A study of over 800,000 people has found that higher levels of lithium in tap water could cut the risk of dementia.
Researchers in Denmark looked at the medical records of 73,731 people with dementia, and 733,653 people without it. The scientists, from the University of Copenhagen, then tested the water in 15 areas of the country for lithium.
They found that people with the highest levels of lithium in their tap water were 17 percent less likely to develop dementia, suggesting that adding lithium to tap water could be a way of preventing the disease.
Lithium is a common metal found in drinking water and food at low levels. Lithium has known biological effects on the brain, and is currently used in much higher doses as a mood stabilizer for people with bipolar disorders. However, this research is the first to investigate the association between lithium in drinking water and the incidence of dementia.
“This study fits well with previous evidence which shows that environmental lithium may have health benefits and lithium may prevent dementia," Professor Allan Young of King’s College London’s Institute of Psychiatry, Psychology and Neuroscience told Science Media Centre.
“At a population level, the effects would be considerable as even if lithium only delayed the onset of dementia by months for each person, over the nation that would amount to a lot of healthier months.”
The researchers didn't add extra lithium to the water, but rather looked at the effect of varying levels of the metal already in water across the country. The findings weren't as simple as saying that increased levels of lithium led to less dementia, however.
The study, published in JAMA Psychiatry, found that where lithium levels were above 15 micrograms per liter the risk was of dementia was lower. However, at moderate levels of between 5.1 and 10 micrograms, the risk of dementia actually increased by 22 percent, compared to lower levels.
Nevertheless, the researchers concluded that "long-term increased exposure to lithium in drinking water may be associated with a lower incidence of dementia".
The Alzheimer's Society (AS) called the study well-conducted, though they said further research was needed before you add lithium to your diet, especially as lithium can be toxic if you take too much.
"Lithium triggers a number of useful responses in brain cells that means, theoretically, it might work as a treatment for Alzheimer’s disease. However, despite some success in animals, there hasn’t been enough positive research of lithium in people with dementia to yet convince us that it works," Dr James Pickett, head researcher at AS, said in a statement.
'It’s almost too good to be true that something as cheap and plentiful as Lithium might have a role in future prevention of Alzheimer’s disease. However, more research including clinical trials are needed, and until then we should not consider increasing lithium in drinking water.'