All About Minerals

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Why magnesium is good for you

Every cell in the body needs magnesium to produce energy. Magnesium is required to make more than 300 different enzymes and to send messages along the nerves.

Magnesium makes the muscles relax and that ensures the heart is healthy and beats regularly, preventing abnormal heartbeat. Magnesium is also needed to keep blood pressure down to normal levels.

Magnesium is required so that the body can use other vitamins and minerals properly – vitamin C and calcium work better, for example, when there is sufficient magnesium in the body.

Magnesium works very closely with calcium to help keep bones strong throughout life.

There is about 25 grams of magnesium in the body and most of it is in the bones and teeth, but there is also a lot in the muscles and blood. The amount in the blood is very important as it ensures there is correct balance in various body processes. In the same way calcium is needed to make the muscles contract (when the heart beats) magnesium is needed to make the muscles relax again. The levels of magnesium and calcium in the blood need to be steady and sufficient. If there are insufficient blood levels of calcium and magnesium, the body will pull it from the bones and send it to the blood, which can result in weakened bones.


Important magnesium facts

Talk to a medical professional about magnesium supplements BEFORE taking them


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Groups at risk of magnesium deficiency

About 75% of the population do not get enough magnesium from their foods to meet the RDI, so they may be borderline deficient. Even so, very few people are really severely deficient in magnesium, as it would require intake of very low amounts of magnesium over a long time to have any major symptoms.

Magnesium deficiency occurs when there is less than 85mg intake of magnesium per day.

Deficiency of magnesium can occur if the following health problems are present:

People in these groups at risk of deficiency should talk to a medical professional about magnesium supplements BEFORE taking them.


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Symptoms of magnesium deficiency

If there is insufficient dietary magnesium, all the tissues in the body will become affected in some way, but mostly the following will be the most adversely affected:

  • Heart
  • Kidneys
  • Nerves


Generally magnesium deficiency symptoms include:

Severe magnesium deficiency


Many doctors and nutritionists feel that breathing problems, such as asthma are cause in part by a magnesium deficiency.


Magnesium and health



  • PMS – Studies show magnesium supplements relieve uncontrollable PMS and PMDD symptoms, such as breast tenderness, headaches and irritability. Studies show that women with severe PMS should try 300-500mg of magnesium per day for the two weeks leading up to menstruation. If severe cramps are a problem at menstruation, keep taking magnesium during that time too – it may help reduce menstrual cramping. Magnesium supplementation may help even more if it is combined with calcium and vitamin B6 (pyridoxine) for PMS and PMDD symptoms

People who wish to take a magnesium supplement should talk to a medical professional BEFORE taking it.



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Magnesium in food

FOOD AMOUNT magnesium (mg)
Black Beans 1 cup 121
Tofu ½ cup 188
White Beans 1 cup 113
Almonds, dry roasted 30g 84
Lima beans 1 cup 82
Kidney beans 1 cup 80
Spinach, cooked ½ cup 79
Chickpeas 1 cup 78
Swiss chard ½ cup 76
Cashews, dry roasted 30g 72
Lentils 1 cup 71
Wheat germ ¼ cup 69
Pinto beans, canned 1 cup 64
Oatmeal, cooked 1 cup 56
Potato, baked with skin 1 medium 55
Peanuts 30g 52
Peanut butter 2 Tbsp 51
Flounder 85g 50
Walnuts 30g 48
Okra ½ cup 46
Soy milk 1 cup 45
Yoghurt 1 cup 40
Milk, low-fat 1 cup 34
Banana 1 medium 33
Peas ½ cup 31
Prawns (shrimp) 85g 29
Bread, whole wheat 1 slice 23
Broccoli, cooked ½ cup 19
Bread, white 1 slice 5


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Magnesium recommended daily intake (RDI)

RDA lifestage age amount
  INFANTS 0-6mths
  CHILDREN 1-3yrs
  CHILDREN 9-13yrs
male: 14-18yrs
female: 14-18yrs
  ADULTS male: 19-30yrs
male: 31-50yrs
female: 19-50yrs
  SENIORS male: 51+yrs
female: 51+yrs
  PREGNANT <18yrs
  LACTATING <18yrs
TOLERABLE UPPER LIMIT lifestage age amounT
  INFANTS 0-12mths n/a*
  CHILDREN 1-3yrs
  CHILDREN 9-18yrs 350mg**
  ADULTS 19-50yrs 350mg**
  SENIORS 51+yrs
  PREGNANT all ages 350mg**
  LACTATING all ages 350mg**
Toxic Levels >2,000mg (can be much lower than this for some individuals)

The tolerable upper limits should only be taken for short periods and only under medical supervision.

* The tolerable upper limit for magnesium for infants aged 0-12 months has not yet been determined due to a lack of data about the adverse effects in this age group. The only source of magnesium intake should be from food (breast milk and/or baby formula).

* The tolerable upper limit for magnesium for adults, pregnant and lactating mothers is for any supplements that are taken beyond any magensium which is obtained in the diet.

There is no upper limit for magnesium in the diet, only an upper limit of magnesium from supplements.


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Magnesium works best with


Overdosage, toxicity and cautions for magnesium

Acute toxicity (>15 grams) - nausea, paralysis of the central nervous system, vomiting, sleepiness, extreme muscle weakness, difficulty breathing, heartbeat irregularity

Chronic toxicity - confusion, dry mouth, flushing, low blood pressure, muscle weakness, sleepiness, thirst


People with kidney failure or congestive heart failure should NOT take magnesium supplements or antacids containing magnesium


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Last reviewed: 10 January 2010 || Last updated: 21 January 2010




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NOTE: Mega doses of vitamins, minerals, amino acids, or other supplements cannot cure illnesses and in fact can be very dangerous and produce toxic side effects and interfere with medicine you are taking. Always ensure you consult your doctor before taking any type of nutrient supplement.
Disclaimer: This guide is not intended to be used for diagnostic or prescriptive purposes. For any treatment or diagnosis of illness, please see your doctor.