Hi Lorraine,
It’s true – there is a lot of conflicting information on when to take probiotics and which brands to take. Individual supplement companies with their own brands may have more specifics on how they suggest their product be used. However, the general rule is to take the probiotic after meals to buffer the effect of the stomach acid and to provide the bacteria with something to thrive on as it makes its way through the digestive tract. I personally prefer to take probiotics at night especially if I am introducing a new strains of bacteria. Some people may experience a bit of gas and bloating as their GI tracts adjust to the presence of new organisms. This effect can be avoided if they take the probiotic at night and allow these new organisms to set up while they are sleeping. Also, the migrating motor complex is more active at night pushing things through the GI tract and allowing these organisms to get to where they need to be.
As for the determination of how much of any product makes it to where it needs to be – the only way to test this is to directly measure levels of certain organisms in the stool. Some are measured on a CDSA panel and values can change through supplementation. Again, individual supplement companies may have more specific data on their products.