Several of you have written to ask about seed cycling, a practice that claims to help with premenstrual syndrome, menopausal symptoms, and general hormonal balance. Does eating certain seeds at certain times really help regulate hormones? Let's look at the research.

What is seed cycling?

Seed cycling is not really new but it is newly trendy. The idea behind seed cycling is that certain types of seeds, such as pumpkin, flax, and chia, can help regulate the levels of estrogen, progesterone and other hormones. Synchronizing your consumption of various seeds with your menstrual cycle can allegedly relieve hormone-related symptoms such as PMS, PCOS, irregular periods, hot flashes, and generally increase your level of well-being. Some even claim that seed cycling can help you get pregnant.

RELATED: Can Diet and Nutrition Help You Get Pregnant?

In a typical seed cycling protocol, you eat two tablespoons of ground seeds every day. You can mix the seeds into a smoothie or sprinkle them on your oatmeal. Purists insist that the seeds be raw and freshly ground. (Chewing well, of course, counts as grinding.)

Phase One: During phase one, which lasts two weeks, you eat a tablespoon of flax and a tablespoon of pumpkin seeds.

Phase Two: During phase two, which also lasts two weeks, you switch to sunflower and sesame seeds. This adds about 100 calories, 9 grams of fat, 4 grams of protein, and 3 grams of fiber to your day.

If you're still menstruating, you'd start phase one (pumpkin and flax) on the first day of your period and switch to phase two (sunflower and sesame) on day 14. If you are no longer menstruating, you can start phase one on the first of the month. Some women like to synchronize their seed cycling to the phases of the moon, beginning phase one on the new moon and phase two on the full moon. Howling is optional.

As the trend has taken hold, seed cycling recipe collections, smoothie mixes, energy bars and cookies have appeared online and in healthfood stores.

During a normal menstrual cycle, your estrogen and progesterone levels ebb and fall in a predictable rhythm. As you approach menopause, your hormone levels may start to fluctuate more erratically. After menopause, production of both hormones settles at a significantly lower level.

Theoretically, seed cycling either enhances or inhibits the production of estrogen and progesterone in the body (depending on what is needed), thereby balancing and optimizing your hormones and relieving symptoms due to hormonal imbalance. A few months of cycling is said to be enough to begin seeing the benefits.

As the trend has taken hold, seed cycling recipe collections, smoothie mixes, energy bars and cookies have appeared online and in healthfood stores.

How do these seeds affect hormone balance?

Flax and sesame both contain lignans, which have been found to affect estrogen activity in human cells and animal models. What effect they have depends on whether there is a surplus or deficit of estrogen already on hand.

Flax and sesame both contain lignans, which have been found to affect estrogen activity in human cells and animal models.

In the absence of estrogen, lignans are mildly estrogenic-that is, they stimulate estrogen receptors on the surface of cells. But In the presence of estrogen, they are mildly anti-estrogenic, blocking some of the estrogen from reaching the receptors.

The lignans in flax and sesame are similar in their estrogen-regulating effects but-for reasons I cannot explain-they are used in opposite parts of the seed cycling protocol. Pumpkin and sunflower seeds, meanwhile, play more of a supporting role: They contribute nutrients, such as vitamin E and zinc, that generally support reproductive health.

Is there evidence that seed cycling works?

Seed consumption does not appear to have a measurable effect on estrogen or progesterone levels in menstruating women. Although the phytoestrogenic activity of these seeds is observable, it's just too mild to actually move the needle on human hormone levels.

Seed consumption does not appear to have a measurable effect on estrogen or progesterone levels in menstruating women.

For post-menopausal women, some research suggests that including flax or sesame seeds in your diet on a regular basis can have some mild benefits, including reduced hot flashes. But in most studies, the effects were similar to a placebo.

Most of these studies involve larger amounts of flax or sesame lignans than you'd get from a typical seed cycling protocol. And while flax and sesame both have potential benefits, there's really little rationale for cycling them.

Is seed cycling safe?

Because seed cycling is very unlikely to have a significant effect on your hormone levels, it is generally safe, even if you are pregnant or nursing or have (or have had) breast cancer or another hormone-sensitive cancer. If you have any concerns, though, you should definitely run them past your doctor.

If you have any concerns, you should definitely run them past your doctor.

All types of seeds are full of good nutrition, including protein, fiber, and healthy fats. And the lignans in flax and sesame, while they may have only minor effects on hormone levels, may offer some cancer-protective benefits.

In short, there are a lot of good reasons to include seeds in your diet. And if you like the idea of consuming them in cycles-or you feel doing this increases your well-being-there's certainly no harm in the practice. But there's also no need to worry about consuming the wrong seed on the wrong day.

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