Lady Macbeth kept scrubbing but she couldn’t get the marks out.

Shakespeare’s character was so wracked with guilt that imaginary blood stains appeared on her hands and, try as she may, she couldn’t get herself clean.

It’s not just fiction: research shows that all of us have a powerful urge to wash, bathe, shower or purge whenever we feel we may have wronged.

In the 21st century, however, we are more likely to feel guilty about a weekend of overindulgences than we are for religious transgressions but instead of washing our hands, we go for a dietary “detox” which is the modern day body cleansing craze.

In fact, detoxing has now become so widely believed that it is difficult to convince most people that it is utter hocus-pocus, even though the British Dietetic Association, NHS and British Nutrition Foundation all agree it is just marketing mythology.

The idea behind the “detox” is that we are being constantly bombarded with pollutants (“toxins”) that accumulate within the body.

These “poisons” are said to include food additives, pesticides, fluoride, prescription drugs, smog, sugar, artificial sweeteners and a whole host of other mystery “chemicals”.

Detox-ers tell us that the only way to remove impurities is by drinking copious amounts of water, eating a plant-based diet and abstaining from coffee and alcohol.

Lasting for three, or even 21 days, and often with supplements or juices, detoxing has essentially no science behind it and studies show that detox diets do not lower levels of “toxins”.

The word “toxin” is misused by dieters and there are no known pollutants that accumulate in the body that can be purged through a detox diet.

Our bodies are extremely efficient at removing poisons; the liver and kidneys work tirelessly to rid the body of harmful substances.

Drinking plenty of water is good but does not flush out harmful “toxins” any more than breathing fresh air will empty a smoker’s lungs of tar.

Eating a plant-based diet is also highly recommended as part of any balanced diet, as is going easy on alcohol and caffeine – but do not miraculously cleanse our insides.

Strict detox diets can be harmful and it isn’t worth swallowing the body cleanse pill.

We should not throw out the baby with the toxic bathwater, however.

Exercising, avoiding processed food, going easy on the wine and coffee, drinking plenty of water and eating lots of fruit and veg – these are all excellent lifestyle choices.

“Detoxing” as an attempt to purge yourself of the sins of modern living goes against what we really know about the human body.

If there is something in your diet that concerns you, then consider cutting it out and speaking with a doctor or trained nutritionist.

There are no quick fixes to a healthy life and we would all do well to cleanse our minds of the “detox” myth.

* Dr Stuart Farrimond is a medical doctor and qualified secondary teacher.

He worked as a hospital doctor at the RUH, Bath, before being diagnosed with a brain tumour in 2008.

Forced to leave medicine, he worked as a lecturer at Wiltshire College and is now editor of Guru Magazine.

You can find him on twitter@realdoctorstu and read his blog at www.realdoctorstu.com