The business of bottled water is booming. And not just plain water: coconut water, birch water, watermelon water. Some brands claim to hydrate you more effectively, others offer extra ‘anti-oxidising manganese’ .
Hard water may clog up your kettle, but there is strong evidence that it helps protect your heart, too.
Hard water, unlike soft water, is rich in minerals. In particular it has a good dose of magnesium. And, while the evidence is far from complete, it seems that magnesium plays a powerful role in keeping our hearts healthy.
So what does it actually do? Magnesium regulates about 350 cellular enzymes in the body. These enzymes control important functions like blood pressure regulation, the stabilisation of heart rhythms and muscle contraction.
Professor Brian E Davies of Clemson University, South Carolina, who has researched consumption of magnesium in the British diet, says: ‘There is a large body of literature suggesting magnesium nutrition is important in a variety of cardiovascular problems.’
He cites an investigation by the World Heath Organisation in 2009, suggesting: ‘Low magnesium status has been implicated in hypertension, coronary heart disease, type 2 diabetes mellitus and metabolic syndrome.’
The British Heart Foundation seems to recognise this. Its senior dietitian Victoria Taylor says: ‘Magnesium is associated with a positive impact on certain heart disease risk factors such as lowering blood pressure.’
So, the evidence. In one meta-analysis, researchers concluded that a 100mg magnesium supplement was linked to an eight per cent reduction in the risk of stroke, specifically ischaemic strokes.
But the biggest observable impact of dietary magnesium comes when scientists look at sudden cardiac death (SCD), a relatively common condition that claims over 100,000 lives in the UK and 350,000 in the US every year.
Researchers first noticed in the 1950s that those living in hard water areas were less likely to suffer from SCD.
And, in the 1980s, a study involving almost 90,000 female nurses in the US showed a strong inverse relationship between levels of dietary magnesium and the likelihood of SCD. Another large-scale US study found that that those with the highest levels of serum magnesium (magnesium in the blood) were up to 40 per cent less likely to suffer from the condition.
More recently a paper in the American Journal of Clinical Nutrition called for research to move beyond the epidemiological, asking for ‘clinical trials to evaluate the potential role of magnesium in the prevention of cardiovascular disease’.
One of the difficulties facing researchers is the lack of a simple test to assess magnesium levels in the human body. Current tests focus on the amount of magnesium in the blood, but this accounts for just one per cent of the total, with the rest stored in bones and soft tissues.
Without this test, it’s unlikely that we will be able to fully understand the full impact of this precious metal.
The NHS claims that all the magnesium we need should be available through a normal diet. However, this is disputed.
Professor Davies and colleagues, in a paper published in the Official Journal of the Society for Environmental Geochemistry and Health, created an average model of consumption that enabled them to assess whether the average British adult was receiving enough magnesium.
‘It was concluded that the adult magnesium intake from solid food is suboptimal,’ he explains.
He claims that up to 48 per cent of the US population consumes less than the daily recommended amount of magnesium and suggests the situation has worsened throughout the 20th century.
Davies argues that all of us could benefit from additional magnesium in our diets, with simple hard water from the tap being the perfect way to restore the balance. ‘Real improvement in magnesium nutrition is seen only where water is hard,’ he says.
Advice from the British Heart Foundation, on the other hand, suggests a ‘healthy, balanced diet’ will ensure a sufficient magnesium intake. ‘Foods like green leafy vegetables, low-fat dairy, nuts, brown rice, bread and fish are all good sources of magnesium,’ says Taylor.
If you live in a hard water area, turning on the tap instead of reaching for a bottle of water is a good start. If you must drink bottled water, it’s better to choose one enriched with minerals rather than purged of ‘impurities’.
While regularly touted by health food shops, research has claimed the health benefits of magnesium supplementation are questionable, and it gains no support from either NICE or the British Heart Foundation.
In the future, additional research will help us to better understand the role magnesium plays in protecting our hearts.