Flaxseed is a plant that is part of the genus Linum, native to the area around the eastern Mediterranean and India. Flaxseed is a rich source of lignans and omega 3 fatty acids. Lignans found in flaxseed are called secoisolariciresinol diglucoside (SDG) and alpha-linolenic acid (ALA). Flaxseed is also a source of fiber. Lignans are a type of phytoestrogen (plant estrogen) that, like soy, is thought to have estrogen agonist-antagonist effects as well as antioxidant properties. Lignans are converted by colonic bacteria to enterodiol and enterolactone, which are metabolites believed to have important physiological properties such as decreasing cell proliferation and inhibiting aromatase, 5-alpha reductase, and 17-beta hydroxysteroid activity. Cell line studies have shown properties of aromatase inhibition with enterolactone but less so with enterodiol. It is thought that these properties can reduce the risk of hormone-sensitive cancers.[74,75,76] In addition, studies have shown that flaxseed can reduce estrogen levels through excretion in the urine.[77,78]
On the basis of preliminary data testing flaxseed for its effect on hot flashes and related endpoints,[79,80][Level of evidence: I] an open-label pilot study was conducted to evaluate 40 g of flaxseed in decreasing hot flashes. This study of 30 women showed a 57% reduction in hot flash scores and a 50% reduction in hot flash frequency over a 6-week period. Results are pending from a large, randomized, controlled trial with a placebo control arm (NCCTG-N08C7), sponsored by the National Cancer Institute within a cooperative group setting, the North Central Cancer Treatment Group.
Many plants and natural products are touted as wonderful remedies for hot flashes. Some of these products are plant phytoestrogens, and some have unknown properties. The agents include dong quai, milk thistle, red clover, licorice, and chaste tree berry. There is incomplete understanding of the biology of these agents and whether taking them would impact breast cancer risk or recurrence in a negative or positive way. Data suggest that these plants have different effects, dependent not only on the dose used but also on a woman's hormone environment when she takes them. Little is known about these agents, and caution with respect to taking them-if a woman is to avoid estrogen supplementation-is needed. [82,83,84,85]
Several pilot trials have evaluated the use of acupuncture to treat hot flashes.[86,87,88,89][Level of evidence: I] Research in acupuncture is difficult, owing to the lack of novel methodology-specifically, the conundrum of what should serve as an adequate control arm. In addition, the philosophy surrounding acupuncture practice is quite individualized, in that two women experiencing hot flashes would not necessarily receive the same treatment. It would be important to study acupuncture utilizing relevant clinical procedures; so far, acceptable research methods to accomplish this are lacking. Therefore, the data with respect to the effect of acupuncture on hot flashes are quite mixed, with many studies suffering from ineffective control arms. Therefore, as concluded in at least one review, there is not a body of evidence to definitively delineate the role or practice of acupuncture for hot flashes. (Refer to the Vasomotor symptoms section in the PDQ summary on Acupuncture for more information.)