size of vegetable pieces as large as you can to minimise oxidation losses. And don’t overcook food: you want your broccoli to emerge firm and green, not wilted and white.
Making sense of it all
An emphasis on eating mainly plant-based foods close to their natural state is indisputably good for your health, no matter how they are cooked. Worry less about how much vitamin C your vegetables are losing from a stir-fry dinner, and focus more on having plates that are full of colourful, nutritious foods.
The healthiest way to cook.…
Broccoli: Steam very lightly, or consume raw
Carrots: Steam or microwave whole, or in large pieces
Chickpeas: Soak overnight, drain and simmer until tender
Tomatoes: Cut into pieces, drizzle with olive oil and roast
Potatoes: Sauté or roast in olive oil, with the skin on.
Article sources and references
- Seongeung Lee, et al. Effect of different cooking methods on the content of vitamins and true retention in selected vegetables.Food Sci Biotechnol. 2018 Apr; 27(2): 333–342. Published online 2017 Dec 12. doi: 10.1007/s10068-017-0281-1https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049644/
- Gao-feng Yuan, et al. Effects of different cooking methods on health-promoting compounds of broccoli. J Zhejiang Univ Sci B. 2009 Aug; 10(8): 580–588. doi: 10.1631/jzus.B0920051https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722699/