system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do fish oil pills have to be so big?

Like seriously why do I have to practice my deep throating skills every time I take one?
gpt
The reason that people buy fish oil pills is for its omega-3 content, and specifically its EPA and DHA content.  But fish oil is only about 25% omega-3, and of that only about half is EPA and DHA.  That means that only about 1/8 of the fish oil is the stuff that people are actually buying the pills for.

To make matter worse, fish oil pills cause stomach problems in most people and also cause a condition called "fish burps" - which causes people to have smelly, foul tasting burps for an hour or two after taking the pills.  Its possible to prevent both of those problems, but the pills need to be given a coating that prevents the pills from dissolving until after they've left your stomach.  That coating takes up a significant amount of space in the pill.  

This means that as you make a fish oil pill smaller a greater percentage of the pill ends up consisting of coating, rather than the actual fish oil.  IE, you can't just take one 1000 mg fish oil pill and turn it into two 500 mg pills because the amount of coating on each of those two smaller pills has to remain the same as the larger, single pill. 

So fish oil pill manufacturers have to give you a huge dose of fish oil in order for you to get a meaningful amount of omega-3.  The easiest way to do that is by making two huge pills.  If they made more pills with the same omega-3 dose it would require 5 or 6 smaller pills (or possibly more), which is more than most people are willing to take.

There are omega-3 pills that are more reasonably sized.  The reason that they are more reasonably sized is because they either source the omega 3 from algae (which doesn't cause stomach problems or fish burps, and so doesn't need the anti-dissolve coating) or they've separated the DHA and EPA out of the fish oil so that those are the only things that the pill contains.  Making an omega-3 pill using either of those methods is about 3-4 times as expensive as just using straight fish oil, but that's why there is such a disparity in terms of omega-3 pill cost.