If you eat whole flaxseeds instead of ground ones, your body gets way less of the healthy compounds they contain—only about 28% as much.

What we've found so far is that the body absorbs far fewer beneficial compounds from whole flaxseeds compared to ground flaxseeds in healthy humans. Our analysis of the available research suggests a significant drop in the amount of enterolignans—the compounds linked to health benefits—that show up in the body after eating whole versus ground flaxseed. We reviewed the evidence and found that when people eat whole flaxseeds, their bodies only get about 28% as many of these compounds as they do when they eat ground flaxseeds [1]. This means that most of the potential benefit may pass through the digestive system without being used. The outer shell of the flaxseed appears to remain largely intact during digestion, which likely limits the release of the nutrients inside. Our current analysis shows the evidence leans toward ground flaxseed being much more effective for increasing enterolignan levels. While we only have one claim to base this on so far, the data point is clear and comes from studies involving healthy humans. That said, we don’t yet know how this might affect long-term health outcomes—only that the body absorbs much less when the seeds are eaten whole. There isn’t enough evidence at this time to say whether chewing whole seeds thoroughly might improve absorption, or if other factors like gut health play a role. But based on what we’ve reviewed so far, the form of flaxseed matters a lot. Practical takeaway: If you want more of the beneficial compounds from flaxseed, ground flaxseed is likely a better choice than whole.