Does Flaxseed Help With Hot Flashes?

Flaxseed turns up on almost every list of foods for menopause, usually a line or two below soy. The reasoning sounds solid: it is one of the richest food sources of lignans, a type of plant compound that acts weakly like oestrogen in the body. If falling oestrogen drives hot flashes, a food that mimics it should help.

It was a reasonable idea, and it has been tested properly. The answer is less exciting than the lists suggest.

What does the research actually show?

The first study to get attention was a small pilot from the Mayo Clinic in 2007. Women eating 40g of crushed flaxseed a day reported their hot flashes roughly halved over six weeks. The catch was that there was no placebo group, so there was no way to tell how much of that drop would have happened anyway.

The same research group then ran the proper version: a phase III, randomised, double-blind trial published in the journal Menopause in 2012. 188 women were given either a flaxseed bar carrying 410mg of lignans or a placebo bar that looked and tasted the same, for six weeks.

Hot flash scores fell in both groups, by about the same amount. In each group, a little over a third of women saw their scores drop by half or more. The difference between flaxseed and placebo was not statistically significant, and the researchers concluded the results did not support flaxseed for reducing hot flashes. A later systematic review pooling the available trials reached much the same place.

Why did the pilot study look so good?

Because hot flashes respond strongly to placebo, and they also shift on their own from week to week. Trials of almost any menopause remedy see a meaningful improvement in the placebo group, often in the region of a quarter to a third.

That is worth knowing whatever you are trying. A result you notice in yourself over a fortnight is real to you, but it cannot tell you whether the food did it or the fortnight did. It is also why the two-week test used across this series ends with putting the food back: if symptoms climb again, that is a much better sign than a drop on its own.

Is flaxseed the same as soy?

No, although they get grouped together as phytoestrogens. Soy carries isoflavones and flaxseed carries lignans, and they behave differently in the body. Soy has the stronger evidence of the two: reviews generally find a small reduction in hot flash frequency against placebo, which is covered in our piece on whether soy helps with hot flashes.

So if you want to try a plant food for hot flashes, soy has more behind it. Flaxseed has been tested and has not shown a clear effect.

Is flaxseed still worth eating?

Yes, for reasons that have nothing to do with hot flashes. A tablespoon of ground flaxseed (about 7g) carries around 2g of fibre and is one of the richest plant sources of alpha-linolenic acid, the plant form of omega-3.

Fibre matters more through menopause than it gets credit for. Many women notice their digestion changes through these years, and bloating and constipation come up often. A spoonful of ground flaxseed stirred into porridge or yoghurt is one of the easiest ways to add fibre without changing anything else about breakfast.

That is a fair reason to keep it. It is not the same as it doing something for your hot flashes, and it is worth being clear with yourself about which one you are buying it for.

Ground, whole or oil?

Ground. Whole flaxseeds often pass through the gut largely undigested, so you get very little of what is inside them. Buy it ground (sometimes sold as linseed meal) or grind it yourself in a spice grinder, and keep it in the fridge, because the oils go rancid quickly once the seed is broken.

Flaxseed oil carries the omega-3 but almost none of the fibre and far less of the lignans, so it is a different product rather than a concentrated version of the same thing.

Supplements of flaxseed lignan extract are what the 2012 trial effectively tested, in bar form, and they did not beat placebo. There is no strong reason to pay more for a capsule.

How much is sensible?

One to two tablespoons of ground flaxseed a day is a common amount in food, and it is roughly what most of the research used. Start with a teaspoon and build up over a week or two. Adding a lot of fibre at once is a reliable way to cause the very bloating you might be trying to settle, and drinking enough water alongside it helps.

Is it safe?

As a food, for most women, yes. A few things are worth knowing:

• Medications. Flaxseed can slow the absorption of some oral medicines taken at the same time. Leaving a couple of hours between the two is a common precaution, and your pharmacist can tell you whether it matters for anything you take.
• Blood thinners. Large amounts of flaxseed or flaxseed oil may add to the effect of anticoagulant medicines. Talk to your doctor before taking it in supplement form if you are on one.
• Breast cancer. Because lignans act weakly like oestrogen, women with a history of hormone-sensitive breast cancer often ask about it. Food amounts have generally not raised concern in the research, and the 2012 trial deliberately included women with a breast cancer history. It is still a question for your oncologist rather than a food website.

Common questions

Does flaxseed reduce hot flashes?

The best trial so far found it did no better than placebo. Some women report fewer hot flashes after adding it, and that is real to them, but a similar share of women eating a placebo reported the same thing.

How long does flaxseed take to work for menopause?

The trials ran for six weeks, which is long enough to see an effect if there were one. If you have been taking it for longer than that with no change, it is unlikely a few more weeks will make the difference.

Is linseed the same as flaxseed?

Yes. Linseed is the common name in Australia and the UK, flaxseed in the US. Golden and brown seeds are nutritionally very similar.

Can flaxseed help with menopause bloating?

The fibre in ground flaxseed can help with regularity, which some women find eases bloating. Too much too fast can make it worse. Our piece on bloating in perimenopause covers the other causes, and the symptoms that mean seeing a doctor rather than changing your diet.

Is flaxseed good for bones after menopause?

There is no good evidence that it protects bone density. Calcium, vitamin D, protein and weight-bearing exercise are where the evidence sits, which is covered in how much calcium you need after menopause.

Should I take flaxseed or soy for hot flashes?

If you want to try a food, soy has more evidence behind it, though the effect is still modest. Neither is a replacement for talking to your doctor if hot flashes are affecting your sleep or your working day.

Where this leaves you

Keep the flaxseed if you like it, for the fibre and the omega-3. Do not keep paying for it on the promise that it will settle your hot flashes, because the best test so far says it probably will not.

Registered Nutritionist Trish Tucker-May is the author of Nourish Your Gut For A Positive Menopause, and the menopause and food guide answers the other food questions one at a time.

Menopause symptoms are worth raising with your doctor, particularly if they are affecting your sleep, your mood or your ability to get through a working day. Nothing here is a substitute for that conversation.

Sources

• Pruthi S, et al. Pilot evaluation of flaxseed for the management of hot flashes. Journal of the Society for Integrative Oncology, 2007.
• Pruthi S, et al. A phase III, randomized, placebo-controlled, double-blind trial of flaxseed for the treatment of hot flashes. Menopause, 2012.
• Effects of flaxseed and Hypericum perforatum on hot flash, vaginal atrophy and estrogen-dependent cancers in menopausal women: a systematic review and meta-analysis
• National Center for Complementary and Integrative Health, Flaxseed and Flaxseed Oil
• Mayo Clinic, Flaxseed and flaxseed oil