WHY DO WE NEED MAGNESIUM?
Magnesium a mineral, is used in building bones, manufacturing proteins, releasing energy from muscle storage, and regulating body temperature.
DO WE GET ENOUGH MAGNESIUM?
According to recent USDA surveys, the average intake of magnesium by women 19 to 50 years of age was about 74 percent of the RDA. Men of the same age got about 94 percent of the recommended amount. About 50 percent of women had intakes below 70 percent of their RDA
HOW MUCH DO WE NEED?
The Recommended Dietary Allowance (RDA) is the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97-98%) individuals in each life-stage and gender group. The 1999 RDAs for magnesium in milligrams (mg) for men are: Ages 14-18: 410 mg, ages 19-30: 400 mg, ages 31 and older: 420 mg. For women the RDA's are 360 mg for 14-18 year olds, 310 mg for ages 19-30, and 320 mg for ages 31 and older. The RDA increases by 40 mg during pregnancy.
Results of two national surveys indicated that the diets of most adult men and women in do not provide the recommended amounts of magnesium. The surveys also found that adults age 70 and over eat less magnesium than younger adults, and that non-Hispanic black subjects consumed less magnesium than either non-Hispanic white or Hispanic subjects.
HOW CAN WE GET ENOUGH MAGNESIUM?
Eating a variety of foods that contain magnesium is the best way to get an adequate amount. Healthy individuals who eat a balanced diet rarely need supplements. Intakes of magnesium tend to be low in relation to recommendations, and there aren't that many foods that are really good sources; thus, it may take special care to ensure an adequate intake. The list of foods will help you select those that are good sources of magnesium as you follow the Dietary Guidelines. The list of good sources was derived from the same nutritive value of foods tables used to analyze information for recent food consumption surveys of the U.S. Department of Agriculture, Human Nutrition Information Service.
HOW TO PREPARE FOODS TO RETAIN MAGNESIUM
Magnesium is lost in cooking some foods even under the best conditions. To retain magnesium: .Cook foods in a minimal amount of water. Cook for the shortest possible time.
WHAT ABOUT WHOLE-GRAIN CEREALS?
Whole-grain ready-to-eat cereals usually contain 10 percent of the U.S. RDA for magnesium. Since cereals vary, check the label on the package for the percentage of the U.S. RDA for a specific cereal.
WHAT IS A SERVING?
The serving sizes used on the list of good sources are only estimates of the amounts of food you might eat. The amount of nutrient in a serving depends on the weight of the serving. For example, 1/2 cup of a cooked vegetable contains more magnesium than 1/2 cup of the same vegetable served raw, because a serving of the cooked vegetable weighs more. Therefore, the cooked vegetable may appear on the list while the raw form does not. The raw vegetable provides the nutrient - but just not enough in a 1/2-cup serving to be considered a good source.
WHAT CAN MAGNESIUM DEFICIENCY OCCUR?
Even though dietary surveys suggest that many Americans do not consume magnesium in recommended amounts, magnesium deficiency is rarely seen in the United States in adults. When magnesium deficiency does occur, it is usually due to excessive loss of magnesium in urine, gastrointestinal system disorders that cause a loss of magnesium or limit magnesium absorption, or a chronically low intake of magnesium.
Treatment with diuretics (water pills), some antibiotics, and some medicine used to treat cancer, such as Cisplatin, can increase the loss of magnesium in urine. Poorly controlled diabetes increases loss of magnesium in urine, causing a depletion of magnesium stores. Alcohol also increases excretion of magnesium in urine, and a high alcohol intake has been associated with magnesium deficiency. Gastrointestinal problems, such as malabsorption disorders, can cause magnesium depletion by preventing the body from using the magnesium in food. Chronic or excessive vomiting and diarrhea may also result in magnesium depletion.
Recommended dietary amounts of magnesium: Mg RDA
In developed countries, the recommended dietary amounts of magnesium have been set at 6 mg/kg day. The magnesium requirements for optimal health in the adult population depend on mesological and constitutional conditioning factors. They may intervene at every stage of magnesium metabolism: absorption, circulation, storage and excretion. The influence of other nutrients is more significant on magnesium absorption than on urinary excretion. Among the multiple interactions it is important to emphasize the maintenance of a Ca/Mg ratio close to 2 in the intake. Magnesium deficit and stress reinforce each other in a pathogenic vicious circle. The Bw35 allele of HLA typing and behavioural type A discriminate two constitutional factors increasing magnesium requirements. The effective passive regulatory mechanism for magnesium overload, the lability of the active regulatory mechanisms for magnesium deficit and the considerable need for exchangeable magnesium are factors which attribute special importance to balance studies in determining the magnesium intake which prevents negative magnesium balance and magnesium deficiency.
Marginal primary magnesium deficit affects a large proportion of the population (15 to 20%), in keeping with a daily mean magnesium intake slightly over 4 mg/kg day versus the Mg RDA of 6 mg/kg day. A physiological oral magnesium load test, evaluated through non-specific and specific clinical and paraclinical items, constitutes the best proof that the clinical pattern depends on an insufficient magnesium intake, confirmed after one month of supplementation. Further research appears necessary. It would be advisable to carry out long-term magnesium balance studies in European countries on the self-selected diets of adults, together with comparisons of direct evaluation of magnesium in the diet with data obtained from tables of food composition. Magnesium intervention trials should be planned to determine whether magnesium supplements decrease the pathogenic consequences of magnesium deficit and particularly to evaluate the efficiency of magnesium supplements in latent tetany (hyperventilation syndrome, "idiopathic" Barlow's disease). Supplementation should consist of a high magnesium density nutrient such as magnesium in water, which has better bioavailability than magnesium-fortified foods.
Magnesium and trace elements in the elderly: intake, status and recommendations
Imbalances between mineral intakes and recommended amounts have been observed in different groups of elderly subjects. Nevertheless, assessment of the status of magnesium and trace elements in the elderly is difficult, even for iron because infection and inflammation increases ferritin. Mineral bioavailability may change due to ageing. Therefore, formulation of mineral recommendations is complex and individual recommendations are sometimes necessary. A number of surveys show magnesium, zinc, selenium and chromium intakes by old persons to be lower than the corresponding reference nutrient intakes. Contrarily, intakes of iron are generally adequate or higher than recommended, and it has been suggested that increased storage of iron in the elderly may be related with the development of age-related diseases through the increase in oxidative stress. Low iron status together with iron excess may be common in an elderly population. The same applies for zinc. Magnesium and selenium deficiencies among the elderly are also well documented, especially among the institutionalised and people with pathologies. Chromium deficiency is associated with type II diabetes mellitus. Recommended iron intake is lower for elderly women compared to young, because menstruation ceases after menopause, but in old men, it is similar to that of young men. Dietary Reference Values for the rest of the elements are similar to those of adults, although several suggestions have been made about the quantities. This review examines various aspects of the changes in mineral bioavailability due to ageing, of data published on mineral intakes and status, and finally the dietary recommendations for this vulnerable population group.
Authored by Vaquero MP.