What are the best sources of Magnesium? All you need to know about Magnesium supplements.

Magnesium is in an essential mineral that is found in a variety of foods. Foods with the greatest amounts of magnesium include nuts, seeds, wholegrains, and some green leafy vegetables.

Unfortunately, many of these foods are absent in adequate amounts in most people’s diets.

For this reason many foods are fortified with magnesium, such as cereals.

Magnesium is involved in hundreds of processes in the body, but is most pivotal roles are in muscle contraction, as an electrolyte and in bone health.

Why is magnesium a popular supplement?

Interestingly, despite these very important functions most people are only aware of magnesium as a sleep aid, assisting in relaxation and the healthy function of nerve and brain cells. It is therefore a popular addition to sleep supplements.

However, the real benefit of magnesium containing supplements is in promoting the essential functions listed above and in the context that many athletes, who we can safely assume have what most would consider a healthy diet, still often present with symptoms of magnesium insufficiency and blood analysis has shown that in these populations magnesium status is sub-optimal in the region of 10% to 60% or even higher… depending on the population studied and the criteria used to define deficiency.


One of the problems with diagnosis with blood markers is that magnesium is stored in tissues, so it is difficult to assess true magnesium status. However, when I have assessed the diets of athlete’s magnesium intake is one of the most under consumed and it is not uncommon for people to be consuming significantly less than 50% of the recommended daily amounts.


From a general health perspective, magnesium helps with blood sugar control and regulating blood pressure in populations who have medical conditions that effect their regulation (diabetes, hypertension etc.)

What are the different types of magnesium?

Although all supplements add to our body stores, not all magnesium is created equal.

Certain types tend to have greater bioavailability compared to others… this basically means that either there is an increased uptake in the digestive system into the blood stream and/or the amount of magnesium ‘released’ from its supplemental form. Meaning there is more available for use in the body.

Although the amount of magnesium present is important, the form in which it comes also plays a role in how well your body can use it.

  • Magnesium Citrate: This form is one of the most commonly used magnesium supplements. It is easily absorbed by the body and often used to support digestive health due to its laxative effects.
  • Magnesium Glycinate: This form is bound to the amino acid glycine, which enhances its absorption and may reduce the likelihood of gastrointestinal side effects. It is often recommended for individuals who have trouble tolerating other forms of magnesium.
  • Magnesium Oxide: While magnesium oxide has a high magnesium content, it is not as well absorbed as other forms and may have a laxative effect in some individuals. It is commonly found in over-the-counter magnesium supplements.
  • Magnesium Chloride: This form is typically used in topical magnesium products such as magnesium oil or lotions. It can also be taken orally, although it may have a bitter taste.
  • Magnesium L-Threonate: This form has gained attention for its potential to cross the blood-brain barrier, leading to increased magnesium levels in the brain. It is touted for its cognitive benefits and is often used to support brain health and cognitive function.
  • Magnesium Sulphate: Also known as Epsom salt, magnesium sulphate is commonly used in baths for its potential to promote relaxation and relieve sore muscles. It can also be taken orally as a laxative in higher doses.
  • Magnesium Malate: This form is bound to malic acid, which is involved in energy production in the body. It is often used to support energy levels and may be beneficial for individuals with fibromyalgia or chronic fatigue syndrome.
  • Magnesium Taurate: This form is bound to the amino acid taurine, which may enhance its cardiovascular benefits. It is often recommended for individuals looking to support heart health.

Marine Magnesium

If you are a follower of CSN Supplements, you may have noticed that there is one absence from this list… Marine Magnesium.

This is because marine magnesium, extracted from sea water and/or seaweed, contains a blend of magnesium salts, the most prevalent of which are magnesium chloride and magnesium sulphate which are the forms of magnesium that are most abundant from natural sources.

How much should you take?

The recommended dietary allowance (RDA) for magnesium in adults is 410–420 mg/day for men and 320–360 mg/day for women, encompassing magnesium intake from various sources like food, drinks, supplements, and medications. The upper intake level (UL) for magnesium in adults is 350 mg, focusing solely on magnesium obtained from dietary supplements and medications.

For individuals aiming to enhance their magnesium levels for general well-being or to address a deficiency, certain forms of magnesium are more advantageous. Magnesium citrate is renowned for its superior bioavailability among all magnesium forms, with magnesium lactate following closely behind. Additionally, magnesium chloride, magnesium gluconate, and magnesium glycinate demonstrate favourable bioavailability.

Conversely, magnesium oxide and magnesium carbonate exhibit notably poor absorption and are not recommended for elevating magnesium levels in the body.

Magnesium citrate, particularly potassium magnesium citrate, and magnesium lactate tend to carry a reduced risk of gastrointestinal side effects and diarrhoea compared to other formulations. Reports suggest that magnesium carbonate and magnesium oxide supplementation may lead to more frequent gastrointestinal issues, although such concerns can arise with any magnesium supplement if excessively high doses are consumed.

About the Author: 
Dr Paul Rimmer is a nutritionist and physiologist specialising in athletic performance.
He is the director of www.athletelabs.uk providing performance data and insight to a wide range of athletes with a focus on performance optimisation. 
His private blog www.hybridathleteblog.co.uk documents his experiences training for powerlifting and ultramarathons and the science of hybrid training.