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If the drugs don’t work, doctors can prescribe a special diet for people with epilepsy that will often stop or reduce their seizures. Emma Young reports.

Of all the ‘miracle diets’ that are touted, there’s perhaps one that lives up to the name. It doesn’t involve eating a crucial nutrient that a person is lacking, or avoiding one that’s causing an unpleasant reaction. In fact, nobody knows exactly how it works. But for people with epilepsy, if they follow it strictly, there’s a real chance their disease can be controlled, even cured.

“Not everyone responds to the diet – just like medicine – but a good response can be a game-changer,” says Adam Hartman, an associate professor of neurology who treats children with epilepsy at Johns Hopkins Hospital in the USA, and who is working on understanding more about how the diet works.

Hippocrates, the ancient Greek ‘father of medicine’, realised that fasting can control fits. “Mention is also made in the New Testament of using fasting and prayer as a means of controlling convulsions,” says Hartman. “The modern diets – as we use them – date back to 1921.”

Though there are variations to the ‘ketogenic diet’, essentially it’s low in carbs, high in fat and contains strictly controlled levels of protein, all of which makes the body think it is fasting. Rather than using glucose, the preferred energy source, the body burns fat. This results in the production of chemicals called ketones – hence the name.

The diet is usually tried on people who have not responded to at least a few anti-epilepsy drugs. Hartman says that’s because it’s generally easier to take a pill or a small amount of liquid than stick to such a radical dietary change. If people manage it, though, various research papers provide evidence of potentially profound impacts.

A randomised controlled trial of the diet, involving 145 children who had seizures at least once a day and who had failed to respond to at least two drugs, found that after three months, 38 per cent of the children on the diet were having half as many seizures as before (compared with only 6 per cent of children not on the diet). A few saw their seizures fall by more than 90 per cent.

Other studies have suggested that the diet can even leave some people seizure- and medication-free, says Hartman. Given that the average person who starts the diet has tried six or seven medications, “I think that is impressive,” he says.

Though no one really knows how the diet works, there are some clues. There is evidence, for example, that metabolites of fatty acids produced in people on the diet affect neurotransmitters and their receptors in the brain. But the diet may also affect gene expression and the function of mitochondria, the tiny powerhouses of our cells, Hartman says.

However it works, the results can clearly be worth it: “One mother told me that anyone who thinks sticking to the diet is tough should compare it to watching a child have more than 100 seizures a day,” says Hartman. “It’s all a matter of perspective.”

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