1) Many cheap products contain inactive or poorly bioavailable nutrients. A common and very prevalent issue are supplements that contain a form of B12 call cyanocobalamin.
This form of B12 is inactive, very poorly absorbed and once absorbed must be converted into the active form methylcobalamin, which is typically poorly converted, and even more so in those with genetics that limit that pathway.
What this means is that not only are cells not obtaining the bioavailable form that they need to function, but blood testing will falsely suggest that there are sufficient B12 levels in the body.
B12 is a common deficiency due to poor gastrointestinal health and poor diets (and the rampant use of antacid medications) which can impact various systems in the body, particularly affecting energy levels and neurological health (as the most common deficiency symptoms are low energy, numbness/tingling and mental health effects).
Unfortunately, this fact is not common knowledge so consumers purchasing a cyanocobalamin B12 supplement will be under the false belief that it is benefiting them when in fact it is arguably harming them.
I advise my patients that if they have purchased a stand-alone B12 product that is cyanocobalamin rather than methylcobalamin to in fact just throw it out.
Another even less known concern along this same vein are supplements that contain folic acid rather than the active form methyl-folate. Though widely used, folic acid is concerning because it's conversion to active folate in the body is very poor and can harm the body.
Folic acid, while similar in structure, is not the same as the natural folate found in foods used by the body, and in fact, it will preferentially bind up the receptors for active folate, leaving it difficult for the active form to even access the receptor sites.
Folic acid has no benefit in the body until it is converted into the active form and not only does it steal away the receptor sites but also preferentially binds to the transport proteins as well.
If inactive forms of B12 and folate are ingested, this limits healthy production of red blood cells, DNA synthesis, and build-up of homocysteine which is a marker for increased cardiovascular disease risk.
2) The non-medicinal ingredients in common drugstore multivitamins are concerning as well. In pulling up the ingredient list of one of the most common multivitamins on the market to name a few of the most concerning: FD&C Yellow #6, Sodium Lauryl Sulfate, mineral oil, hydrogenated soybean oil.
It can be argued that in small doses there isn't a "concern" but when the fundamental purpose of a multivitamin is for health promotion, these ingredients are completely counter to that intention.
Professional line products never contain these additives which indicates that they are not required, however, their use likely makes them more cost-effective.
We know trans fats (ie: hydrogenated soybean oil) promote cardiovascular disease, that mineral oil is a petroleum-based product and a toxin, just like SLS is a toxin and rarely is colourant is ever health-promoting; FD&C Yellow#6 may also be a petroleum-derived product.
3) The fillers and non-medicinal ingredients further compromise the bioavailability of the multivitamin by the mere fact that it can be incredibly difficult to break down.
Particularly in more senior populations who have relatively more reduced digestive capacity yet an increased need for nutrients, these common multivitamins can pass right through the digestive system and be passed in the stool. This is where the term "bedpan bullets" came from, with nurses who observed the intact multivitamin.
The harm therefore comes in the way of not supplying the nutrient load expected and not meeting physiological and metabolic needs for health. Every system of the body can be impacted since vitamins and minerals are essential co-factors in a myriad of metabolic pathways.
Given the combination of an increased environmental load of chemicals and toxins, and a decreased nutrient load in the plants grown and processed foods consumed (approximately 30-40% reduction of nutrients even in organically grown vegetables), there is a necessary increased need for nutrient repletion in this day and age.
Selecting a good quality multivitamin that can both offset and support the increased needs of the body is more important than ever.