The Best Way To Cook Your Vegetables, According To a Dietitian
Sure, they’re not the sexiest topic in nutrition (unless you’re partial to an eggplant or peach emoji), 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.
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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 fruit. With the average daily intake in Australia coming in at only 2.4 serves of vegetables/legumes and 1.4 of fruit, there’s some room for improvement.
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 those nutrients are absorbed by the body. So what’s the most nutritious way to prep produce?
Well, in short, it depends on the vegetable and the nutrients in question.
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, riddling, 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 vegie, overall, results showed that microwaving and griddling produced the lowest nutrient losses, while pressure-cooking and boiling led to the greatest.
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 percent — 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 vegies 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
Prep School
Peas: A source of vitamin C, folate, and fiber. 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.