Flaxseed
HerbalAlso called · 6 names▾▴
flax, flax seed, linseed, flaxseed oil, linseed oil, Linum usitatissimum
Herbal supplement (fiber and omega-3)
Herbs and supplements are not FDA-approved before sale. About these sources
- Food / spice
- Powder
- Other
- Topical
Research strength: 2 / 5
NCCIH says some studies of flaxseed in pregnancy raise a possible concern, but the evidence is not conclusive. It does not give first-trimester results. The European Medicines Agency (EMA) does not recommend medicinal flaxseed (linseed) use in pregnancy because data are lacking. EMA also notes that linseed may act like estrogen, a hormone. ACOG lists ground flaxseed and flaxseed oil as omega-3 food sources, but its page does not assess supplement doses or pregnancy outcomes. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 2 / 5
NCCIH says some studies of flaxseed in pregnancy raise a possible concern, but the evidence is not conclusive. It does not give second-trimester results. The European Medicines Agency (EMA) does not recommend medicinal flaxseed (linseed) use in pregnancy because data are lacking. EMA also notes that linseed may act like estrogen, a hormone. ACOG lists ground flaxseed and flaxseed oil as omega-3 food sources, but its page does not assess supplement doses or pregnancy outcomes. Ask your provider about your situation.
Last reviewed: 2026-10-16
Research strength: 2 / 5
NCCIH says some studies of flaxseed in pregnancy raise a possible concern, but the evidence is not conclusive. It does not give third-trimester results. The European Medicines Agency (EMA) does not recommend medicinal flaxseed (linseed) use in pregnancy because data are lacking. EMA also notes that linseed may act like estrogen, a hormone. ACOG lists ground flaxseed and flaxseed oil as omega-3 food sources, but its page does not assess supplement doses or pregnancy outcomes. Ask your provider about your situation.
Last reviewed: 2026-10-16
Flaxseed — Breastfeeding
Research strength: 2 / 5
LactMed reports that a small study in seven nursing mothers found flaxseed oil raised ALA, a type of omega-3 fat, in milk but not DHA, another omega-3 fat. The study measured milk, not infant health outcomes. LactMed says data on oil use in nursing mothers or infants are very limited, but flaxseed used as a laxative or a poultice placed on the skin is not expected to adversely affect a breastfed infant. NCCIH says little is known about flaxseed or oil during breastfeeding, and EMA does not recommend medicinal linseed because data are lacking. A 2023 cookie trial with flaxseed, oats, brewer's yeast, and fenugreek found no difference in milk production from control cookies, so it cannot show what flaxseed alone does. Ask your provider about your situation.
Last reviewed: 2026-10-16
Sources
- LactMed: FlaxseedUS government
- NCCIH: Flaxseed and Flaxseed OilUS government
- EMA: European Union herbal monograph on Linum usitatissimum L., semenEU agencyEuropean guidance
- CDC: Maternal Diet and BreastfeedingUS government
- Francois et al., American Journal of Clinical Nutrition 2003US government
- Palacios et al., American Journal of Clinical Nutrition 2023US government
Pregnancy
NCCIH says some studies of flaxseed during pregnancy raise a possible concern, but the evidence is not conclusive. The EMA monograph for medicinal linseed says use in pregnancy is not recommended because data are insufficient; it reports that no harmful effects have been reported and notes a possible estrogen-like effect based on investigations in healthy women. ACOG's 2026 pregnancy nutrition FAQ lists ground flaxseed and flaxseed oil as omega-3 sources, but does not assess supplement doses or pregnancy outcomes. A 2020 randomized trial in 60 women with gestational diabetes tested omega-3 fatty acids from flaxseed oil for six weeks and measured metabolic markers, not pregnancy or infant outcomes. The journal published an expression of concern about that trial in 2022. A 2025 rat study examined a maternal diet containing flaxseed oil during pregnancy and lactation; animal findings do not establish human outcomes.
Breastfeeding
In a 2003 study, seven lactating women took 20 g of flaxseed oil daily for four weeks. Milk ALA, EPA, and DPA increased, but DHA did not; the study measured milk composition, not infant health outcomes. LactMed says information on oil use in nursing parents or infants is very limited. A 2023 randomized trial assigned 176 breastfeeding parents to cookies with flaxseed, fenugreek, oats, and brewer's yeast or control cookies for one month. The trial found no significant difference in milk production, perceived milk supply, or breastfeeding self-efficacy; because the cookie contained several ingredients, it cannot identify the effect of flaxseed alone. EMA's 2024 addendum reviewed a 2014 high-oil rat lactation study and said its relevance to humans is unclear. A 2026 rat study compared fish, flaxseed, and walnut oils during lactation; it does not provide human infant outcome data.
Flaxseed (Linum usitatissimum) is used as whole or ground seed, powder, mucilage, lignan extract, oil, and topical preparations. Whole seed contains fiber and mucilage, which absorb water and add bulk. Flaxseed oil contains alpha-linolenic acid (ALA), an omega-3 fat. LactMed reports that oil raises ALA in breast milk but not DHA, another omega-3 fat. Findings about oil do not automatically describe whole seed, fiber, or lignan extracts.
What was tested
Human pregnancy evidence includes a six-week trial of flaxseed-oil omega-3 fatty acids in 60 women with gestational diabetes; the measured outcomes were metabolic markers, and the journal later published an expression of concern. Human lactation evidence includes a seven-person oil study measuring milk fatty acids and a 2023 randomized cookie trial with 176 participants that tested a mixture of flaxseed, fenugreek, oats, and brewer's yeast. The 2014, 2025, and 2026 lactation or pregnancy studies described here used rats, not pregnant or breastfeeding people.
Pregnancy guidance for flaxseed foods and medicinal linseed
- Source A says
- ACOG's pregnancy nutrition FAQ lists ground flaxseed and flaxseed oil among omega-3 food sources. It does not discuss supplement doses or pregnancy outcomes. (ACOG: Healthy Eating During Pregnancy)
- Source B says
- EMA's medicinal linseed monograph says use during pregnancy is not recommended because data are insufficient and notes a possible estrogen-like effect. (EMA: European Union herbal monograph on Linum usitatissimum L., semen)
- Why they differ
- ACOG discusses food sources of omega-3s, while EMA's monograph addresses medicinal linseed use. The pages address different forms and purposes, not the same dose or use.
- Other sources
- NCCIH says some pregnancy studies raise a possible concern but calls the evidence inconclusive; it also says little is known about flaxseed oil during pregnancy. (NCCIH: Flaxseed and Flaxseed Oil)
- What the evidence shows overall
- ACOG's nutrition statement is not an endorsement of supplement doses. EMA's caution is based on missing data, not established human harm. The available sources support an insufficient rating for medicinal products, with food use distinguished from medicinal use.
How to interpret limited breastfeeding evidence and general food guidance
- Source A says
- LactMed says flaxseed oil can be used during lactation and that seed used as a laxative or topical poultice is not expected to adversely affect a breastfed infant. (LactMed: Flaxseed)
- Source B says
- NCCIH says little is known about flaxseed or oil during breastfeeding. EMA does not recommend medicinal linseed during lactation because data are insufficient. (NCCIH: Flaxseed and Flaxseed Oil, EMA: European Union herbal monograph on Linum usitatissimum L., semen)
- Why they differ
- LactMed's positive wording distinguishes oil from seed used as a laxative or topical poultice, while NCCIH describes limited knowledge and EMA's medicinal monograph addresses seed use. Human infant-outcome evidence is very limited.
- Other sources
- CDC's 2026 maternal-diet page says breastfeeding mothers generally do not need to limit or avoid specific foods. It does not mention flaxseed or assess concentrated supplements. (CDC: Maternal Diet and Breastfeeding)
- What the evidence shows overall
- The small human study measured milk fatty acids, not infant outcomes. CDC's general food guidance is not a flaxseed supplement assessment. The evidence supports an insufficient rating for medicinal use, while LactMed's statements remain specific to oil and seed used as a laxative or topical poultice.
- ACOG lists ground flaxseed and flaxseed oil as omega-3 food sources during pregnancy; its page does not provide supplement doses or pregnancy outcome guidance. (ACOG)
- EMA's monograph says medicinal linseed use during pregnancy and lactation is not recommended because sufficient data are lacking. (European Medicines Agency)
- LactMed says flaxseed oil can be used during lactation, while noting very limited information on its use in nursing parents or infants. (LactMed)
General research, not specific to pregnancy.
NCCIH says flaxseed oil contains ALA, an omega-3 fat, and that higher amounts of flaxseed or oil may cause digestive symptoms. EMA describes medicinal linseed as a bulk-forming laxative that may delay absorption of other medicines.
- NCCIH says higher amounts of flaxseed or flaxseed oil may cause bloating, fullness, and diarrhea. (NCCIH: Flaxseed and Flaxseed Oil)
- EMA says medicinal linseed can delay absorption of medicines taken at the same time and advises spacing them by at least one-half to one hour. (EMA: European Union herbal monograph on Linum usitatissimum L., semen)
- NCCIH: Flaxseed and Flaxseed OilUS governmentSecondary
- LactMed: FlaxseedUS governmentSecondaryPage dated 2024-05-15
- EMA: European Union herbal monograph on Linum usitatissimum L., semenEU agencySecondaryPage dated 2015-03-10Independent checkEuropean guidance
- EMA: Addendum to Assessment report on Linum usitatissimum L., semenEU agencySecondaryPage dated 2024-11-20Independent checkEuropean guidance
- ACOG: Healthy Eating During PregnancyProfessional societySecondary
- CDC: Maternal Diet and BreastfeedingUS governmentSecondaryPage dated 2026-08-25
- Francois et al., American Journal of Clinical Nutrition 2003US governmentPrimaryIndependent check
- Palacios et al., American Journal of Clinical Nutrition 2023US governmentPrimaryIndependent check
- Jamilian et al., British Journal of Nutrition 2020US governmentPrimary
- Journal expression of concern for Jamilian et al. 2020US governmentPrimary
- Guarda et al., Food and Chemical Toxicology 2014US governmentPrimaryIndependent check
- Santos et al., Anais da Academia Brasileira de Ciências 2025US governmentPrimary
- Mutlu Durğut et al., Molecular Nutrition and Food Research 2026US governmentPrimary
Last reviewed 2026-10-16
Independent check 2026-10-16
Not yet clinician-reviewed
Ask your provider about your situation.
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