What is magnesium?

Magnesium is a mineral that our bodies need for a variety of functions, including: making proteins, producing energy (cell respiration), making DNA, sending nerve signals, muscle contraction and control of blood sugar.

Like other minerals (and vitamins), magnesium is a micronutrient – a substance that we require only in small amounts.

The average adult body contains about 25 g of magnesium, with the majority of this stored in bones and tissues. There is also magnesium present in our bloodstream. Levels of magnesium in the blood are kept within a constant range. This process is largely regulated by the kidneys, which alter the degree to which they excrete magnesium into urine.

KEY POINTS

• Magnesium is a key micronutrient needed for several life-sustaining functions.
• Magnesium levels in the blood are kept in check by the kidneys.

Why does my body require magnesium?

In order to sustain life, our body must carry out trillions of chemical reactions each second. To ensure this happens, these reactions are sped up (or ‘catalysed’) by special biological molecules (usually proteins) called enzymes. Enzymes often require another ‘helper’ molecule to successfully carry out a chemical reaction. These helper molecules are termed ‘cofactors’ and typically include vitamins, vitamin-derived compounds, and ions of metals, such as zinc, iron, copper and, you’ve guessed it, magnesium.

In fact, over 300 different enzymes in the body use magnesium as a cofactor. These enzymes and therefore, by extension, magnesium, are involved in lots of important processes in cells and tissues. For example, magnesium is a cofactor for key enzymes involved in cell respiration – the process by which cells produce chemical energy (in the form of ATP) from glucose. Magnesium is also required by enzymes that build DNA and protein molecules.

For nerves to send signals and for muscles to contract, your nerve and muscle cells must control the concentration and movement of various electrically charged ions, particularly potassium, sodium and calcium ions. To facilitate this, your nerve and muscle cells have specialised pumps that move ions between the inside and outside of cells. Lots of these ion pumps require magnesium to function. Consequently, magnesium is important for efficient nerve signalling and muscle contraction.

Magnesium also acts as a cofactor in reactions linked to the secretion and function of insulin, a hormone that controls our blood sugar (or blood glucose) levels. An adequate intake of magnesium is therefore important for maintaining healthy blood sugar levels.

KEY POINTS

• Magnesium is an important co-factor – it is needed by several enzymes to carry out chemical reactions.
• Magnesium is required for cell respiration: the process by which cells get energy.
• Magnesium is needed to make DNA and proteins.
• Magnesium is required for efficient nerve and muscle function.
• Magnesium is important in the control of blood sugar.

Magnesium, insulin and blood sugar

Our cells and tissues need chemical energy to survive and function efficiently. For example, your muscles use chemical energy (in the form of a molecule called ATP) to contract and move your body. Typically, our cells generate this energy by the breakdown of glucose. However, to do this, our cells must first get their hands on glucose. This is where insulin comes into play.

Insulin is a hormone that allows cells to take up and use glucose that is circulating in the bloodstream. There are several, complex ways by which insulin facilitates the uptake of glucose into cells. Where muscles are concerned, your muscle cells have specific receptors for insulin on their surface. When insulin binds to this receptor, it triggers a series of chemical reactions which causes your muscle cells to embed specialized glucose transporter proteins on their surface. These transporter proteins are known as GLUT4 transporters and allow the passage of glucose from the blood into cells.

So how does magnesium fit into this? Magnesium is a cofactor for one of the enzymes (tyrosine kinase) associated with the insulin receptor. Magnesium is therefore very important in the intermediate chemical reactions that result in GLUT4 transporters being embedded into the cell surface. Furthermore, magnesium is also involved in the production and secretion of insulin by the pancreas. Overall then, adequate levels of magnesium are required for both the formation and action of insulin.

To highlight this fact, studies suggest that low levels of magnesium are linked to poorer insulin function. This makes it harder for cells in your body to take glucose from the bloodstream and use it for energy. A related issue is that, as it cannot enter cells, glucose levels in the blood start to rise. Elevated blood glucose levels in the long term can cause damage to blood vessels and inflammation.

If insulin function is poor and blood glucose levels remain high, your body may try to compensate by producing more insulin. Unfortunately, this may lower levels of magnesium even further, as insulin causes the kidneys to excrete more magnesium into the urine. For this reason, people with poor insulin function (e.g. people with Type II diabetes) are at greater risk of low magnesium levels and may need to get more magnesium from their diet and/or supplements.

KEY POINTS

• Insulin is a hormone that facilitates the uptake of sugar (glucose) from the bloodstream to be used by cells for energy.
• Magnesium is required both for the production and actions of insulin.
• Low levels of magnesium may cause poor insulin function and high blood sugar levels.
• Poor insulin function may further lower levels of magnesium by increasing excretion of magnesium in the urine.
• Magnesium is important for maintaining healthy blood sugar levels.
• People with poor blood sugar control are at greater risk of low magnesium levels.

Genetics

As explained above, blood glucose, insulin and magnesium levels are all complexly intertwined. Given this relationship, genes that affect blood sugar and insulin function will also have an impact on your magnesium levels.

In this regard, variants of your PPARG and SLC30A8 genes, which affect insulin function and blood sugar levels, also influence your requirement for magnesium. Generally speaking, people at a higher genetic risk of high blood glucose levels are also at a greater risk of low magnesium levels. Accordingly, such people may need to increase their intake of magnesium

There are also other gene variants which affect the transport, metabolism and excretion of magnesium in the kidney. These include TRPM genes, which encode magnesium transporter proteins.

KEY POINTS

• Gene variants affecting insulin function and blood glucose levels (e.g. PPARG and SLC30A8) also affect magnesium levels.
• Gene variants that increase your risk of poor insulin function and high blood sugar also increase your risk of low magnesium levels.

Magnesium and training

Exercise, particularly intense endurance and HIIT (High Intensity Interval Training) exercise, increases your body’s demands for magnesium.

This may partly result from the fact that your muscles are working hard for long periods of time, placing higher demands on metabolic and energy-producing pathways that use magnesium as a cofactor.

Another reason is that magnesium is lost in sweat and endurance exercise tends to involve prolonged periods of sweating!

Ultimately, then, if you perform a lot of endurance exercise, you may need to increase your intake of magnesium through your diet or with supplements.

KEY POINTS

• Endurance exercise and HIIT may deplete magnesium levels.
• Magnesium is lost in sweat.

How much magnesium do I need?

There are various ways of classifying how much of a particular nutrient you need. One popular classification which you’ve probably already encountered is the Recommended Dietary Allowance (RDA). This refers to the average amount of a nutrient needed to be consumed each day to meet the requirements of 97%–98% of healthy individuals.

Due to differences in physiology and dietary needs, RDAs vary depending on sex, age, pregnancy status and breastfeeding status. Below are the basic RDAs for magnesium:

• Males 19-30 years old - 400 mg.
• Females 19-30 years old - 310 mg.
• Males over 30 years old – 420 mg.
• Females over 30 years old – 320 mg.

What foods are rich in magnesium?

Generally speaking, legumes, nuts, green leafy vegetables, seeds and whole grains are rich sources of magnesium. Specifically, peanuts, almonds, cashews, spinach, soybeans, black beans and edamame beans are all good sources of magnesium.

Should I supplement with magnesium?

As explained above, people with (or at risk of) high blood sugar levels are more likely to have low levels of magnesium. Similarly, if you perform a lot of endurance exercise, you are also at greater risk of magnesium depletion.  

If you fall into either of these groups, it may be beneficial to take magnesium supplements. Typically, people are recommended to 200-400 mg daily with food.

KEY POINTS

• Consider taking supplements if you have poor insulin function / high blood sugar.
• Consider taking supplements if you perform a lot of endurance exercise (e.g. running, cycling, swimming).
  
• 200 - 400 mg of magnesium (taken daily with food) is the usual dose.