Macronutrient PowerPoint
Sylviameng
Magnesium.pptxMagnesium
Emily Foss, Kenzi Cavanaugh
Magnesium- Quick facts
The fourth most abundant mineral in the body is Magnesium
An adult body has 25g of Magnesium which can be mostly found within the skeleton and the rest in muscle, soft tissue and blood
The 2015-2020 Dietary Guidelines for Americans listed Magnesium as an under consumed nutrient
g can be found within the body
Structure and forms
The absorption of Magnesium varies…
Forms which dissolve well in liquid are more completely absorbed in the gut than less soluble forms
A few small studies which show magnesium in the aspartate, citrate, lactate and chloride forms is absorbed more completely and is more bioavailable than magneisum oxide and magnesium sulfate
Why do we need Magnesium?
Biochemical reactions such as energy production, nutrient metabolism, fatty acid and protein synthesis, transmission of nerve impulses, glucose control, blood pressure regulation and transport of potassium and calcium ions all require Magnesium
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An appropriate intake of Magnesium has been associated with a reduced risk of cardiovascular disease and may prevent pancreatic cancer
Current recommendations include:
-80 mg for children 1-3 years old
-360 mg for adolescent females
-410 mg for adolescent males
Sources- where we can get it from!
An abundant amount can be found in plant and animal sources as well as tap or bottled waters
Fortified and enriched grains are another source
If taking Magensium as a supplement it should be taken with meals to avoid diarrhea
The top 2 excellent food sources are….
1 oz dry roasted almonds
½ cup of boiled spinach
Sources continued….
Others include:
-Soy milk
-Whole-wheat bread
-Avocado
-Fortified breakfast cereals
Mg2+ homeostasis depends on three organs:
•The intestine, facilitating Mg2+ uptake
•Bone, the main Mg2+ storage system of the body
• The kidneys: responsible for Mg2+ excretion
Absorption
•Magnesium is mostly absorbed in the jejunum, ileum, and colon, and absorption depends on the amount ingested / magnesium status.
•At normal intake, absorption is primarily passive
•In the intestine, about 80–90% of Mg2+ is absorbed passively through paracellular transport and the remaining is absorbed via active Mg2+ transporters, which account for the fine-tuning of Mg2+ regulation
•When intestinal magnesium concentration is low, absorption occurs via active transcellular transport
•Lower magnesium levels= more is absorbed in the gut, so relative magnesium absorption is high when intake is low and vice versa.
Of the total dietary magnesium consumed, only about 24–76% is absorbed in the gut and the rest is eliminated
Two transport systems for magnesium in the gut & kidneys
•Majority absorbed by passive paracellular mechanism, driven by an electrochemical gradient and solvent drag
•relies on tight junction permeability and involves absorption of Mg2+ through the small spaces between the epithelial cells
•ileum & distal parts of the jejunum =most permeable for ions due to relatively low expression of ‘tightening’ claudins
•Small, fine tuning fraction, transported via transcellular absorption pathway
•active transport of Mg2+ to the blood through the interior of the epithelial cell
•tight regulation since the ions have to pass through 2 cell membranes
•Transient receptor potential channel melastatin member 6 (TRPM6) and TRPM7 Mg2+ channels mediate transcellular absorption
•TRPM6 and TRPM7 expression restricted to the luminal membrane of the enterocytes
Magnesium storage
•Mg2+ can be stored in muscle fibres, where it plays an important role in the regulation of muscle contraction by antagonizing the action of Ca2+
•bone tissue is the largest Mg2+ store in the human body, where it also contributes to the density and strength of the skeleton
•bone surface Mg2+ concentrations are closely related to serum Mg2+ concentrations, indicating a continuous exchange of Mg2+ between bone and blood
Mg2+ is mainly excreted in the kidney.
•About 2400 mg of Mg2+ is filtered daily by the glomeruli. About 90–95% of daily filtrated Mg2+ is reabsorbed in the kidney; the remaining 100 mg leaves the body via the urine
•Approximately 10–25% of Mg2+ is reabsorbed in the proximal tubule (PT).
• Bulk transport (50–70%) of Mg2+ is achieved along the thick ascending limb (TAL) of the loop of Henle.
The final Mg2+ concentration in urine is determined in the distal convoluted tubule (DCT) where only 10% of Mg2+ is reabsorbed
RDA and tolerable upper intake levels (UL)
•The recommended daily allowance (RDA) for magnesium in adults is
4.5 mg/kg/day
•Upper limit for magnesium in dietary supplements and medications is 350mg/day for adults
