Home Ingredients Borage Leaf and Flower (Borago officinalis)
Respiratory Health

Borage Leaf and Flower (Borago officinalis)

Borago officinalis L.
Evidence Level
Limited
4 Clinical Trials
4 Documented Benefits
2/5 Evidence Score

Borage leaf and flower come from the same Mediterranean garden plant (Borago officinalis) whose seeds are pressed for borage oil, but they are a different product. The leaves are eaten as a vegetable in parts of Europe and both leaves and flowers are used in herbal teas. Unlike refined seed oil, the leaves contain pyrrolizidine alkaloids such as lycopsamine, intermedine and amabiline, which can damage the liver. EU food law caps them at 750 micrograms per kg in fresh borage leaves and 1,000 in dried borage, and EU herbal medicines may supply at most 1.0 microgram a day to an adult. Human evidence is one placebo-controlled trial: a month of a flower and leaf extract syrup improved asthma control scores, cough and breathlessness, but not lung function, in adults with moderate asthma. Everything else is laboratory work. Not for use in pregnancy, while breastfeeding, by children or by people with liver disease.

Studied Dose No recommended dose exists. The one human trial gave 5 mL of a flower and leaf extract syrup three times daily for one month; its alkaloid content was not reported. EMA limits these alkaloids in herbal medicines to 1.0 microgram a day for an adult.
Active Compound Dried or fresh leaves and flowers of Borago officinalis, containing phenolics such as rosmarinic acid plus flavonoids, coumarins, sterols and tannins. The leaves also contain 1,2-unsaturated pyrrolizidine alkaloids (lycopsamine, intermedine, amabiline, supinine and acetylated forms), mostly as N-oxides.

Benefits

Breathing symptoms and control scores in one placebo-controlled trial

The leaves carry liver-toxic pyrrolizidine alkaloids, limited to 1.0 microgram a day for adults in EU herbal medicines and 750 micrograms per kg in fresh leaves under EU food law. In a one-month double-blind trial in 38 adults with moderate asthma, a flower and leaf syrup raised control scores and cut cough and breathlessness more than placebo; lung function, exhaled nitric oxide and attacks did not differ. It is a single trial.

Supported by Trial 1

Smooth muscle relaxation in isolated animal tissue

Laboratory work only. A crude borage leaf extract relaxed contractions of isolated rabbit gut and windpipe tissue and relaxed precontracted rabbit aorta, in a pattern resembling calcium channel blockers, and it weakened the force and rate of isolated guinea pig heart tissue. These tissue-bath results have not been tested in people.

Supported by Trial 2

Blood glucose response in a rat study

Animal work only. In rats made diabetic with alloxan, a single 500 mg/kg dose of a methanol extract of borage leaves given by stomach tube lowered blood glucose 4 hours later; the 250 mg/kg dose did not show a relevant effect. Concentrated extract doses in rats do not show an effect from borage tea in people.

Supported by Trial 3

Genetic damage tests in fruit flies and cultured human cells

Laboratory work only. Freeze-dried borage leaves and stalks did not damage DNA in a fruit fly test and reduced DNA damage from hydrogen peroxide, and they slowed growth of a human leukemia cell line in a dish. The highest concentrations also lowered fly survival. Alkaloid levels were not measured, so these results do not show the leaves are safe to eat often.

Supported by Trial 4

Mechanism of action

1

Phenolic compounds in the leaf

Borage leaf extracts test positive for flavonoids, coumarins, sterols and tannins, and rosmarinic acid is one of the main phenolics in the leaves. In fruit fly and cell studies these phenolics showed DNA-protective and cell-killing effects similar to the whole leaf. Whether tea or salad amounts do this in people is unknown.

2

Calcium channel-like muscle relaxation in lab tissue

In isolated rabbit gut tissue, borage leaf extract shifted calcium response curves the way the calcium channel blocker verapamil does, which the authors proposed explains its relaxation of gut, windpipe and blood vessel tissue. This is a tissue-bath finding, not a measured effect in people.

3

How pyrrolizidine alkaloids injure the liver

Unsaturated pyrrolizidine alkaloids are harmless until liver CYP enzymes convert them into reactive pyrroles. These bind proteins and DNA and damage the cells lining the small liver blood vessels, which can block blood flow (hepatic sinusoidal obstruction syndrome, also called veno-occlusive disease). Some metabolites reach the lungs, and the damage can build up slowly.

Clinical trials

1
Borage Flower and Leaf Extract Syrup in Moderate Asthma: Placebo-Controlled RCT
PubMed

Randomized, double-blind, placebo-controlled phase 2 trial of a hydroalcoholic extract of borage flowers and leaves made into a syrup by a local herbal company, 5 mL three times daily for one month, with salbutamol allowed as a reliever; registered as IRCT201209302695N4. Computer-generated randomization; patients, clinicians and outcome assessors were blinded. Funded by Islamic Azad University, Mashhad branch; the syrup maker supplied the syrup and an identical placebo. (Mirsadraee et al. 2016, Tanaffos)

42 people older than 15 with moderate persistent asthma (FEV1 60 to 79% of predicted) at a pulmonary clinic in Mashhad, Iran; 38 completed (15 women, 23 men, mean age 46.8).

After one month the asthma control test score was significantly higher with borage than placebo (15.4 vs 11.2; this compared end-of-trial values, and the borage group started lower, 10.8 vs 13.1), and fewer people on borage still had cough (16% vs 84%), shortness of breath (42% vs 94%), sputum, airway hyperresponsiveness or reflux symptoms. Exhaled nitric oxide, the co-primary outcome, spirometry, sputum eosinophils and neutrophils, and attack and emergency visit rates did not differ between groups; the drops in attacks and emergency visits were within the borage group only. Two people on borage had a skin rash and one stopped after a severe attack. The syrup was checked for alkaloids by a pharmacist, but no pyrrolizidine alkaloid levels were reported, and the discussion section misstates the sample size as 52.

2
Borage Leaf Extract on Isolated Gut, Windpipe, Aorta and Heart Tissue (lab study, not a human trial)
PubMed

Laboratory study of a crude extract of borage leaves tested on isolated rabbit jejunum, trachea and aorta and guinea pig atria, with verapamil as a reference drug. (Gilani et al. 2007, J Ethnopharmacol)

Isolated rabbit and guinea pig tissues; no human participants.

The extract relaxed spontaneous and potassium-induced gut contractions and shifted calcium concentration-response curves to the right, like verapamil. It relaxed carbachol and potassium contractions of tracheal tissue, relaxed phenylephrine and potassium contractions of aorta, and reduced the force and rate of atrial contractions. Tissue-bath results only; not tested in people.

3
Borage Leaf Extract and Blood Glucose in Diabetic Rats (animal study, not a human trial)
PubMed

Randomized rat study comparing methanol extracts of the leaves of four plants, including Borago officinalis, at 250 and 500 mg/kg given once by stomach tube, against saline. (Rodríguez-Magaña et al. 2019, J Diabetes Res)

72 male Wistar rats made diabetic with alloxan, 9 per group; no human participants.

Four hours after dosing, the 500 mg/kg borage extract showed relevant glucose lowering (p = 0.0112); the 250 mg/kg dose did not. The test compared glucose before and after dosing within each group, not against the control group. The extract showed no toxicity in a brine shrimp test. A single-dose, 4-hour animal result; not tested in people.

4
Borage Leaves in Fruit Fly DNA Tests and a Human Cell Line (lab study, not a human trial)
PubMed

Fruit fly somatic mutation and recombination test (SMART) and HL-60 human leukemia cell assays of freeze-dried leaves and stalks from blue-flowered and white-flowered borage, plus rosmarinic, syringic and sinapic acids. (Lozano-Baena et al. 2016, Nutrients)

Drosophila melanogaster larvae and cultured HL-60 cells; no human participants.

Borage material was not genotoxic in the fly test and reduced DNA damage caused by hydrogen peroxide. It reduced HL-60 cell viability with IC50 values of 0.49 and 0.28 mg/mL for the two varieties. Alone, the highest concentration lowered fly survival to 82% (blue-flowered) and 71% (white-flowered) of controls; combined with hydrogen peroxide, the highest white-flowered concentration cut survival to about 17%. Pyrrolizidine alkaloid content was not measured. Lab results only; not tested in people.

Side effects and drug interactions

Common Potential side effects

Liver toxicity from pyrrolizidine alkaloids: borage leaves contain lycopsamine, intermedine, amabiline, supinine and acetylated forms, reported at about 2 to 10 mg/kg in leaves and stems in an older analysis. Repeated intake of these alkaloids can cause hepatic sinusoidal obstruction syndrome, and slow, chronic liver and lung damage is possible. Stop and see a doctor promptly for abdominal swelling, right upper belly pain, yellow skin or eyes, or dark urine.
Amounts in food can be large compared with medicine limits. All 13 fresh borage leaf samples tested on the Italian market contained these alkaloids, averaging about 531 micrograms per kg (up to 3,410). At that average, 100 g of fresh leaves supplies roughly 53 micrograms, about 50 times the 1.0 microgram daily limit the European Medicines Agency applies to herbal medicines.
EU food law caps the regulated alkaloids at 750 micrograms per kg in fresh or frozen borage leaves sold to consumers, 1,000 in dried borage and 400 in botanical food supplements. Acetylated forms that are among the main alkaloids in borage leaves are not part of the regulated sum, and US law sets no such limits, so ask sellers for an alkaloid test.
Flowers have been studied less than leaves. One older analysis found only thesinine, a different alkaloid type, in the flowers, but flower products are rarely tested, the trial syrup combined flowers with leaves, and teas often mix both.
Pregnancy, breastfeeding and children: avoid. NIH LactMed says the alkaloids might pass into breast milk and that leaf products should be avoided by nursing mothers. The EMA notes that in rats these alkaloids cross the placenta and harm suckling young, and that children are particularly vulnerable.
In the one human trial, 2 of 19 people on borage syrup developed a skin rash and one stopped after a severe asthma attack.
When foraging, borage leaves have been mistaken for foxglove leaves, which contain heart glycosides; this has caused hospital admissions with digitoxin poisoning and heart rhythm problems. Buy from an identified source.
A 2020 systematic review found no published case reports of alkaloid poisoning that involved borage. Because the damage builds slowly and is hard to trace to a food, that does not show regular use is safe.

Important Drug interactions

Medicines and herbs that induce liver CYP enzymes: the EMA notes that enzyme induction could significantly increase the toxicity of these alkaloids, because the liver must activate them before they cause harm. Ask a pharmacist before combining.
Other pyrrolizidine-containing herbs such as comfrey or coltsfoot: they add to the same alkaloid load, and the EMA counts alkaloids from the active herb and any contamination together against its 1.0 microgram daily limit, so do not combine them.
Anything that already strains the liver, including liver disease, heavy alcohol use or medicines with liver warnings: the EMA notes that other liver-damaging agents, such as viruses and aflatoxins, act together with these alkaloids. Avoid borage leaf in these situations.
Blood pressure and heart rhythm medicines: in isolated animal tissue the leaf extract acted like a calcium channel blocker and slowed heart tissue. This is lab-only and untested in people, but an added effect is possible.
Glucose-lowering medicines: a leaf extract lowered blood glucose in diabetic rats. Untested in people; monitor blood sugar if combining.

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Frequently asked questions about Borage Leaf and Flower (Borago officinalis)

How is borage leaf different from borage seed oil?

They come from the same plant but are different products. Borage seed oil is pressed from the seeds for its gamma-linolenic acid, and processed oil samples have tested below detection limits for pyrrolizidine alkaloids. The leaves are eaten as a vegetable or brewed as tea and naturally contain these liver-toxic alkaloids, so the safety picture is very different. The seed oil has its own page.

Why does the EU limit pyrrolizidine alkaloids in borage?

Once the liver activates them, these alkaloids can damage the small blood vessels of the liver, and animal studies link them to cancer. Borage leaves make them naturally, so the EU caps the regulated alkaloids at 750 micrograms per kg in fresh leaves and 1,000 in dried borage. For herbal medicines the European Medicines Agency uses a limit of 1.0 microgram a day for an adult.

What did the human trial of borage flower and leaf find?

In one month-long placebo-controlled trial in 38 adults with moderate asthma, an extract syrup improved asthma control scores and cough and breathlessness, but did not change lung function, airway inflammation markers or attack rates compared with placebo. It is a single trial, and it did not report how much alkaloid the syrup contained.

Who should avoid borage leaf and flower?

Pregnant or breastfeeding women, children, and anyone with liver disease, heavy alcohol use or medicines that strain the liver or induce liver enzymes. Do not combine it with other alkaloid-containing herbs such as comfrey or coltsfoot, and if you forage, make sure you are not picking foxglove by mistake.

What is Borage Leaf and Flower?

Borage leaf and flower come from the same Mediterranean garden plant (Borago officinalis) whose seeds are pressed for borage oil, but they are a different product. The leaves are eaten as a vegetable in parts of Europe and both leaves and flowers are used in herbal teas.

What is Borage Leaf and Flower used for?

Borage Leaf and Flower is researched primarily for Respiratory Health. The leaves carry liver-toxic pyrrolizidine alkaloids, limited to 1.0 microgram a day for adults in EU herbal medicines and 750 micrograms per kg in fresh leaves under EU food law.

What is the recommended dosage of Borage Leaf and Flower?

No recommended dose exists. The one human trial gave 5 mL of a flower and leaf extract syrup three times daily for one month; its alkaloid content was not reported. EMA limits these alkaloids in herbal medicines to 1.0 microgram a day for an adult. Always follow the product label and check with a healthcare provider for personal advice.

Is Borage Leaf and Flower safe, and does it have side effects?

Side effects and cautions reported for Borage Leaf and Flower include: Liver toxicity from pyrrolizidine alkaloids: borage leaves contain lycopsamine, intermedine, amabiline, supinine and acetylated forms, reported at about 2 to 10 mg/kg in leaves and stems in an older analysis. It may also interact with some medications. Borage Leaf and Flower is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Borage Leaf and Flower interact with any medications?

Possible interactions include: Medicines and herbs that induce liver CYP enzymes: the EMA notes that enzyme induction could significantly increase the toxicity of these alkaloids, because the liver must activate them before they cause harm. Ask a pharmacist before combining. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Borage Leaf and Flower?

NutraSmarts rates the evidence for Borage Leaf and Flower as Limited (2 out of 5). It is backed by 4 study summaries and 16 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(16 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Mirsadraee M, Khashkhashi Moghaddam S, Saeedi P, Ghaffari S. Effect of Borago Officinalis Extract on Moderate Persistent Asthma: A Phase two Randomized, Double Blind, Placebo-Controlled Clinical Trial. Tanaffos. 2016;15(3):168-174..PubMedUsed to support: Randomized double-blind placebo-controlled trial of a hydroalcoholic borage flower and leaf extract syrup, 5 mL three times daily for one month, in 38 completers with moderate persistent asthma. Asthma control scores, cough, shortness of breath, sputum and airway hyperresponsiveness improved more than on placebo; exhaled nitric oxide, spirometry, sputum cells and attack rates did not differ between groups. Two rashes and one severe attack on borage; alkaloid levels in the syrup were not reported.
  2. Gilani AH, Bashir S, Khan AU. Pharmacological basis for the use of Borago officinalis in gastrointestinal, respiratory and cardiovascular disorders. J Ethnopharmacol. 2007;114(3):393-9. doi: 10.1016/j.jep.2007.08.032.PubMedUsed to support: Isolated tissue study: a crude borage leaf extract containing flavonoids, coumarins, sterols and tannins relaxed rabbit jejunum, trachea and aorta preparations and reduced guinea pig atrial force and rate, with a verapamil-like effect on calcium response curves. Lab tissue only.
  3. Rodríguez-Magaña MP, Cordero-Pérez P, Rivas-Morales C, Oranday-Cárdenas MA, Moreno-Peña DP, García-Hernández DG, Leos-Rivas C. Hypoglycemic Activity of Tilia americana, Borago officinalis, Chenopodium nuttalliae, and Piper sanctum on Wistar Rats. J Diabetes Res. 2019;2019:7836820. doi: 10.1155/2019/7836820.PubMedUsed to support: Rat study: a methanol leaf extract of borage at 500 mg/kg by stomach tube lowered blood glucose 4 hours later in alloxan-diabetic rats; the extract was nontoxic in a brine shrimp test. Animal work only.
  4. Lozano-Baena MD, Tasset I, Muñoz-Serrano A, Alonso-Moraga Á, de Haro-Bailón A. Cancer Prevention and Health Benefices of Traditionally Consumed Borago officinalis Plants. Nutrients. 2016;8(1):48. doi: 10.3390/nu8010048.PubMedUsed to support: Fruit fly and cell culture study of freeze-dried borage leaves and stalks: not genotoxic and antigenotoxic in the fly SMART test, cytotoxic to HL-60 cells (IC50 0.49 and 0.28 mg/mL), with reduced fly survival at the highest concentrations. Lab work only; alkaloid content not measured.
  5. Schramm S, Köhler N, Rozhon W. Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants. Molecules. 2019;24(3):498. doi: 10.3390/molecules24030498.PubMedUsed to support: Review summarizing borage alkaloid chemistry: leaves contain amabiline and supinine plus lycopsamine and intermedine and their 7-acetyl forms, at about 2 to 10 mg/kg in vegetative tissue in an older analysis and mostly as N-oxides in fresh leaves; one analysis found only thesinine in flowers; seeds contain mainly thesinine and its glucoside, and refined seed oil had no detectable alkaloids. Also describes CYP activation of these alkaloids to toxic pyrroles.
  6. Peloso M, Minkoumba Sonfack G, Paduano S, De Martino M, De Santis B, Caprai E. Pyrrolizidine Alkaloids in Food on the Italian Market. Molecules. 2023;28(14):5346. doi: 10.3390/molecules28145346.PubMedUsed to support: Survey of 602 Italian food samples from 2019 to 2022: all 13 fresh borage leaf samples contained pyrrolizidine alkaloids, mean 530.8 micrograms per kg, with one sample at 3,410 above the 750 EU limit; lycopsamine N-oxide was the main alkaloid. One dried borage sample had 2,959 micrograms per kg, above the 1,000 limit.
  7. Sattler M, Müller V, Bunzel D, Kulling SE, Soukup ST. Pyrrolizidine alkaloids in borage (Borago officinalis): Comprehensive profiling and development of a validated LC-MS/MS method for quantification. Talanta. 2023;258:124425. doi: 10.1016/j.talanta.2023.124425.PubMedUsed to support: Analytical study profiling pyrrolizidine alkaloids and their N-oxides in borage leaves, which are eaten as a herb and tea. In the leaf samples, acetylated alkaloids that EU limits do not regulate were among the quantitatively most relevant.
  8. Drugs and Lactation Database (LactMed), National Institute of Child Health and Human Development. Borage. Drugs and Lactation Database (LactMed). 2006;Bethesda (MD): National Institute of Child Health and Human Development; 2006-. Revised 2021 Feb 15..PubMedUsed to support: NIH LactMed monograph: borage plant parts such as the leaf and flower contain pyrrolizidine alkaloids that are toxic to the liver and lungs and possibly carcinogenic and might pass into breast milk; no valid trials support use to increase milk supply; leaf products should be avoided, and only seed oil certified free of these alkaloids should be used.
  9. Ruan J, Yang M, Fu P, Ye Y, Lin G. Metabolic activation of pyrrolizidine alkaloids: insights into the structural and enzymatic basis. Chem Res Toxicol. 2014;27(6):1030-9. doi: 10.1021/tx500071q.PubMedUsed to support: Mouse, human liver microsome and recombinant enzyme study: alkaloids with an unsaturated necine base are activated by liver CYP enzymes into reactive metabolites that form pyrrole-protein adducts; a saturated-base alkaloid did not form adducts.
  10. Neuman MG, Cohen L, Opris M, Nanau RM, Hyunjin J. Hepatotoxicity of Pyrrolizidine Alkaloids. J Pharm Pharm Sci. 2015;18(4):825-43. doi: 10.18433/j3bg7j.PubMedUsed to support: Literature review: herbal remedies containing pyrrolizidine alkaloids can cause liver damage including hepatic sinusoidal obstruction syndrome (veno-occlusive disease); stopping the herb prevents further harm, and chronic use may contribute to cancer.
  11. Avila C, Breakspear I, Hawrelak J, Salmond S, Evans S. A systematic review and quality assessment of case reports of adverse events for borage (Borago officinalis), coltsfoot (Tussilago farfara) and comfrey (Symphytum officinale). Fitoterapia. 2020;142:104519. doi: 10.1016/j.fitote.2020.104519.PubMedUsed to support: Systematic review of case reports of possible alkaloid harm from comfrey, coltsfoot or borage: of 11 eligible reports none involved borage, and plant identification was often uncertain. Funded by the UK National Institute of Medical Herbalists.
  12. Iraci F, Herdeg C, Holzwarth M, Storz MA. Of mixed vegetables and cardiac arrhythmias - Digitalis purpurea confused with Borago officinalis: A case series of accidental digitoxin intoxications. J Cardiol Cases. 2023;28(2):86-90. doi: 10.1016/j.jccase.2023.04.007.PubMedUsed to support: Case series of two women poisoned by garden leaves thought to be borage but likely foxglove, with high digitoxin levels, vomiting and heart rhythm changes; both recovered. The authors note that confusing foxglove with borage leaves is not uncommon.
  13. Chen L, Zhang Q, Yi Z, Chen Y, Xiao W, Su D, Shi W. Risk Assessment of (Herbal) Teas Containing Pyrrolizidine Alkaloids (PAs) Based on Margin of Exposure Approach and Relative Potency (REP) Factors. Foods. 2022;11(19):2946. doi: 10.3390/foods11192946.PubMedUsed to support: Analysis of 68 alkaloids in 21 types of tea and herbal tea: for borage tea, the margin of exposure based on potency-corrected levels fell below 10,000 assuming one cup daily for a lifetime, which the authors read as a possible concern.
  14. Fabrés R, Rietjens IMCM, Widjaja-van den Ende F. Exploring time dependent trends and risks of pyrrolizidine alkaloids and their N-oxides in food. Food Chem Toxicol. 2026;208:115847. doi: 10.1016/j.fct.2025.115847.PubMedUsed to support: Analysis of 3,752 food samples from 2011 to 2023: alkaloid levels in herbal infusions and herbal supplements fell after 2017, but a high share of borage and other naturally alkaloid-containing foods still raised concern in the margin of exposure assessment.
  15. European Medicines Agency, Committee on Herbal Medicinal Products (HMPC). Public statement on the use of herbal medicinal products containing toxic, unsaturated pyrrolizidine alkaloids (PAs) including recommendations regarding contamination of herbal medicinal products with PAs. EMA/HMPC/893108/2011 Rev. 1. European Medicines Agency. 2021;EMA/HMPC/893108/2011 Rev. 1, final, adopted 7 July 2021..SourceUsed to support: Official EU agency statement, not PubMed-indexed. Sets an acceptable oral intake of 1.0 microgram a day of toxic unsaturated alkaloids for an adult (based on 50 kg body weight), scaled down for children (0.5 microgram for 20 kg), applying to the total from active ingredient plus contamination, and covering pregnant and breastfeeding women. Names Borago among plants long known to contain these alkaloids; describes liver sinusoid damage (veno-occlusive disease or sinusoidal obstruction syndrome), lung effects, placental transfer and harm to suckling young in animals, and notes that CYP enzyme induction and other liver-damaging agents can increase toxicity.
  16. European Commission. Commission Regulation (EU) 2023/915 of 25 April 2023 on maximum levels for certain contaminants in food and repealing Regulation (EC) No 1881/2006. Official Journal of the European Union. 2023;OJ L 119, 5.5.2023, p. 103. Annex I, section 2.4..SourceUsed to support: EU regulation, not PubMed-indexed. Sets maximum levels for the lower-bound sum of 21 listed pyrrolizidine alkaloids plus 14 co-eluting ones: 750 micrograms per kg for fresh or frozen borage leaves sold to consumers, 1,000 for dried borage (with lovage, marjoram and oregano), 200 for most dried herbal infusions and 400 for food supplements containing botanical preparations.