Tapioca is used as the starch source in some "no grain" pet foods.
Tapioca (cassava root, manioc) is first and foremost a source of carbohydrates, but very little else. It is actually a nutritionally poor substitute for grains. (See What Are The Healthier Grains?) Due to its poor nutritional quality, special attention must be given to formulations to compensate for this problem. Tapioca contains very little protein, and the small quantity that is naturally present is of inferior quality to grains. This necessitates the addition of ingredients to supply the amino acids methionine and lysine. Meat naturally contains these amino acids, but formulating with tapioca rather than grains and legumes effectively robs the meat of these essential amino acids. This creates a net deficiency of them as compared to the same formulations if they were to contain grains.
In pet food kibbles, the "no grains" claim is almost assuredly made to imply that the grains have been replaced by a superior ingredient. However, the idea that ridding the food of grains creates a superior product is not supported by the facts. The truth is, tapioca poses some unique and very serious pet health risks.
The high carbohydrate concentration in tapioca results in high doses of sugar, which is what starch converts to when digested. In terms of sugar concentration, tapioca is second only to sugar cane. In carnivores, high levels of sugar are toxic over time and lead to a host of chronic diseases including dental deterioration.
Tapioca is often chemically modified before formulation in food products and as such, presents a threat to health by binding essential minerals that play key roles in many critical enzyme systems, and also producing the disease, parakeratosis.
Furthermore, natural tapioca contains cyanogenic glycosides (specifically linamarin and lotaustralin) which yield hydrocyanic acid upon hydrolysis (as occurs in the stomach). Hydrocyanic acid (hydrogen cyanide) is highly toxic to humans and animals. In fact, hydrogen cyanide is a chemical warfare agent and was used in Germany’s gas chambers and is used for execution today in the U.S. The toxicity is dose dependent and therefore animals or humans fed a steady diet of any food that yields hydrogen cyanide are at risk.
Cyanide is an irreversible enzyme inhibitor in cellular respiration pathways. Cyanide ions bind to the iron atom of the enzyme cytochrome c oxidase (also known as aa3) in the fourth complex in mitochondrial membranes. This denatures the enzyme, and the final transport of electrons from cytochrome c oxidase to oxygen cannot be completed. As a result, the electron transport chain is disrupted, meaning that the cell can no longer aerobically produce ATP for energy. In effect, it stops the body from "breathing."
Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Acute poisoning with high concentrations of cyanide causes coma with seizures, apnea and cardiac arrest, with death following in a matter of minutes.
At lower doses, loss of consciousness may be preceded by general weakness, giddiness, headaches, vertigo, confusion, and perceived difficulty in breathing. At the first stages of unconsciousness, breathing is often sufficient or even rapid. But then the victim progresses towards a deep coma, sometimes accompanied by pulmonary edema, and finally cardiac arrest. Skin color goes pink from high blood oxygen saturation.
At doses insufficient to cause loss of consciousness, the symptoms can also include faintness, drowsiness, anxiety, and excitement. Dizziness, nausea, vomiting and sweating are also common. The situation is complicated by the non-specific nature of the symptoms.
Exposure to lower levels of cyanide over a long period of intake, as occurs in people in tropical Africa, and could occur in pets fed "complete and balanced grain-free" extruded foods, results in increased blood cyanide levels. This may lead to weakness of the digits, difficulty walking, dimness of vision, deafness, decreased thyroid gland function, and Tropical Ataxic Neuropathy (TAN). TAN is characterized by lesions of the skin, mucous membranes, optic, auditory, spinal, and peripheral nerves resulting in myelopathy, bilateral optic atrophy, bilateral hearing loss, and polyneuropathy. Stomato-glossitis, motor-neurone disease, psychosis, and dementia are diseases prevalent in humans who regularly consume tapioca (cassava) products. Although many of these maladies have thus far only been described in humans, this is likely because only humans have been consuming large quantities of tapioca in lieu of grains. That could certainly change if pets are converted from grain-based to tapioca-based pet foods.
Birth defects were seen in rats that ate diets of cassava roots. Effects on the reproductive system were also observed. Moreover, when tapioca is ground into flour with milling, the powder has been reported to produce ulcerogenic effects in the gastric mucosa. Personnel working in pet food plants compounding tapioca based pet foods could experience skin irritation and sores from exposure to tapioca dust.
When cassava (tapioca) chips are sun-dried on the floor to reduce the hydrocyanic acid, they can be infected by microorganisms. This can predispose to aflatoxicosis, a potentially lethal mycotoxin disease.
The problem with microbial infestation can be avoided by using fresh cassava root. However, cassava root, either fresh or parboiled, has resulted in deaths due to the high degree of cyanide toxicity found in the fresh root.
As it stands, appropriate measures have not been taken to produce tapioca products of guaranteed quality that will meet the nutritional requirements of pets. A pet owner is well advised to ask any producer of tapioca-based pet foods for answers to the following:
Nutrient levels: energy, protein, fiber, and mineral levels
The exact amount of tapioca used in the formula
Levels of anti-nutritional factors: hydrocyanic acid, phytates, and oxalates
Microbial counts: levels of Aspergillus and Eschericia species
Levels of other contaminants: those introduced during the drying process
The levels that could be reached in a "no grain" tapioca-based pet food could certainly reach dangerous levels. Levels of hydrogen cyanide above 100 parts per million (ppm) in a finished food are considered unacceptable. In a "no grain" formulated pet food, depending upon the type and amount of tapioca used, levels in a typical formula could reach over 1026.3 mg/kg, or 718.85 ppm! The minimal lethal dosage in humans is about 50-60mg. A 60 lb. dog eating an average amount of a "no-grain" tapioca-based pet food could be ingesting 17.6 mg of hydrogen cyanide per day. Considering that this dog is about one third the weight of an average human, on a per weight basis it would be receiving 52.8 mg (3 X 17.6 mg) of hydrogen cyanide, which is within the lethal dose (50-60 mg) range. Even if this calculation is on the high side, lower hydrogen cyanide levels would at the least put the animal at risk of chronic toxicity.
The above is not to say that moderate levels of tapioca cannot be consumed by animals and humans without ill effect. However, eating it as a mainstay, or as a substitute for grains that have been proven safe and nutritionally beneficial for thousands of years, is not only unwarranted, but potentially dangerous.