Roots and Tubers: Disease-Fighting Diets

Diets prepared from root and tuber crops have the potentials to be used for prevention, management or treatment of diseases because of many active nutrients and compound in them. Aside from being a very rich sources of fiber, complex carbohydrates, vitamins and minerals, they contain bioactive compounds such as bioactive proteins, phenolic compound, saponin (sapogenin), glycoalkaloids and carotenoid (Chandrasekara, et al., 2016).

Fiber which is abundant in root and tuber diets is known to have health benefit. Evidence from individual randomized controlled trials, systematic reviews and meta-analyses of randomized controlled trials have shown that different sources of viscous soluble fibre result in improvements in glycemic control evident from lowered glycated haemoglobin or fasting blood glucose (Vuksan, et al.

, 1999; Post, et al., 2012). The study of Brown et al., (1999) also confirmed the lowering

effect of dietary fiber on cholesterol (Brown et al., 1999). Due to the viscous properties of fiber, when breakdown it attract nutrients such as cholesterol, sterol, glucose and other deleterious compound and pull them out of the body through the faeces.

Get quality help now

Dr. Karlyna PhD

Verified writer

Proficient in: A Healthy Diet

4.7 (235)

“ Amazing writer! I am really satisfied with her work. An excellent price as well. ”

+84 relevant experts are online

Hire writer

This invariably reduce overall cholesterol level in the body and reduce the risk of cardiovascular diseases. Evidence also support the fact that fiber may prevent or control for diabetes, overweight, obesity, constipation, diverticulitis, haemorrhoids, irritable bowel disease, gallstone and kidney stone. The daily recommended intakes for fiber for women and men ages 19-50 years is 25 g/day and 38 g/day respectively while women and men ?51 years of age, is 21 g/day and 30 g/day respectively (Diabetes Canada, 2018). The systematic analysis for the Global Burden of Disease Study 2017 reported that the daily intake of fiber in many region of the world is below recommended intake per day (GBD collaborators, 2019).

The consumption of root and tuber diet being a rich source of fiber can provide enough amount of fiber needed to meet the daily recommended intake.

Root and tuber based diets are also rich sources of vitamins A, C, K, folate, and niacin. Sweet potatoes in particular are remarkably high in vitamin A which is a leading cause of blindness in children worldwide. World Health Organization (WHO) estimated that about 250,000 to 500,000 children suffering from chronic malnutrition in low and medium income countries of the world go blind each year from a deficiency of vitamin A, while many of the children die due to the blindness. Maternal mortality, poor outcomes in pregnancy and during lactation, weakened immune system, diarrheal and poor growth in children have all been reported to be associated with vitamin A deficiency (WHO, 2017). Sweet potatoes contain carotenoids which include alpha-carotene, beta-carotene, lutein, and zeaxanthin. Systematic review on orange fleshed sweet potatoes reported that various studies show a positive impact on vitamin A status due to the introduction of this sweet potato (Jenkin, et. al., 2015). Also, Girard, et al., (2017) reported in their study that orange fleshed potato increased vitamin A intake in women.

Ascorbic acid commonly called vitamin C is another important vitamin in root and tuber crops. It naturally occurred in their root and almost all root and tuber crops have considerable amount of it. Cassava, white fleshed potatoes and yam in particular has ?20.6, ?17.1 and ?19.7 milligram per 100g respectively (USDA, 2015; Chandrasekara, et al., 2016). The vitamin C in root and tuber crops might be lost due to preparation method, as studies has shown that baked and microwaved potatoes have approximately twice the amount of vitamin C than do potatoes that have been boiled or fried (Han, et al., 2004; King and Slavin, 2015). However, evidence has shown they could be a reliable source of vitamin C to the general populace. According to the report of the analysis of dietary data from the NHANES II study on nutrient in the American diet from 1976 to 1980, potatoes and fried potatoes were ranked 6th and 7th contributors of total ascorbic acid respectively to the participants diet, with each accounting for ?4% of total ascorbic acid in the diet (Block, et al., 1985; King and Slavin, 2015). Potatoes also was found to contribute ?5-12% of ascorbic acid to the diet of adult participants in the 10-country European Prospective Investigation into Cancer and Nutrition (Olsen, et al., 2009).

Root and tuber crops can serve as alternate sources of folate, a water-soluble B vitamin which is also known as vitamin B9 or folacin. Folate is essential for the body to make DNA and RNA and metabolise amino acids, which are required for cell division (Bailey and Caudill, 2012). It is important element in the conversion of homocysteine to methionine in the synthesis of S-adenosyl-methionine, an important methyl donor. The methylation of deoxyuridylate to thymidylate in the formation of DNA for proper cell division, is dependent on folate. The inability of this reaction to takes place can lead to megaloblastic anaemia (NIH, 2019). The recommended intake of folate for children ranges between 65-200 micrograms-DFE, for adolescents its 300-400 micrograms-DFE while adult daily intake of 400 micrograms-DFE from foods or dietary supplements (NIH, 2019). White potatoes, sweet potatoes, cassava and yams contain ?18, ?11, ?27, and ?23 micrograms-DFE respectively (USDA, 2015; Chandrasekara, et al., 2016).

Root and tuber crops are also rich sources of vitamin B-6. Potatoes for instance provide ?0.2 mg/100 g or 15% of the RDA for adult males. According to the report of the analysis of dietary data from the NHANES study on nutrient in the American diet 2003-2006, white potatoes contributed between 14-18% of the total vitamin B-6 intake for children and adolescents (Freedman, and Keast, 2011; King and Slavin, 2015). Potatoes also was found to contribute ?17% of vitamin B-6 to the diets in United Kingdom and the Netherlands, while it contributed ?7% to that of Greece, Spain, and Italy (Olsen, et al., 2009). Cassava contains calcium which is necessary for keeping strong bones and teeth. The Vitamin-K which found in Cassava leaves also has a potential role in bone mass building by promoting osteotrophic activity in the bones and preventing losing minerals especially calcium.

Root and tuber diets are also good sources of bioactive compounds and phytochemicals which are capable of having pharmacological or toxicological effects in humans. The phenolics compounds present in tubers provides several health benefits and evidence has shown that they are capable of antibacterial, anti-inflammatory, and antimutagenic activities, among many others, in humans. Evidence from several studies implicated oxidative stress in initiation of many diseases such as cardiovascular disease, ischemic cascade which includes both strokes and heart attacks, chronic fatigue syndrome, tissue injury following irradiation and hyperoxia, as well as in diabetes, age related development of cancer, and cause mutation as a result of damage to the DNA (Nijs, et al., 2006; Handa et al., 2011).

Antioxidants counter the effects of oxidative stress. Root and tubers diets are good sources of antioxidants. They contain phytochemicals, many of which function as antioxidants. The total phenolic antioxidant index for potatoes was estimated to be 124.5 mg vitamin C equivalents/150 g of fresh weight (Chu, 2002). The study of Hsu et al., (2011) on the antioxidant activity of water and ethanolic extracts of yam peel on tert-butyl hydroperoxide (t-BHP) induced oxidative stress in mouse liver cells (Hepa1-6 and FL83B) reported that ethanolic extracts of yam peel exhibited a better protective effect on t-BHP treated cells compared to that of water extracts (Hsu et al., 2011; Chandrasekara, et al., 2016). Furthermore, the administration of tuber extracts in treated rats, showed their ability of restoring enzyme activities.

Saponins abundant in root and tuber diet especially in cassava are a type of phytochemical known to help reduce cholesterol levels. They work by binding to cholesterol and bile acid which prevents their absorption via the small intestine. Saponins also have antioxidant properties which can help prevent oxidative damage and reduce the risk of disease including serious illnesses like heart disease or cancer (Healthy focus, 2019). Emerging findings is also supporting steroidal saponins to be a novel class of prebiotics to lactic acid bacteria which is known to be effective for treating fungal and yeast infections in humans and animals (Huang, et al., 2012). Though saponins, phytate and tannins in cassava have been reported to have anti-nutrient properties but method of preparation can reduce this negative effect.