The quality of food supplements

Vitamins and minerals must be taken in the form of chemical compounds. There are good and not so good compounds available for this, below are some examples:

Vitamin C

Natural vitamin C, e.g. from acerola, is better absorbed by the body and excreted more slowly than synthetic ascorbic acid. Also important is the tolerance, which is rather poor with the very acidic ascorbic acid. It is better to take it in the form of calcium ascorbate, i.e. buffered, non-acidic vitamin C.

Folate

Mostly synthetic folic acid is used for the production of food supplements, but it only becomes effective in the body after conversion into 5-methyltetrahydrofolate (5MTHF).
One in two people cannot convert synthetic folic acid into the active form for genetic reasons. Therefore, folic acid should generally be taken in the form of 5MTHF. The enzymatic conversion step, which is problematic for many people, is no longer necessary in this case.

Calcium

Calcium carbonate must first be converted into calcium citrate by the body. Stomach acid is needed for it to be absorbed. People with low stomach acid (e.g. because of taking stomach acid blockers, many elderly people) should take calcium citrate instead of calcium carbonate, especially as this is generally better absorbed and can be taken independently of meals.
Other forms such as calcium lactate and calcium gluconate are less practical for calcium supplements as they have a lower calcium content.

Selenium

The main selenium supplements used for selenium intake are selenomethionine and sodium selenite, but they have very different effects. Selenomethion, which is also in selenium yeast, has hardly any toxic effect on cells if the dosage is too high, but it accumulates in the cell and has a damaging effect on genes in the long term.
Sodium selenite does not damage genes and can be used in a more controllable way because of its short-term effect, but it has a toxic effect on cells when overdosed. It is therefore better to use sodium selenite as a source of selenium, making sure to follow the dose recommended by the therapist.

Conclusion

It is therefore worth looking at the list of ingredients to see which substances have been used before buying. If manufacturers avoid more precise information, e.g. if instead of ester C calcium ascorbate they simply state "vitamin C", the reason is usually the use of the cheapest ingredients.
Of course, products with better ingredients are also somewhat higher in price. However, in terms of the cost/benefit ratio, they are usually much "cheaper" in the sense of the word, than cheap products with low value.