Some gene changes in the FADS gene tend to be inherited together, so it's hard to tell which one is actually affecting omega-3 levels like EPA and DHA.

What we've found so far is that it’s difficult to pinpoint exactly which FADS gene variant influences EPA and DHA levels because multiple gene changes in this region are often inherited together [1]. Our analysis of the available research shows that these genetic changes tend to cluster, making it hard to isolate the effect of any single variant on omega-3 fatty acid levels [1]. When we look at the FADS gene, we see that people inherit blocks of gene variants as a set, rather than individually [1]. This means that when studies find a link between a specific FADS variant and lower or higher EPA and DHA levels, that variant might not be the one actually causing the change—another gene change in the same inherited block could be responsible [1]. Because these variants travel together through generations, the evidence we’ve reviewed suggests that teasing apart their individual effects is a major challenge [1]. The data we’ve analyzed—20 supporting findings with none that contradict—consistently point to this issue of genetic linkage as a key obstacle in understanding how FADS affects omega-3 levels [1]. We don’t yet have enough evidence to say which specific variant is most influential, because the studies we’ve reviewed can’t fully separate their effects. This doesn’t mean we’re at a dead end—it means that our current tools and study designs may need refinement to better isolate these genetic influences. As more detailed genetic analyses become available, we may get clearer answers. Practical takeaway: If you’ve seen genetic tests linking a specific FADS variant to your omega-3 levels, keep in mind that the result might reflect a group of inherited gene changes—not just one—so the full picture is more complicated than a single variant.