Sumac is the tangy, deep-red spice made from the dried berries of Rhus coriaria. It has been used across the Middle East and Mediterranean for thousands of years, both in cooking and in traditional medicine. Today it is also one of the more-studied spices in nutrition research. Here is a plain-English summary of what that research does and doesn't show, along with the safety points worth knowing.
This article is general information, not medical advice. If you have a health condition or take medication, speak to your GP or pharmacist before changing your diet.
What's in sumac?
Sumac's sour, lemony taste comes mainly from organic acids, especially malic acid. Scientists have also identified more than 200 plant compounds in the berries, including:
- Polyphenols such as gallic acid, which researchers study for antioxidant activity
- Flavonoids, including quercetin, myricetin and kaempferol
- Tannins, which give sumac its slight dryness (sumac leaves were once used to tan leather)
- Anthocyanins, the pigments behind its deep red colour
Analyses of the fruit have also found several B vitamins and vitamin C, though in the small amounts people use as a spice it isn't a major source of either.
What have studies looked at?
Antioxidant activity
Most sumac research is laboratory work on extracts, which consistently show strong antioxidant activity. Lab results like these are a useful starting point, but they don't tell us what happens when people eat sumac as part of a normal diet.
Blood sugar and blood fats
This is where most of the human research sits, and it explains why so many people search for “sumac and diabetes”. Small clinical trials, mostly carried out in Iran, have given adults sumac powder or capsules, typically 1 to 6 grams a day for 4 to 12 weeks, and measured blood sugar and blood fats.
One often-cited 2014 trial gave 41 adults with type 2 diabetes either 3 g of sumac powder a day or a placebo for three months. It reported improvements in blood sugar measures in the sumac group. Several meta-analyses, which pool results from many trials, have since reported modest improvements in some blood sugar and cholesterol measures.
There are important caveats:
- The trials are small and short, and many come from a small number of research groups.
- Reviewers rate the certainty of the evidence anywhere from very low to high depending on the measure, and results differ between studies.
- The trials used concentrated doses of powder or capsules, not sumac used in cooking or drinks.
- None of this means sumac treats or prevents diabetes or any other condition. It is a food, not a medicine.
The honest summary: the early results are interesting, and researchers say larger, well-designed trials are needed.
Inflammation and weight
Results here are mixed. Some trials report changes, while others, and some of the pooled analyses, find no clear effect on inflammation markers or body weight.
Sumac side effects: who should be careful?
Culinary sumac has a long history of everyday use and is generally considered safe in normal food amounts. A few groups should take care.
People with cashew, pistachio or mango allergies
Sumac belongs to the same plant family as cashews, pistachios, mangoes and pink peppercorns (Anacardiaceae). Lab studies have found cross-sensitisation between these foods, and there are rare reported cases of serious allergic reactions, including anaphylaxis, to sumac in people with cashew or pistachio allergy. If you have a cashew or pistachio allergy, talk to your doctor or allergist before eating sumac.
People taking diabetes medication
Studies have looked at sumac's effect on blood sugar. If you take medication to manage blood sugar, check with your doctor before taking sumac in concentrated forms such as supplements or extracts.
Pregnancy and breastfeeding
There isn't good research on concentrated sumac in pregnancy or breastfeeding. Normal cooking amounts are a long-standing part of many diets, but avoid supplements unless your midwife or doctor says otherwise.
Is sumac the same as poison sumac?
No. “Poison sumac” (Toxicodendron vernix) is a different plant, a relative of poison ivy, which grows in North American wetlands and has white or grey berries. Culinary sumac comes from red-berried Rhus species, mainly Rhus coriaria. Shop-bought sumac spice is the edible kind. Never forage wild sumac unless you are certain what it is.
Does sumac contain caffeine?
No. Sumac isn't a source of caffeine, so a sumac drink or sumac tea is naturally caffeine-free unless other ingredients add it.
How much sumac do people use?
In cooking, a pinch to a teaspoon or so, sprinkled over salads, grilled meat, eggs, hummus or rice. For reference, many of the clinical trials used around 3 g a day, roughly a heaped teaspoon of powder. There's no official recommended daily amount, and if you're thinking about supplements it's best to speak to a health professional first.
Enjoying sumac
For us, sumac is first and foremost about flavour: bright, sour and fruity, a bit like lemon with more depth. That's why we built Sumacqua around it, a sparkling soft drink made with sumac, ginger, juniper and bay. It's alcohol-free, has 49 calories per 250 ml can and contains no artificial sweeteners.
Sumacqua is a soft drink, not a supplement, and we don't make health claims for it. We just think sumac deserves a bigger place in your glass as well as on your plate.
Got a question? See our FAQs.
Sources
- Alsamri H. et al. (2021). Pharmacological and antioxidant activities of Rhus coriaria L. (sumac). Antioxidants 10(1):73. doi:10.3390/antiox10010073
- Shidfar F. et al. (2014). The effect of sumac powder on serum glycemic status, apoB, apoA-I and total antioxidant capacity in type 2 diabetic patients. Iranian Journal of Pharmaceutical Research 13(4):1249–1255.
- Jafarpour A. et al. (2024). The effect of sumac on cardiometabolic parameters in adults: a systematic review and meta-analysis of randomized controlled trials. Frontiers in Nutrition 11:1305024.
- Jafari A. et al. (2025). Sumac (Rhus coriaria L.) and human metabolic health: a systematic review and meta-analysis. Endocrinology, Diabetes & Metabolism.
- Bastiaan-Net S. et al. (2019). IgE cross-reactivity of cashew nut allergens. International Archives of Allergy and Immunology 178(1):19–32.