To further expound on your interest in flax, I might be more concerned about the "phytoestrogen" content of flaxseeds and ground flaxseeds than the blood vessel dilation potential. The term "phytoestrogen" refers to a class of plant compounds that have mild estrogen-like effects when consumed. The "lignans" found in flax seeds are considered phytoestrogens. Research is ongoing in this area to better understand the impact of these phytoestrogens on hormone-sensitive cancers such as breast cancer. Until more is known, it would be most prudent to limit or avoid intake of phytoestrogen-containing foods as they may contribute to growth of estrogen-sensitive cancers. It should be noted that most flax oil products (whether in liquid form or in gelcaps) do not contain lignans unless clearly stated on the label of the product. Thus, individuals seeking the omega 3 benefits of flax but trying to avoid lignans could consider regular use of flax oil.