Daily dose for the omega-3s that you are aiming for is at least 1000 mg/day.
There's simply no way I'd get that many pills down dd10. I could up her intake of flax seeds, walnuts, and similar. The reason we are trying the pills is b/c they are DHA not EPA, which is what she'd get from vegetarian food sources of O-3.
According to my nutrition book, NIH recommendation is 650mg/day of DHA *plus* 650mg/day of EPA, age not specified. TBH I don't think we have the science to know what's optimal for anyone, let alone taking size/age into account. I'm not finding a source for that simple recommendation but here's a
MedlinePlus page with a complicated list at the bottom. A reason why it might not scale with size is that fat needs don't and the omega 3/omega 6 ratio seems to be important, though it's clearly not simple.
Take this fwiw. I was a strict vegetarian for 15 years. I finally started to eat fish, after a lot of research over years of wondering (but it was a long time ago, and science has moved on), when we decided to try for a child. There was enough evidence to convince me that optimal nutrition, omega 3s in particular, could not practically speaking be had from what I was eating. For a little while I used supplements, but I came to feel that that just made no sense for me: none of my complex reasons for vegetarianism actually applied, actually bound me, if I felt I had to take supplements to compensate for deficiencies in that diet. YMMV, e.g. it's bound to depend on what your reasons are. And it did take me years to get to a point where I could actually see fish as food! But I enjoy it, with care for sustainability, now, and don't regret the change at all. Just fwiw.
