Map that shows if chemicals in your tap water could be putting you at risk of dementia, strokes or even cancer: As experts urge action, the dangers revealed - and how to protect yourself

Why do people in some parts of the country seem to be more at risk of certain diseases than others? ‘But the evidence that drinking hard water with higher magnesium may prevent heart disease and stroke is mixed – the debate is ongoing,’ says Professor Hunter. ‘My view is that association between the minerals in hard water and any health benefits is probably real, but the effect is only seen in populations that otherwise have a low dietary intake of magnesium.’ It may be good for your bones Research by Dr Cecilie Dahl, an associate professor of epidemiology at the University of Oslo in Norway, suggests higher levels of minerals in hard water, particularly magnesium, may be associated with a reduced risk of bone fractures. ‘While the contribution of magnesium from drinking water to overall dietary intake is small – approximately 0.2 per cent for men and 0.3 per cent for women in our study – its bioavailability in water is typically higher compared to food sources.’ ‘This may explain why even small amounts of magnesium in water can have measurable health benefits,’ says Dr Dahl. Genetics also play a part: ‘Babies living in a hard water area with a mutation in the filaggrin gene have a significantly higher risk of developing eczema,’ he says.