People worried about dementia should consider their intake of magnesium. The problem is that, though the mineral may be a key to protection from dementia and Alzheimer’s disease, both high and low levels of magnesium can make dementia more likely, according to new research, even when those levels are within the normal range.

The evidence comes from a Dutch study that looked at the blood levels of magnesium for over 9,500 older adults, for an average of eight years. None of the participants, whose average age was 65, had dementia when the study began.

People whose magnesium levels were in highest or lowest categories were more likely to develop dementia than people whose magnesium level fell in the middle.

Roughly 825 of the people in the study were diagnosed with dementia after eight years, 80 percent of whom were ultimately diagnosed as having Alzheimer’s disease.

Researchers divided participants into five groups according to their magnesium levels. Those in the study whose magnesium levels were in highest or lowest categories were more likely to develop dementia than people whose magnesium level fell in the middle.

Just over 1,700 people were in the group with the lowest levels of magnesium, and they developed dementia at a rate of 10.2 per 1,000 person-years. The group with the highest levels of magnesium also included about 1,700 people, and their rate was 11.4.

Among the approximately 1,400 people in the middle group, the rate was 7.8 per 1000 person-years. The results were the same even after they were adjusted for any other factors that might affect the risk of dementia.

The results need to be confirmed with additional studies, but the findings are intriguing, according to Brenda C.T. Kieboom, of Erasmus University Medical Center in Rotterdam, one of the study authors. “Since the current treatment and prevention options for dementia are limited, we urgently need to identify new risk factors for dementia that could potentially be adjusted. If people could reduce their risk for dementia through diet or supplements, that could be very beneficial.”

Some of the foods that are rich in magnesium are nuts and legumes, green leafy vegetables, avocadoes, yogurt and whole grains.

This study shows only that there is an association between the mineral and the disease. Participants’ magnesium levels were also only measured at the beginning of the study and could have changed over its course. In addition, the level of magnesium in the blood doesn't necessarily indicate the amount of magnesium in the body. Nevertheless, the research adds a piece to the puzzle surrounding the causes of dementia.

According to Kieboom, if future studies confirm the results, your magnesium level could one day be used as a screening tool for dementia and head it off before it takes hold.

The study is published in Neurology.