Magnesium Absorption: Diet and Supplements

Magnesium is an essential mineral that plays a pivotal role in numerous physiological functions. However, the human body only absorbs a fraction of the magnesium consumed through food and supplements.

Magnesium Deficiency

Magnesium deficiency may contribute to the onset of various health conditions such as cardiovascular diseases, osteoporosis, and asthma. It's also been associated with dysmenorrhea and premenstrual syndrome. Subclinical magnesium deficiencies, which are mild deficiencies that don't trigger classic deficiency symptoms, are believed to affect a significant portion of the population. These deficiencies may still contribute to the onset of various disorders.

In essence, many people's dietary intake of magnesium is sufficient to avoid a deficiency condition, but it does not allow the establishment of a normal plasma concentration that can protect against various pathologies.

Absorption of Magnesium

Magnesium absorption takes place in the intestines, from the duodenum (initial section of the small intestine) to the colon (large intestine). On average, 40% of the magnesium consumed is absorbed in the small intestine, 5% is absorbed in the large intestine, and the remaining 55% is lost in the feces.

Before absorption, magnesium must be separated from the substances to which it is bound, a process that occurs thanks to hydrochloric acid in the stomach. Magnesium absorption can be facilitated through two mechanisms: passive diffusion and facilitated diffusion.

Passive diffusion involves the passage of magnesium from a point of higher concentration to one of lower concentration, exploiting specific channels. Facilitated diffusion, on the other hand, involves a specific transport protein which transports magnesium from one part of the enterocyte to another, from where it passes into the interstitial fluid and then into the blood.

Once absorbed, the regulation of the body's magnesium reserves is mainly entrusted to the kidney, which acts on the quantity of the mineral excreted in the urine, exploiting mechanisms similar to those described for the intestine.

Magnesium Supplements Bioavailability

Magnesium supplements are available in various chemical forms, broadly categorized into organic and inorganic salts. The bioavailability—or the extent to which magnesium is absorbed and utilized by the body—varies significantly among these forms.

Organic Magnesium Salts

Organic magnesium salts, such as magnesium citrate, glycinate, and aspartate, are generally more water-soluble and tend to have higher bioavailability compared to inorganic salts. This increased solubility facilitates better absorption in the gastrointestinal tract. For instance:

• Magnesium citrate is known for its high solubility and is often used to address magnesium deficiencies effectively.
• Magnesium glycinate, which combines magnesium with the amino acid glycine, is well-absorbed and may have calming effects, making it suitable for individuals with anxiety or sleep disorders.
• Magnesium aspartate has also demonstrated good absorption rates and is used in various clinical settings.

Inorganic Magnesium Salts

Inorganic magnesium salts, such as magnesium oxide and magnesium sulfate, typically have lower solubility, which can result in reduced bioavailability:

• Magnesium oxide contains a high percentage of elemental magnesium but is poorly absorbed due to its low solubility.
• Magnesium sulfate, commonly known as Epsom salt, is more soluble than magnesium oxide but is often used for its laxative properties rather than as a magnesium supplement.

Factors Influencing Magnesium Absorption

The absorption of magnesium is influenced by a variety of factors. Certain foods, for instance, can reduce magnesium absorption, including those high in insoluble, non-fermentable fibers, oxalates, and phytates.

However, it's important to note that these foods should not be removed from the diet as they are a valuable source of magnesium and other micronutrients. Techniques like soaking legumes and whole grains before cooking and consuming sprouted seeds can increase the bioavailability of the magnesium they contain.

Other factors that can decrease magnesium absorption or increase its losses include the presence of certain drugs, health conditions like reduced gastric acidity, alcohol abuse, and certain diseases. Natural diuretics also tend to increase urinary excretion of magnesium.

On the other hand, the absorption of magnesium can be promoted by factors such as fructose and complex carbohydrates, animal proteins, medium-chain triglycerides, soluble or fermentable fibers, and Vitamin D.

In conclusion, those who consume large quantities of dairy products, follow a diet poor in fresh fruit and vegetables, or consume a lot of phosphorus-containing drinks should consider regularizing their eating style and resorting to a specific magnesium supplement. The same applies to individuals taking medications or suffering from conditions that can reduce magnesium levels in the body.