Over the last few years it seems that all foodies talk about is kale. Yup, that dark green, iron-rich, curly leafed cousin of the cabbage.

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Once kale got plastered with the ultimate seal of approval – that of ‘superfood’ status – it was all supermarkets could do to keep up with demand for the stuff. 

From raw salads to grass-coloured smoothies, or doused in butter and garlic and stir-fried, kale is king. Or should that be was king?

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New York yoga and wellness guru Lauren Imparato has announced to the world that kale might not be as good for us as we thought.

She says that the green stuff can in fact cause bloating and kidney stones, and can even affect your thyroid gland, slowing your metabolic rate.

But is she right, and are the online rumours that kale is ‘toxic’ true?

The good news

Let’s look at the facts. It is nutritionally accurate that kale is packed with nutrients, minerals, folic acid, fibre and vitamin A, C and K – as all good green vegetables are. There are even traces of calcium and protein to be gained from munching on it.

Award-winning nutritional therapist and author of The De-Stress Effect, Charlotte Watts says: “Kale, like broccoli and cabbage, is one of the brassica family – which is high in detoxifying sulphur compounds called glucosinolates.

“The dark green also shows rich content of fat-soluble antioxidant carotenoids that protect our fatty areas like eyes, skin, liver and brain. They are also mineral and chlorophyll-rich.”

So far, so healthy.

The bad news

Watts explains that humans have evolved with “plenty of leaves in our diet”, so we shouldn’t automatically start binning bags of kale, but admits there are issues when it comes to digesting the vegetable. 

“Humans have been cooking foods for around 300,000 years and this is how we were able to digest difficult plant fibres, as we have smaller digestive tracts and less chewing time to direct energy towards our large brains. Our closest relative, the chimpanzee, can spend up to 14 hours a day chewing,” she says.

“So the recent trend for juicing oceans of kale can be a bit harsh on the digestive tract as the fibres are neither chewed (and so mixed in with digesting saliva), or broken down with long and slow cooking processes, like in a stew – my preference for darker greens.

“It is also goitrogenic when raw, [which means it] negatively affects the thyroid gland, so my advice for those with thyroid issues is to avoid all brassica veg raw.”

The answer?

As with all foods, from burgers to kale, moderation – and sensible preparation – is key.

“Kale is a superfood, but so is the rest of what nature can provide – we need a variety of foods,” says Watts. “Kale is wonderfully beneficial, but you can’t live on the stuff, and I don’t recommend juicing loads each day. Foods we easily eat raw, like celery, cucumber and carrot are better for juices. No food is just ‘good’ or ‘bad’ and we need to mix it all up.”

If you are concerned about kidney stones, bloating and your thyroid gland, always seek medical advice.