Sweet Potato
Scientific Name(s): Ipomoea batatas L.
Common Name(s): Caiapo, Camote, Kumara, Nyamis, Sweet potato, Yam
Medically reviewed by Drugs.com. Last updated on Jun 9, 2022.
Clinical Overview
Use
Limited clinical studies of sweet potato use in type 2 diabetes, vitamin A deficiencies, or for its antioxidant, cardiovascular, and immune effects have been conducted.
Dosing
Diabetes: 4 g/day of a sweet potato preparation (Caiapo tablets) given for 3 to 5 months has been used in clinical studies. Clinical studies evaluating efficacy of the nutraceutical Caiapo used 2 g (low dose) or 4 g (high dose) daily, for a total of 4 tablets daily (each containing either 168 or 336 mg of powdered white-skinned sweet potato). Sweet potato supplements are also available in powder and tablet (Caiapo) forms. Dosage regimens vary, but most commercial manufacturers suggest 2 tablets 30 minutes before meals, up to a total of 6 tablets daily. Vitamin A deficiency: Daily consumption of beta-carotene–rich sweet potato (orange-fleshed varieties) has been used to improve vitamin A status.
Contraindications
Hypersensitivity to any of the chemical components of the plant species.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Women with hypersensitivity reactions to the plant should avoid use.
Interactions
None well documented.
Adverse Reactions
Historical and clinical data report no serious adverse reactions. Patients with known hypersensitivity reactions to the plant may develop generalized urticaria, hypotension, and edema of the hands and face. Dizziness, loss of consciousness, nausea, vomiting, and a sensation of tickling and tightness in the throat have been documented.
Toxicology
No data.
Scientific Family
- Convolvulaceae
Botany
The sweet potato plant is an herbaceous perennial vine that originated in Central America. Although China is considered the leading producer of sweet potatoes, the plant is widely cultivated and consumed throughout the world. It has alternate, heart-shaped, lobed leaves and medium-sized flowers. The root is edible and is often long and tapered. The skin may be red, purple, or brown and white. The interior, or "flesh," may be white, yellow, orange, or purple. The leaves and shoots are sometimes eaten as greens. Synonyms include Convolvulus tiliaceus auct. non Willd.; Ipomoea fastigiata (Roxb.) Sweet; Ipomoea tiliacea auct. non (Willd.) Choisy; Ipomoea triloba auct. non L.(USDA.2017, Zhao 2005)
History
Sweet potato is one of the world's largest food crops and is important for growing populations in Asian and African countries. The plant has been used medicinally in Japan for treating diabetes and other diseases. American Indians also used sweet potato to treat thirst and weight loss attributed to diabetes.(Konczak-Islam 2003, Kusano 2001, Ludvik 2003, Yoshimoto 1999)
Chemistry
Numerous extensive phytochemical investigations focusing on the nutraceutical properties and physiological functions of sweet potato have been conducted.(Mohanraj 2014, Ooi 2012) The root and skin contain most of the studied medicinal components. High levels of polyphenols, such as anthocyanins and phenolic acids (eg, caffeic acid), have been isolated from sweet potato. Chlorogenic, dicaffeoylquinic, and tricaffeoylquinic acids are derivatives of caffeoylquinic acid, which protect the root from fungal diseases and have potential cancer chemoprotective effects. Sweet potato anthocyanins are extracted from the root or stem. They are stable and have antioxidant, antimutation, antitumor, liver protection, hypoglycemic, and anti-inflammation functions, which give purple sweet potato various application prospects.(Li 2019) The structural properties of the anthocyanins which are important for bioactivity include phenolic esters of the sugar, 2 hydroxyl groups on the aromatic ring, and an unsaturated alkyl chain in the acylated moiety.(Goda 1997, Konczak-Islam 2003, Konczak 2004, Matsui 2004, Wilson 1979)
The plant's antioxidant activity is associated with its alpha-tocopherol content. Alpha-tocopherol being the most common form of vitamin E and comprising of 25 mg per 100 g of sweet potato shoots. The 2 storage proteins sporamins A and B account for more than 80% of the total protein isolated from the roots of the sweet potato.(Ching 2001, Maeshima 1985)
Uses and Pharmacology
Antioxidant effects
Animal and in vitro data
The major phenolic components in a 70% methanol extract of sweet potato showed strong antioxidant activity in a linoleic acid–aqueous system.(Hayase 1984)
Anthocyanins of purple sweet potato have antioxidant activity. Levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were increased in the collected urine samples of purple sweet potato anthocyanin–injected rats and in 6 human volunteers who were administered a purple sweet potato beverage. The degree of radical scavenging activity for some of the anthocyanins was higher than that of ascorbic acid.(Kano 2005)
A phosphorylation polysaccharide modification product obtained from purple sweet potato could improve the scavenging effect on the hydroxyl radical and superoxide anion.(Yang 2021)
Clinical data
A clinical trial reported modulation of antioxidative status and decreased exercise-induced oxidative damage in healthy young males (N=15) following 7 days of purple sweet potato leaf consumption after completing a running exercise protocol.(Chang 2010)
The bioavailability of polyphenols in purple sweet potato leaves was demonstrated in a clinical study, with reported potential for enhanced antioxidant defense and decreased oxidative stress in young healthy adults.(Chen 2008)
Cardiovascular effects
Animal data
A sweet potato leaf extract was examined for relaxant activity in isolated rat vascular aortic preparations. Sweet potato showed 97% relaxation activity for endothelium-intact aortic ring preparations but only 35% in the mesenteric vascular bed. The vasorelaxation mechanism of action was similar to that of the pharmacological agent acetylcholine.(Runnie 2004)
Diabetes
Animal data
Various blood glucose-lowering activities of the sweet potato have been demonstrated in animal studies.(Ooi 2012)
In a free-glucosidase (AGH) assay system, potent AGH inhibitory activity was observed with anthocyanin extracts from the storage roots of purple sweet potato (50% inhibitory concentration [IC50]=0.36 mg/mL). The extracts also inhibited alpha-amylase activity, indicating a potential role in suppressing the increase in postprandial glucose levels.(Matsui 2001)
The antidiabetic activity of white-skinned sweet potato versus troglitazine was examined in Zucker fatty rats over a period of 8 weeks. Oral dosing of white-skinned sweet potato reduced hyperinsulinemia by 23%, 26%, 60%, and 50%, at 3, 4, 6, and 8 weeks, respectively. White-skinned sweet potato also inhibited increases in blood sugar levels after administration of a glucose challenge test during week 7. Histology of the pancreas showed regranulation of pancreatic islet beta cells. However, isolation and purification of the antidiabetic component in white-skinned sweet potato was unsuccessful.(Kusano 2001, Kusano 2000)
A sweet potato leaf extract given for 5 weeks decreased glucose levels in mice with type 2 diabetes; additional studies demonstrated stimulated secretion of glucagon-like peptide-1, resulting in increased insulin secretion.(Nagamine 2014)
Evidence and similar experiments in rats indicate that acylated anthocyanins (eg, caffeoylsophorose) are responsible for alpha-glucosidase inhibitory activities of the extract. The production of adiponectin by sweet potatoes has gained pharmaceutical interest. Low levels of this cytokine or protein are associated with type 2 diabetes mellitus, obesity, and hypertension.(Berberich 2005, Matsui 2004)
Clinical data
A Cochrane review evaluated randomized clinical trials comparing sweet potato with a placebo or a comparator intervention in type 2 diabetes. In 2 of the included trials (N=122), administration of sweet potato (Caiapo tablets) produced significant improvement in glycosylated hemoglobin A1c at 3 to 5 months compared with the placebo (mean difference, −0.3% [95% confidence interval, −0.6 to −0.04]; P=0.02). The trials included were all conducted by the same group of researchers.(Ooi 2012) A systematic review in the context of diabetic retinopathy, and the potential effects of sweet potato in hyperglycemia and dyslipidemia, concluded that I. batatas is effective in treating a hyperglycemic condition and is able to regulate dyslipidemia.(Naomi 2021)
Immune system effects
Animal data
Sweet potato fiber, in combination with other therapeutic agents, may be useful in skin wound therapy. The healing effect of sweet potato fiber was evaluated for burns and decubital wounds in rats over 19 days. In rats treated with the sweet potato fiber covering, wound areas were reduced by 21% at day 9, 19.5% at day 11, and 18.7% at day 13 compared with the controls. Healing times for both groups were 19 days for treated rats and 21 days for the controls.(Suzuki 1996)
In a mouse model, purified sweet potato polysaccharide (PSPP) isolated from the roots, also acted as a biological response modifier. In mice treated with PSPP (50, 150, and 250 mg/kg body weight for 7 days), phagocytic function, hemolytic activity, and serum immunoglobulin concentration all increased in a dose-dependent manner.(Zhao 2005)
Clinical data
A randomized, crossover study involving 16 healthy, nonsmoking adults (7 men and 9 women) examined the effects of physiological doses of purple sweet potato leaves over a period of 6 weeks. During week 1, control and experimental groups were subjected to a low-polyphenol diet. During weeks 2 and 3, the experimental group consumed a diet consisting of 200 g daily of purple sweet potato leaves, and the control group consumed a diet consisting of low polyphenols and carotenoids adjusted to the same level as those of purple sweet potato leaves. A washout diet followed during week 4. During weeks 5 and 6, the experimental and control groups switched diets. Results from blood and urine samples indicate that dietary intervention in the form of purple sweet potato leaf consumption modulated various aspects of immune function, including increased proliferation responsiveness of peripheral blood mononuclear cells, secretion of cytokines IL-2 and IL-4, and lytic activity of natural killer cells.(Chen 2005) Similarly, a clinical trial in healthy young males (N=15) reported decreased proinflammatory cytokine secretion after 7 days of consuming purple sweet potato leaves after completing a running exercise protocol.(Chang 2010)
Beneficial immune system effects have also been documented for white-skinned sweet potato.(Miyazaki 2005)
Other uses
Chemoprotective effects may be associated with anthocyanins and phenolic acids in sweet potato. Intake of an anthocyanin-rich purple sweet potato beverage improved serum hepatic biomarkers in Japanese men with borderline hepatitis who were otherwise healthy.(Suda 2008) The effects of purple sweet potato anthocyanins (PSPA) on doxorubicin-induced cardiotoxicity were investigated in vitro and in vivo (in mice). The results indicated that PSPA could significantly ameliorate doxorubicin-induced heart failure. The obtained results could provide the potential application of PSPA as an alternative therapy for cardiotoxicity caused by doxorubicin in the functional food industry.(Tang 2021)
Sweet potato also gained attention in sub-Saharan Africa, where research has focused on its use in alleviating micronutrient deficiencies, such as vitamin A deficiency, particularly the orange-fleshed variety of sweet potato.(Amagloh 2021) Clinical studies also document the use of sweet potato, due to its provitamin A (or beta-carotene) content, as a potential long-term, food-based strategy to improve vitamin A deficiency in children in many developing countries.(Haskell 2004, Hotz 2012, Hotz 2012, Jamil 2012, Turner 2013, van Jaarsveld 2005)
Dosing
Diabetes
4 g/day of a sweet potato preparation (Caiapo tablets) given for 3 to 5 months has been used in clinical studies.(Ooi 2012)
Clinical studies regarding efficacy of the nutraceutical Caiapo used 2 g (low dose) or 4 g (high dose) daily, for a total of 4 tablets daily (each containing either 168 or 336 mg of powdered white-skinned sweet potato). Sweet potato supplements are available in powder and tablet forms.(Ludvik 2003, Ludvik 2002) Dosage regimens vary, but most commercial manufacturers suggest 2 tablets 30 minutes before meals, up to a total of 6 tablets daily.
Vitamin A deficiency
Daily consumption of beta-carotene–rich sweet potato (orange-fleshed varieties) has been used to improve vitamin A status.(Hotz 2012, Hotz 2012, Jamil 2012, Turner 2013)
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Women with a history of hypersensitivity reactions to the plant should avoid use.(Velloso 2004)
Interactions
None well documented.
Adverse Reactions
Historical and clinical data report no serious adverse reactions. No serious adverse effects were reported in a Cochrane review of clinical trials of Caiapo usage in type 2 diabetes.(Ooi 2012)
Patients with known hypersensitivity reactions to the plant may develop generalized urticaria, hypotension, and edema of the hands and face. Other case reports also document dizziness, loss of consciousness, nausea, vomiting, and a sensation of tickling and tightness in the throat.(Velloso 2004)
Toxicology
Limited toxicity data are available. Animal studies document temporary neurological effects followed by extensive liver necrosis for 3 sesquiterpenoids in sweet potato, with a median lethal dose ranging from 184 to 266 mg/kg.(Wilson 1979) Sweet potato consumption should be avoided in individuals hypersensitive to any of the chemical components of the plant species.(Velloso 2004)
References
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