Many people say that steaming vegetables is healthier and more nutritious than boiling them, but is it true?
Vegetables are a readily available source of dietary fibre, vitamins, minerals, phytochemicals that function as antioxidants, phytoestrogens and anti-inflammatory agents and benefit our health in many ways. So, when eating vegetables, we clearly want to absorb as many of those nutrients as possible.
The fibre and fat-soluble vitamins in vegetables, such as vitamin A and E, generally aren’t greatly affected by boiling or steaming. The bioavailability of some nutrients, such as the lycopene found in tomatoes and the beta-carotene in carrots, may actually improve with cooking.
However, vegetables also contain water-soluble vitamins and phytochemicals. And it’s these nutrients that are readily lost through leeching when vegetables are boiled.
Chinese researchers studied the effect on the nutrient content of broccoli of steaming, microwaving, boiling, stir-frying, and stir-frying followed by boiling. They found all cooking treatments, except steaming, caused significant vitamin C losses. Steaming also reduced losses of glucosinolates – the sulphur-containing compounds found in broccoli that are credited with protecting us from cancer and cardiovascular disease.
So, yes, steaming is preferable to boiling for retaining nutrients. However, many variables can affect cooked vegetables’ nutrient content, including cooking time, the amount of water used, how the vegetables are cut and their type.
However you cook your veges, keep them as intact as possible, and if you’re boiling or microwaving them, use as little water as possible.
This article was first published in the July 21, 2018 issue of the New Zealand Listener.