A list of supplements that don’t work very well in the versions sold in the US

Updated October 22, 2020. Originally posted November 19, 2011. Over the years I’ve learned that some of the nutrient supplements on the shelves in the US don’t work very well, either because a significant part of the population can’t process them, or because the version used is poorly absorbed by the body, or because they are so cheaply formulated that the filler would make you sick before you could get enough of the active ingredient to resolve your deficiency.

Here’s everything I know so far. Needless to say, the better versions are more expensive and harder to find.

Folic acid

Processing this synthetic vitamin into its active form requires methyl groups and those of us who are methyl-challenged (low methylators) need to use the methylfolate version. Some sources say that the folic acid formulation is pointlessly inefficient for anyone.

Calcium carbonate

Calcium carbonate requires stomach acid to work, and is hard on the stomach for some people. Calcium citrate absorption doesn’t require stomach acid. (This issue isn’t as big a concern as the others listed here.)

Magnesium oxide

This is not as bioavailable as other options, such as magnesium citrate. According to the National Institutes of Health’s Office of Dietary Supplements, magnesium lactate and magnesium chloride are even better options, but they are harder to find in pill form. You can also absorb magnesium through the skin in the form of epsom salts (magnesium sulfate) and magnesium chloride, which can be found in a spray oil.

Vitamin B1, aka thiamine hydrochloride

This is poorly absorbed by the body. If you are only mildly deficient, it might be all you need, but I needed a fairly large dose and couldn’t stomach it at all. When I switched to the more efficient benfotiamine, I had no trouble and noticed results much faster. Another version is thiamine tetrahydrofurfuryl disulfide (TTFD), which is what I use.

Vitamin B2, aka riboflavin

This is also poorly absorbed. Riboflavin phosphate AKA riboflavin-5′-phosphate AKA flavin mononucleotide (FMN) is a better formulation.

Vitamin B6, aka pyridoxine

Some people have trouble converting pyridoxine to its active form, pyridoxal-5-phosphate (P5P). You can buy the active version in supplement form, usually referred to as P5P. Some experts say you just have to use a part of your dose in that form; the rest can be pyridoxine.

Vitamin B12, aka cobalamin or cyanocobalamin or hydroxocobalamin (used in injections)

Like folic acid, it requires a methyl group to convert to its active form. I’ve followed a discussion group on B12 whose members are adamant that these types are pathetically inefficient and that methylcobalamin should be used. (There is also adenosylcobalamin AKA dibencozide AKA coenzyme B12, but I was never clear what the difference is.) If you are having injections, you might have to search a bit to find a compounding pharmacy that can prepare the methylcobalamin shots, which is less stable than the other versions and has to be carefully shipped and stored.

The reason B12 tablets come in doses with such large numbers, such as 1,000 micrograms or 5,000 micrograms, is because the body can only absorb about one percent of it at a time.

Vitamin D2, aka ergocalciferol

Depending on what you read, vitamin D3 (cholecalciferol) is either three or five times more bioavailable than vitamin D2.

Vitamin K1, aka phylloquinone

Vitamin K2 (menaquinone) is the preferred version, but I don’t know a lot about it. Vitamin K3 (menadione) has been banned so you shouldn’t have to worry about that one.