Kaydees behavior has been slightly deteriorating again, and some muscle problems have re-appeared. I realised that I have been lazy about keeping on top of what I am giving her to eat, especially while away, she has just been getting kibble. SO I have read more about magnesium in the diet, and thought perhaps other people might find this interesting too.
Most of this information has been obtained from a human perspective, gleaned from a google internet search.
What it is:
Magnesium is a mineral needed by every cell in the human body and is required for more than 300 biochemical reactions. Magnesium is usually referred to as a "macromineral" (The other macrominerals that all humans must get from food are calcium, phosphorus, sodium, potassium and chloride).
Most of our magnesium is found in our bones (60-65%) combined with calcium and phosphorus. Magnesium is also found in our muscles (25%), with only a very small amount, approximately 1%, found in our blood. The human body regulates the level of magnesium in the blood to keep it at a fairly constant level. This makes detecting deficiencies difficult, as blood tests will not show up a deficiency until reserves stored in the bones and muscles are severely depleted.
Like all minerals, magnesium cannot be made in our body and must therefore be plentiful in our diet in order for us to remain healthy.
What it does:
Nerve and Muscle Relaxation
Magnesium and its fellow macronutrient, calcium, act together to help regulate the body's nerve and muscle function. In many nerve cells, magnesium serves as a chemical gate blocker - as long as there is enough magnesium around, calcium can't rush into the nerve cell and activate the nerve. This gate blocking by magnesium helps keep the nerve relaxed. If our diet provides us with too little magnesium, this gate blocking can fail and the nerve cell can become over-activated. When some nerve cells are over-activated, they can send too many messages to the muscles and cause the muscles to over-contract. This chain of events helps explain how magnesium deficiency can trigger muscle tension, muscle soreness, muscle spasms, muscle cramps, and muscle fatigue.
Other functions of magnesium:
Many chemical reactions in the body involve the presence of an enzyme. Enzymes are special proteins that help trigger chemical reactions. Over 300 different enzymes in the body require magnesium in order to function. For this reason, the functions of this mineral are especially diverse. Magnesium is involved in the metabolism of proteins, carbohydrates, and fats. It helps genes function properly. Some fuels cannot be stored in our muscle cells unless adequate supplies of magnesium are available.
The metabolic role of magnesium is so diverse that it is difficult to find a body system that is not affected by magnesium deficiency. Our cardiovascular system, digestive system, nervous system, muscles, kidneys, liver, hormone-secreting glands, and brain all rely on magnesium for their metabolic function.
What happens when there is a deficiency:
Early signs of magnesium deficiency in humans 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. 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).
Because magnesium plays such a wide variety of roles in the body, the symptoms of magnesium deficiency can also vary widely. Many symptoms involve changes in nerve and muscle function. These changes include muscle weakness, tremor, and spasm. In the heart muscle, magnesium deficiency can result in arrhythmia, irregular contraction, and increased heart rate.
Because of its role in bone structure, the softening and weakening of bone can also be a symptom of magnesium deficiency. Other symptoms can include: imbalanced blood sugar levels; headaches; elevated blood pressure; elevated fats in the bloodstream; depression; seizures; nausea; vomiting; and lack of appetite.
What factors might contribute to a deficiency of magnesium?
In addition to poor dietary intake, problems in the digestive tract are the most common cause of magnesium deficiency. Magnesium is water soluble, so anything causing increased elimination of water from the body may also cause the loss of magnesium, although healthy kidneys should be able to recoup most the magnesium from fluids before they are eliminated from the body. Digestive tract problems causing magnesium loss include malabsorption, diarrhea, and ulcerative colitis. Many kinds of physical stresses can contribute to magnesium deficiency, including cold stress, physical trauma, and surgery. Kidney disease and alcoholism can contribute to a deficiency of this mineral.
There is anecdotal evidence that stress and very high activity levels can also cause a higher requirement for magnesium, and that ‘hypey’ excitable dogs could suffer from deficiencies.
How to get enough:
In humans, eating a variety of whole grains, legumes, and vegetables (especially dark-green, leafy vegetables) every day will help provide recommended intakes of magnesium and maintain normal storage levels of this mineral.
In dogs, most of the high magnesium recommended human foods do not form part of a normal balanced canine diet, although I would have thought a fish based diet would be better, I have not found any figures on this. It might be useful to know that whole grain rice has some magnesium but white rice has hardly any. However, even if whole grain rice is used in the production of high quality ‘complete’ dogs foods, my big question is, is this enough for high energy, ‘hypey’ dogs that are regularly competing in agility? Adding fish to the diet may be very beneficial, as many types of fish are known to be high in magnesium (and also omega 3 oils which also have many health benefits). Finely, freshly ground sunflower and pumpkin seeds should also provide good quantities of magnesium. Finely chopped dark green leafy vegetables served with eggs (to aid digestion and absorption of the magnesium) may also be beneficial. Although you would expect to find magnesium in bones, I have not come across any dietary figures for the levels of magnesium to be found in bone, only that ‘the amount of bone magnesium is only 1/40 to 1/50 that of calcium (Duckworth et al., 1940). However, it is reported that there is relatively little magnesium to be had from eating meat, therefore it does seem likely that a meat based canine diet would not provide enough magnesium.
How do other nutrients interact with magnesium?
The relationship between magnesium and calcium is one of the most actively researched, and yet not fully understood mineral-to-mineral relationships. On one hand, magnesium is required in order for calcium to maintain a balanced role in the body's metabolism. On the other hand, magnesium can compete with calcium and prevent calcium from trigger certain events, like the relay of a nerve message or the contraction of a muscle.
Because of the complex relationship between calcium and magnesium, healthy diets almost always need to contain foods rich in both minerals. Magnesium also has an important relationship with potassium, and helps regulate the movement of potassium in and out of our cells. Finally, because magnesium can be attached to certain building blocks of protein (called amino acids), increased intake of protein can sometimes help improve the body's magnesium status.
Although on one hand it may take a long time for magnesium deficiency to show up as there are stores in the muscles and bones, once the diet is enriched in magnesium, it will also take a long time before those stores are replenished.
Magnesium deficiency may be of significance to performance dogs who may have a higher requirement for this mineral (especially ‘highly strung’ personalities), because foods that contain high amounts of magnesium do not form part of many normal commercially available ‘complete dog food’ ingredients lists. Additionally, dogs are not good at digesting high fibre, high carbohydrate foods, where magnesium may be found (they do not chew foods or have amylase enzymes in their saliva), therefore adding high magnesium content foods, such as spinach and seeds, may only be useful if they are prepared by grinding them up first (do not boil!)
Impact of Cooking, Storage and Processing
The impact of cooking and processing on magnesium can vary greatly from food to food, since magnesium is found in different forms in different types of food. In some foods, where a greater percent of magnesium is found in water-soluble form, blanching (boiling or steaming for 1-4 minutes), steaming, or boiling of these foods can result in a substantial loss of magnesium. For example, about one third of the magnesium in spinach is lost after blanching. Similarly, when navy beans are cooked, they lose 65% of their magnesium.
In other foods that are rich in magnesium, like almonds or peanuts, there is very little loss of magnesium either from roasting or from processing into almond or peanut butter (as long as the whole almond or peanut is used).
What forms of magnesium are found in dietary supplements?
Magnesium can be purchased as a dietary supplement in one of two basic forms: chelated or non-chelated. "Chelated" means connected with another molecule. In the case of magnesium, the most common chelates fall into the category of amino acid chelates. In these supplements, magnesium is attached to a building block of protein (called an amino acid). The most widely-available amino acid chelates are magnesium glycinate, magnesium aspartate, and magnesium taurate.
Magnesium can also be attached to an organic acid (like citrate) or to a fatty acid (like stearate). The non-chelated forms of magnesium include magnesium oxide, magnesium sulfate, and magnesium carbonate. There is some research evidence that the chelated forms of magnesium (like magnesium citrate) are better absorbed than the non-chelated forms (like magnesium oxide).
Nutrient Rating System Chart
Have a look at:
· Abbott LG, Rude RK. Clinical manifestations of magnesium deficiency. Miner Electrolyte Metab 1993;19:314-322 1993.
· Bengtsson BL. Effect of blanching on mineral and oxalate content of spinach. J Food Technol 1969;4:141-145 1969.
· Duckworth J, Warnock GM: The magnesium requirements of man in relation to calcium requirements, with observations on the adequacy of diets in common use. Nutr Abstr Rev 12:167-183, 1942.
· Duckworth S, Godden W, Warnock GM: The effect of acute magnesium deficiency on bone formation in rats. Biochem J 34:97-108, 1940.
· Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995.
· Iseri LK, French JH. Magnesium: Nature's physiologic calcium blocker. Am Heart J 1984;108:188-193 1984.
· Lindberg JS, Zobitz MM, Poindexter JR, et al. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr 1990;9:48-55 1990.
· Meiners CR, Derise NL, Lau HC, et al. (1976). The content of nine mineral elements in raw and cooked mature dry legumes. J Arg Food Chem 1976;24:1126-1130 1976.
· National Research Council. Recommended dietary allowances. 9th edition. National Academy of Sciences Press, Washington, DC, 1980;134-136 1980.
· Pearson HA, Campbell V, Berrow N, et al. Modulation of voltage-dependent calcium channels in cultured neurons. Ann N Y Acad Sci 1994;747:325-335 1994.
· Shils ME. Magnesium. In: Shils ME, Olson JA, and Shike M. Modern nutrition in health and disease. 8th Edition. Lea and Febiger, Philadelphia, 1994;164-184 1994.
· Touyz RM. Role of magnesium in the pathogenesis of hypertension. Mol Aspects Med 2003 Feb 6;24(1-3):107-36.
· Wester PO. Magnesium. Am J Clin Nutr 1987;45(suppl):1305-1312 1987.
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