Your body needs magnesium to regulate a variety of biochemical reactions. The kidneys help your body get rid of waste products and regulate magnesium levels by determining how much magnesium to excrete in your urine. The function of the kidneys determines how much magnesium the body needs.
Magnesium in the Body
Some of the major roles of magnesium in your body include helping manage nerve and muscle function, ensuring appropriate bone growth, regulating energy production and protein synthesis, and easing nausea and constipation. Magnesium deficiency is rare in most healthy people. If your intake of magnesium is low, your kidneys help keep your body from getting rid of too much magnesium. However, magnesium levels may be deficient if your dietary intake is poor, if you have alcoholism or a malabsorptive disorder, or use certain medications. Foods such as nuts, seeds, whole-grains and green leafy vegetables are good sources of magnesium.
Magnesium and Kidney Stones
Maintaining adequate magnesium levels may help prevent calcium oxalate kidney stones, the most common type. Calcium and magnesium competitively bind to oxalate. If calcium binds with oxalate, the crystals formed may lead to the formation of stones. However, if magnesium binds to oxalate, the crystals formed are more soluble and will likely not lead to stone formation. In most people the ratio of calcium and magnesium is appropriate to prevent calcium oxalate stone formation. In populations deficient in magnesium or more prone to stone formation, additional dietary or supplemental magnesium intake, along with other measures in kidney stone prevention, such as adequate fluid and limited sodium intake, may be beneficial.
Magnesium Intake and Impaired Kidney Function
If your kidney function is impaired, as is the case in chronic kidney disease and end-stage renal disease, your body may not be able to rid itself of excess magnesium. This may lead to toxic levels in your body, and can be identified by measuring a serum magnesium level. Magnesium toxicity can cause nausea, vomiting, diarrhea, low blood pressure and, in more extreme cases, may lead to muscle weakness, irregular heartbeat and cardiac arrest. In some people, the kidney is unable to rid the body of high magnesium levels from supplements or antacids. The Food and Nutrition Board's upper limit for magnesium intake from supplements is 350 milligrams daily.
Disorders of Magnesium Handling
In rare cases, some people may have a disease or condition that causes their kidneys to rid the body of too much magnesium. These conditions are often first identified in infancy and are usually accompanied by symptoms such as fatigue, weakness, muscle contractions and cramps, and low calcium and potassium levels. High magnesium intake may be appropriate with these conditions.