Magnesium Flashcards
What are some dietary sources of magnesium?
Ubiquitous.
High sources include legumes, leafy greens (loves binding to chlorophyll), and nuts.
Moderate sources can be meats and fruits.
What is the general risk level of Mg deficiency?
Pretty low. It’s rare since in so many foods.
What is the general RDA for male and female for Mg? Provide units
Males ~ 0.4mg/d
Females ~ 0.3mg/d
Pregnant women require a small bit more.
What % of Mg is normally absorbed and where in the intestine?
30-50% along the entire intestine but mainly in the last half.
What transport fxns in Mg absorption?
Active and passive (so can be upregulated and is inverse to about ingested).
What are 2 factors that increase and decrease Mg absorption?
Increase - low Mg status and protein potentially.
Impair - Fiber and super high doses of other divalent cations.
What are the 3 most bioavailable forms of Mg?
Citrate, Glycinate and Malate.
Why is Mg reabsorption relatively efficient?
70% of Mg is filtered as free Mg (not bound to proteins like calcium) therefore most can be reabsorbed.
What part of the kidney does most Mg reabsorption occur and what does it require for reabsorption?
In the proximal and thick ascending tubules. Requires potassium ions to be excreted.
What are some causes of Mg deficiency?
Usually a secondary disease (since reabsorption quite effective).
Vomiting/diarrhea, kidney dysfxn, chronic electrolyte imbalance/chronic exercise.
Mg role in heart function?
- Required for proper muscle contraction.
- Essential for maintaining normal heart rhythm.
- Helps regulate calcium channels
- Necessary for ATP production/energy metabolism
What are 3 main body systems that are affected by Mg deficiency?
- Muscular (weakness, spasms)
- Cardiovascular (dysrhythmias or tachycardia)
- Biochemical (hypokalemia since trying to reabsorb Mg and hypocalcemia since affects PTH and renal functioning).
How does magnesium relate to calcium levels?
Low Mg impairs PTH secretion and also caused renal and skeletal resistance to PTH thus causing hypocalcemia when Mg low.
What is Mg main role?
It can bind to highly charged molecules/anions that other ions cannot and acts primarily as a stabilizer and complexer. Often competes with Ca.
Where is Mg usually found in the body?
54% in skeleton, 45% in soft tissues, and 1% in ECF (mainly as free Mg)
What compounds does Mg like to complex?
organic phosphates and nucleic acids. (last 2 phosphates)
What 4 essential functions is Mg intimately apart of?
- Cellular E metabolism
- Nucleic acid and protein synthesis
- 2nd messenger systems
- ion channel (stabilizer)
How is Mg involved in the 2nd messenger system?
Needed for G-protein and adenylate cyclase stabilization and also to produce ATP for cAMP.
What is the system other than the adenylate cyclase system that Mg is involved in and how?
Phosphoinositol cycle. Without Mg it becomes less efficient and affects amount of calcium being released since this cycle produces IP3 which stimulates the ER to release Ca to propagate intracellular signals.
How is Mg important for ion channels?
Important for many, but especially for active transport of K out of cells by Na/K ATPase and passively by K channels. It stabilizes the channel.
