Sciencemadness Discussion Board

Why do supplements have to be taken incrementally

CrimpJiggler - 19-4-2015 at 07:47

For example, someone with zinc deficiency will be (I'm guessing) instructed by a doctor to take say 15 mg of zinc daily for a couple of months or so rather than taking a big dose of 500 mg of zinc. Whats the reasoning behind this? I assume larger doses will get more zinc into the blood stream, and ultimately into cells where they're needed.

Chemosynthesis - 19-4-2015 at 08:00

Water soluble vitamins and supplements are generally difficult to store in the body, as their solubility allows easy excretion in urine. Because of this, loading with a high dose is not nearly as efficient in combating a deficiency as maintaining a steady dosing regimen.

CrimpJiggler - 19-4-2015 at 09:52

What about lipophilic vitamins? Like oral vitamin D for example. I've heard of vitamin D shots which last for the year, but in that case I'm guessing they're intramuscular shots in which the vitamin D gets slowly released into the blood over the course of a year (I say that because they do these type of shots with antipsychotics like risperdone). Also, wouldn't the bioavailability still be dosage dependent? In the case of cheap substances like zinc, more of the substance being wasted via excretion isn't that big a problem.

Metacelsus - 19-4-2015 at 09:59

https://en.wikipedia.org/wiki/Zinc_toxicity

Taking a lot of zinc at once is asking for trouble.

[Edited on 19-4-2015 by Cheddite Cheese]

mayko - 19-4-2015 at 11:26

Quote: Originally posted by CrimpJiggler  
For example, someone with zinc deficiency will be (I'm guessing) instructed by a doctor to take say 15 mg of zinc daily for a couple of months or so rather than taking a big dose of 500 mg of zinc. Whats the reasoning behind this? I assume larger doses will get more zinc into the blood stream, and ultimately into cells where they're needed.


Iron is a major concern in this respect: high doses of iron are actually not good for people with severe anemia! The reason is that body fluids are kept iron-deficient to deter the growth of bacteria, using a binding protein called transferrin. Limiting free iron limits bacterial growth. So, if iron is provided to an anemic person faster than they can increase their transferrin levels to compensate, they can develop nasty infections on top of their weakened state.

Further reading:
Why We Get Sick: The New Science of Darwinian Medicine. Randolph Nesse & George Williams. Vintage Books: New York, 1994 (p.29-30 in particular)

Chemosynthesis - 19-4-2015 at 15:40

Quote: Originally posted by CrimpJiggler  
What about lipophilic vitamins? Like oral vitamin D for example. I've heard of vitamin D shots which last for the year, but in that case I'm guessing they're intramuscular shots in which the vitamin D gets slowly released into the blood over the course of a year (I say that because they do these type of shots with antipsychotics like risperdone). Also, wouldn't the bioavailability still be dosage dependent? In the case of cheap substances like zinc, more of the substance being wasted via excretion isn't that big a problem.
Sometimes toxicity. As noted by CC, this is an issue with heavy metals too. The route of administration is important because it can be used to tailor the dose. Bioavailability and absorption differ depending on route. You can get an IM dose and have a steady taper into the bloodstream, much like an IV or continuous ingestion. Relative bioavailability is considered consistent. Total bioavailability is dose dependent. It is best to stay within the therapeutic dosing range with no toxic spikes or wasteful dips below efficacious blood concentration. With a water soluble substance, you might hit a toxic dose and then suddenly excrete much of the excess, only remaining in a therapeutic range for a short time with additional problems. This may also be of potential benefit if your target protein has high turnover. Saturating it and having your body eliminate the rest of the drug is not going to help long.