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Oca Root: Nutrition Facts and Health Benefits

Oca, Oxalis tuberosa, is a perennial plant extensively cultivated in the central and southern Andes for its edible root. In Peru and Bolivia, for example, this tuberous root vegetable is the second most widely grown root crop behind the potato. In these countries, the large edible rhizomes of oca are extremely important to local food security because of the nutrients and health benefits oca provides. The highly nutritious oca root is also grown commecially in New Zealand where it has become a popular root vegetable and where it is commonly known as yam.

In North America and Europe, oca root is relatively unknown and not cultivated commercially. However, many people living in the UK and North America have reported great success in growing oca in their gardens. This is not surprising since oca is known to tolerate poor soil and different climatic conditions. The major challenge vegetable gardeners are facing in these regions is the difficulty to find oca seeds in the stores. However, searching for oca seeds may be well worth the effort — this nutrition-packed, health-promoting tuber boasts a wide range of micro and macro nutrients including vitamin C, iron, zinc, flavonoids, B vitamins, and fiber. It is also low in calories.

Nutritional Value and Health Effects

A 100-gram (3.5 oz) serving of oca provides almost 40 milligrams of vitamin C, an important antioxidant that plays a key role in maintaining a healthy immune system and preventing premature aging. The amount of vitamin C found in 100 grams of oca equals to more than 60% of the daily value for vitamin C!

Some varieties are also loaded with iron (up to 70% of the daily value); however, other oca varieties have been found to contain much less iron. Oca is also an excellent source of zinc (100 grams of oca covers 12% of the daily value for zinc) and vitamin B2 (55% of the daily value). Furthermore, oca is a good source of fiber, with a 100-gram portion of oca providing around 8 grams of dietary fiber. In addition to vitamins, minerals, and macronutrients, many oca varieties are also notable sources of anthocyanidins and other flavonoids.

Oca Root - Oxalis Tuberosa

In addition to being a valuable source of nutrients, oca is very low in calories, which makes it a great, healthy weight loss food for overweight people. A 100-gram serving of unpeeled oca delivers only about 30 calories (kcal).

Like other members of the Oxalidaceae (or wood sorrel) family of plants, oca contains oxalic acid as its scientific name Oxalis tuberosa implies. The oxalic acid provided by oca and other foods that contain oxalates — such as spinach — is known to bind with calcium to form oxalates. These oxalates are usually passed through the urine. However, in susceptible individuals and in people who indigest excessive amounts of oxalic acid, oxalates may crystallize and form kidney stones which require immediate medical attention.

There are several ways to reduce the oxalic acid concentration of an oca-containing meal. One way is to select a variety that is lower in oxalic acid. South American farmers distinguish between two types of oca, sour and sweet, of which the latter is low in oxalic acid. If you live in New Zealand and want to reduce your intake of oxalic acid from oca, you might want to opt for the relatively newly introduced cultivars 'Mellow Yellow' and 'Apricot Delight'. According to a 2001 study published in the Journal of the Science of Food and Agriculture, these varieties contain less oxalic acid than the traditional pinkish-red cultivar.

Furthermore, peeling oca can have a great impact as the oxalic acid in oca is concentrated in the skin. If you're planning to cook oca, it is best to peel the tuber before cooking it if you want to limit your intake of oxalic acid. The same study that compared the oxalic acid content of oca varieties grown in New Zealand found that baking, steaming, and boiling oca causes a migration of oxalic acid from the skin to the underlying flesh.

What to Do With Oca

Oca is grown primarily for its edible and nutritious tuber which can be eaten raw or cooked. There are many ways to cook oca, including baking, boiling, steaming, roasting, and stir frying. Steamed or boiled oca can also be turned into delicious mashed oca — a nutritious alternative to mashed potatoes! Those who like their food raw can slice washed oca and add it to salads. Oca has a slightly tangy flavor and a crunchy texture when eaten raw. When cooked, oca boasts a mealy texture.

Although oca is usually cultivated for its undeground tuber, also oca leaves and young shoots are edible, boasting a tangy flavor similar to that of sorrel. This is not surprising since oca belongs to the wood sorrel family of plants.

Chart: Nutrition Facts

Nutritional information

Nutrition facts for oca (Oxalis tuberosa) are provided per 100 grams in the chart below. The chart provides both the absolute amount and the percent daily value for each nutrient.

Nutrient Amount per 100 g % Daily Value Comment
Water 87 g NA Very high water content
Protein 0.8 g 1.5 %
Fat NA NA Contains practically no fat
Carbohydrates 10.4 g 3.5 %
Fiber 8 g 32 % Excellent source of dietary fiber
Vitamin B1 (Thiamine) 0.05 mg 3.3 %
Vitamin B2 (Riboflavin) 0.94 mg 55 % Better source of riboflavin than most root vegetables
Vitamin B3 (Niacin) 1.09 mg 5.5 %
Vitamin C (Ascorbic Acid) 39.7 mg 66 %
Calcium (Ca) 17.2 mg 1.7 %
Iron (Fe) 12.5 mg 70 % Only some oca varieties provide this much iron
Phosphorus (P) 28.2 mg 2.8 %
Zinc (Zn) 1.8 mg 11.9 %

The absolute amounts in the nutrition facts table above are provided by two primary sources: 1) Marrou, Gonzalez, and Flores (2011). Composición química de "oca" (Oxalis tuberosa), "arracacha" (Arracaccia xanthorriza) y "tarwi" (Lupinus mutabilis) — Formulación de una mezcla base para productos alimenticios. Asociación RVCTA. 2) Tablas Peruanas de Composición de Alimentos, Centro Nacional de Alimentación y Nutrición, Instituto Nacional de Salud.
The percent daily values or %DV above have been calculated by healwithfood.org and are based on recommendations for a 2,000 calorie reference diet. Your daily values may be different depending on your individual needs.

Other sources:
Penarrieta (2009). Antioxidants in Bolivian Plant Foods. Antioxidant Capacity, Flavonoids and other Phenolic Compounds. Department of Chemistry, Lund University.
Albihn and Savage (2001). The effect of cooking on the location and concentration of oxalate in three cultivars of New Zealand-grown oca (Oxalis tuberosa Mol). Journal of the Science of Food and Agriculture, 81 (10), 1027-33.

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