Without getting too technical here food grade standard is essentially what all foods are made too.
For example lets look at chocolate chip cookies. No two are the same. No two have the same size and have the same number of chocolate chips and that’s ok because its a biscuit. But its not ok for a supplement you are trusting to help prevent cancer and other chronic illness!
99% of all supplements are made to this food grade standard, so no two pills are the same and also because of this standard the manufacturer doesn't have to guarantee that what is on the label is inside each and every tablet. So you may get inadequate doses or too much of one element which can even be toxic to your body.
This is the standard to which all drugs are made too. The highest standard in the world and guarantees product to product, pill to pill that they are the same, that they are potent, pure, bio-available (which means in a form that your body can absorb it not pass it straight through)
So don’t even look at a product that isn’t Pharmaceutical grade. The product I use is made to the highest standard available on the planet for anything that can go into your mouth its called "US Pharmacopoeia and British Pharmacopoeia standards".
This also means that doctors and physicians can use and recommend this type of supplement as it conforms to the very highest standards they use everyday in their medical practices. In fact many doctors and physicians use and recommend this particular product range that I use. You wont find too many doctors who actively use and recommend products and the ones that do will only use Pharmaceutical grade products. This is the reason why until recently most doctors have been unanimous that supplements are a waste of time and money, well they were right, most of them are. With the overwhelming exception of a few Pharmaceutical grade products.