Unfortunately there is never a guarantee, because every person and every health condition is unique to a certain extent. Many variables are in play, so some trial and error is unavoidable. Despite that, here are some tips to maximize the chance of positive effects:
1. Choose an extract
According to research 80% of people either have trouble or cannot digest non-extracted mushroom products at all because they lack the enzyme chitinase in their stomach. This enzyme is essential to deal with the chitin that locks the bioactive compounds in the cell walls of the mushroom. Chitin restricts the bioavailability. Only an extract can guarantee bioavailability - otherwise a therapeutic effect is completely unpredictable. See this link for a detailed explanation.
2. Compare the product claims from the website against the supplement facts label
- it is unlawful to exaggerate or lie on that label, but on a website or a front label vendors have much more leeway to market a product. The supplement facts label should show a breakdown of beta-glucans at least. Nowadays beta-glucans can be tested very accurately using the AOAC-approved Megazyme® assay.
Many supplements specify polysaccharides, but that's using 20th century standards. Beta-glucans are polysaccharides, but not all polysaccharides are beta-glucans; e.g. starch, chitin, cellulose and dextrin are also -completely useless- polysaccharides found in many mushroom products.
A high polysaccharide percentage does not mean it is a good product.
You can easily test for the presence of starch and dextrin at home: open a capsule and mix the powder inside with a bit of cold water to make a liquid solution. Then add a few drops of iodine. See this youtube video. If the solution changes color (black, blue, red) it contains non-mushroom polysaccharides or starch. Percentages of up to 30% are not uncommon. Rice powder is also added often to increase the weight and to prevent cakeing of the extract powder.
3. f a vendor is marketing his product as a 10:1 extract
(or whatever ratio)
but does NOT specify any bioactives (beta-glucan, triterpenes, polyphenols) on the supplement facts label this might mean it's just dried and powdered mushroom, non-extracted. (also check: "What ratio are your mushroom extracts ?")
.There simply is only one reason NOT to test for beta-glucan or other active compounds - testing is pretty cheap and the results are what the consumer wants to see. Logic tells us the only reason to keep it vague or leave it out is because the outcome is unfavourable and will make the product look bad.
4, If you want more quality confirmation we recommend to ask the online vendor for a Certificate of Analysis (COA), issued by a third party lab. Many vendors simply write their own COA or will send you a fancy-looking Technical Data Sheet / Specifications Sheet, but it is obvious this proves nothing.