Supplement Forms Explained

The same ingredient can come in many different forms. And the form you choose can make a huge difference in how well your body absorbs it.

Magnesium is a classic example. Magnesium oxide is cheap and widely available, but your body only absorbs about 4% of it. Magnesium glycinate, citrate, and threonate all have much better absorption rates. If you’re taking magnesium oxide for a deficiency, you’re mostly paying for expensive urine.

Curcumin has terrible bioavailability on its own. Your body breaks it down before it can do much. But formulations like Longvida, Meriva, and CurcuWIN use different technologies to boost absorption by 20x or more. Plain turmeric capsules aren’t going to deliver meaningful blood levels of curcumin.

CoQ10 comes in two forms: ubiquinone and ubiquinol. Ubiquinol is the active, reduced form that your body can use directly. It’s more expensive but better absorbed, especially as you get older and your body gets worse at converting ubiquinone.

Omega-3 fatty acids come as ethyl esters, triglycerides, or phospholipids. Triglyceride-form fish oil absorbs better than ethyl ester form. Krill oil delivers omega-3s as phospholipids, which some research suggests absorbs better still.

This is why we note the specific form used in clinical trials on each supplement page. If the research was done on magnesium glycinate, we can’t assume magnesium oxide will give you the same results. Form matters. Always check what was actually studied.

For more on how we evaluate the research, see How We Rate Supplements.