"The stable balance of calcium in the intracellular and external fluids is vital to normal cell metabolism."
The human metabolism is regulated by the autonomic, sympathetic, and parasympathetic nervous system. Hormones, metabolism, and other physiological processes are linked to the autonomic nerves—but if the autonomic nervous response is abnormal or irregular, the body's metabolism will almost definitely be affected. Calcium metabolism plays an integral role here.
To this end, we should work hard to maintain the calcium concentration in the extracellular fluid—especially during calcium metabolism. The calcium concentration in the cytoplasm is typically in the range of 100 nmol/L, which is only 1/10th-1/20,000th of the extracellular fluid concentration when calcium flows out. This means that when calcium flows in, the amount of calcium will increase by 5 to 10 times. Talk about a significant jump.
With that, some math: 100nmol/L translates to 4000 ng of calcium per l of cytoplasm (Nano Gram). 1 ng is 1/10 billion g, and the calcium content in every liter of intracellular fluid is 0.004 mg (as a point of reference, there are 10,000 times more calcium ions in the extracellular fluid, meaning every liter contains 40 mg of calcium). So, if the amount of calcium in the cells drops, the nucleus in our DNA will be abnormal. Its function may well decline, and mutations could occur as a result.
Given all of this, how can we determine the specific dosage recommendations? If 70% of the body weight of a 70 kg adult consists of water, then this translates to about 50 L of water. As such, the recommended SAC calcium dosage of 5 mg is equal to 0.1 mg per liter of body weight, or 25 times higher than one’s intracellular fluid intake.
Why is this? The idea here is to correct the body’s sodium ions. Because SAC calcium is the absorption pathway of Passive Transport Movement, the recommended dosage already incorporates the amount of calcium in the extracellular and intracellular fluids. In short, there’s a lot of thought put into this science-backed dosage recommendation.
Now, in the event of a large difference in calcium concentration between the extracellular fluid and the cell membrane, the calcium will flow into the intracellular fluid pretty quickly. This recalibration, if you will, is the product of the intracellular calcium reservoir, which features various forms of calcium pathways, including the high-calcium affinity Ca2+/H+ ATPase and the low-affinity Na+/Ca2+ exchanger.
Some additional numbers for your reference: There is 1200 mg of sodium per kg of body weight, of which 30-40% is found in the bone tissue, with the remaining portion located in bodily fluids like the cells. Specifically, 10% is in the cells, while 310~340 mg/dL is found in the serum.
Keep in mind that since sodium is an electrolyte, the amount of sodium in the serum is more than 4 times the amount of calcium in the serum, while the Standard Heat of Formation (SHF) content is about 3 times higher.
○ Ca2+(CaCO₃) -288,450 cal/g mol at 25℃
○ Na+ (NaCl) -98,232 cal/g mol at 25℃
SHF is Material Thermodynamics energy. This means that to maintain balance, the calcium of divalent cations can reach 4 × 3 × 2 = 24 times. And so, the standard recommended amount for each dose translates to 5 mg.