What is the menstrual cycle?
The menstrual cycle is a carefully regulated sequence of events that prepares the female body for a potential pregnancy. It starts with the follicular phase, which includes menstruation and the maturation of the ovarian follicle. This is followed by ovulation (mature follicle releases egg) and then by the luteal phase (during which the egg moves through fallopian tubes); if pregnancy doesn’t occur, then the cycle re-starts again with the follicular phase and menstruation.[1]
These events are primarily driven by hormonal communication between the brain (specifically, the hypothalamus and pituitary gland) and the female reproductive system, collectively called the hypothalamic-pituitary-ovarian (HPO) axis.[2] The first menstruation (menarche) occurs around age 12 (median; range of 10-16), and reoccurs regularly every 24 to 38 days,[3] stopping at menopause (near age 50), which signifies the end of reproductive fertility. The menstrual cycle also stops during pregnancy and often during lactation.[4]
How is menstrual cycle health measured?
The menstrual cycle is an important component of overall health. As such, the menstrual cycle is considered a vital sign by some clinicians.[5] There are a variety of ways to measure menstrual cycle health, ranging from simple, at-home tracking methods to bloodwork and ultrasound imaging. A basic assessment of the menstrual cycle starts with measurements of frequency (menstruation or bleeding occurs every 24 to 38 days), regularity (the number of days between menstruation is similar each month), duration (bleeding does not last longer than eight days), and volume (loss of no more than 80 mL of menstrual blood per cycle).[6] The phases of the menstrual cycle are sometimes measured via basal body temperature and hormone levels in saliva, urine, or blood.[1] If there are abnormalities, like infrequent menstruation (oligomenorrhea), too frequent menstruation (polymenorrhea), the total absence of menstruation (amenorrhea), or very heavy bleeding (menorrhagia), a clinician can perform additional assessments to better understand the underlying cause of the abnormality.
These additional assessments may include bloodwork and imaging. Blood tests can detect the levels of different hormones that affect the menstrual cycle (e.g., progesterone, estrogen, thyroid hormone, androgens, prolactin). They can also measure iron levels, which are sometimes affected by menstrual bleeding, and may aid in the diagnosis of underlying bleeding disorders or infections. In some cases, imaging of the reproductive system is also necessary, usually beginning with an ultrasound. Serial transvaginal ultrasounds can visualize the changes that occur in the ovaries and endometrial lining throughout the menstrual cycle.[7]
How does physical activity affect menstrual cycle health?
Regular exercise may alleviate pain and other negative symptoms before and during menstruation.[8][9][10] Regular exercise can also shorten the length of menses.[11]
Conversely, too much exercise can be detrimental to menstrual cycle health, causing menstrual irregularities or even the total absence of menstruation.[12][13] This is not a normal response to exercise and should be evaluated by a clinician. It may be a sign of relative energy deficiency in sport (RED-S), a condition indicating that the body does not have enough energy to meet its demands.[14] The consequences of RED-S are far-reaching, serious, and potentially irreparable.[15][16]
Have any supplements been studied for menstrual cycle health?
Supplements for the menstrual cycle are often studied in the context of correcting deficiencies and/or reducing the symptoms of conditions like premenstrual syndrome, endometriosis, dysmenorrhea, and polycystic ovary syndrome. For example, vitamin D deficiency is associated with dysmenorrhea and abnormal menstrual bleeding patterns, in which case supplementing with vitamin D to correct the deficiency could be beneficial.[17][18] Additional supplements that might improve menstrual-related symptoms (with varying levels of efficacy) include chaste tree, magnesium, vitamin B6 and B1, ginger, calcium, selenium, omega-3 fatty acids, curcumin, and inositol.[19][20][21][22][23][24][18]
Another supplement that is often studied in menstruating people is iron because blood loss via menstruation can reduce iron levels in the body, especially if the bleeding is heavy.[17] Iron may also be lost during exercise.[25] Because iron is used to make red blood cells, a deficiency in iron can lead to anemia, which means that the blood cannot carry enough oxygen throughout the body. Iron supplementation is an effective treatment for iron deficiency.[26][27]
Before beginning any supplements, it is important for menstrual-related symptoms to be evaluated by a clinician. Some supplements, like iron, can cause damage if excessive amounts accumulate in the body. Such accumulation is rarely the result of excessive oral intake and is instead secondary to other underlying medical problems, both congenital and acquired. [28]
How can diet affect menstrual cycle health?
Eating a nutritious diet with an appropriate amount of kilocalories is integral to menstrual cycle health. Dietary patterns that include a diversity of fruits and vegetables, dairy products, fish, green tea, and plant-derived compounds and avoid excessive intakes of alcohol, red and processed meats, and caffeine are correlated with fewer menstrual-related disorders.[29][30][31] There are also associations (but no robust data) between a more “proinflammatory” dietary pattern and reduced levels of sex hormone binding globulin, which might affect menstrual-related symptoms in some people.[32]
Diet is also implicated in the timing of menarche (or the first menses). Menstruation requires energy, so malnourishment and low body weight can result in a later onset of menarche, whereas overnutrition and obesity are associated with an earlier age at menarche.[33][34][35]
Which other factors affect the menstrual cycle?
The menstrual cycle is affected by numerous internal and external factors, all of which can alter the cycle’s length, regularity, and symptoms. Some of these factors are not modifiable, such as race/ethnicity, age, intrauterine exposures, family history, adverse childhood events, and genetics.[36][37] Other factors are related to the environment, like exposure to air pollution, endocrine-disrupting chemicals, and certain viruses and bacteria, as well as the geographic climate.[36][38] There are also important personal and lifestyle factors to consider, including mental health,[39][40], sleep health,[41][42] body mass index,[43][44][45] use of tobacco and cannabis,[46][43] lactation,[47][48] use of contraceptives (oral medications, intrauterine devices, ect.),[49][50] shift work,[37] and possibly even a history of concussions.[51]
Of these factors, psychological stress is a common target for interventions aimed at restoring normal menses, reducing menstrual-related symptoms, and improving fertility. For example, acupuncture and acupressure may help some people with premenstrual syndrome or menstrual irregularity.[52][53] Psychosocial interventions, particularly cognitive behavioral therapy and mindfulness-based therapies, may increase pregnancy rates in people with infertility[54] and improve mood in people with premenstrual syndrome.[55][56]
Examine Database: Menstrual Health
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Frequently asked questions
The menstrual cycle is a carefully regulated sequence of events that prepares the female body for a potential pregnancy. It starts with the follicular phase, which includes menstruation and the maturation of the ovarian follicle. This is followed by ovulation (mature follicle releases egg) and then by the luteal phase (during which the egg moves through fallopian tubes); if pregnancy doesn’t occur, then the cycle re-starts again with the follicular phase and menstruation.[1]
These events are primarily driven by hormonal communication between the brain (specifically, the hypothalamus and pituitary gland) and the female reproductive system, collectively called the hypothalamic-pituitary-ovarian (HPO) axis.[2] The first menstruation (menarche) occurs around age 12 (median; range of 10-16), and reoccurs regularly every 24 to 38 days,[3] stopping at menopause (near age 50), which signifies the end of reproductive fertility. The menstrual cycle also stops during pregnancy and often during lactation.[4]
The menstrual cycle is divided into two main phases: the follicular (or proliferative) phase and the luteal (or secretory) phase, both of which contain subphases (e.g., early follicular, late follicular, ovulatory, early luteal, late luteal). Each subphase is marked by a unique hormonal profile and an accompanied response from the reproductive organs.[57] The follicular phase lasts approximately 14 to 21 days, begins with menstruation (colloquially known as “a period”), and ends with ovulation. During this phase, follicle stimulating hormone causes follicles in the ovaries (which store eggs) to grow, and the lining of the uterus thickens as estrogen levels rise. About halfway through the cycle (around day 14), a surge in luteinizing hormone stimulates ovulation or the release of a mature egg(s) from the follicle.
During the approximately 14 days of the luteal phase, the egg travels through the fallopian tube and into the uterus. Meanwhile, the follicle that released the egg (now called the corpus luteum) releases hormones, primarily progesterone, which prepares the uterus for implantation of the egg, should it become fertilized. If the egg is not fertilized, the corpus luteum stops releasing hormones, progesterone and estrogen levels fall, and the lining of the uterus sheds in the form of bloody discharge through the vaginal canal. The time when bleeding begins is considered day 1 of the next menstrual cycle and the start of a new follicular phase.[58]
The above description, although factual, does not capture the unique complexities of the menstrual cycle. The exact timing and amplitude of the peaks and troughs of reproductive hormones (as well as the menstrual cycle phases they bring about) vary both between and within individuals. Most of this dissimilarity is prompted by differences or changes in the length of the follicular phase, whereas the luteal phase remains relatively constant. On average, a person’s onset of menses can deviate by up to 4 days, compared to a previous cycle. The regularity of the menstrual cycle is also affected by age, with younger and older people more likely to experience cycle irregularities and anovulatory cycles (menstrual cycles that do not result in the release of an egg).[58]
Many people experience certain signs and symptoms during different phases of the menstrual cycle, especially a few days before and during menstruation. This is usually due to hormone fluctuations, which can affect everything from digestion to mood to acne to joint laxity to sleep. Although each person’s menstrual cycle is unique, there are some common symptoms to note and track to better manage them.
During menstruation, estrogen and progesterone are at their lowest, and, for some people, energy levels are equally low. Abdominal cramping, bloating, irritability, headaches, tender breasts, mood swings, and low back pain may also be experienced during this phase. If cramping is particularly intense and recurrent with each menses, it may be diagnosed as dysmenorrhea and should be assessed by a clinician for secondary causes, like endometriosis.[59]
As the follicular phase progresses and estrogen rises, the symptoms of menstruation should subside. Mood and energy levels often improve,[60] and, as ovulation nears, sexual desire may increase while hunger/appetite decreases.[61][62] When ovulation occurs, some people feel abdominal pain (called mittelschmerz), likely related to the rise in luteinizing hormone that stimulates prostaglandin production and the consequential contraction of the ovary to release an egg.[63]
With ovulation complete, the luteal phase begins, and progesterone levels rise. The precise effects of progesterone on mood are unclear and likely affect people differently.[64] However, if a pregnancy does not occur, the subsequent drop in circulating progesterone and estrogen levels can cause negative symptoms. This is why the late luteal phase is often associated with food cravings, mood swings, gastrointestinal discomfort, breast tenderness, and poor sleep.[65][66][67] If the symptoms are severe, it may be a sign of premenstrual syndrome (PMS).
The menstrual cycle is an important component of overall health. As such, the menstrual cycle is considered a vital sign by some clinicians.[5] There are a variety of ways to measure menstrual cycle health, ranging from simple, at-home tracking methods to bloodwork and ultrasound imaging. A basic assessment of the menstrual cycle starts with measurements of frequency (menstruation or bleeding occurs every 24 to 38 days), regularity (the number of days between menstruation is similar each month), duration (bleeding does not last longer than eight days), and volume (loss of no more than 80 mL of menstrual blood per cycle).[6] The phases of the menstrual cycle are sometimes measured via basal body temperature and hormone levels in saliva, urine, or blood.[1] If there are abnormalities, like infrequent menstruation (oligomenorrhea), too frequent menstruation (polymenorrhea), the total absence of menstruation (amenorrhea), or very heavy bleeding (menorrhagia), a clinician can perform additional assessments to better understand the underlying cause of the abnormality.
These additional assessments may include bloodwork and imaging. Blood tests can detect the levels of different hormones that affect the menstrual cycle (e.g., progesterone, estrogen, thyroid hormone, androgens, prolactin). They can also measure iron levels, which are sometimes affected by menstrual bleeding, and may aid in the diagnosis of underlying bleeding disorders or infections. In some cases, imaging of the reproductive system is also necessary, usually beginning with an ultrasound. Serial transvaginal ultrasounds can visualize the changes that occur in the ovaries and endometrial lining throughout the menstrual cycle.[7]
Outside of general health, many people measure the menstrual cycle with the goal of achieving or preventing a pregnancy. This requires detecting the time of ovulation because the likelihood of pregnancy is highest when sexual intercourse occurs during the period from 2 days before to the day of ovulation.[68] In people with a normal menstrual cycle, there are several simple, inexpensive ways to potentially predict the time of ovulation. These include menstrual cycle charting, oral basal body temperature monitoring, and assessing cervical mucus changes, although the reliability of these methods is questionable.[69]
There are more accurate ways to detect ovulation. Commercially available tests determine the time of ovulation by measuring the levels of luteinizing hormone and/or estrogen metabolites in a urine sample or by carefully monitoring body temperature, either under the arm or in the vagina, with special devices.[7] People with an irregular menstrual cycle or difficulty getting pregnant may require more extensive testing to determine when and if ovulation is occurring, such as bloodwork and imaging studies (e.g., ultrasound). It is important to work with an experienced clinician for any menstruation or fertility issues.
Regular exercise may alleviate pain and other negative symptoms before and during menstruation.[8][9][10] Regular exercise can also shorten the length of menses.[11]
Conversely, too much exercise can be detrimental to menstrual cycle health, causing menstrual irregularities or even the total absence of menstruation.[12][13] This is not a normal response to exercise and should be evaluated by a clinician. It may be a sign of relative energy deficiency in sport (RED-S), a condition indicating that the body does not have enough energy to meet its demands.[14] The consequences of RED-S are far-reaching, serious, and potentially irreparable.[15][16]
There is speculation that the rise and fall of hormones throughout the menstrual cycle could affect exercise performance. Put very simply, one prevailing theory is that performance may be enhanced during the late follicular phase, when menstruation and its potential accompanying symptoms are gone and estrogen (an anabolic hormone) is high, compared to the luteal phase, when progesterone is elevated, which may counteract the actions of estrogen, increase body temperature, and negatively affect recovery and neuromodulation.[70] However, whether exercise performance fluctuates alongside these hormonal shifts likely depends on the individual. For example, some people find that the symptoms of menstruation, like cramping and gastrointestinal discomfort, interfere with their ability to engage in athletic pursuits (especially if they suffer from dysmenorrhea or PMS), whereas other people are unaffected by menses.[71] This heterogeneity makes it difficult to prescribe general guidelines regarding exercise and the menstrual cycle.
In fact, studies on the menstrual cycle and exercise performance have failed to find robust and consistent differences between performance (strength or aerobic) at different phases of the menstrual cycle.[72] A 2020 meta-analysis reported that in eumenorrheic female athletes, there may be a trivial reduction in exercise performance during the early follicular phase (the time of menses).[73] Other studies find that muscle recruitment and recovery may be impaired during the luteal phase, when progesterone is at its peak, but that this does not necessarily affect performance.[72][74] Nonetheless, menstrual-related symptoms can negatively affect a person’s perception of their performance, mental sharpness, and balance.[75] Studies of higher quality are needed to determine whether training based on menstrual cycle phases provides added benefit over that of a well-structured exercise program.
Similarly, there is insufficient evidence that the risk for exercise-related injuries (particularly ligament injuries) varies across the menstrual cycle, but it is possible that hormonal fluctuations increase the risk for injuries.[76][77][78]
Supplements for the menstrual cycle are often studied in the context of correcting deficiencies and/or reducing the symptoms of conditions like premenstrual syndrome, endometriosis, dysmenorrhea, and polycystic ovary syndrome. For example, vitamin D deficiency is associated with dysmenorrhea and abnormal menstrual bleeding patterns, in which case supplementing with vitamin D to correct the deficiency could be beneficial.[17][18] Additional supplements that might improve menstrual-related symptoms (with varying levels of efficacy) include chaste tree, magnesium, vitamin B6 and B1, ginger, calcium, selenium, omega-3 fatty acids, curcumin, and inositol.[19][20][21][22][23][24][18]
Another supplement that is often studied in menstruating people is iron because blood loss via menstruation can reduce iron levels in the body, especially if the bleeding is heavy.[17] Iron may also be lost during exercise.[25] Because iron is used to make red blood cells, a deficiency in iron can lead to anemia, which means that the blood cannot carry enough oxygen throughout the body. Iron supplementation is an effective treatment for iron deficiency.[26][27]
Before beginning any supplements, it is important for menstrual-related symptoms to be evaluated by a clinician. Some supplements, like iron, can cause damage if excessive amounts accumulate in the body. Such accumulation is rarely the result of excessive oral intake and is instead secondary to other underlying medical problems, both congenital and acquired. [28]
Eating a nutritious diet with an appropriate amount of kilocalories is integral to menstrual cycle health. Dietary patterns that include a diversity of fruits and vegetables, dairy products, fish, green tea, and plant-derived compounds and avoid excessive intakes of alcohol, red and processed meats, and caffeine are correlated with fewer menstrual-related disorders.[29][30][31] There are also associations (but no robust data) between a more “proinflammatory” dietary pattern and reduced levels of sex hormone binding globulin, which might affect menstrual-related symptoms in some people.[32]
Diet is also implicated in the timing of menarche (or the first menses). Menstruation requires energy, so malnourishment and low body weight can result in a later onset of menarche, whereas overnutrition and obesity are associated with an earlier age at menarche.[33][34][35]
Specific diets, such as the Mediterranean diet,[79] low-carbohydrate diet,[80] DASH diet,[81] low-fat vegetarian diet,PMID10674588 low glycemic index diet,[82] and ketogenic diet,[83] may support menstrual cycle health in people with certain conditions, but there is no evidence to support a single “best” diet for all menstruating people. In fact, some studies find that the Mediterranean diet, low carbohydrate diets, and diets with too much fiber are associated with irregular menstrual cycles.[84][85] Still other studies report that in people with overweight and obesity, weight loss improves menstrual regularity more than a specific dietary composition.[86] This variety of findings highlights the importance of an individualized approach to diet. However, it is very clear that overly restrictive diets and eating disorders negatively affect reproductive health.[14]
It is possible for the menstrual cycle to affect diet. In some people, cravings for sweet and salty foods, as well as overall appetite, may be increased during the luteal phase, compared to other phases.[66] This might be related, in part, to the way hormones can affect appetite, the perception of taste and smell, and water regulation.[87]
The body’s ability to utilize certain macronutrients for energy appears to fluctuate throughout the menstrual cycle. When estrogen is elevated during the follicular phase, carbohydrates are used more readily, and glycogen storage may be reduced. Conversely, when progesterone is elevated during the luteal phase, there is a greater breakdown of protein, increased utilization of fat, and a slight increase in basal metabolic rate.[88][89] Whether altering dietary macronutrient intake alongside these metabolic shifts is advantageous for health outcomes — including fertility, exercise performance, and menstrual-related symptoms — requires further research.
There is no research to support rotating certain foods into and out of the diet based on the menstrual cycle phase with the goal of “supporting” hormonal health. Menstrual cycle-based diets usually recommend some variation of the following: eating anti-inflammatory and iron-rich foods, (like salmon, red meat, and dark leafy green vegetables) during menstruation, eating “proestrogenic” foods (like flax seeds and kimchi) during the follicular phase, and eating foods that “balance” blood sugar and support progesterone (like complex carbohydrates, avocados, tofu, dark chocolate, and pumpkin seeds) during the luteal phase. These recommendations (e.g.,like eating iron-rich foods when losing blood through menstruation) certainly aren’t unhealthful or completely unfounded, but they are not an evidence-based way to “balance hormones”.
There are no controlled trials on the practice of seed cycling for hormonal health, and, consequently, there is no evidence to support or refute its benefits to the menstrual cycle. Seed cycling involves eating specific seeds (e.g., pumpkin, flax, sesame, sunflower) during certain phases of the menstrual cycle to “support” hormone production and function. The idea is that as reproductive hormones ebb and flow, so too does the body’s nutritional needs, and different seeds can be cycled in and out of the diet to “match” these needs and thereby optimize hormonal health.
During the follicular phase, flax seeds (which contain phytoestrogens) and pumpkin seeds (for micronutrients like zinc and magnesium) are consumed to support and “balance” the rise in estrogen. During the luteal phase, sunflower seeds (for micronutrients like vitamin E and selenium) and sesame seeds (for micronutrients like calcium and B vitamins) are consumed to support progesterone production. The “dosage” for each seed is 1 to 2 tablespoons per day, preferably raw and freshly ground.
Although there are no trials on seed cycling, there is some evidence on the effect of certain seeds and micronutrients on the menstrual cycle. For instance, a small crossover study in 18 women found that supplementation with flax seed powder reduced the number of anovulatory cycles (a menstrual cycle with no egg release), but there were no significant differences in estrogen levels.[90] Supplementation with zinc for 4 to 6 days before (and possibly during) menstruation may reduce menstrual pain in people with primary dysmenorrhea.[91] Similarly, calcium supplementation may reduce symptoms of PMS,[92] as may vitamin E supplementation.[93] A retrospective cohort study in infertile women with PCOS also found that vitamin E supplementation reduced markers of oxidative stress, but it did not improve ovulation or the chance of getting pregnant.[94]
Seeds do contain important vitamins and minerals and can be a healthful addition to most diets. However, it is important to seek the help of a clinician if hormonal issues are suspected.
The menstrual cycle is affected by numerous internal and external factors, all of which can alter the cycle’s length, regularity, and symptoms. Some of these factors are not modifiable, such as race/ethnicity, age, intrauterine exposures, family history, adverse childhood events, and genetics.[36][37] Other factors are related to the environment, like exposure to air pollution, endocrine-disrupting chemicals, and certain viruses and bacteria, as well as the geographic climate.[36][38] There are also important personal and lifestyle factors to consider, including mental health,[39][40], sleep health,[41][42] body mass index,[43][44][45] use of tobacco and cannabis,[46][43] lactation,[47][48] use of contraceptives (oral medications, intrauterine devices, ect.),[49][50] shift work,[37] and possibly even a history of concussions.[51]
Of these factors, psychological stress is a common target for interventions aimed at restoring normal menses, reducing menstrual-related symptoms, and improving fertility. For example, acupuncture and acupressure may help some people with premenstrual syndrome or menstrual irregularity.[52][53] Psychosocial interventions, particularly cognitive behavioral therapy and mindfulness-based therapies, may increase pregnancy rates in people with infertility[54] and improve mood in people with premenstrual syndrome.[55][56]
Certain contraceptives can affect the menstrual cycle. Two examples are oral contraceptive pills and intrauterine devices. Combined estrogen-progestin oral contraceptives (colloquially known as “the birth control pill”) externally regulate the menstrual cycle by providing sex hormones in the form of a pill and consequently suppressing the body’s production of hormones. This inhibition of internal hormone formation means that ovulation does not occur, thus preventing pregnancy.[95] Some people find that oral contraceptives alleviate the symptoms of certain conditions, like dysmenorrhea and PCOS, but they may also have adverse effects.[96] The FDA is a good resource for more information on oral contraceptives.
A intrauterine device (IUD) is a small device that is inserted into the uterus by a clinician to prevent pregnancies. IUDs are the most common form of long-acting, reversible birth control used worldwide.[97] In the United States, there are two main types of IUDs, ones that contain copper and ones that release the hormone levonorgestrel (a form of progesterone). Because these devices work locally, they usually do not suppress the body’s hormone production, and the menstrual cycle continues. However, they can have short-term and long-term effects on menstrual-related symptoms in some people.
IUDs can increase cramping and bleeding and can cause unscheduled bleeding and spotting; this usually subsides within the first 6 months, but it can be severe and/or prolonged enough to cause discontinuation.[98][99] Conversely, in the long term, they can cause amenorrhea and lighter bleeding and can even reduce pelvic pain and dysmenorrhea.[100][101][50]
It is important to speak with a clinician when weighing the risks and benefits of different contraceptives because the choice is highly individualized.
Endocrine-disrupting chemicals (EDCs) are exogenous substances that interfere with the normal functions of the endocrine system, often by disrupting hormone synthesis, secretion, metabolism, and/or transport.[102] These substances are found in the environment (air, water, soil) as well as in foods, medical devices, and personal care and household products. Some occur naturally, like the phytoestrogens in soy, whereas others are manufactured, like flame retardants and bisphenol A. Endocrine-disrupting chemicals are ubiquitous and have been detected in human urine, blood, sweat, hair, and even breastmilk.[103][104]
There is evidence suggesting that EDCs can negatively affect reproductive health. Exposure to certain air pollutants, parabens, and polybrominated biphenyls is associated with irregular menstrual cycles,[105] and EDCs may also increase the risk for ovarian aging (which may result in a decline in fertility).[106] More research is needed to determine the causal effects of EDCs in humans as well as the dosages at which they could potentially do harm.[107]
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