• Profile
Close

This root vegetable is both a nutritious superfood and a potentially lethal poison

MDlinx Jun 19, 2024

Cassava is a staple crop in Nigeria, Brazil, the Philippines, and many other countries around the world. For people in the Congo, cassava supplies 1,000 daily calories per person.

Adebayo WG. Cassava production in Africa: A panel analysis of the drivers and trends. Heliyon. 2023;9(9):e19939.

It’s easy to grow and versatile, with starchy roots and nutritious leaves. But there’s just one problem: it’s poisonous. 

 

 

Cassava contains neurotoxins that can wreak havoc on the central nervous system, especially with long-term high exposure.

Rivadeneyra-Domínguez E, Rodríguez-Landa JF. Preclinical and clinical research on the toxic and neurological effects of cassava (Manihot esculenta Crantz) consumption. Metab Brain Dis. 2020;35(1):65–74.

So, how does the world’s fourth most popular agricultural food prevail against this fatal flaw? It’s all about how you prepare it.

 

 

Cassava’s nutritional contributions

 

Cassava is a tuber that’s often boiled, fried, toasted, or processed into a naturally gluten-free flour. Cassava is also used to engineer food additives like tapioca and sorbitol.

Adebayo WG. Cassava production in Africa: A panel analysis of the drivers and trends. Heliyon. 2023;9(9):e19939.

 

Cassava roots are an important food because they’re so hardy and resilient.

Morgan NK, Choct M. Cassava: Nutrient composition and nutritive value in poultry diets. Anim Nutr. 2016;2(4):253–261.

They can be left in the ground and harvested when other crops aren’t available. Cassava is tolerant to a range of rainfall levels and can thrive in substandard soil. Cassava leaves are less calorie-dense but more rich in nutrients than the roots. They contain vitamins B1, B2, and C, along with beta-carotene.

 

Cassava is higher in insoluble fiber but lower in total protein than many other cereal grains. It's also a poor source of the essential amino acids lysine and methionine, and as it is often grown on land with low nutrient content, it may be lacking vitamin A, iron, and zinc.

 

Acute and chronic cyanide poisoning

 

 

Acute cyanide poisoning from improperly prepared cassava flour has been reported, including a 2017 case in Uganda that sickened 98 people and caused 2 fatalities.

Alitubeera PH, Eyu P, Kwesiga B, et al. Outbreak of cyanide poisoning caused by consumption of cassava flour — Kasese District, Uganda, September 2017. MMWR Morb Mortal Wkly Rep. 2019;68:308–311.

Illness set in within a few hours of ingestion and continued for a few days afterward.

 

The most noted signs and symptoms include the following (listed in order of highest prevalence).

  • Vomiting

  • Diarrhea

  • Malaise

  • Dizziness

  • Tachypnea

  • Syncope

  • Tachycardia

  • Fever

Patients were treated for cyanide poisoning with injectable cobalamin (vitamin B12) along with IV antibiotics and oral rehydration salts.

According to an article in the Journal of Water Process Engineering, “The continuous ingestion of cassava and its by-products, when processed incorrectly (without cooking, drying or fermenting properly), brings a series of problems to human health [...] or even death."

Maciel AC, da Silva Pena R, do Nascimento LD, et al. Health exposure risks and bioremediation of cyanide in cassava processing effluents: An overview. J Water Process Engineering. 2023;55:104079.

 

As a result, regulating bodies around the world (including the European Union, World Health Organization, and Environmental Protection Agency) have established maximum permissible limits of cyanide in cassava foods.

Maciel AC, da Silva Pena R, do Nascimento LD, et al. Health exposure risks and bioremediation of cyanide in cassava processing effluents: An overview. J Water Process Engineering. 2023;55:104079.

 

While some levels of toxins remain, there’s less concern when the cassava comes from reputable sources and is consumed in moderate amounts rather than as a primary source of calories.

 

Safe ways to prepare cassava

 

The main cyanoglycosides in cassava are linamarin and lotaustralin. They’re present in all parts of the plant.

Maciel AC, da Silva Pena R, do Nascimento LD, et al. Health exposure risks and bioremediation of cyanide in cassava processing effluents: An overview. J Water Process Engineering. 2023;55:104079.

Fortunately, both free and bound cyanide in cassava can be processed out through various methods, such as drying, boiling, and fermentation.

Morgan NK, Choct M. Cassava: Nutrient composition and nutritive value in poultry diets. Anim Nutr. 2016;2(4):253–261.

 

In fact, sun-drying cassava tubers and leaves decreases their free cyanide content by 90% (for six days at 82.4 degrees Fahrenheit). Oven drying is another option, but slightly less effective. Another way to reduce free cyanide by 90% is by boiling cassava chips for 15 minutes, or soaking or fermenting cassava before cooking. Ultimately, using multiple processing methods is the most effective way to minimize cassava toxins.

Morgan NK, Choct M. Cassava: Nutrient composition and nutritive value in poultry diets. Anim Nutr. 2016;2(4):253–261.

 

 

Insufficient processing time for cassava can lead to an unacceptable reduction in toxins. In addition, the use of wild cultivars is particularly problematic, as they have a high cyanogenic content.

Alitubeera PH, Eyu P, Kwesiga B, et al. Outbreak of cyanide poisoning caused by consumption of cassava flour — Kasese District, Uganda, September 2017. MMWR Morb Mortal Wkly Rep. 2019;68:308–311.

 

Wild cultivars are not recommended for human consumption. The fact that wild cultivars are resistant to pests and produce high-yielding crops makes them a desirable product for irresponsible or untrained farmers. One sign of wild cultivars is the pure white color of their flour, rather than a cream color. Farmers and food regulators can use a rapid and inexpensive test to determine the cyanide content in cassava flour. The recommended safe level is <10 ppm.

What this means for you

Cassava appeals to people who prepare it in traditional recipes or as part of a gluten-free diet. It’s safe to eat as long as it’s from a reputable source and properly processed. However, caution is warranted for those who obtain cassava from unregulated farmers or who consume it in large quantities over long periods of time.

 

Only Doctors with an M3 India account can read this article. Sign up for free or login with your existing account.
4 reasons why Doctors love M3 India
  • Exclusive Write-ups & Webinars by KOLs

  • Nonloggedininfinity icon
    Daily Quiz by specialty
  • Nonloggedinlock icon
    Paid Market Research Surveys
  • Case discussions, News & Journals' summaries
Sign-up / Log In
x
M3 app logo
Choose easy access to M3 India from your mobile!


M3 instruc arrow
Add M3 India to your Home screen
Tap  Chrome menu  and select "Add to Home screen" to pin the M3 India App to your Home screen
Okay