Magnesium and Bone Health: Another Key Mineral For Strong Bones
An update on magnesium and bone health
In 2009 EFSA Panel concludes that a cause and effect relationship has been established between the dietary intake of magnesium (Mg) and maintenance of normal bone. After 2009, numerous studies have been published, but no reviews have made an update on this topic. So, the aim of this narrative review was to consider the state of the art since 2009 on relationship between Mg blood levels, Mg dietary intake and Mg dietary supplementation (alone or with other micronutrients; this last topic has been considered since 1990, because it is not included in the EFSA claims) and bone health in humans. This review included 28 eligible studies: nine studies concern Mg blood, 12 studies concern Mg intake and seven studies concern Mg supplementation, alone or in combination with other nutrients. From the various studies carried out on the serum concentration of Mg and its relationship with the bone, it has been shown that lower values are related to the presence of osteoporosis, and that about 30–40% of the subjects analyzed (mainly menopausal women) have hypomagnesaemia. Various dietetic investigations have shown that many people (about 20%) constantly consume lower quantities of Mg than recommended; moreover, in this category, a lower bone mineral density and a higher fracturing risk have been found. Considering the intervention studies published to date on supplementation with Mg, most have used this mineral in the form of citrate, carbonate or oxide, with a dosage varying between 250 and 1800 mg. In all studies there was a benefit both in terms of bone mineral density and fracture risk. Keywords: Magnesium, Bone, Dietary supplementation, Bone mineral density, Nutrients Go to: Introduction
Magnesium (Mg) is an intracellular cation (second in abundance after potassium), ubiquitous in the human body where it is present (adult organism) in quantities of about 20–28 g: 60% is found in the bones, 39% in the intracellular compartments and about 1% in the extracellular liquids. Mg is present in almost all foods in varying concentrations. It is contained in leaf vegetables in a concentration of 30–60 mg/100 g, being in the center of the pyrrolic core of chlorophyll. Larger quantities are contained in legumes (80–170 mg/100 g), nuts (130–264 mg/100 g) and whole grains (up to 550 mg/100 g in wheat bran). More than 80% of the Mg is removed from the grain refining treatments (white bread contains only 15 mg/100 g). High quantities are present in the coffee (80 mg/100 g in the ready-to-drink) (US Department of Agriculture 2009). Dried fruit in general, potatoes and food of animal origin (meat, fish, milk and derivatives) are less rich in Mg (20–70 mg/100 g) (Carnovale and Marletta 2013). The concentration of Mg in the water is highly variable depending on its origin. The labels of the 150 bottled waters consumed in the scope of the INRAN-SCAI 2005–06 survey (Leclercq et al. 2009) show that the content varies from 1 to 109 mg/L, with an average of 15 mg/L. The bioavailability of Mg varies in the presence of specific components of the diet: phytates, calcium, phosphorus and long chain fatty acids decrease its absorption, while there are conflicting evidences about the effect of oxalic acid.
So, the potential benefits of consuming magnesium might be masked with the effects of other nutrients.
Cooking food also reduces its bioavailability (Dilworth et al. 2007), which instead increases in the presence, for example, of proteins, fructose, inulin, fruit- and galact-oligosaccharides (Roth and Werner 1979; Seelig 1981; Lönnerdal 1997; Coudray et al. 2003, 2005).
The recommended intake levels (RDA) of Mg were provided by the United States Food and Nutrition Board (Food and Nutrition Board 1997).
Several dietary surveys conducted in the United States show that many people consume less than the recommended amounts of Mg constantly. A 2013–2016 National Health and Nutrition Examination Survey (NHANES) data analysis found that 48% of Americans of all ages take less Mg from food and drink than their average needs; adult men 71 years of age and older, teenagers are more likely to show low Mg intake (US Department of Agriculture 2019).
So the dietary intake of Mg is on average insufficient, but clinical diagnosis of Mg deficiency is not simple, as symptoms associated with Mg deficiency are unspecific, and generally confounded by low consumption of other nutrients.
Unfortunately, routinely measured serum Mg levels do not always reflect total body Mg status, so normal level of serum Mg does not rule out moderate to severe Mg deficiency (Razzaque 2018).
In 2009, EFSA issued an opinion on health claims related to Mg with the diet, establishing that there is sufficient scientific evidence to indicate that dietary Mg contributes to various functions of the body, including electrolyte balance, the energy performance of the metabolism, neurotransmission and muscle contraction, including heart muscle, cell division, protein synthesis and finally the maintenance of bones and teeth (European Food Safety Authority 2009).
In particular, considering bone health, Mg has a pivotal role.
Mg deficiency might affect bone directly (by reducing bone stiffness, increasing osteoclasts and decreasing osteoblasts) and indirectly (by interfering with PTH and vit D, promoting inflammation/oxidative stress and subsequent bone loss) (Castiglioni et al. 2013).
Mg is an essential cofactor for vitamin D synthesis and activation and, in turn, can increase intestinal absorption of Mg and establish a feed-forward loop to maintain its homeostasis (Uwitonze and Razzaque 2018; Erem et al. 2019).
Given this background, the aim of this narrative review was to consider the state of the art since 2009 on relationship between Mg blood levels, magnesium dietary intake and Mg dietary supplementation (alone or with other micronutrients; this last topic has been considered since 1990, because it is not included in the EFSA claims) and bone health in humans.