I occasionally encounter people who use the expression “developed a tolerance” to describe that annoying phenomenon in which a supplement works for a while to treat whatever symptoms you’re complaining of, and then stops. Tolerance is more accurately used in the case of prescription drugs or, alas, controlled substances like alcohol or da ganja, and doesn’t really apply to supplements. Although tolerance to drugs and controlled substances builds up for different reasons, they are much different mechanisms than what happens with most supplements such as vitamins, minerals, amino acids, etc.
A common cause of tolerance to a drug is that the drug causes your body to produce less of whatever substance the drug was meant to enhance. This happened to me when I first took clonazepam for insomnia. The drug was originally designed to control seizures, but my doctor at the time prescribed it for my two-hour-a-night sleep problem. For four days I slept NINE HOURS A NIGHT. I’ve never felt so good in my life. Then it stopped working. The doctor said it was a pretty common experience.
Turns out it’s a benzodiazepine (hereafter to be referred to as benzo), a class of drug that affects GABA levels in the brain. GABA is one of the few inhibitory neurotransmitters — it slows everything down, calms an overactive mind, gives you space between your thoughts, plays a big role in sleep. Benzos very quickly convince your body it can produce less GABA, which is why you’re not supposed to take the stuff for more than several weeks. The drug is only active for a few hours, after which you’ve got none of your own GABA to fill in that timing gap, so you take more of the benzo, or take it more often. (Here’s an overview of the different benzo Rx and their relative strengths.)
Many experts feel that supplements of the hormone melatonin have a similar effect. But then you can also find experts who don’t. (FYI in Canada and Europe, hormones are classified as drugs and are not sold over the counter as supplements.)
In the case of supplements that work briefly and then stop, it’s most likely because that supplement helped the uptake of another nutrient (or, more likely, a bunch of them — it’s unlikely that you’re deficient in only one thing) for a while, until it got to the bottom of the barrel.
Every time you take a supplement, a whole bunch of other substances in your body are ushered forth to process it. These are sometimes referred to as cofactors, and each nutrient has its own set, although obviously there’s a lot of overlap. Some of the more famous cofactor relationships are calcium and magnesium, magnesium and vitamin B6, and iron and vitamin C, but it gets even more complicated. Tryptophan needs B6, B2 and iron in order to convert into niacin, and iodine needs enough iron, selenium, and magnesium to do its thang. You can go nuts trying to remember it all.
So either you just happened to take a supplement that was cofactor to something you REALLY needed, or the supplement you took was in fact what you needed, but it used up all its cofactors. The former case is what happened to me with B-complex. The B-complex stopped my leg pain as long as I took it. After two days without it, the pain returned. What finally got rid of it was several months of calcium, which needs the B vitamins for absorption. The B-complex pulled just enough calcium into my bones to make a difference for a few days.
That’s why supplementation is an imperfect, and occasionally downright tedious, way to fix a deficiency — foods have more of the cofactors built in. But our anemic food supply, and the limited number of foods we typically eat, can’t provide enough nutrients to correct a serious deficiency. Or not quickly, anyway.