Description and Function
Magnesium is a mineral that affects the metabolism of calcium, sodium, and potassium. About 50-60% is in bone. Most of the rest is inside cells. It is a cofactor for over 300 enzymes, many of which participate in the generation of energy as ATP from carbohydrate, fat and protein. It is necessary for the proper functioning of the nerves and muscles, including the heart. It is important for DNA and RNA synthesis and for almost every step in protein synthesis.
Magnesium is a component of chlorophyll and therefore found in leafy greens such a spinach and kale. Nuts, seeds, bananas and the germ and bran of whole grains are also good sources. Processed foods are generally poor sources. For example, removing the bran and germ of a whole wheat kernel reduces the magnesium content of a cup of white flour to only 28 mg, compared with the 166 mg in a cup of whole-wheat flour. One cup of whole grain cereal, spinach or legumes contain about 100 mg of magnesium.
According to my textbook, deficiency is rare in the healthy population, but does occur in alcoholism, kidney disease, and gastrointestinal disease. Some medications such as diuretics (commonly taken for hypertension) can contribute by increasing magnesium loss in the urine. Proton pump inhibitors (PPI‘s) taken to prevent GERD, may cause low blood magnesium by interfering with magnesium absorption. Talk to your doctor about any medications you take and their drug-nutrient interactions.
Deficiency symptoms include muscle weakness and cramping, irritability, anxiety and changes in blood pressure and heartbeat. Low blood levels of magnesium affect levels of blood calcium and potassium so some of the symptoms may be due to alterations in these minerals as well.
Nevertheless, the typical intake of magnesium in the U. S. is below the RDA of 400 mg/day for young men and 310 mg/day for young women. After 30 years of age, the recommended intake increases to 420 and 320 mg/day for men and women, respectively.
There has been no large systematic study of the adequacy of magnesium body stores in Americans. In 2009, the World Health Organization published a report that stated that 75% of Americans consumed less magnesium than needed. Some say that we have a nationwide magnesium deficiency, especially those who sell supplements. It would be helpful if the National Institutes of Health or the Centers for Disease Control and Prevention could fund serious research to determine the status of Americans’ magnesium body stores. I fully have supported getting our nutrients from the diet and not from supplements, most of which are unnecessary. However, the current American processed food diet as well as our fast food intake may warrant magnesium supplementation for some consumers.
Low intakes of magnesium have been associated with heart disease; type 2 diabetes, hypertension and osteoporosis.
There are no adverse effects of magnesium intake from foods, but supplements of all types may have some side effects. Some elderly patients who have impaired kidney function may suffer from toxic effects of magnesium-containing laxatives and antacids such as milk of magnesia. The Tolerable Upper Intake Levels (UL) for adults and adolescents over 9 years of age is 350 mg from nonfood sources of magnesium.
Calcium in the diet decreases absorption in the digestive tract; therefore, the use of calcium supplements can reduce the absorption of magnesium.
Source: Smolin, Grosvenor: Nutrition, Science and Applications, Third Edition, Wiley.
Little is known about the relationship of diet and pancreatic cancer. Mortality rates from pancreatic cancer are increasing and there is a great need for more research in its prevention. FYI article follows on magnesium deficiency and its proposed association with pancreatic cancer.