BAD: Crisps.
They may seem more virtuous than other savoury snacks, but store-bought kale crisps can have as much fat and calories (50 per 10g) as Kettle Chips. And they may contain only powdered kale, not the vitamin-rich and high-fibre whole veg. You could crisp lightly oiled kale leaves in the oven.
GOOD: Boiled.
Kale stands up to boiling well, but it has a detrimental effect on some nutrient levels, which leach out. Although 100g of raw kale has 34mg magnesium (which is good for bones and energy) — nearly 10 per cent of your recommended daily intake — that same amount of boiled kale has 8mg magnesium.
BEST: Stir-fried.
A quick stir-fry in oil boosts the nutrient content as it helps the body better absorb fat-soluble compounds such as beta carotene, which the body uses to make vitamin A. Wilting it with heat helps cut the content of goitrogens — compounds that in large amounts can interfere with the thyroid gland.
Daily Mail