Taking measurements before and after the treatment is good, but that is not the same as having a separate control group, which could filter out effects of timing, taking the dose with food or water, etc.
Also note, that the abstract doesn't say that 200mg is ideal as the science daily description does it says:
"It is concluded that low consumption of DHA could be an effective and nonpharmacological way to protect healthy men from platelet-related cardiovascular events."
The abstract also claims "Therefore, supplementation with only 200 mg/d DHA for 2 wk induced an antioxidant effect." It is likely that there was a more complete conclusion in the full article.
But the abstract does not make any "just right" claims, unlike the summary on science daily. Which is what you where complaining about.
The abstract reads - we did an incremental test, and even at the lowest dosage we found an effect. This suggest that low dosages could be effective. I don't see anything wrong with that reasoning.
The science daily summary is simply misrepresenting it. So, the original commenter isn't missing something in the science news, it is science daily who made the error.
I declare this Open Thread open for discussion of Less Wrong topics that have not appeared in recent posts.