There is some effect, but the studies are sparse and the results, while good, are unimpressive edit

Like these... https://www.hindawi.com/journals/joph/2017/1468716/

https://www.hindawi.com/journals/omcl/2018/1278392/

It is pretty hard to read and analyze the correctness of the procedure and conclusions, and even the data provided shows only some effect, and not a miracle drug one might expect. But the results in the rats (at least) seem to be consistent (p<0.05 or so.) They use a funny method for measuring the blood pressure of the rats.

But a double-blind human study has shown some nice results: "Results: There was no significant difference between the baseline characteristics and target variables at baseline between the two groups. After gamma oryzanol supplementation, there was no significant difference in the means of anthropometric and skin fold measurements between the supplement and placebo groups. However, there were significant differences between the supplement and placebo groups for 1-RM of bench press and leg curl, which showed that gamma oryzanol improved muscle strength following resistance training."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4164998/