My guess is, a stomach busy processing food will give the pill time to dissolve.
Does a pill swallowed hours either side of meal time or eating of any food still enter the system properly? What about pills without the ‘at mealtimes’ instruction?
I think it’s to prevent stomach irritation.
It means that the medicine/nutrient/vitamin is fat soluble rather than water soluble, meaning it needs a fat source in order for it to be absorbed in the body.
Some things, like Vitamin E, always come in a gell cap for this reason.
Also, some substances - like vitamins - will combine with whatever is in your stomach as it’s digested, and if there isn’t any food, it’ll combine with your stomach lining. I learned this the fairly hard way. Didn’t throw up, but really felt like it was a good idea.
Another reason, completely unrelated to the digestability, absorbability, irritability, etc. of the medication:
Telling people to take their medicine at mealtimes means it’s less likely to be forgotten.
Stomach irritation is always the reason doctors have told and, boy, follow that advice. I’ve taken pills without meals that literally made my stomach feel like it was on fire.
I’ve always thought absorption was the main reason, as having food in the stomach typically reduces the absorption rate substantially. There are other factors which might affect absorption, such as the presence of oils and changes in pH. Some drugs are absorbed better in the stomach than in the small intestine, and taking such a drug with food would mean it would spend more time in the stomach. Reduced irritation is another factor. But several others have already been suggested – including one I hadn’t ever thought of, even though it’s probably the simplest: it makes patients less likely to forget.*
Lamar Mundane: Most drugs are poorly water soluble in their pure (‘free base’)form. But most drugs contain nitrogen, often in an amino group (R-NH[sub]2[/sub]), which makes the drug slightly basic. Such drugs, even if the pure form is not water-soluble, can be made water-soluble by treatment with acid, usually hydrochloric acid, but sometimes an organic acid such as tartaric or succinic acid. For example, paroxetine (Paxil®) is treated with hydrochloric acid to give paroxetine HCl. These acid salts are usually water-soluble. A very few drugs, particularly those which do not contain nitrogen, cannot easily be made into salts. These are usually dissolved in oil and delivered in a soft gelatin capsule. Vitamin E (which does not contain nitrogen) is an example of such a drug. Lecithin is also typically packaged this way, along with some other drugs, including the pure medicinal form of the active ingredient in marijuana, dronabinol (Marinol®).
Three reasons, depending on the type of medication.
Some medications will indeed attack your stomach liing if taken on an empty stomach.
Some medications are absorbed BETTER when they are taken with food.
Some medications are absorbed BETTER on an empty stomach (these are the ones with “take on an empty stomach/before meals”).