Somebody told you a year. Maybe two.

So you waited it out. The fan came first, then the cool pillow, then the spray that costs twelve dollars and smells like a hotel lobby. You slept on a towel. And here you are in September, peeling off a cardigan in a room where no one else is warm.

Nobody lied to you. The old number was just wrong.

Nancy Avis and her team at Wake Forest School of Medicine tracked 3,302 women through the change, at seven sites across the country, for years on end. The hot flashes ran a middle span of 7.4 years. Women whose flashes started early ran closer to twelve.

Seven years. Not one.

If you're a man reading this, stay with me. You live with it too, and you're the one who does the shopping on Saturday...

A top sleep expert from the University of Washington points to something that takes thirty seconds and one cherry.

Studies show it releases a sleep-regulating hormone: you fall asleep faster, stay asleep, and gain 84 minutes of total sleep — which science puts at ten times better than melatonin.

It is working for 36,498 people.

See the 30-second cherry trick

In the 1930s, farmers in Western Australia had a problem they could not name.

Their sheep grazed a low green clover that grew well on poor ground. The wool came in fine. But the lambs stopped coming. Whole flocks went quiet, year after year, and no one could say why.

A veterinary pathologist named Hubert Bennetts went and looked. He worked it through with Eric Underwood and F. L. Shier, and in February 1946 the three of them laid it out in the Australian Veterinary Journal. The pasture was doing it. That clover was building a compound that acted, inside a body, like the female hormone estrogen.

Science had no idea plants could do that. And once people went looking, they found the same trick all over the plant kingdom — strong in clover, mild in most things, and mildest and best studied of all in a bean you can buy frozen for a couple of dollars.

Which brings us back to you, and to the switch behind your forehead...

Deep in the brain sits the switch that holds you near 98.6 degrees.

It works like the one on your wall, with one difference. The switch does not hold a single number. It holds a band. Drift above the top and you sweat. Drop below the bottom and you shiver. In between, nothing happens at all, and you never once think about it.

Estrogen holds that band open. Take a look at what happens when the hormone goes.

Robert Freedman, at Wayne State University School of Medicine in Detroit, warmed two groups of women and tracked the heat in their core the whole time. Twelve of them had hot flashes. Eight did not. In the women with flashes, the gap between "start sweating" and "start shivering" had nearly shut.

The Detroit finding: your body is not running hot. What narrowed is the band it will accept, so a rise of a fraction of a degree — the kind you would never feel at 50 — now trips the whole cooling machine at once. Blood floods the skin, the sweat comes, the heat dumps. Then you are cold and reaching for the quilt again.

That is why the fan helps and never fixes it. You are cooling a body that was never the problem. The band is the problem.

Soybeans carry the same family of compounds that clover made.

They are weak — a tiny fraction of the strength of your own hormone. What they can do is sit in the same docks on your cells and pass along a faint version of the message. People in East Asia have eaten this bean that way for thousands of years, boiled whole, pressed into curd, or left to ferment.

So does any of that widen the band? Here's the biggest count anyone has run.

Oscar Franco and his team at Erasmus University Medical Center in Rotterdam pooled 62 trials and 6,653 women. Those taking the plant compounds had about 1.3 fewer hot flashes a day than those on a dummy pill. Night sweats did not budge at all.

One and a third a day. That is not a switch, and I'll say it plain: anyone selling you a switch is selling you something. It is a small, real, repeatable dent...

And the dent may be far bigger for some women than others. You see, one of the soy compounds only turns strong after certain gut bugs get hold of it. They rebuild it into a thing called equol, which grips the docks much harder. Roughly one adult in four in Western countries carries those bugs. In Japan it runs closer to half. No one can tell you which group you're in without a lab test — which may be exactly why the beans are a godsend for your neighbor and a shrug for you.

One trial used food instead of capsules, and it is worth your time.

A research group in Washington, D.C., put 38 women past the change on a low-fat plant diet with half a cup of cooked soybeans a day, for twelve weeks. Total hot flashes fell 79 percent. In the group told to change nothing, they fell 49 percent.

Hold that one loosely. Everything moved at once — the beans, the fat, the meat, the weight — so nobody can hand the credit to the soy. Only 38 women took part. The team that ran it campaigns for plant-based eating, which you deserve to know before you read the number. And the do-nothing group still improved by half, which tells you what a cool autumn and a bit of attention will do on their own.

What that trial does give you is a dose. Half a cup of cooked soybeans, daily, for twelve weeks.

Look for shelled edamame — green soybeans picked young. Five minutes in boiling water, a little salt, and they're done. Eat them warm, or cold out of the fridge by the handful. A bag runs a couple of dollars and a heaped cup gets you most of the way to the dose used in the trials.

Firm tofu, cubed and dropped in soup, is the cheapest slab of this stuff in the store. Tempeh slices and fries like bacon. A spoon of miso stirred into hot broth at the end carries the same compounds, with some of the work already done by the ferment. Vary them so you don't get bored by week three.

Plenty of women were told to fear soy. Sarah Nechuta and Xiao Ou Shu at Vanderbilt pooled 9,514 women who had been through breast cancer, in the United States and China. Eating soy food afterward did not raise the odds of it returning, and the women eating the most had somewhat lower odds. That was food, not extracts. If you take a breast cancer medicine or any hormone therapy, ask your own doctor before you change a thing.

Those farmers in Western Australia were not hunting for a hormone. They wanted their lambs back.

What they turned up instead is that a plant can speak, faintly, in your body's own language. Eighty years on, the same faint voice is sitting in a two-dollar bag in the freezer aisle, saying something small to a switch in your head that has grown too easy to startle.

Small is not nothing. One fewer flash a day, across seven years, is a lot of nights you get back.

Buy the bag this week. Count what happens by Christmas.