Fortified with magnesium
Magnesium is attracting increasing attention in the functional foods and supplements industry. Several human studies have highlighted the beneficial effect of this important mineral on muscle functionality, bone health, hypertension, inflammation, asthma, headaches and even diabetes.
In Europe, the Regulation on fortification and claims has enabled manufacturers as of July 1, 2007, to use magnesium salts such as trimagnesium citrates for fortification purposes. In the US, Jungbunzlauer's trimagnesium citrates recently obtained GRAS (generally recognised as safe) status and can from now on be used for fortification of food and beverages as well.
Magnesium in the human body
Magnesium is the fourth most abundant cation in the human body and can be found in every human cell. Adults have about 1,000 mmol (24g) of magnesium, which is distributed between muscles and tissues (about 40%), extracellular fluids (about 1%) and the remainder in the skeleton. A portion of the bone magnesium is exchangeable and appears to act as a buffer against fluctuations in the extracellular magnesium concentration.
The physiological importance of magnesium is its involvement in a large variety of biological functions, its intervention in enzymatic reactions (more than 300 enzymes) and its role in membrane function and neuromuscular excitability. Furthermore, magnesium deficiency is associated with various chronic diseases including increased insulin resistance and diabetes, hypertension, hyperlipidemia and atherosclerosis, reduced bone density and alcoholism.
The diagnosis of magnesium deficiency is still a crucial problem, because it is rather asymptomatic, except in severe cases. However, the occurrence of nightly muscle cramps is connected to a lack of electrolytes, in particular magnesium.
Most unprocessed foods contain magnesium. The highest concentrations are found in whole seeds such as nuts, legumes and unmilled grains. Green vegetables such as broccoli are another source, as are bananas. Human milk contains about 28-40mg per litre.
Nutritionists assume that in developed western countries dietary magnesium generally does not meet the recommended intake for adults, especially in the elderly, because of changes in lifestyle and increased consumption of processed food. That deficiency is not uncommon among the general population and supplementation could be beneficial in some cases.
At the end of the 1990s, deliberations by the US Food Nutrition Board of the Institute of Medicine resulted in an increase in the estimated average requirement and recommended daily allowances for magnesium to substantially more than the mean intake for US males and females, indicating that a significant proportion of the population falls far short of the estimated requirements. In a recent French study of more than 5,000 subjects, 23% of the women and 18% of the men consumed less than 66% of the recommended dietary allowance.
Bioavailability of magnesium salts
Bioavailability is defined as the proportion of a nutrient that is absorbed and adequately utilised for normal body functions. If data on internal utilisation and metabolism of the nutrient are lacking, fractional absorption or retention can be taken as a measure of true bioavailability.
Absorption, retention and bioavailability of magnesium depend on several factors, including the amount ingested, meal and matrix effects and the active ingredient content. Individual factors also play a part, such as age, the magnesium status of the body and in some cases a disturbed intestinal absorption.
Organic and inorganic ions and other substances, as well as renal excretion, and the nature of the magnesium compound ingested also influence magnesium metabolism.
Generally, absorption of magnesium is higher when it is ingested together with a meal, whereas a higher magnesium load in a meal (at least 10mmol) decreases its fractional absorption and prolongs the absorption half-life. Absorption of magnesium begins within one hour of ingestion and continues at a steady rate for two to eight hours.
The suitability of a magnesium salt as dietary supplement or for food fortification depends on the content and the availability of magnesium. Generally, water soluble inorganic and organic magnesium salts and chelates offer high availability and are significantly more readily available in vitro than poorly soluble magnesium oxide.
These differences, however, may vanish under physiological conditions, given that insoluble salts of magnesium will be dissolved by gastric acid. In clinical studies published in 2001, no significant differences were found with respect to plasma concentration, urinary excretion and bioavailability in vivo between several therapeutically used magnesium salts.
Magnesium citrate comes top
However, in a study published in 2005 on magnesium-depleted rats, the comparison of 10 inorganic and organic magnesium salts revealed higher bioavailability for organic salts, with magnesium gluconate having the highest absorption.
In a human study on the bioavailability of four commercially available US magnesium supplements, magnesium oxide showed poor absorption compared to magnesium chloride and the organic salts magnesium lactate and magnesium aspartate.
In a more recent study, magnesium citrate was found to be more bioavailable than magnesium amino-acid chelate and magnesium oxide when administered in daily doses of 300mg over 60 days. Magnesium citrate led to the greatest serum magnesium concentration and mean salivary magnesium concentration, whereas magnesium oxide supplementation resulted in no differences compared to a placebo.
The superior bioavailability of magnesium citrate has also been proven to be significant in comparisons with magnesium oxide in vitro and in vivo.
At the biochemical and cellular level, magnesium and calcium act against each other. At the physiological level, however, intestinal absorption of normal amounts of magnesium occurs by paracellular passive diffusion, which is only minimally impaired by dietary calcium, and vice versa.
Based on the absorption rates and dietary intake recommendations for calcium and magnesium, it can be concluded that the optimal calcium to magnesium molar ratio in the diet, and thus in mineral supplements and fortified food, would range from 2:1 to 4:1.
Health claims
As a consequence of the new EU Nutrition and Health Claims Regulation, health claims made for foods need to be approved and must fulfil two criteria according to article 13 of the Regulation. They must be based on generally-accepted scientific evidence; and they must be well understood by the average consumer.
In this respect, the European food industry has jointly developed and consolidated a list of possible health claims for food and for substances added to food.
Together with a comprehensive compilation of scientific references, this list is now being submitted to the European Food Safety Authority (EFSA) for evaluation and approval. The contribution is a joint initiative of the Confederation of the Food and Drink Industries of the EU (CIAA), the European Responsible Nutrition Alliance (ERNA), the European Federation of Health Products Manufacturers (EHPM) and the European Botanical Forum (EBF).
Jungbunzlauer, an expert on calcium, magnesium and potassium fortification, actively participated in the consolidation of the health claims on minerals. For magnesium, the health claims include beneficial effects on bone and teeth structure, energy metabolism, electrolyte balance, muscle function and nerve transmission/function (see box, left).
All of these claims refer to 'authoritative body' and underlying scientific studies. Thus, if approved by the EFSA and the EU Commission as planned for January 31, 2010, these health relationships and claims could be used in the EU for products with added magnesium.
The future
The need for in-depth nutritional studies to justify health claims, means only salts which are proven to provide magnesium to the human body will do the job.
Trimagnesium citrates (trimagnesium citrate anhydrous and trimagnesium citrate nonahydrate) are highly soluble as well as bioavailable organic mineral salts and have been widely used in sports nutrition, food supplements, baby food and other dietary products so far. Due to recent changes in US and EU food legislation in favour of trimagnesium citrates, these two magnesium salts will offer new possibilities for the development of innovative magnesium fortified food and beverage products.
Dr Gerhard Gerstner is senior technical service manager at Jungbunzlauer Ladenburg. treuneq.trefgare@whatohamynhre.pbz References in this article are available upon request.
