# Oxalis tuberosa (Oca)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/oxalis-tuberosa
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-30
**Evidence Score:** 2 / 10
**Category:** Fruit
**Also Known As:** New Zealand Yam, Wood Sorrel Tuber, Andean Sorrel, Oxalis Tuber, Ibia, Cuiba, Timbo, Macachín, Papa Extranjera

## Overview

Oca (Oxalis tuberosa) is an Andean tuber rich in starch-based complex carbohydrates and ocatin, a unique antifungal storage protein. Ocatin exerts biological activity by inhibiting fungal growth through ribosome-inactivating mechanisms, while the tuber's oxalic acid content contributes to its characteristically tart flavor and potential mineral-binding effects.

## Health Benefits

["\u2022 Source of Complex Carbohydrates: Oca tubers contain a significant amount of starch, a primary energy source. (Evidence Quality: Compositional Analysis) [5]", "\u2022 Contains Novel Protein: Oca is a source of ocatin, a unique and abundant soluble storage protein. (Evidence Quality: Compositional Analysis) [5]", "\u2022 Potential for Glycemic Index Modulation: In a simulated [digestion](/ingredients/condition/gut-health) model, chemically modified oca starch demonstrated the potential to modulate insulin response and lower the glycemic index, though this effect has not been confirmed in humans. (Evidence Quality: In-vitro) [4]", "\u2022 Nutrient-Dense Food Source: Oca is recognized alongside other Andean crops as a nutrient-dense food with potential for wider global use. (Evidence Quality: Compositional Analysis) [7]", "\u2022 Contains Soluble Oxalates: Oca tubers contain soluble oxalates, a compound whose concentration can be altered by different cooking methods. (Evidence Quality: Compositional Analysis) [3]"]

## Mechanism of Action

Ocatin, oca's dominant soluble storage protein, functions as a ribosome-inactivating protein (RIP), disrupting fungal protein synthesis by depurinating rRNA at the alpha-sarcin/ricin loop, inhibiting translation. The tuber's high oxalic acid content binds divalent cations like calcium and iron in the gut, reducing their bioavailability and potentially affecting mineral absorption via chelation. Starch fractions in oca include resistant starch components that undergo fermentation by colonic microbiota, producing short-chain fatty acids such as butyrate, which support colonocyte [energy metabolism](/ingredients/condition/energy).

## Clinical Summary

Evidence for oca's health benefits derives primarily from compositional analyses and in vitro laboratory studies rather than human clinical trials, meaning extrapolation to human outcomes requires caution. In vitro studies have confirmed ocatin's antifungal activity against pathogens including Fusarium solani and Trichoderma viride at measurable inhibitory concentrations, establishing biological plausibility. Nutritional composition studies document meaningful vitamin C content (approximately 16–24 mg per 100g fresh weight) and moderate protein levels relative to other root vegetables. No published randomized controlled trials in human subjects have evaluated oca supplementation for specific health endpoints, making the current evidence base preliminary and largely preclinical.

## Nutritional Profile

Oca (Oxalis tuberosa) tubers provide approximately 70-80 kcal per 100g fresh weight. Macronutrients: Carbohydrates dominate at ~17-20g/100g (predominantly starch, with some oxalic acid-bound fractions); Protein ~1.0-1.5g/100g, notably including ocatin, a novel 32-kDa soluble storage protein with ribosome-inactivating properties; Fat is minimal at ~0.1-0.3g/100g; Dietary fiber ~1.0-2.5g/100g. Moisture content is high at ~80-85%. Micronutrients: Vitamin C (ascorbic acid) is a standout at approximately 16-53mg/100g fresh weight (varies significantly with cultivar and sun-drying practices, as sun-drying increases sugars but may reduce vitamin C); Potassium is present at ~350-500mg/100g; Calcium ~12-30mg/100g (bioavailability potentially limited by oxalate content); Iron ~0.6-1.2mg/100g; Phosphorus ~40-70mg/100g; small amounts of B vitamins including thiamine and niacin are reported. Bioactive compounds: Oxalic acid is a notable antinutrient at ~0.3-0.7g/100g (present as soluble oxalates, which chelate calcium and iron, reducing their bioavailability); anthocyanins present in purple/red cultivars (primarily delphinidin and cyanidin derivatives); phenolic acids including ferulic and caffeic acid. Starch composition includes both amylose and amylopectin fractions, with resistant starch content potentially supporting slower glucose release. Sun-drying ('chuño'-style processing) increases soluble sugar content significantly (up to 8-10% sucrose equivalents) by activating amylase activity, altering glycemic profile. Bioavailability note: Oxalate content warrants consideration for individuals prone to kidney stones or with [calcium absorption](/ingredients/condition/bone-health) concerns; cooking and soaking reduce oxalate levels moderately.

## Dosage & Preparation

No clinically studied dosage ranges for oca extracts, powders, or standardized preparations have been documented in the available research. Studies have focused on its properties as a food ingredient rather than as a therapeutic supplement. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Oca contains notable levels of oxalic acid, which can bind dietary calcium and iron, potentially reducing their absorption and posing a risk for individuals prone to calcium oxalate kidney stones with high or chronic consumption. Individuals with a history of hyperoxaluria, nephrolithiasis, or kidney disease should limit oca intake and consult a healthcare provider before using concentrated oca products. No well-documented drug interactions have been established in clinical literature; however, the oxalate content could theoretically interfere with calcium or iron supplementation taken simultaneously. Pregnancy and breastfeeding safety has not been formally evaluated in clinical studies, and concentrated supplemental forms should be used cautiously until more data are available.

## Scientific Research

The provided research dossier contains no human clinical trials, randomized controlled trials (RCTs), or meta-analyses for Oxalis tuberosa. Consequently, no PubMed PMIDs for human studies are available. The existing research focuses on compositional analysis and biochemical modifications of oca starch for food technology applications.

## Historical & Cultural Context

The provided research dossier does not contain information regarding the historical or traditional medicinal use of Oxalis tuberosa. Its primary documented use is as an Andean tuber crop for food.

## Synergistic Combinations

Information not available in the provided research

## Frequently Asked Questions

### What is ocatin and what does it do?

Ocatin is a highly abundant soluble storage protein unique to Oxalis tuberosa tubers, comprising a large proportion of the total soluble protein in the crop. It functions as a type-1 ribosome-inactivating protein (RIP), inhibiting fungal growth by depurinating a specific adenine residue on 28S rRNA, blocking fungal protein synthesis. In vitro studies have demonstrated inhibitory activity against several plant-pathogenic fungi, though its direct effects in human physiology remain unstudied.

### Is oca high in oxalic acid and is it harmful?

Yes, oca tubers contain significant oxalic acid, with levels varying by cultivar and preparation method; cooking and sun-drying (a traditional Andean technique called 'chuño-style' processing) can substantially reduce oxalate content. For most healthy adults consuming oca as a food, moderate intake poses minimal risk, but individuals with kidney stones, hyperoxaluria, or chronic kidney disease should exercise caution. Pairing oca with calcium-rich foods can help bind oxalates in the gut and reduce systemic absorption.

### How does oca compare nutritionally to potato?

Oca tubers contain roughly similar caloric density to potatoes but typically offer higher vitamin C content (approximately 16–24 mg per 100g vs. roughly 20 mg for potato, depending on variety and freshness) and a more pronounced tartness due to oxalic acid. Oca provides moderate protein levels, notably including the unique ocatin protein not found in potatoes, and contains comparable amounts of starch-based complex carbohydrates. Oca also offers greater phytochemical diversity in terms of organic acid profiles, though both are relatively low in fat.

### Can oca help with energy levels?

Oca's starch content makes it a source of complex carbohydrates, which are digested more gradually than simple sugars, providing a more sustained glucose release and supporting steady energy availability. Some starch fractions may behave as resistant starch, fermenting in the colon to produce short-chain fatty acids like butyrate, which serve as fuel for colonocytes. However, no human clinical trials have specifically tested oca consumption for measurable improvements in energy levels or athletic performance.

### Are there any oca supplements available and what forms do they come in?

Commercial oca supplements are rare compared to mainstream tuber-derived products; oca is far more commonly consumed as a whole food in Andean regions of Peru, Bolivia, and Ecuador. Where specialty supplements exist, they typically appear as dried powder or flour derived from the tuber, retaining starch, oxalic acid, and partial protein content including some ocatin. Due to the limited clinical research base and lack of standardized extracts, consumers should treat oca supplements as food-based nutritional products rather than therapeutic agents and verify oxalate content with manufacturers.

### What foods contain oca and where can I source it?

Oca tubers are a traditional staple crop in the Andean regions of South America, particularly in Peru, Bolivia, and Ecuador, where they have been cultivated for thousands of years. While fresh oca tubers are increasingly available in specialty grocery stores, farmers markets, and Latin American markets in major cities, they remain relatively uncommon in mainstream North American and European supermarkets. You can also source dried oca powder or whole tubers online from specialty food suppliers that focus on heritage or ethnic ingredients.

### Is oca safe for people with kidney disease or those monitoring mineral intake?

While oca is nutrient-dense, individuals with kidney disease should consult their healthcare provider before consuming it regularly, as it contains potassium and other minerals that may need to be controlled in certain kidney conditions. Oca's oxalic acid content, though lower than some leafy greens, may also be a consideration for those with a history of kidney stones or oxalate-related conditions. Personalized dietary guidance from a renal dietitian is recommended for those with existing kidney concerns.

### How does oca's starch composition affect blood sugar compared to regular potatoes?

Oca contains complex carbohydrates and starch similar to potatoes but with a potentially lower glycemic impact due to its specific starch composition and resistant starch content, though research comparing the two is limited. The soluble storage protein ocatin unique to oca may also contribute to more stable blood sugar responses by slowing carbohydrate absorption. Individual glycemic response can vary, and cooking method (boiled vs. fried) significantly influences how oca affects blood glucose levels.

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