I'm still at the stage where I get a small jolt each time I hear the words "President Trump".

I can't get my head around that particular combination of syllables.

I also had a shock when I heard the Trump spokesperson introducing the concept of "alternative facts".

And I was pleased to hear the interviewer's response at the time. "Alternative facts are not facts. They're falsehoods," he said.

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It's good to have this idea brought front and centre in popular culture. In the nutrition world, alternative facts have been around almost as long as science.

The idea that established facts are not, in fact, facts, has exploded with the growth of social media. Often it is paired with the idea that somehow "they" (the establishment, government, doctors, scientists) have conspired to give us false information or advice.

We see it on emotive topics such as climate change, fluoridation and vaccination. And we see it about food and health.

These are all areas where the basic scientific facts are established and there is wide scientific consensus, even when it's acknowledged that science is always moving.

The alternative facts tend to be presented in emotional, although often plausible, language.

Sometimes the media plays into this, in a phenomenon known as false balance, which is when someone with true expertise - say a climate scientist - is given the same weight in a media report as a tinfoil-hat wearing, unqualified climate change sceptic.

This gives the false impression their views are equally valid and accurate.

In the world of nutrition, a prominent online source of alternative facts is Dr Joseph Mercola.

Of all the links I am sent from people who have taken issue with something I've written, most come from his site.

Mercola is outspokenly against vaccination and fluoridation.

He believes diet can cure a wide range of diseases. He claims microwave ovens and pasteurised milk are dangerous. He says vitamin D can cure cancer and that sunscreen can cause it.

Much of the nutrition information on his site is presented in "science-ish", if sensational, fashion. It sounds plausible and quotes research studies.

And despite being critical of government health organisations - which he says are motivated by greed - he sells a vast array of Mercola-branded products, earning him millions of dollars a year.

At mercola.com you can buy vitamin supplements, Mitomix Pure Power Bars ("to help optimise mitochondrial function and cellular health") and "biocharged" kitty litter. It may not surprise you Mercola has been officially warned by the FDA several times about unsubstantiated claims for his products and supplements.

When someone advocates a supplement or diet and also sells that supplement and diet-related food products, it's worth asking: What am I really being offered here?

Facts? Or their alternatives?