"When all 14 studies were pooled, no statistically significant results emerged. However, when the studies were divided according to whether vitamin D3 was taken daily in a low dose* or in higher doses administered at longer intervals*, a large difference was seen." This sounds fishy. Sounds like their primary result was nothing, and then they looked for something else. Would require some checking if they had a prereg…
If you combine results from a bunch of studies that really didn't do anything, it's going to mask the results from the ones that did.