Benefits
LDL cholesterol and triglycerides in a 10-week dried leaf trial
In a double-blind trial in adults with metabolic syndrome (47 analyzed), 450 mg of dried summer savory leaf daily for 10 weeks lowered LDL cholesterol by 27.1 mg/dL and triglycerides by 39.1 mg/dL more than placebo. Total cholesterol and HDL changes did not differ from placebo. Diet and weight stayed stable, but the savory group started with higher LDL (138.6 vs 124.2 mg/dL).
Diastolic blood pressure in a 10-week dried leaf trial
In the same 10-week trial, diastolic blood pressure fell by 7.6 mmHg more on savory than on placebo, from an average of 83.1 to 75.3 mmHg in the savory group. Systolic pressure did not differ between groups. Blood pressure was one of several outcomes in one trial of 47 people, so a lasting effect has not been shown.
hs-CRP, a blood marker of inflammation, in a 10-week dried leaf trial
In the same 10-week trial, hs-CRP fell from 3.03 to 1.51 on savory and rose from 2.31 to 3.32 on placebo, a between-group difference of 2.5 (the paper labels the units ng/mL, while hs-CRP is normally reported in mg/L). Part of the gap came from the rise on placebo, and the savory group started higher. This was one outcome in a single trial of 47 people.
Upper digestive symptom scores in a 4-week capsule trial
In a placebo-controlled trial in adults with mild to moderate GERD who all received written lifestyle advice, 500 mg of powdered savory three times daily for 4 weeks lowered symptom scores, but placebo lowered them by the same amount (39 analyzed). No score differed between groups. The paper calls the trial double-blind but also open-label, so blinding is unclear.
Gut muscle relaxation and pain responses in lab and animal studies
In isolated rat intestine, summer savory essential oil relaxed contractions in a concentration-dependent way, and in mice it reduced castor oil induced diarrhea. In mice and rats, oral doses of the oil and extracts reduced pain behavior in the formalin test and paw swelling. Doses were high by body weight and no human trial has tested these effects.
Antimicrobial activity of the essential oil in lab tests
In dish tests, summer savory essential oil inhibited all 23 bacteria and 15 fungi and yeasts tested, an effect usually credited to its carvacrol and thymol, while in a separate screen a methanol extract of the herb was inactive against 83% of the microbes tested. No trial has tested swallowed savory against an infection.
Mechanism of action
Carvacrol and thymol, the main phenols of the oil
Like oregano oil and thyme, savory oil carries the phenols carvacrol and thymol plus their precursors gamma-terpinene and p-cymene. The balance shifts with origin and growth stage: one oil was 69.4% carvacrol with no thymol listed, another 29.0% thymol and 26.5% carvacrol, and gamma-terpinene led the oil at most growth stages in a third analysis.
Lipid effects proposed by the trial authors
The authors of the 10-week trial suggest that savory flavonoids and carvacrol may act on cholesterol production, including the enzyme HMG-CoA reductase, and on fat-handling receptors called PPARs. The trial measured blood lipids only, so these routes are proposals drawn from other research, not results of the trial.
Relaxation of intestinal smooth muscle
Applied to isolated rat intestine, the essential oil damped contractions triggered by potassium chloride and blunted the maximum response to acetylcholine, which fits the herb's traditional use for stomach and intestinal complaints. Tissue in a bath receives oil directly, so how much of this happens after a person swallows dried leaf is unknown.
Platelet adhesion in a lab study
A methanol extract of summer savory leaf, at 200 micrograms per mL, reduced the adhesion of activated human platelets to coated plates by 48% and also altered their aggregation and protein secretion. This was platelets in a dish; no one took the herb, but it is the basis for a theoretical bleeding caution.
Clinical trials
Randomized (each participant drew a slip numbered 1 or 2, and a third party decided which number got placebo), double-blind, placebo-controlled trial (IRCT2014012616372N1) in adults with metabolic syndrome: one capsule of 450 mg dried summer savory leaf powder or a starch placebo daily before breakfast for 10 weeks. Funded by a Shiraz University of Medical Sciences research grant as part of a master's thesis; the journal is not PubMed-indexed (Nikaein et al. 2017, Iran Red Crescent Med J)
60 adults with metabolic syndrome from a heart institute screening program in Shiraz, Iran; 47 analyzed (24 savory, 23 placebo). People taking lipid-lowering or glucose-lowering drugs, aspirin or other NSAIDs were excluded.
Against placebo, LDL cholesterol fell 27.1 mg/dL more (P < 0.001), triglycerides 39.1 mg/dL more (P = 0.005), diastolic pressure 7.6 mmHg more (P = 0.001) and hs-CRP 2.5 more (P = 0.008; units printed as ng/mL), partly because hs-CRP rose on placebo. Fasting glucose, systolic pressure, total cholesterol and HDL did not differ between groups. One savory-group participant withdrew with a skin rash; two people (group not stated) reported stomach irritation.
Randomized, double-blind, placebo-controlled pilot trial (IRCT2015072215860N2) in adults with mild to moderate GERD: 500 mg capsules of powdered dried summer savory or cornstarch placebo three times daily before meals for 4 weeks, with written lifestyle advice for both groups. Funding is not stated; the methods say only statisticians were blind to allocation and the text also calls the design open-label, and the journal is not PubMed-indexed (Faghihi Kashani et al. 2018, Iran Red Crescent Med J)
58 adults aged 18 to 65 at a referral hospital in Tehran, Iran; 39 analyzed (the flow diagram gives 18 on savory and 21 on placebo, but Table 1 gives 21 and 18).
Null result. The total symptom score (FSSG) fell from 18.83 to 10.11 on savory and from 18.23 to 10.14 on placebo, with no difference between groups after treatment (P = 0.989). Reflux-type, fullness-type, gas, belching and visual analogue scores also did not differ. The authors attribute the improvement in both groups to the lifestyle advice. Adverse events were not reported.
Laboratory study of summer savory essential oil on isolated rat ileum contracted with potassium chloride or acetylcholine, compared with reference antispasmodics, plus a castor oil diarrhea test in mice at 0.1 mL of oil per 100 g of body weight (Hajhashemi et al. 2000, J Ethnopharmacol)
Isolated rat intestinal tissue and mice; no human participants.
The oil relaxed potassium chloride induced contractions in a concentration-dependent way and lowered the maximum response to acetylcholine, and it inhibited castor oil induced diarrhea in mice. The mouse dose equals about 1 mL of oil per kg of body weight. These results have not been tested in people.
Animal study of a hydroalcoholic extract, a polyphenol fraction and the essential oil of summer savory aerial parts given by mouth, using tail flick, formalin and acetic acid writhing tests in mice and carrageenan paw swelling in rats (Hajhashemi et al. 2002, J Ethnopharmacol)
Mice and rats; no human participants.
None of the preparations changed the tail flick test. The extract (500 to 2000 mg/kg), polyphenol fraction (250 to 1000 mg/kg) and oil (50 to 200 mg/kg) reduced pain behavior in the formalin test, and the polyphenol fraction (1000 mg/kg) and oil (200 mg/kg) reduced paw swelling. Naloxone and caffeine did not reverse the effect. Doses were high by body weight.