For most comparisons , the credibility of evidence was rated very low to moderate , with the exception for the DASH vs. the low-fat dietary approach for which the quality of evidence was rated high .
Conclusion : The present network meta- analysis suggests that the DASH dietary approach might be the most effective dietary measure to reduce blood pressure among hypertensive and pre-hypertensive patients based on high quality evidence
ABSTRACT Background : Pairwise meta-analyses have shown beneficial effects of individual dietary approaches on blood pressure but their comparative effects have not been established .
Objective : Therefore we performed a systematic review of different dietary intervention trials and estimated the aggregate blood pressure effects through network meta- analysis including hypertensive and pre-hypertensive patients .
On the comparison of effects.
In a recent communication , ' Poole has proposed that epidemiologists draw an occasional p-value function in order to help them avoid misinterpreting confidence intervals ( CIs ) . Such an exercise might well have some value , and certainly the p-value function does impart more information than a single CI . However , I doubt that such functions are appreciably less subject to misinterpretation than are CIs , and I take strong exception to the suggestion by Poole that my perspective on CIs2 leads to fallacious conclusions that would be averted by a consideration of p-value functions . Poole offers two examples of insights that might be provided by the plotting of  p-value functions .  First , he plots such functions for the two examples given in Figures 1 and 2 ofmy paper.2 From the plots he concludes that " the two point estimates are virtually identical , but one estimate is much more precise than the other . " ' Even the most cursory inspection of my figures would lead to exactly the same conclusion , and I would hope that even without benefit of a picture most readers are able to make similar sense out of reported point estimates and CIs of 2.3 ( 95 per cent CI = 0.4 - 17.3 ) versus 2.5 ( 95 per cent CI = 1.3 - 4.7 ) . The second of Poole 's examples concerns a study of spermicides and Down 's syndrome in which Rothman compared cases to each oftwo control groups.3 In that study , the odds ratio for the comparison between cases and r and om controls was 3.6 ( 90 per cent CI = 1.2 - 9.0 ) , as opposed to 2.8 ( 90 per cent CI = 0.9 - 7.3 ) for the comparison involving controls with congenital heart disease . Although Poole cl aims that the " full utility " of p-value functions  comes when one result is compared with another , I fail to see how in this example inspection of such functions would provide any special insight . It is clear from examination of the point estimates themselves and from the considerable overlap of the CIs that comparison of the cases with the control group that would presumably be subject to a corresponding recall bias yields a result that is not strikingly different from that for the comparison with r and om controls . Consequently , it is difficult to agree with Mills , et al , who have cl aim ed that the results suggest " that recall bias may have caused the higher rate of spermicide use reported in the Down 's group . 4 Poole maintains that an erroneous conclusion such as that of Mills , et al , follows " almost to the letter " my perspective on the interpretation of CIs .  This cl aim is patently false . In fact , I warned explicitly against the very type of fallacious reasoning of which Mills , et al , were guilty . In my discussion of interaction,2 I described the pitfalls
For most comparisons , the credibility of evidence was rated very low to moderate , with the exception for the DASH vs. the low-fat dietary approach for which the quality of evidence was rated high .
Conclusion : The present network meta- analysis suggests that the DASH dietary approach might be the most effective dietary measure to reduce blood pressure among hypertensive and pre-hypertensive patients based on high quality evidence
ABSTRACT Background : Pairwise meta-analyses have shown beneficial effects of individual dietary approaches on blood pressure but their comparative effects have not been established .
Objective : Therefore we performed a systematic review of different dietary intervention trials and estimated the aggregate blood pressure effects through network meta- analysis including hypertensive and pre-hypertensive patients .