TWO grams of magnesium would be a medicinal dosage, like what doctors occassionally use for hospitalized heart patients.
However, it turns out that a high fat diet inhibits the absorption of magnesium, so maybe that is why some people on these boards can tolerate such a seemingly high amount.
Many of the magnesium rich foods are those which also tend to be high in carbohydrates.
People who have Crohn's or IBS or Celiac Disease also have problems assimilating magnesium.
If you are taking Vitamin D, it is essential to take extra magnesium.
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"....Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. As magnesium deficiency worsens, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary spasms can occur [1,3-4]. Severe magnesium deficiency can result in low levels of calcium in the blood (hypocalcemia). Magnesium deficiency is also associated with low levels of potassium in the blood (hypokalemia) [1,19-20].
Many of these symptoms are general and can result from a variety of medical conditions other than magnesium deficiency. It is important to have a physician evaluate health complaints and problems so that appropriate care can be given....
http://ods.od.nih.gov/factsheets/magnesium.asp
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"What foods provide magnesium?
Green vegetables such as spinach are good sources of magnesium because the center of the chlorophyll molecule (which gives green vegetables their color) contains magnesium. Some legumes (beans and peas), nuts and seeds, and whole, unrefined grains are also good sources of magnesium [5]. Refined grains are generally low in magnesium [4-5]. When white flour is refined and processed, the magnesium-rich germ and bran are removed. Bread made from whole grain wheat flour provides more magnesium than bread made from white refined flour. Tap water can be a source of magnesium, but the amount varies according to the water supply. Water that naturally contains more minerals is described as "hard". "Hard" water contains more magnesium than "soft" water.
Eating a wide variety of legumes, nuts, whole grains, and vegetables will help you meet your daily dietary need for magnesium. Selected food sources of magnesium are listed in Table 1.....
http://ods.od.nih.gov/factsheets/magnesium.asp