I’ve been intrigued by the recipes I’ve been seeing on the Internet that substitute cassava flour for wheat flour.  The recipes are intended to provide wheat substitutes for followers of the paleo diet and for people who are avoiding gluten.  Here are just a few of the recipes I found with a quick search:  (Sandwich Bread,  many recipes on Pinterest, and Grain-free Naan Bread.

Since I was not familiar with cassava flour, I thought I should do some research to find out just what it is before I tried any of the recipes.  Could it be a safe and healthy alternative for people who can’t or don’t eat wheat?

While researching cassava flour, I found references to cassava chips, which I will also discuss briefly below.

What is cassava?

Cassava, as it is known in the U.S., is the starchy root of a shrub in the spurge family native to South America.  The root is known by many other common names, including manihot, mandioca, Brazilian arrowroot, manioc, tapioca, and yuca.  Its scientific name is Manihot esculenta. Though it is called yuca in Spanish, it is not related to the yucca, a fruit-bearing shrub.  Tapioca is a fermented and dried extract of cassava. (source) and (source)

Cassava was probably introduced into West Africa from South America by Portuguese slave-traders in the 1500’s. The traders also probably spread cassava into East Africa, Madagascar, India, Ceylon, Malaya, and Indonesia by the 1700s.  (source)  Indigenous people in Africa, Asia and South American have used it as staple food source for centuries. Along with other tropical roots and starchy foods like yam, taro, plantains, and potato, it is an indispensable carbohydrate in the diet of millions of people living in these regions. (source)   It is a “nutrition source in certain ecosystems because cassava is one of the most drought-tolerant crops, can be successfully grown on marginal soils, and gives reasonable yields where many other crops do not grow well.” (source)

Cassava (manihot esculenta) is the primary crop for the Machiguenga culture, a hunter-gatherer people with swidden agriculture, where cassava is grown in small plots that are cut and burned out of the rain forest. (source)

“Cassava is the third largest source of food carbohydrates in the tropics, after rice and maize. Cassava is a major staple food in the developing world, providing a basic diet for over half a billion people.” (source)

How was cassava traditionally prepared?

Traditional preparation methods varied widely by region; however, it is very interesting to note that fermentation is mentioned as part of the preparation in many of the methods.  For example,

In South America,

For Amerindians, the most common ways of preparing high-cyanide cassava were as a bread (casabe, cazabe, beiju ), a roasted granular meal (fariña, farinha), and as a beer (chicha ). In the northwest Amazon the bread is a large, thick (one inch or more) flat bread made by peeling and grating the roots, and then sieving the grated mash with water to separate the liquids and starch from the more fibrous portion. The starch is allowed to settle, and the liquids decanted off the top, then boiled to make a drink (manicuera ). The starch and fibrous portion of the roots are stored separately and allowed to ferment for forty-eight hours before being dewatered, and then recombined and baked on a large clay griddle. In Venezuela and Guyana the bread is a thinner, hardtack-like bread made without the starch extraction step.
arinha is made by soaking the roots of yellow-fleshed, high-cyanide varieties in water until they ferment. The roots are then peeled, grated, mixed with fresh grated roots and the mixture allowed to ferment for a week or more. The mash is then dewatered, sprinkled onto a hot griddle, and roasted while being stirred. The resulting product is a dry granular meal that can be stored almost indefinitely. It is most commonly consumed as chive, a drink that is made by putting a handful of meal in water and swirling to mix. Well-made meal can expand five times in volume and results in a full feeling.

Chicha, a mildly alcoholic beer, is made from both low-cyanide and high-cyanide cassava. With low-cyanide varieties it is prepared by peeling, cooking, and mashing the roots, then adding water and some masticated roots and allowing the mixture to ferment. With high-cyanide varieties it is prepared from manicuera (the cooked juices) and a very thin bread, some of which is masticated, and other cooked roots or tubers.

In the national cuisines of South America, low-cyanide cassava is used as a vegetable (boiled, or boiled and fried). In Brazil, farinha is part of a number of traditional dishes, and in Colombia several breads are made with the fermented starch of high-cyanide cassava. (source) [emphasis added]

“A safe processing method used by the pre-Columbian people of the Americas is to mix the cassava flour with water into a thick paste and then let it stand in the shade for five hours in a thin layer spread over a basket. In that time, about 83% of the cyanogenic glycosides are broken down by the linamarase; the resulting hydrogen cyanide escapes to the atmosphere, making the flour safe for consumption the same evening.” (source)

In Africa,

“The majority of the cassava-based foods made in Africa rely on fermentation in one form or another.” (source)

BANKU is a popular staple consumed in Ghana. It is prepared from maize or a mixture of maize and cassava. The preparation involves steeping the raw material in water for 24 hours followed by wet milling and fermentation for three days. The dough is then mixed with water at a ratio of 4 parts dough to 2 parts water; or 4 parts dough to 1 part cassava and 2 parts water. Continuous stirring and kneading of the fermented dough is required to attain an appropriate consistency during subsequent cooking. Microbiological studies of the fermentation process revealed that the predominant microorganisms involved are lactic acid bacteria and moulds. (source) [emphasis added]

“The traditional method used in West Africa is to peel the roots and put them into water for three days to ferment. The roots then are dried or cooked. In Nigeria and several other west African countries, including Ghana, Benin, Togo, Ivory Coast, and Burkina Faso, they are usually grated and lightly fried in palm oil to preserve them. The result is a foodstuff called gari. Fermentation is also used in other places such as Indonesia . . . The fermentation process also reduces the level of antinutrients, making the cassava a more nutritious food.” (source)

In the South Pacific,

“On some islands cassava is also used to prepare ma, a traditional fermented product typically made from breadfruit.” (source) [emphasis added]

Can cassava cause health problems?

Traditional preparation methods as described above are necessary to mitigate the antinutrient qualities of cassava.  If not properly prepared, these are some of the possible health problems:

Goitrogens

“The reliance on cassava as a food source and the resulting exposure to the goitrogenic effects of thiocyanate has been responsible for the endemic goiters seen in the Akoko area of southwestern Nigeria.” (source)

Cruciferous goitrogens also inhibit the transfer of iodine into milk by the mammary gland. The goitrogens themselves cross the placenta into the fetal bloodstream during pregnancy and pass into the maternal milk during lactation.10 Milk from cows grazing on especially goitrogen-rich crucifers resulted in an outbreak of goiter in Finland in the 1960s, and researchers believe that high maternal consumption during pregnancy and lactation of improperly detoxified cassava—a starchy vegetable with goitrogens similar to those that occur in crucifers—plays a role in the endemic cretinism that plagues the children of many third world populations.  (source)

Cyanide

The high cyanide content of cassava is one of the most serious health risks.

“Cassava is classified as either sweet or bitter. Like other roots and tubers, both bitter and sweet varieties of cassava contain antinutritional factors and toxins, with the bitter varieties containing much larger amounts. They must be properly prepared before consumption, as improper preparation of cassava can leave enough residual cyanide to cause acute cyanide intoxication, goiters, and even ataxia or partial paralysis.” (source)

“Excess cyanide residue from improper preparation is known to cause acute cyanide intoxication, and goiters, and has been linked to ataxia (a neurological disorder affecting the ability to walk, also known as konzo). It has also been linked to tropical calcific pancreatitis in humans, leading to chronic pancreatitis.” (source)

“Cassava root contains natural toxic cyanogenic glycoside compounds linamarin and methyl-linamarin. Injury to tuber releases linamarase enzyme from the ruptured cells, which then converts linamarin to poisonous hydrocyanic acid (HCN). It is therefore, consumption of raw cassava root results in cyanide poisoning with symptoms of vomiting, nausea, dizziness, stomach pains, headache, and death. In general, cyanide content is substantially higher in its outer part and peel.” (source)

Cyanide content can be reduced significantly by proper processing:

“While peeling lessens the cyanide content, sun drying, and soaking followed by boiling in salt-vinegar water results in evaporation of this compound and makes it safe for human consumption.” (source)

“Brief soaking (four hours) of cassava is not sufficient, but soaking for 18–24 hours can remove up to half the level of cyanide. Drying may not be sufficient, either.”  (source) “When properly soaked and dried, and especially when people have protein in their diet, bitter cassava is okay; but when any of the process is skimped on, problems arise.” (source) [emphasis added]

Allergies

“A small number of people are also allergic to the plant — the American Cancer Society warns that those with a latex rubber allergy might be more susceptible and should consider opting for a different dessert [tapioca, derived from cassava].” (source)

High Carbohydrates

People who limit the carbohydrates in their diets, such as diabetics, need to be aware that cassava flour is very high in carbohydrates.  Cassava flour contains an even higher percentage of carbohydrates than wheat flour (see the detailed nutrient information and chart below for both cassava and wheat flours).

What do other countries say about the safety of cassava?

Hong Kong,

The Centre for Food Safety of the government of Hong Kong provides an interesting discussion of the risks and proper preparation of cassava:

Cassava contains more than one form of cyanogenic glycosides. Different varieties of cassava are generally classified into two main types: sweet cassava and bitter cassava. Sweet cassava roots contain less than 50 mg per kilogram hydrogen cyanide on fresh weight basis, whereas that of the bitter variety may contain up to 400 mg per kilogram.

Sweet cassava roots can generally be made safe to eat by peeling and thorough cooking. However, bitter cassava roots require more extensive processing. One of the traditional ways to prepare bitter cassava roots is by first peeling and grating the roots, and then prolonged soaking of the gratings in water to allow leaching and fermentation to take place, followed by thorough cooking to release the volatile hydrogen cyanide gas. Cutting the roots into small pieces, followed by soaking and boiling in water is particularly effective in reducing the cyanide content in cassava. Whilst fresh cassava requires traditional methods to reduce its toxicity, adequately processed cassava flour and cassava-based products have very low cyanide contents and are considered safe to use. (source)

Australia and New Zealand,

According to the Food Standards of Australia and New Zealand, “Only sweet cassava, containing low levels of cyanogenic glycosides (50mg/kg), is permitted to be used for food in Australia and New Zealand.” They also say, “Processed cassava, such as cassava chips, cassava flour and tapioca pearls used for tapioca pudding, is considered safe as processing reduces cyanogenic glycosides to safe levels.” (source)

How are currently available sources of cassava flour prepared?

I found several sources of cassava flour available on the Internet.  One source of cassava flour recommended by multiple recipes is Otto’s Naturals.  Otto’s website specifically says they do not include fermentation in the preparation of their product, which raises concerns based on the possible health problems described above.

Otto’s Cassava Flour is the very highest quality cassava flour available. Other cassava flours are hand peeled and sun dried. That sounds romantic, but it can produce undesireable [sic] results. As the cassava dries in the sun it ferments and takes on a sour, musty smell and taste. If it happens to rain, it must sit longer, allowing opportunity for mold to grow.”

Otto’s Naturals Cassava Flour, on the other hand, is thoroughly peeled and baked into a beautifully clean smelling and tasting flour you can count on again and again. This proprietary method leaves no chance for mold or fermentation to develop.  (source) [emphasis added]

In addition to Otto’s cassava flour, Amazon lists several additional sources.  I could not find very much information about the preparation methods for other sources of cassava flour.

Moon Rabbit Foods gives no information about the preparation of their cassava flour other than to say, “All of our products are produced in a dedicated gluten free facility in Savannah, New York.”

Is cassava flour a nutritious food?

Cassava root is essentially a source of carbohydrates and calories.  It has very little protein and a comparatively low content of vitamins and minerals, with the possible exception of calcium and vitamin C plus a few B vitamins.  (source)

Not only does fermentation reduce the antinutrients of cassava, but one study found that fermentation increased the nutrient content.  The protein content of fresh cassava root was increased by as much as 13.5% and fat by 3.0%.  (source)

One nutrition source, says that, per 100 gram serving, cassava flour contains: 79.8 grams of carbohydrates, 1.6 grams of protein, 1.6 grams of fat, 11.9 grams of fiber, and 417 milligrams of sodium.  No other vitamins or minerals are mentioned.  (source)

Food Nutrition Table lists a few additional nutrients in 100 grams of cassava flour, the largest amount being 5 milligrams of vitamin C.  This source lists less than a tenth of a milligram each of several B vitamins. This source also lists slightly different values for carbohydrates (82 grams), fiber (2 grams), and protein (2.8 grams). It also lists 150 mg of calcium (15% of RDA), 100 mg of phosphorus (14% of RDA), and 20 mg of potassium (0.4% of RDA). (source)

One source claims that cassava flour is “Rich in Minerals.”  “Cassava is a good source of minerals such as calcium [16 mg], phosphorus [27 mg], manganese 90.4 mg], iron [0.3] and potassium [271 mg].” (source)   It’s overstatement to list these values as support for being “Rich in Minerals.”

Livestrong also says cassava flour is high in copper [0.2 mg] and manganese [0.8 mg]. (source)

With this much variability in listed nutrient content, it might be best to assume cassava flour is high in carbohydrates and fiber and low in fat and protein with possible content of some vitamins and minerals.

How does cassava flour compare nutritionally to wheat flour?

Since one of the principle uses of cassava flour, at least in the US, is as a substitute for wheat, I thought it might help to compare the nutrients in cassava flour to whole wheat flour.

Based on the USDA data, whole wheat flour is much higher in most nutrients, especially protein, fat, fiber, B vitamins, and minerals. (source)  100 grams of whole wheat flour provides these RDA percentages: 39% of magnesium, 41% of thiamin, 31% of vitamin B6, 31% of niacin, and 13% of iron.  (source)  RDA percentages may vary by age, sex, and lactation/pregnancy.

Some people may need to avoid wheat; however, my research does not support considering cassava flour to be an adequate nutritional substitute for wheat. The necessary macro and micro nutrients provided by whole wheat would need to be obtained from other dietary sources.

The table below uses nutrients in widely recommended Otto’s Cassava Flour because the USDA only lists nutrients for raw cassava, which would not be comparable.  See above nutrient information for other values for cassava flour.

Nutrients in Otto’s Cassava Flour (source) vs. Whole Wheat Flour (source) and All-purpose White Flour (source), per 100 grams

 

Cassava Chips

I found reference to two kinds of cassava chips, both apparently substitutes for potatoes.  The first is a cassava chip, similar to potato chips, available on Amazon and elsewhere or you can find recipes (here and here) for making your own.  The second kind of cassava chip is found in Great Britain, where potato chips are equivalent to French fries in the U.S.  (They call our potato chips, potato crisps.)  The Guardian tells how to prepare cassava chips (we would call them cassava fries).  Since both of these cassava chip methods start with fresh cassava root and do not long-soak, dry, or ferment the roots before frying, I would be reluctant to eat very many of them.

Conclusion

Cassava prepared with traditional methods, usually including fermentation, appears to be a reasonably safe food that has sustained people for thousands of years; however, since it’s not clear if all, or any, of the cassava flours being used in the recipes now found on the Internet are prepared according to traditional methods, it may be safer to limit their use.  Also, based on the nutrient content, cassava is probably not a good nutritional substitute for whole wheat or all-purpose white flour and would need to be supplemented with other foods to provide adequate protein, vitamins, and minerals.

Update May 11, 2024: Recent lab tests have shown that cassava products may also have high levels of lead contamination in addition to arsenic. Post by Tamara Rubin, Lead Safe Mama.

Update February 4, 2022: A recent study provides additional information about the nutritional content of cassava compared to other common flours. Progress in research and applications of cassava flour and starch: a review.  Table of compared nutritive values.

Update August 25, 2019: There is an excellent post about cassava on the Weston A. Price website, Cassava: A Versatile and Satisfiying Grain-Free Option.

Additional Information about cassava (This list does not include all source links in the article above):

Enriching nutritive value of cassava root by yeast fermentation
5 Things You Need to Know About Cassava Flour
Julia Cassava Flour, Shopwell.com
Cassava – not always so healthy
Cassava Benefits
Cassava-based dishes [interesting listing by country of common cassava dishes]
How to prepare Cassava Manioc and how to cook Cassava Manioc
Attiéké [a side dish made from cassava that is a part of the cuisine of Côte d’Ivoire in Africa. The dish is prepared from fermented cassava pulp that has been grated or granulated.]
World production and trade of cassava products, The Food and Agriculture Organization of the United Nations
What is Cassava?
Facts about Cassava and Cyanide

Photo credit: By Amada44 – Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=12603188