By Meg Perdew
Magnesium (Mg2+) supplements have started rising in popularity among competitive and recreational athletes as a ‘must-have’ supplement that supports muscle recovery, bone health and sleep. However, very few of us actually know if we are deficient in magnesium nor are we aware of the critical role magnesium plays in energy metabolism. Particularly, Mg2+ is a critical component of bone and plays an important role in bone mineralization, partly by influencing the synthesis of active vitamin D metabolites that support intestinal calcium and phosphate absorption.
Mg2+ is the fourth most abundant mineral in the human body and acts as a cofactor for more than 350 enzymes that are involved in energy metabolism – making it one of the most important regulatory minerals for maintaining optimal cellular function. Mg2+ homeostasis is maintained by renal absorption and urinary excretion and the rate of intestinal absorption is determined by the amount consumed as well as an individual’s current magnesium status.
Many naturally grown foods contain Mg2+, but in the past few decades its consumption has substantially declined due to increased consumption of processed foods, which often have undergone removal of Mg2+ during processing. Foods that are typically high in Mg2+ include: almonds, bananas, black beans, broccoli, brown rice, flaxseed, green vegetables (spinach), nuts, oatmeal, soybeans, tofu and whole grains. Nonetheless, it is critical to consider that today’s farmland has been depleted of many important minerals such as Mg2+, therefore, crops and vegetables grown in our soil are not as rich in Mg2+ as they once were.
Even individuals who eat a diet containing primarily whole foods can fall short of meeting recommended daily intake, which for the average adult is between 300-400 mg/day, because of the removal of this mineral that occurs during food processing (i.e., packaged, pre-prepared foods and non-organic produce) in addition to Mg2+ bioavailability (i.e., absorption is influenced by the type of nutrients consumed with Mg2+). For example, foods high in dietary fibre can decrease fractional absorption of Mg2+. Interestingly, diets high in vegetables containing large amounts of Mg2+ also provide a significant amount of fibre, this high amount of dietary fibre results in decreased absorption of the mineral. The reason for this being that foods high in fibre contain phytates, which reduce intestinal absorption of Mg2+, since Mg2+ is capable of binding to the phosphate groups on phytic acid.
Magnesium and the Athlete
In contrast to less active individuals, highly active people and especially the elite athlete, may place higher demands on the homeostatic mechanisms that regulate the body’s Mg2+ balance and thus may require a higher daily intake of Mg2+ compared to inactive individuals. For example, extended periods of increased energy expenditure are typically associated with an essential and amplified turnover of soft-tissue and bone as well as increased urinary excretion and surface losses of magnesium, which could in turn increase the risk of highly active individuals becoming magnesium deficient. Mg2+ is involved in both anabolic and catabolic processes that impact muscular performance during intense bouts of exercise. A recent study examined Mg2+ supplementation among professional male cyclists; the study included two groups: group A cyclists were given 400mg per day of magnesium and group B did not receive a supplement during their 3 weeks of competition racing. Results demonstrated that overall serum magnesium levels decreased during the race, but in the group receiving the magnesium supplement the observed increase in myoglobin was alleviated. In other words, magnesium supplementation may exert a protective effect on muscle damage. Additionally, research shows that among individuals participating in strength training a suboptimal intake of magnesium can lead to inefficient energy metabolism and ultimately decreased endurance. Overall, multiple human studies suggest that magnesium supplementation may improve performance in both aerobic and anaerobic exercise modalities.
Should you supplement with Mg2+? And if so, what kind of supplement should you purchase?
If you are engaging in any kind of intense exercise for an hour or more each day, it may benefit you to take a daily magnesium supplement. Magnesium supplements have the potential to a) improve bone health, b) support high-intensity or extreme sports training and recovery, and c) improve sleep:
a. How does magnesium support bone health? Magnesium supports the maintenance of bones and teeth by helping to regulate calcium levels in the body. Specifically, magnesium is required for calcium to bind to teeth enamel, and it aids the conversion of vitamin D into its active form.
b. Does magnesium support high-intensity and/or extreme training for sport? Despite the fact that magnesium is available in many high-quality whole foods, research suggests that elite athletes may consume an inadequate amount of magnesium to support higher volume training programs (i.e., the elite CrossFit athlete training 2+ hours per day; endurance athletes such as competitive cyclists or triathletes). Athletes need magnesium to support optimal training and recovery due to its critical role in electrolyte balance, normal muscle function and protein synthesis, as well as energy metabolism.
c. How does magnesium improve sleep? In addition to magnesium’s contribution to normal muscle function and relaxation, it also impacts biochemical pathways in the brain that may promote both relaxation and sleep. Specifically, magnesium binds to gamma-aminobutyric acid (GABA) receptors; GABA is a neurotransmitter that plays a crucial role in how our bodies respond to stress and is responsible for calming nerve activity.
It is important to consider what form of magnesium is the best option for supplementation for athletes as there are currently numerous options available. Overall, the form of magnesium generally recommended for athletes is magnesium glycinate, but below we have provided a list of some of the current options available and their primary purposes:
- Magnesium Citrate – form of magnesium bound with citric acid. Some evidence postulates that this is the most bioavailable form of magnesium (i.e., rapidly absorbed in the digestive tract). However, magnesium citrate generally provides a natural laxative effect and thus is often used at to treat constipation.
- Magnesium Oxide – often seen in milk of magnesia products because of its strong laxative effect; this form of magnesium has poorer bioavailability and is not an optimal form to use as a supplement.
- Magnesium Aspartate – provides increased bioavailability in comparison to magnesium citrate and oxide; early research has demonstrated that a combination of magnesium and potassium aspartates reduced the effects of fatigue and muscle hyper-excitability. Generally, this form of magnesium is used to treat chronic fatigue syndrome.
- Magnesium Glycinate – this combination of mineral and amino acid (i.e., glycine) has good bioavailability and typically does not have a laxative effect due to the fact that glycine is actively transported through the wall of the small intestine. Magnesium glycinate is often used to alleviate chronic pain and muscle tightness, stiffness or soreness. Additionally, evidence shows that magnesium glycinate is more bioavailable than magnesium oxide.
- Magnesium Taurate – magnesium and the amino acid taurine both share the capacity to improve cardiac function. Taurine is the most abundant amino acid in the heart tissue and magnesium contributes to normal muscle function. Research has shown that these compounds can improve insulin sensitivity and have a calming effect on neuromuscular excitability.
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