Capers: a salty condiment with a small, early liver signal

The best evidence on capers is a meta-analysis its own authors call preliminary. Five small trials in 178 adults with fatty liver, type 2 diabetes, metabolic syndrome or high blood lipids, lasting 2 to 12 weeks, found caper fruit lowered the liver enzyme ALT by 12.29 U/L (95% CI -24.47 to -0.11). The interval nearly touches zero, the change in AST was not significant, and the trials mixed extracts with pickles. The one food trial behind it enrolled 44 people with fatty liver in Iran. Eating 1.4 to 1.8 oz (40 to 50 g) of pickled caper berries with meals daily for 12 weeks lowered ALT and AST more than in controls (p < 0.001 and p = 0.02), and the salt in those pickles was not reported. These were caper berries, the fruit, while the USDA record is for canned capers. That record lists 2,348 mg of sodium per 3.5 oz (100 g), 102 percent of the daily label value, from a single entry. Brands differ in brine and salt, and a real serving is about a tablespoon.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Canned capers carry 2,348 mg of sodium per 3.5 oz (100 g) in USDA data, more than a full day's label value, alongside 42 percent of the copper value. — USDA FoodData Central SR Legacy record for canned capers Evidence E source
  Sodium 2348 mg per 3.5 oz (100 g) (102% DV), copper 0.374 mg (42% DV), vitamin K 24.6 ug (20% DV)

What your body absorbs

• In simulated digestion, about 78 percent of phenolics from raw capers and 73 percent from pickled capers were released, and pickling did not lower phenolic content. — raw and pickled capers digested in vitro Evidence D source
  Bioaccessibility of total phenolics 77.8% raw vs 72.9% pickled; rutin fell during digestion, kaempferol-3-O-rutinoside stable

What cooking and storage change

• Lab analysis found that dry-salting and brining raised free quercetin, kaempferol and isorhamnetin in caper buds and berries, and dry-salting kept total phenolics better than brine. — fresh caper (Capparis spinosa) buds and berries, fermented by dry-salting or brining Evidence D source
  Fresh buds 1843.71 mg/100 g DW phenolics vs fermented buds 1198.54-1539.49; flavonol aglycones up after fermentation; dry-salted better preserved than brined

What it does to your health

• A preliminary meta-analysis of 5 RCTs in 178 adults found caper fruit lowered the liver enzyme ALT by 12.29 U/L, while the change in AST was not significant. — five RCTs, 178 adults with NAFLD, type 2 diabetes, metabolic syndrome or hyperlipidemia, 2 to 12 weeks (n = 178) Evidence A source
  ALT -12.29 U/L (-24.47 to -0.11); HDL +0.72 mg/dL (0.10 to 1.34); weight -2.2 lb (-3.2 to -1.2; metric: -1.00 kg, -1.44 to -0.56); triglycerides, LDL, total cholesterol and fasting glucose not significant
• In a 12 week RCT in 44 people with fatty liver disease, eating 1.4 to 1.8 oz (40 to 50 g) of caper fruit pickles with meals daily lowered ALT and AST more than control. — 44 NAFLD patients in Iran, 22 eating 1.4-1.8 oz (40-50 g) caper fruit pickles with meals daily and 22 controls, 12 weeks (n = 44) Evidence B source
  Greater ALT and AST reduction vs control (p<0.001 and p=0.02), sizes not in abstract; TG, TC and LDL fell only in the control group

Safety, limits and interactions

• In a 2 month RCT in 54 people with type 2 diabetes, 400 mg of caper fruit extract three times a day lowered fasting glucose and HbA1c versus placebo, with no liver or kidney side effects. — 54 type 2 diabetic patients in Iran on standard therapy, 28 on 400 mg caper fruit extract and 26 on placebo three times a day for two months (n = 54) Evidence B source
  Fasting glucose lower (p=0.037) and HbA1c lower (p=0.043) vs control; sizes not in abstract; no liver, kidney or other side effects

Who this works differently for

• In a 10 week RCT in 69 healthy adults aged 50 to 80, the gut microbiome gains came from the group eating the most strawberries without capers in olive oil. — 69 healthy elderly German adults with stool samples, five groups eating varying amounts of strawberries, freeze-dried strawberries and capers in olive oil for 10 weeks (n = 69) Evidence B source
  Beta diversity up (P = 0.0035) and potentially pathogenic bacteria down (P = 0.04) in group 4, which had no capers

What is still unknown

• The only allergy trial involving caper used Pantescal, a four-plant extract, in 60 allergic patients, so it says nothing about capers as food. — 60 patients allergic to common aeroallergens, Pantescal (Capparis spinosa, Olea europaea, Panax ginseng, Ribes nigrum) or placebo (n = 60) Evidence B source
  CD63 expression inhibited 64.8% and sulphidoleukotriene production 43.3% after 10 days, measured in vitro on blood samples

The bottom line

In 54 people with type 2 diabetes in Iran, 400 mg capsules of caper fruit extract three times a day for 2 months lowered fasting glucose (p = 0.037) and HbA1c (p = 0.043) against placebo. That was an extract in capsules, the abstract gives no sizes, and it tells you little about the jar. Pickling seems to keep the plant compounds. In lab analysis, dry-salting and brining raised free quercetin, kaempferol and isorhamnetin in buds and berries, and dry-salted capers held their total phenolics better than brined ones. In simulated digestion, 77.8 percent of phenolics from raw capers and 72.9 percent from pickled ones were released. Both are lab results with no outcome in people. Two trials that mention capers say nothing about eating them. In a 10 week trial in 69 healthy older Germans, capers in olive oil were an add-on to strawberries, and the gut changes came from the group that ate no capers. The only allergy trial used Pantescal, a mix of caper, olive, ginseng and blackcurrant extracts, measured on blood samples in the lab. Who should take care. The only safety data come from the extract trial, which saw no liver, kidney or other side effects over 2 months. We found no readable study on caper allergy, pregnancy or drug interactions. The concern the data do support is salt, so if you have been told to limit sodium, count capers as a salt source.

Sources

1. capr-r5-01 · USDA FoodData Central, dataset
   Capers, canned (FDC 172238, SR Legacy, Spices and Herbs): sodium 2348 mg per 100 g = 102% DV; copper 0.374 mg = 42% DV; vitamin K 24.6 ug = 20% DV; Foundation samples 0, CoFID match none
   USDA FoodData Central, SR Legacy, FDC 172238 · checked 2026-09-28
2. capr-r5-06 · in vitro study
   TPC, TFC, and antioxidant activity of capers were not affected by pickling. The bioaccessibility of TPC in RC and PC was 77.8% and 72.9%, respectively.
   J Food Sci Technol, 2024 · checked 2026-09-28
3. capr-r5-05 · food composition analysis
   The amounts of isorhamnetin, quercetin, and kaempferol increased in fermented buds and berries compared to fresh samples. ... When total phenolics and antioxidant properties were evaluated, it was observed that they were better preserved in the dry-salted samples than the brined samples.
   Food Chem, 2021 · checked 2026-09-28
4. capr-r5-02 · meta-analysis of RCTs
   Five randomized controlled trials, which involved a total of 178 adults, were included. According to the results, caper fruit seems to decrease liver enzymes ALT -12.29 U/L [-24.47, -0.11], AST -2.20 U/L [-4.70, 0.31].
   Biomed Pharmacother, 2023 · checked 2026-09-28
5. capr-r5-03 · RCT
   Adjusted to the baseline measures, serum ALT and AST reduction were significantly higher in the caper than control group from baseline up to the end of the study (p<0.001 and p=0.02, respectively).
   Adv Pharm Bull, 2017 · checked 2026-09-28
6. capr-r5-04 · RCT
   Results showed significant decrease in fasting blood glucose levels (p=0.037) and glycosylated hemoglobin (p=0.043) in caper treated patients compared to control group at the end of the study. ... No liver, kidney and other side effects were observed in these two groups.
   Complement Ther Med, 2013 · checked 2026-09-28
7. capr-r5-07 · RCT
   The intervention group featuring the highest amounts of fresh and freeze-dried strawberries without capers in olive oil (group 4) showed changes in gut microbial diversity and differential abundance that could be linked to improved health.
   Microbiol Spectr, 2025 · checked 2026-09-28
8. capr-r5-08 · RCT
   Pantescal is a mixture of plant extracts, such as Capparis spinosa, Olea europaea, Panax Ginseng and Ribes nigrum.
   Int Immunopharmacol, 2008 · checked 2026-09-28