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For decades, in terms of heart health, we’ve concentrated on the harm that could be inflicted by saturated animal fat.

Sugar wasn’t even considered.

We were wrong. When sugar did eventually get a mention it was because it contributed to obesity - and thereby to diabetes - because it’s high in calories and linked to weight gain.

But to do that ignores the dreadful harm we now know sugar itself can do.

It’s not innocent white stuff. It’s toxic. So believes science writer Gary Taubes.

He thinks we’re missing the point in believing diabetes results from too many calories working alongside a sedentary lifestyle. Sugar isn’t benign, he says.

The theory is that sugar has harmful effects on the human body ­independent of its calories and it will cause disease. How, you ask?

It’s all to do with the fructose component of sugar (and high fructose syrup), which is metabolised primarily in the liver. This can lead to the ­accumulation of liver fat which promotes insulin resistance, the fundamental cause of Type 2 diabetes.

(Image: GETTY)

The sugar industry’s PR campaign to support the villain, sugar, set research back by 20 years – but didn’t end it, thank heavens. Gradually ­information emerged that large doses of sugar could cause a cluster of ­metabolic errors that link to heart disease, insulin resistance and Type 2 diabetes, fatty liver and accumulation of fat.

We’re still trying to confirm for sure if raised blood sugar and high insulin levels lie behind the current epidemic of Type 2 diabetes we’re living through.

But if it turns out that the fructose content of sugar and high fructose syrups makes them uniquely toxic, then the dietary advice of the past 40 years has been very wrong. We’ve ­been fooled.

(Image: PA)

So what do we do? Setting an upper limit to the amount of sugar we should consume is a good start. But what’s the safe level? Whatever level we choose it could be too high for some people and causing damage.

It could be that for people who have obesity or diabetes, or both, even a little sugar is too much.

However, if sugar can trigger fatty liver, insulin resistance and Type 2 diabetes, and I believe that it does, what do we do given the evidence is still ­ambiguous?

Well, due to the scale of the obesity and diabetes epidemics, I think we should be recommending strongly against consuming sugar while we wait for proof to come.