What's the most nutritious way to cook vegetables?

a person holding a basket of vegetables
Most nutritious way to cook vegetablesHearst Owned

You know that eating your greens - and reds, oranges and purples - is fundamental for fuelling your body optimally. But could your prepping methods be draining their health benefits? Dietician Laura Tilt gives us the facts.

Sure, they’re not the sexiest topic in nutrition, but fruit and vegetables offer some attractive benefits. Evidence shows that, when consumed daily, they help reduce the risk of diseases, including heart disease and some cancers. There’s also research to suggest they may protect against type 2 diabetes.

Currently, the global recommendation for fruit and vegetable intake (set in 2003 by the World Health Organization) is a minimum of 400g a day. Meanwhile, national guidelines suggest aiming for five servings of veggies/legumes daily and two of fruit.

Portions aside, the way you prepare veggies also affects the benefits. While most fruits are ready to eat, vegetables typically undergo some sort of cooking before they hit your plate, which affects nutrient levels and how the body absorbs those nutrients. So what’s the most nutritious way to prep produce? Well, in short, it depends on the vegetable and the nutrients in question.

The research

One Chinese study investigated the effects of five cooking methods (five minutes each of steaming, microwaving, boiling, stir-frying, or boiling and stir-frying) on the nutrient levels in broccoli. The researchers found that, except for steaming, all cooking methods led to significant losses of vitamin C and glucosinolates – compounds associated with protective effects against cancer. Steaming: one, boiling: nil.

Other studies have investigated the impact of cooking on a broader range of vegetables. A Spanish study tested the effects of boiling, microwaving, pressure-cooking, frying, griddling and baking on the antioxidant activity of 20 types of vegetables, including Brussels sprouts, green beans and zucchinis. While there were variations according to the type of veggie, overall, results showed that microwaving and griddling produced the lowest nutrient losses, while pressure-cooking and boiling led to the greatest.

Steaming or boiling?

This mix of results might be confusing in isolation, but when taken together, the evidence suggests that submerging your vegetables in water isn’t your best bet to preserve precious nutrients. Steam to avoid this (a colander over a pan of simmering water works a treat as a DIY steamer), or if you’re boiling (or stir-frying), keep it brief and, if possible, throw the nutrient-filled cooking water into a soup.

As ever, there are exceptions. Carotenoids and lycopene (yellow, orange and red pigments with antioxidant effects, found in foods like pumpkin and tomatoes) tend to be more bioavailable when boiled or stewed for a longer period, as cooking softens the cell walls, facilitating their absorption. One study found that cooking tomatoes for 30 minutes increased lycopene levels by 35 per cent – evidence, if you needed it, that pomodoro sauce is a legit health food.

Getting nutritional bang for your buck isn’t just about prep; how you store veggies counts too. A 2017 study found the frozen kind retained more nutrients than fresh ones that were kept in the fridge for five days. So, if you’re not eating them within a couple of days, adding frozen produce to your shopping list could serve you well. Something to chew over.

Prep School

Peas: A source of vitamin C, folate and fibre. Microwave or steam for 2 to 3 mins to retain their C content.

Tomatoes: Eaten raw, they’re another good go-to for vitamin C. Roasted or cooked into a sauce, they’re high in the antioxidant lycopene – add a drizzle of olive oil to cooked tomatoes to increase absorption.

Broccoli: High in folate, vitamin C and fibre. Steam lightly and serve crunchy in salads or dip in hummus.

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