Low magnesium concentrations in the blood may increase the risk of total and hip fractures in middle-aged men, according to the observational study. However, the team behind the research stressed the need to replicate their results in women and other populations to assess any relevance in fracture prevention.
“The findings do suggest that avoiding low serum concentrations of magnesium may be a promising though unproven strategy for risk prevention of fractures," said Dr Setor Kunutsor, lead study author and research fellow from the University of Bristol's Musculoskeletal Research Unit.
The finding that dietary magnesium intake was not linked with fracture incidence is especially significant, said the team - noting that increasing the intake of foods rich in magnesium, such as dark leafy greens, nuts, seeds and avocados, do not necessarily increase blood magnesium levels.
This is the case in the elderly or those people with specific digestive or bowel conditions. Indeed, low blood levels of magnesium are very common in the population, especially among middle-aged to elderly individuals who are also prone to fractures.
however, by treating any underlying conditions and providing magnesium supplementation, the team believe it may be possible for many more to avoid low blood levels of magnesium.
A number of human and animal studies have shown that magnesium supplementation is associated with improvement in bone mineral density and suppression of bone turn over markers.
A 2-year study of a group of menopausal women, concluded that magnesium therapy resulted in greater bone density and may have prevented the risk of fractures.
Bone study details
Data analysed from 2245 men aged 42–61 years that included a follow-up period of 25.6 years, a total of 123 fractures were recorded. Of these fractures, 78 were located at the hip.
Based on the suggested normal reference range of 1.8–2.3 mg/dl for serum magnesium, 136 men had low magnesium levels (less than 1.8 mg/dl) and only 22 men had excess serum magnesium levels (greater than 2.3 mg/dl) in the study population.
The research, published in the European Journal of Epidemiology, found that the risk of experiencing a fracture was decreased by 44% in men with higher blood levels of magnesium.
The men found to have a lower level of magnesium in the blood had an increased risk of fractures, particularly fractures of the hip.
In the 22 men, who had very high magnesium levels, none of these subjects experienced a fracture during the follow-up phase.
"The overall evidence suggests that increasing serum magnesium concentrations may protect against the future risk of fractures,” said lead author Professor Jari Laukkanen from the University of Eastern Finland,
“However, well-designed magnesium supplementation trials are needed to investigate these potential therapeutic implications."
Mechanisms of action
Current EFSA recommendations have set Adequate Intakes (AI) for magnesium at 350 mg/day for men and 300 mg/day for women. For children this ranged from 170 to 300 mg/day according to age.
The team proposed a series of mechanisms to explain their observations including impaired bone growth, decreased bone density, and bone fragility or osteoporosis.
Other mechanisms include a nitric oxide-dependent mechanism, in which magnesium directly affects osteoblast activity and number of osteoclasts.
The researchers also put forward possibilities that prove a link between magnesium levels and bone fractures was tenuous. They cited the fact that food sources of magnesium are also frequently high in nutrients such as potassium and calcium.
Their interaction with other micronutrients could maintain bone health and therefore was difficult to evaluate the separate effect of each nutrient.
There was also the possibility that individuals dietary intake of magnesium may not correlate with their total body stores or serum levels, according to the team.
“Though a low serum magnesium concentration generally signifies low total body magnesium status; serum magnesium concentrations do not accurately reflect total body magnesium stores,” the study explained.
“Thus, it is not uncommon to find normal serum magnesium concentrations in the presence of depleted total body stores and vice versa.”
Source: European Journal of Epidemiology
Published online ahead of print: DOI: 10.1007/s10654-017-0242-2
“Low serum magnesium levels are associated with increased risk of fractures: a long-term prospective cohort study.”
Authors: Setor Kwadzo Kunutsor, Michael Richard WhitehouseAshley William Blom, Jari Antero Laukkanen