Seed Cycling Basics and Personal Interpretation

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Seed cycling, or seed synching, is becoming a popular natural method for women to try to regulate her period without medication.  If you love eating foods that contain flax, pumpkin seeds, sesame seeds, and sunflower seeds, then this method will be a dream come true for you.  Many women with irregular periods incorporate seed cycling into their diet to attempt to naturally regulate it. Others use it to reduce negative PMS symptoms.  But what does the evidence say?  




First, let’s start off with the basics. What exactly is seed cycling?  The theory behind it is to naturally support the hormone levels that should be increasing during a stage of the menstrual cycle by eating certain seeds daily.  During the follicular phase of your cycle, which typically occurs during the first two weeks of your cycle, ground FLAXSEEDS and ground PUMPKIN SEEDS are consumed. During the luteal phase, which typically occurs during the second two weeks of a menstrual cycle, SUNFLOWER SEEDS and SESAME SEEDS are consumed.  You would be cycling your seed consumption, or synching your consumption with your cycle, get it?!?  Hence the name seed cycling!  People believe that following this cycle supports the body’s ability to maintain desired sex/reproductive hormone levels while also supporting elimination (poopies/number twos) to get rid of excess hormones that may be in the body. 



In summary:

First two weeks of cycle: eat ground flax seeds and ground pumpkin seeds

Second two weeks of cycle: eat sesame seeds and sunflower seeds




Sounds great in theory, but being a dietitian who prides herself on practicing evidence-based medicine, I needed to dig into the research before I could consider encouraging this practice.  What surprised me is despite how popular seed cycling is, there are zero clinical trials evaluating it’s effectiveness. 


OK…lets dig into the next best thing. Let’s research each individual seed and their effect on hormone regulation and menstrual cycle.  


When I turned to Dr. Google, the evidence for seed cycling was overwhelming. Many health bloggers are very convincing with their words and are very firm that seed cycling will be the answer to many prayers.  However, when I clicked on the hyperlinks embedded in the posts to read the studies they refer to, I was disappointed to learn that many blog authors either did not interpret the data they were referring to correctly, used animal studies, or used results from studies evaluating a different patient population than women with amenorrhea or generally healthy women who want to support their period or fertility.  None of these studies evaluated seed cycling specifically.  If a single seed was being evaluated, the women in the study consumed it consistently for a period of time and not just over a two-week span.  Data is heavy on using these seeds with postmenopausal women.  If we are focusing on hormones, we all know that the natural production of female hormones in a 35-year-old woman is vastly different than that of an 80 year old woman. 




Flax is the seed that appears to have been studied the most, but no studies evaluated flax seed intake in a cyclical manner.  In each study, flax was consumed consistently WITHOUT a two week “break” like what occurs in seed cycling.  



When I did a research search about flax and estrogen, over 200 studies came up.  However, when I sorted for only human studies, that number was cut by more than half.  Although animal studies give insight into what may happen in humans, I do not base recommendations only on results from studies conducted on animals. It is known that rodents and primates metabolize a specific dietary estrogen called an isoflavone differently than humans do (look up Dr. Messina. He discusses this a ton). Although it has never been stated that the same goes for the dietary estrogen called a lignin that is found in flax, one does need to look at the animal studies and flax with a grain of salt. 


Thankfully, there are some decent studies evaluating flax intake in humans. From breast cancer risk to menopausal symptoms to blood glucose control, incorporating flax into a human’s diet appears to have a benefit.   But here is where I get stuck and cannot bring myself to extrapolate the data: none of the studies had the women eat the flax in a cyclical manner. In other words, the flax was being taken every day, not just for 14-ish days each month.  


In one study evaluating flax’s role on the menstrual cycle, women were instructed to consume their typical diet for 3 months, and then were told to consume their typical diet PLUS flax supplements for another three months.  Menstrual cycles were studied.  What the researchers found was that there were some cycles where a woman did not evaluate ONLY when a woman was not consuming flax. If a woman was consuming flax, she ovulated.  There was no significant difference in estradiol (a type of estrogen) concentration between both the flax and no flax groups.  The luteal phase progesterone/estradiol ratios were significantly higher during the flax cycles.  


Please keep in mind that this study only evaluated 18 women, it is not long-term data, and the results were never repeated or proved by another study.  Typically, I like to see more than one study conducted and showing the same results before I consider including a recommendation into my practice. But considering the risk/benefit, I have no problems recommending flax in this situation. 





There is evidence to support the consumption of other seeds too.  For example, pumpkin seeds contain phytoestrogens like β-sitosterol, which might be acting as agonists or antagonists of estrogen and testosterone. 



The sesamin lignan is found in sesame seeds and is thought to be a natural estrogen. Like flax and pumpkin seeds, the sesame seed has been shown to offer some estrogenic benefit to humans as well,  especially in breast cancer cells. 




So, does seed cycling truly work?  I don’t know. I am unsure if the success some people see when seed cycling is due to the specific eating schedule of these seeds, or if it is because they are having a consistent intake of healthy fats, vitamins, minerals, antioxidants, fiber, and plant-based proteins. I have to wonder if it is the timing of the seeds that are offering a benefit, or the fact that these women are consuming such nutrient-rich ingredients daily that is playing a role.  


When a woman is telling me that she is seed-cycling, I do not discourage her to do so unless it appears that compliance is causing her stress or if she has a GI condition that does not allow her to consume seeds. I do not believe that eating these foods will go against fertility goals by any means. However, if I am going to commit to practice dietetics that is truly evidence-based, I cannot proactively recommend seed-cycling.  Once well-designed trials are conducted and repeated, and depending on the results, I may change my tune in a few years.  


Foods that contain healthy fats and a concentration of vitamins and minerals is not limited to these four seeds.  Other seeds, certain nuts, and avocados are other fabulous options that offer a host of benefits to women. I think seed cycling is over-simplifying the data and making some generous leaps in the data interpretation. 



Please note that just because no clinical trials exist evaluating this method doesn’t mean it doesn’t work.  As a dietitian who practices evidence-based medicine, I will not proactively suggest it to clients, but I do not see any harm to trying it out if a woman wants to explore it and comes to that decision on her own. In my opinion, consuming hefty doses of healthy fats, fiber, plant-based protein, and loads of vitamins and minerals is an amazing addition to one’s diet and will likely be a great addition to a fertility lifestyle plan or PMS management plan, regardless of the timing of the seed consumption.