Omega-3 in perimenopause

Omega-3 supplements do not reduce hot flashes, and the evidence for mood is weak. For the heart, eating fish is well supported, while supplements lower triglycerides and may slightly reduce coronary events without changing overall cardiovascular risk in generally healthy people. If you take one, the number that matters is milligrams of EPA plus DHA, not the size of the capsule.

What it is

Omega-3s are polyunsaturated fats. Three dominate the research: alpha-linolenic acid (ALA) from flaxseed, chia, walnuts, canola and soybean oil, and the long-chain fats eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fatty fish such as salmon, herring, sardines and mackerel. The body can convert ALA to EPA and DHA, but poorly: reported rates are under 15 percent. Eating EPA and DHA directly is the only practical way to raise them.

The only official intake target is for ALA, an Adequate Intake of 1.1 g a day for adult women. There is no recommended amount for EPA or DHA. US adults get about 90 mg a day of EPA plus DHA from food, which is low compared with the amounts tested in trials.

Supplements include fish oil, krill oil, cod liver oil and algal oil, the plant-based source.

Why women in midlife take it

Fish oil is one of the most commonly used non-vitamin supplements in the US. In midlife it is marketed for heart health, joints, brain fog, mood and, increasingly, hot flashes. The heart and brain claims rest largely on observational studies of people who eat more fish, which cannot separate the effect of omega-3 from the rest of their diet and habits.

What the evidence shows

Hot flashes. MsFLASH, a US multicenter trial, randomized 355 healthy perimenopausal and postmenopausal women to 1.8 g of omega-3 or placebo daily for 12 weeks. Women started with an average of 7.6 hot flashes a day. Hot flashes fell by 2.5 a day on omega-3 and 2.7 a day on placebo, a difference that was not statistically significant. Hot flash bother, sleep quality, insomnia, depressive symptoms and anxiety did not improve either.

An earlier Canadian trial studied 120 women aged 40 to 55 with moderate to severe psychological distress; the 91 who had hot flashes were analyzed. Starting from 2.8 hot flashes a day, frequency fell by 1.58 a day on an EPA-rich supplement versus 0.50 on placebo over 8 weeks. Quality of life did not differ. The authors said the finding needed confirmation in more symptomatic women, and MsFLASH, which enrolled exactly that group, did not confirm it.

Mood. The Office of Dietary Supplements cites a 2015 Cochrane review of 26 studies that found insufficient evidence that omega-3s help major depression in adults, and a small effect on depressive symptoms that was not clinically meaningful. NCCIH describes a 2021 review of 35 studies with the same conclusion: if there is an effect, it may be too small to matter.

Heart and cancer. VITAL randomized 25,871 US adults (women 55 and older, men 50 and older) to 1 g a day of omega-3 (460 mg EPA, 380 mg DHA) or placebo. Over a median 5.3 years, major cardiovascular events (hazard ratio 0.92) and invasive cancer did not differ significantly. Heart attacks were 28 percent lower (hazard ratio 0.72), but stroke and cardiovascular death were unchanged, and there was no excess bleeding.

The 2020 Cochrane review pooled 86 trials with 162,796 participants. Increasing long-chain omega-3 had little or no effect on death from any cause or on cardiovascular events, and may slightly reduce death from coronary heart disease. ODS reports that supplementation in these trials lowered triglycerides by about 15 percent.

The American Heart Association recommends one to two servings of seafood a week, suggests about 1 g a day of EPA plus DHA for people with existing coronary heart disease under a physician’s direction, and does not recommend supplements for people without high cardiovascular risk. High-dose prescription omega-3 products used for very high triglycerides are a separate category from supplements.

Dose and form used in studies

MsFLASH used 1.8 g a day of a mostly EPA ethyl ester formula (each capsule held 425 mg EPA, 100 mg DHA and 90 mg other omega-3s). VITAL used 1 g a day providing 840 mg EPA plus DHA. For comparison, a typical 1,000 mg fish oil capsule contains about 180 mg EPA and 120 mg DHA, and algal oil supplements usually provide 100 to 300 mg DHA.

Omega-3s come as natural triglycerides, re-esterified triglycerides, free fatty acids, ethyl esters and, in krill oil, phospholipids. The triglyceride and free fatty acid forms are absorbed somewhat better than ethyl esters, but all forms raise blood EPA and DHA. Evidence that krill oil is better absorbed than fish oil is mixed.

Safety, interactions and who should be careful

Side effects are usually mild: fishy taste, bad breath, heartburn, nausea, stomach upset, diarrhea, headache and fishy-smelling sweat.

FDA has concluded that supplements providing up to 5 g a day of EPA plus DHA are safe as directed, and asks that supplement labels not recommend more than 2 g a day. Two large trials of 4 g a day for several years found a slightly higher risk of atrial fibrillation in people with or at high risk of cardiovascular disease.

High intakes, roughly 2 to 15 g a day, may lengthen bleeding time. In people on warfarin, most research shows 3 to 6 g a day of fish oil does not significantly change anticoagulation, but prescription omega-3 labels advise periodic INR checks when combined with anticoagulants. If you take a blood thinner or antiplatelet drug, or have surgery planned, tell your clinician.

ODS does not describe interactions with hormone therapy, SSRIs or thyroid medication. That reflects an absence of reported problems rather than formal study, so include omega-3 on your medication list.

Cod liver oil also supplies vitamins A and D; count those toward your totals if you take other supplements.

How to choose a product

Read the Supplement Facts panel for EPA and DHA in milligrams per serving, and check whether a serving is one capsule or two. “Fish oil 1,000 mg” tells you the weight of the oil, not the omega-3 content. Choose a single-ingredient product rather than a blend that combines omega-3 with herbs. Mercury has not been found in omega-3 supplements because it is removed during processing. Algal oil is a fish-free option. A third-party mark such as USP Verified or NSF confirms the label amounts and contaminant limits, though not whether the product will help you.

Bottom line

Omega-3 supplements are not a treatment for hot flashes, sleep or perimenopausal mood. For long-term heart health, two servings of fatty fish a week is the better-supported habit; a supplement is reasonable if you rarely eat fish, but expect at most modest effects. If hot flashes, low mood or sleep loss are wearing you down, track them with the symptom check and talk to a clinician who treats menopause; see how to find a menopause specialist or the clinician finder.