The goal of this clinical trial is to study the effect of four magnesium-based products on the magnesium concentration in plasma of volunteers upon oral intake. 40 healthy volunteers will be on a low magnesium diet for 1 week; then, after a 8-hour fasting, a blood sample will be taken from a digital puncture before (0 hours) and 1, 2, 4, 6 and 8 hours after the oral intake of one of the products. This 1-week procedure (1 week diet, fasting, oral intake of the product and sample collection) will be repeated for all 4 tested products, summing a total of 4 weeks (1 week per product). On the day of the sample collection, volunteers will be provided with a standardized low-magnesium breakfast (1:15 hours after oral intake), low-magnesium lunch (6:15 hours after oral intake) and water ad libitum. All the meal plans (products, quantities and hours of the meals) will be identical in all the periods of the study. Plasma will be obtained from blood samples by centrifugation and the magnesium concentration in plasma will be measured by ICP-MS (inductively coupled plasma mass spectrometry).

Magnesium is essential to the basic nucleic acid chemistry of all cells in all known living organisms. It is essential for DNA, RNA, and ATP synthesis, as well as for many other biological functions. Oral supplementation may improve the dietary intake of magnesium, which has been identified as a shortfall nutrient. In this study, the investigators will investigate the bioavailability of four magnesium-based products as food supplements by quantifying the magnesium levels in the plasma of volunteers after oral intake.

The study will be a double-blind trial to compare the bioavailability of four different magnesium products (Microencapsulated Magnesium, Magnesium Oxide, Magnesium Citrate and Magnesium Bisglycinate).

40 healthy volunteers between 20-55 years old will be enrolled in the study. Volunteers will be on a low magnesium diet for 1 week, including the consumption of low mineralization water; then, after a 8-hour fasting, a blood sample will be taken from a digital puncture before (0 hours) and 1, 2, 4, 6 and 8 hours after the oral intake of one of the products. This 1-week procedure (1 week diet, fasting, oral intake of the product and sample collection) will be repeated for all 4 tested products, summing a total of 4 weeks (1 week per product). On the day of the sample collection, volunteers will be provided with a standardized low-magnesium breakfast (1:15 hours after oral intake), low-magnesium lunch (6:15 hours after oral intake) and water ad libitum. All the meal plans (products, quantities and hours of the meals) will be identical in all the periods of the study. After every sample collection, participants will be allowed to leave the clinic, and asked to return at the required time-points. Volunteers will be requested not to practice any sport or to take part in any kind of strenuous exercise/activity during the day of collection.

Blood samples will be taken by digital puncture (non-invasive fingerstick procedure, by using VeriFine safety lancets 21G). The blood samples will be collected in EDTA-containing tubes (Minicollect tube K3E EDTA), centrifuged at 1000 rpm, 5 minutes at 4ºC, and plasma (supernatant) will be collected. Then, the magnesium levels in plasma will be measured by mass spectrometry ICP-MS (Mass Spectrometry with Inductively coupled plasma). The plasma samples of the 8-hour time point will not be analyzed by ICP-MS in principle, instead the samples will be stored at -80ºC and may be analyzed in further stages of the project.

There will be no consumption of supplements or specific food containing high levels of magnesium in the previous 7 days before the beginning of the experiment and during the experiment. Low mineralization water will be provided to the volunteers.

Inclusion Criteria:

• Healthy volunteers between 20 and 55 years of all races/ethnicities.
• Body mass index of 18-35 kg/m2.
• Last participation in a clinical study of this type must be at least 15 days before the start of this study.
• Fasting conditions during 8 hours before the experiment (with the exception of low mineralization water).
• No consumption of food supplements or specific food containing high levels of magnesium (see attachment) during the week before the start of the treatment.

Exclusion Criteria:

• People with gastrointestinal diseases (diabetes, gastritis, Crohn's disease, celiac disease, ulcers, intolerances, etc.).
• People with cardiorespiratory diseases (chronic bronchitis, chronic obstructive pulmonary disease, pulmonary emphysema, asthma and bronchiectasis, thrombi, heart disease, heart disorders, arrhythmias, insufficiencies, etc.).
• Pregnant or lactating women or who plan to become pregnant during the study.
• People under medical treatment in the weeks prior to the study that could interfere with the evaluations of the present study (according to the investigator's criteria).
• People who are within a dietary period outside their usual habit.
• People who demonstrate manifest incapacity to understand or follow the protocol or the informed consent.
• Allergy or reactivity to any of the components of the product, or to a product with a category similar to the tested one.
• Surgically operated for a heart condition.
• People with forecast of changing routine or relevant way of life, during the period of the study.