Magnesium is found in whole foods

Magnesium is a mineral found in many whole foods, but supplements are plentiful and are often promoted as a “good” thing.

Do we need supplements, or can we get enough of this important mineral from food?

Magnesium rich plant foods at a market

Photo by Alexandr Podvalny on Unsplash

Key facts about magnesium

It is an essential mineral

  • 50% is found in the bones
  • 33% found in soft tissues and muscle
  • Absorbed from the small intestine
  • Used in most tissues of the body
  • Involved in over 300 processes
  • Supports the production of energy
  • Involved in the contraction and relaxation of muscles
  • Regulates the nervous system through the production of neurotransmitters
  • Involved the formation of protein
  • Helps create and repair DNA and RNA (maintenance of our genes)
  • Regulates potassium
  • Involved in the metabolism of calcium

Food sources of magnesium

Widely distributed in plant and animal based foods

Best sources

  • Green leafy vegetables, such as spinach
  • Legumes and lentils, for example black beans
  • Beans
  • Nuts and seeds, such as pumpkin seeds, almonds, cashews
  • Shellfish and fish
  • Spices
  • Whole grain cereals, such as quinoa

The absorption of this mineral is tightly regulated. Absorption ranges from 25 to 75%.

If the magnesium supply from food is low, the body absorbs more.

  • High zinc intakes may reduce absorption
  • High fibre intakes (40-50g per day) lower absorption
  • Low protein (less than 30g per day) lowers absorption
  • High protein (over 94g per day) increases urinary excretion

The kidneys also help to regulate levels in the body.

Magnesium deficiency

Deficiency is rare

It can be caused by

  • Poor diet
  • Prolonged diarrhoea or high losses in the urine

Symptoms that occur over time

  1. Anorexia (loss of appetite)
  2. Nausea
  3. Muscle weakness
  4. Lethargy
  5. Weight loss
  6. High irritability
  7. High excitability
  8. Muscle spasm
  9. Tetany
  10. Convulsions

Other facts about deficiencies

  • Low calcium occurs in severe magnesium deficiency
  • Can be a risk in post menopausal osteoporosis

Interactions with medications

Medications can interfere with magnesium levels

  • Magnesium supplements and medications
  • Decrease the absorption of bisphosphonates, medications used to treat osteoporosis.
  • Bind with antibiotics containing tetracyclines and quinolone.
  • Diuretics increase the loss of magnesium in the urine.
  • Longterm use (over 12 months) of proton pump inhibitors, medications for the treatment of a number of gastric conditions, can cause low magnesium levels.

Are magnesium supplements safe?

Too much magnesium is not a concern if you are in good health, as your body will excrete excess amounts of the mineral in your urine.

High doses from supplements and medications can lead to:

  • Diarrohea
  • Nausea
  • Abdominal cramping

Toxicity has occurred at intakes above 5000mg/day, and can cause death.

Supplements and health

There is emerging evidence for the use of supplements, but unless you have a specific health condition, whole foods supply adequate amounts of the mineral.

  • Type 2 Diabetes. Magnesium has an active role in the action of insulin, making blood sugar easier to regulate, but more research is required.
  • Reducing insulin resistance, before Type 2 Diabetes develops. But there is also solid evidence for dietary and lifestyle changes too.
  • Assisting the lowering of high blood pressure, however there is ample evidence for eating whole foods and making healthy lifestyle changes without the requirement for medication or supplements.
  • Reducing symptoms of premenstrual syndrome (PMS), such as abdominal cramps, irritability, tiredness, and water retention.

Discuss your personal health requirements with your healthcare practitioner. It is important to let all of your healthcare practitioners know what medications and supplements you take.

Magnesium is an essential mineral required by the body to support our physical and mental health. The best source is from whole foods.

As an experienced and accredited dietitian and nutritionist I am sorry that supplements are often promoted as essential. Practising mindful eating is the best way to nourish yourself with whole foods, alongside a balanced lifestyle.

For more information on mindful eating and living, please take a look at the Eating for You book.


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