Cashew

Indigenous peoples of the Amazon have used and cultivated A. occidentale medicinally for centuries, and the tradition uses each part of the tree differently ^{42Reference 42Taylor · 2005The Healing Power of Rainforest Herbs: A Guide to Understanding and Using Herbal Medicinals}.

The bark is the astringent. It is given for diarrhoea and for infant colic, used as a douche and as a mouth rinse after tooth extraction, and taken for diabetes, weakness and muscular debility, urinary disorders and asthma ^{42Reference 42Taylor · 2005The Healing Power of Rainforest Herbs: A Guide to Understanding and Using Herbal Medicinals}.

The leaf is taken as a tea called casho for diarrhoea, mouth ulcers, tonsillitis and sore throat, and used externally to wash wounds. Leaf and bark are used interchangeably for eczema, psoriasis, scrofula, dyspepsia, genital complaints and sexually transmitted infections, impotence, bronchitis and colic, and as a general tonic ^{42Reference 42Taylor · 2005The Healing Power of Rainforest Herbs: A Guide to Understanding and Using Herbal Medicinals}.

The cashew apple and its juice are used for influenza, diarrhoea and syphilis, and as a stimulant, diuretic and aphrodisiac. By the 1600s Europeans in Brazil were drinking the juice for fever, to sweeten the breath and, in the phrase of the time, to conserve the stomach ^{42Reference 42Taylor · 2005The Healing Power of Rainforest Herbs: A Guide to Understanding and Using Herbal Medicinals}.

The seed oil, the caustic liquid in the shell rather than the edible kernel, is applied to the skin against botfly larvae ^{42Reference 42Taylor · 2005The Healing Power of Rainforest Herbs: A Guide to Understanding and Using Herbal Medicinals}.

Contemporary Brazilian practice uses the leaf and bark for eczema, psoriasis, scrofula, dyspepsia, genital and venereal complaints, impotence, bronchitis, cough, intestinal colic, leishmaniasis and the skin disorders of syphilis.

In northeastern Brazil, where the tree is common, leaf extracts are a traditional treatment for a range of complaints ^{13Reference 13Souza et al. · 2017In vitroAntioxidant and anti-inflammatory properties of Anacardium occidentale leaf extract — in vitroView study →}.

In Côte d’Ivoire the tree is commonly used to treat high blood pressure ^{3Reference 3Tchikaya et al. · 2011AnimalAnacardium occidentale stem-bark extract induces hypotensive and cardio-inhibitory effects in experimental animal models — animal studyView study →}. In traditional African medicine the stem bark is used for arthritis, fever, aches and pains ^{4Reference 4Olajide et al. · 2013In vitroMechanisms of the anti-inflammatory property of Anacardium occidentale stem bark: inhibition of NF-κB and MAPK signalling in microglia — in vitroView study →}, and the leaf for inflammation and asthma ^{6Reference 6Awakan et al. · 2018AnimalAnti-inflammatory and bronchodilatory constituents of leaf extracts of Anacardium occidentale — animal modelsView study →}. In southwestern Nigeria the leaf is an ingredient in many herbal recipes ^{24Reference 24Taiwo et al. · 2020In vitroPentagalloylglucose, isolated from the leaf extract of Anacardium occidentale, elicits rapid and selective cytotoxicity in cancer cells — in vitroView study →}.

The human evidence here comes from the nut. A 2020 meta-analysis of RCTs (392 participants) found cashew-nut consumption lowered systolic blood pressure by −3.39 mmHg (95% CI −6.13 to −0.65), with no effect on diastolic pressure or lipids ^{1Reference 1Jalali et al. · 2020Meta-analysisThe effects of cashew nut intake on lipid profile and blood pressure — systematic review and meta-analysis of randomised controlled trialsView study →}.

A 12-week RCT in 300 Asian Indians with type 2 diabetes (30 g nuts/day) found a greater systolic fall and an HDL rise versus a diabetic-diet control, with no change in body weight ^{2Reference 2Mohan et al. · 2018RCTCashew nut consumption increases HDL cholesterol and reduces systolic blood pressure in Asian Indians with type 2 diabetes — a 12-week randomised controlled trialView study →}.

The traditional hypotensive use of the bark has separate, animal-only support: an aqueous stem-bark extract given intravenously lowered blood pressure in rabbits and depressed the contractions of isolated rat hearts, and atropine did not block either effect ^{3Reference 3Tchikaya et al. · 2011AnimalAnacardium occidentale stem-bark extract induces hypotensive and cardio-inhibitory effects in experimental animal models — animal studyView study →}. Anacardic acid also attenuated pressure-overload cardiac hypertrophy in mice by inhibiting histone acetyltransferases ^{35Reference 35Li et al. · 2019Anacardic acid attenuates pressure-overload cardiac hypertrophy through inhibiting histone acetylases — animal studyView study →}.

Gap: the human effect is small and belongs to the nut as a food; the medicinal bark preparation has only animal data, and no trial has tested a bark or leaf decoction for blood pressure in people.

A stem-bark extract suppressed nitric oxide, PGE2, TNF-α and IL-6 in LPS-stimulated microglia, downregulating COX-2, iNOS and mPGES-1 through NF-κB and MAPK inhibition ^{4Reference 4Olajide et al. · 2013In vitroMechanisms of the anti-inflammatory property of Anacardium occidentale stem bark: inhibition of NF-κB and MAPK signalling in microglia — in vitroView study →}.

A 1985 study showed bark tannins, mostly given by injection, reduced carrageenan- and dextran-induced paw oedema, granuloma and adjuvant arthritis in rats ^{5Reference 5Mota et al. · 1985AnimalAnti-inflammatory actions of tannins isolated from the bark of Anacardium occidentale — animal study (rat)View study →}. An ethanolic leaf extract was anti-inflammatory and bronchodilatory in histamine-challenged animals, and oleamide was identified as one of its active constituents ^{6Reference 6Awakan et al. · 2018AnimalAnti-inflammatory and bronchodilatory constituents of leaf extracts of Anacardium occidentale — animal modelsView study →}.

Anacardic acid inhibits NF-κB ^{7Reference 7Sung et al. · 2008In vitroAnacardic acid, an inhibitor of histone acetyltransferase, suppresses NF-κB–regulated gene products and potentiates apoptosis — in vitroView study →}.

A leaf extract also reduced inflammatory infiltration in the livers of IL-10 knockout mice given paracetamol ^{14Reference 14Baptista et al. · 2020AnimalAntioxidant and anti-inflammatory effects of Anacardium occidentale and A. microcarpum extracts on the liver of IL-10 knockout mice — animal studyView study →}.

All of it is animal and in-vitro, with doses and extract types varying widely and no human anti-inflammatory trial.

Antimicrobial activity has been found across parts and pathogens. An ethanol leaf extract was active in vitro against Enterococcus faecalis, Staphylococcus aureus, Streptococcus mutans, Escherichia coli and Candida albicans, and suppressed their biofilms ^{8Reference 8Anand et al. · 2015In vitroIn vitro antimicrobial and cytotoxic effects of Anacardium occidentale and Mangifera indica in oral care — in vitroView study →}.

Leaf and bark extracts inhibited every bacterial species tested, but were toxic to zebrafish embryos ^{9Reference 9Amorim et al. · 2022In vitroIn vitro antibacterial and anti-inflammatory effects of Anacardium occidentale extracts and their toxicity on PBMCs and zebrafish embryos — in vitroView study →}.

A leaf extract slowed the growth of C. albicans and C. auris by triggering oxidative stress in the yeast cells ^{10Reference 10Quejada et al. · 2024In vitroUnmasking the antifungal activity of Anacardium occidentale leaf extract against Candida albicans — in vitroView study →}.

A hydroalcoholic leaf extract inhibited Plasmodium falciparum transketolase and stopped the growth of cultured malaria parasites ^{11Reference 11Kaushik et al. · 2023In vitroAntimalarial activity of Anacardium occidentale leaf extracts against Plasmodium falciparum transketolase — in vitroView study →}.

The single human test of a medicinal preparation sits here: in a crossover trial of 30 adults, a 10% A. occidentale mouthwash reduced dental plaque and gum bleeding over a month, to the same degree as 0.12% chlorhexidine ^{12Reference 12Gomes et al. · 2016RCTClinical effect of a mouthwash containing Anacardium occidentale on plaque and gingivitis control — randomised controlled trialView study →}.

Almost all of it is in-vitro minimum-inhibitory-concentration work. The clinical evidence stops at that one oral-health trial, and systemic antimicrobial use is unproven.

Antioxidant activity tracks the plant’s phenolic content. Leaf extracts reduced oxidative damage in macrophages ^{13Reference 13Souza et al. · 2017In vitroAntioxidant and anti-inflammatory properties of Anacardium occidentale leaf extract — in vitroView study →} and lowered hepatic oxidative markers in knockout mice ^{14Reference 14Baptista et al. · 2020AnimalAntioxidant and anti-inflammatory effects of Anacardium occidentale and A. microcarpum extracts on the liver of IL-10 knockout mice — animal studyView study →}.

The one human signal is indirect: in a 12-week RCT, adolescents with obesity eating 30 g roasted cashews daily alongside nutrition education showed reduced waist circumference and lower TBARS versus education alone ^{15Reference 15de Oliveira et al. · 2025RCTCashew nut consumption reduces waist circumference and oxidative stress in adolescents with obesity — randomised clinical trialView study →}.

The cashew apple carries glycosides of quercetin and myricetin ^{37Reference 37de Brito et al. · 2007Determination of the flavonoid components of cashew apple (Anacardium occidentale) by LC-DAD-ESI/MSView study →}, and the leaf carries gallic acid and catechin ^{14Reference 14Baptista et al. · 2020AnimalAntioxidant and anti-inflammatory effects of Anacardium occidentale and A. microcarpum extracts on the liver of IL-10 knockout mice — animal studyView study →}.

The human trial measured oxidative-stress markers rather than clinical outcomes, and it used the nut.

A crossover controlled-feeding RCT in 51 adults found that 28–64 g of cashews a day, added to a typical American diet for four weeks, reduced total and LDL cholesterol versus a potato-chip control ^{18Reference 18Mah et al. · 2017RCTCashew consumption reduces total and LDL cholesterol — a randomised, crossover, controlled-feeding trialView study →}. A second, tightly controlled crossover in 42 adults at the FDA health-claim dose (42 g/day) found no lipid effect, though it lowered PCSK9 ^{19Reference 19Baer et al. · 2019RCTConsumption of cashew nuts does not influence blood lipids or other markers of cardiovascular disease — randomised controlled trialView study →}.

The meta-analyses split. A cashew-specific meta found no effect on total or LDL cholesterol or triglycerides ^{1Reference 1Jalali et al. · 2020Meta-analysisThe effects of cashew nut intake on lipid profile and blood pressure — systematic review and meta-analysis of randomised controlled trialsView study →}; a broader nut meta found cashew raised HDL (SMD 0.24, 95% CI 0.04–0.43) ^{16Reference 16Gunathilake et al. · 2022Meta-analysisEffects of nut consumption on blood lipid profile — meta-analysis of randomised controlled trialsView study →}; and a network meta-analysis ranked pistachio, walnut and almond diets highest for lowering LDL and total cholesterol ^{17Reference 17Liu et al. · 2020Meta-analysisComparative effects of different types of tree-nut consumption on blood lipids — network meta-analysis of randomised trialsView study →}.

Gap: the results contradict each other. A small HDL rise is probable, LDL and total-cholesterol effects are inconsistent across trials, and cashew does not rank among the strongest nuts for lowering cholesterol.

Diabetes is cashew’s headline traditional use. Bark and leaf extracts repeatedly lower blood glucose in streptozotocin-diabetic rats ^{20,21Reference 20Bamisaye et al. · 2022AnimalHypoglycemic, hypolipidemic and antioxidant potentials of ethanolic stem-bark extract of Anacardium occidentale in streptozotocin-induced diabetic rats — animal studyView study →Reference 21Ukwenya et al. · 2023AnimalAnacardium occidentale leaf extract and riboceine mitigate hyperglycemia through antioxidative effects and gene modulation — animal study (rat)View study →}, and two hypoglycaemic principles, stigmast-4-en-3-one and its alcohol, were isolated from a hexane bark extract that lowered blood glucose when injected into dogs ^{22Reference 22Alexander-Lindo et al. · 2004Hypoglycaemic effect of stigmast-4-en-3-one and its corresponding alcohol from the bark of Anacardium occidentale — animal studyView study →}.

In humans the nut shows no such effect. A meta-analysis of six RCTs (521 participants) found no effect of cashew-nut consumption on fasting glucose, insulin or HOMA-IR ^{23Reference 23Jamshidi et al. · 2021Meta-analysisEffects of cashew-nut consumption on body composition and glycemic indices — meta-analysis of randomised controlled trialsView study →}, and the type 2 diabetes nut RCT saw no change in any glycaemic variable ^{2Reference 2Mohan et al. · 2018RCTCashew nut consumption increases HDL cholesterol and reduces systolic blood pressure in Asian Indians with type 2 diabetes — a 12-week randomised controlled trialView study →}.

Gap: the two bodies of evidence test different parts of the plant. The positive animal data use bark and leaf extracts, the medicinal parts, while the null human data use the nut, a food. Neither refutes the other, and the traditional bark and leaf use remains untested in people.

Research centres on CNSL alkylphenols and a histone-modifying mechanism. Anacardic acid inhibits the histone acetyltransferase p300 and suppresses NF-κB-regulated gene products, potentiating apoptosis in tumour cells ^{7Reference 7Sung et al. · 2008In vitroAnacardic acid, an inhibitor of histone acetyltransferase, suppresses NF-κB–regulated gene products and potentiates apoptosis — in vitroView study →}.

Pentagalloylglucose from the leaf was selectively cytotoxic to cervical and lung cancer cell lines within hours ^{24Reference 24Taiwo et al. · 2020In vitroPentagalloylglucose, isolated from the leaf extract of Anacardium occidentale, elicits rapid and selective cytotoxicity in cancer cells — in vitroView study →}.

Cashew gum reduced melanoma tumour mass in mice by about 37–43% without killing tumour cells in vitro ^{25Reference 25Barros et al. · 2020AnimalEvaluation of the antitumor potential of cashew gum from Anacardium occidentale — animal study (mouse melanoma)View study →}.

In onion-root and brine-shrimp bioassays, natural CNSL (mostly anacardic acid) was toxic and mutagenic, while heat-processed CNSL (mostly cardanol) was not, and low concentrations of both protected against copper-induced chromosome damage ^{26Reference 26Leite et al. · 2015In vitroEvaluation of toxic, cytotoxic, mutagenic and antimutagenic activities of natural and technical cashew nut shell liquids — in vitro bioassaysView study →}.

The work is in-vitro with a little in-vivo, largely at the isolated-compound level, and nothing shows that eating cashew delivers active anacardic acid to a tumour.

Cashew apple juice given by mouth to mice reduced ear oedema and sped wound contraction; juice from unripe fruit was the more active ^{28Reference 28da Silveira Vasconcelos et al. · 2015AnimalAnti-inflammatory and wound-healing potential of cashew apple juice (Anacardium occidentale) — animal study (mouse)View study →}.

A hydroalcoholic bark extract applied to skin wounds in rats slowed healing compared with saline ^{29Reference 29Silva et al. · 2023AnimalAnacardium occidentale (cajueiro) in the healing of skin wounds — an experimental study in ratsView study →}.

Anacardic acids, cardols and 2-methylcardols from the cashew fruit inhibit tyrosinase, the melanin-synthesis enzyme ^{30Reference 30Kubo et al. · 1994In vitroTyrosinase inhibitors from Anacardium occidentale fruits — in vitroView study →}.

All of it is animal or in-vitro. The CNSL phenols behind the tyrosinase effect are the same caustic agents that cause the shell’s severe contact dermatitis.

Most of this work is on anacardic acid. It induced IL-33 and promoted remyelination in two mouse models of demyelination ^{31Reference 31Ljunggren-Rose et al. · 2020In vitroAnacardic acid induces IL-33 and promotes remyelination in CNS — animal/in vitroView study →}, and improved neurological deficits after traumatic brain injury by limiting ferroptosis and inflammation ^{32Reference 32Liu et al. · 2023Anacardic acid improves neurological deficits in traumatic brain injury by anti-ferroptosis and anti-inflammation — animal studyView study →}. A leaf extract reduced neuroinflammation biomarkers and memory deficits in L-NAME-treated rats ^{33Reference 33Oyagbemi et al. · 2023AnimalLeaf extract of Anacardium occidentale ameliorates neuroinflammation, memory loss and neurobehavioral deficit in L-NAME-treated rats — animal studyView study →}.

Early-stage work on an isolated compound in injury models, with no clinical translation and no demonstration that the whole herb does any of it.

A single, specific in-vitro finding. Anacardic acid inhibited HCV entry, replication, translation and virion secretion dose-dependently without measurable cytotoxicity, apparently through histone-acetyltransferase inhibition ^{27Reference 27Hundt et al. · 2015In vitroThe inhibitory effects of anacardic acid on the hepatitis C virus life cycle — in vitroView study →}. The effects needed low-micromolar concentrations held for 12 to 72 hours in cell culture.

Gap: the oral bioavailability of anacardic acid from cashew is unmeasured. One study, no animal or human data.

Shell oil. The shell of the nut contains an acrid, blistering juice. Its irritant is cardol, which acts on the skin in the same way as poison ivy. Heat destroys it, and roasting the nut in its shell makes the kernel safe ^{44Reference 44Fern · 2026Anacardium occidentaleView study →}.

Allergy. Cashew allergy appears to be becoming more common, and a minimal amount of cashew can cause a severe allergic reaction, including anaphylaxis ^{38Reference 38van der Valk et al. · 2014Systematic reviewSystematic review on cashew nut allergy — systematic reviewView study →}. In one Israeli clinic, 35 of 50 cashew-allergic patients were also allergic to pistachio ^{46Reference 46Elizur et al. · 2022ObservationalCashew oral immunotherapy for desensitizing cashew-pistachio allergy (NUT CRACKER study) — cohort studyView study →}. Cashew is related to mango and pistachio, and anyone with a tree-nut allergy is best to avoid the bark and leaf preparations as well as the nut.

Bark and leaf extracts. Leaf and bark extracts were not toxic to human blood cells at low concentrations, but they harmed zebrafish embryos ^{9Reference 9Amorim et al. · 2022In vitroIn vitro antibacterial and anti-inflammatory effects of Anacardium occidentale extracts and their toxicity on PBMCs and zebrafish embryos — in vitroView study →}. A leaf extract caused no toxicity in mice at oral doses up to 300 mg/kg ^{11Reference 11Kaushik et al. · 2023In vitroAntimalarial activity of Anacardium occidentale leaf extracts against Plasmodium falciparum transketolase — in vitroView study →}. No human drug-interaction study has been done.