Potato
Scientific Name(s): Solanum tuberosum L. Family: Solanaceae (nightshade)
Common Name(s): Potato , Irish potato , white potato , US russet
Uses
Potatoes are rich in starch and may affect glycemic control and insulin levels in people with diabetes. Antioxidant effects and protease inhibitor action are being studied.
Dosing
There is no clinical evidence to support specific dosage of potato. The widespread use of the tubers as food is tempered by the occurrence of toxic alkaloids in sprouting potatoes and in foliage.
Contraindications
Contraindications have not been identified. Excessive consumption of potatoes in people with severe renal function impairment may lead to hyperkalemia.
Pregnancy/Lactation
Generally recognized as safe for use as food. Avoid excessive consumption because safety and efficacy are unproven.
Interactions
None well documented.
Adverse Reactions
Allergic reaction to raw and cooked potato has been documented and includes anaphylaxis. GI symptoms (eg, abdominal pain, diarrhea, nausea, vomiting) are generally associated with the consumption of blighted, greening, or sprouted tubers. Case reports of fatalities exist.
Toxicology
Two primary types of toxins are associated with potatoes: acrylamide and glycoalkaloids, with levels of acrylamide dependent on the cultivar as well as on postharvesting and processing methods.
Botany
The potato is a weedy plant recognized for its tuberous growth and valued as a commercial food. Potatoes are propagated from the underground runners of the plant from the “eyes.” 1 , 2
History
Potatoes have been cultivated since 500 BC; Central and South American Indians were probably among the first to select hardy cultivators of the potato as a food staple. 2 , 3 Despite the Spanish introduction of the plant into Europe in the late 1500s, the tubers did not become a popular food source until the 17th century because of religious and mythological concerns about the toxicity of the plant. Once accepted, potatoes were widely disseminated to Germany, other parts of Europe, and Russia.
By the 17th and 18th centuries, potatoes formed such a large part of the Irish diet that intake for adults exceeded 8 lb/day. The fungal disease known as potato blight destroyed more than 80% of the crop in the 1840s, resulting in the starvation of more than 3 million Irish and the emigration of many more. 3
Raw potato has been used traditionally in poultices for arthritis, infections, boils, burns, and sore eyes; potato peel tea has been used to soothe edema or bodily swelling; and raw potato juice has been ingested to soothe gastritis or stomach disorders. 4
The potato remains an important food crop, with over 200 million metric tons harvested annually worldwide, surpassed only by wheat. 3 Potatoes are also used as a source of starch and in the manufacture of alcoholic beverages. 5
Chemistry
Potatoes are rich in starch, with potato maltodextrin used in the preparation of commercial foods. Varying amounts of potassium, iron, riboflavin, folate, and vitamins are found primarily in the thick periderm of the skin. 3 , 6 , 7 Potatoes are a poor source of protein, with only about 2% to 10% as protein content. 3
The potato contains a variety of steroidal alkaloids chemically related by the cholestane ring structure. The major toxic glycoalkaloids are alpha-chaconine and alpha-solanine, with others, including the leptines and teptidine, found in the leaves of some, but not all, species. 3 , 8 Protease inhibitors, phenolic compounds, and lectins have also been identified. 3 , 9 , 10 Processing can induce the toxic compound acrylamide. 11 , 12 Pesticide residues can be found in the skin of the potato tuber, but are largely removed by washing in water, acetic acid, or salt, as well as by peeling or frying. 13
Uses and Pharmacology
DiabetesThe relationship between the consumption of potatoes and risk of type 2 diabetes is unclear. A gender-related response has been suggested. 14 , 15 In the Nurses' Health Study, the risk of type 2 diabetes was higher with increased potato consumption, especially among obese women. 15 A study conducted among men and women with type 2 diabetes found the intake of potatoes was directly related to insulin resistance and fasting plasma glucose levels in men, but the same relationship was not found for women. An unresolved, confounding issue was that men consumed approximately 50% more potatoes per day, leading to the suggestion of a threshold effect. 14
The glycemic index of potatoes is influenced by the cultivar and the cooking method. The common US russet potato has a moderately high glycemic index (approximately 71 when baked, similar to that of white bread). 16 A reduced glycemic response is obtained when potatoes are precooked and eaten cold or reheated. 16 , 17 , 18
Lipid profile/antioxidant actionExperiments in rats found decreased plasma cholesterol and triglyceride levels with a whole (including the skin) potato-enriched diet over a 3-week period. The plasma antioxidant capacity was also increased. 19 In vitro experiments have also evaluated the antioxidant effect of potato tubers; however, equivalent clinical experiments are lacking. 20 , 21
Other usesAn antiproliferative effect on human colon and liver cancer cells has been demonstrated in vitro. 3 , 22 Glycoalkaloids from other species have demonstrated inhibitory action on tumors in mice and human solid tumor cell lines, as well as on basal and squamous cell carcinomas and adenocarcinomas. 20 , 22 , 23 The traditional use of potato juice for the management of dyspepsia has been supported by limited clinical trials. 24
Proteins derived from potato tubers have demonstrated proteolytic activity. The elucidation of protease inhibitors from different potato species and potential clinical applications is an area of ongoing research. 25 , 26 , 27
Dosage
There is no clinical evidence to support a specific potato dosage. The widespread use of the tubers as food is tempered by the occurrence of toxic glycoalkaloids, especially in sprouting potatoes.
Excessive consumption of potatoes in people with severe renal function impairment may lead to hyperkalemia, although dicing and boiling reduces the potassium content. 6 , 17 , 18
Studies among volunteers suggest that adverse GI symptoms result from total glycoalkaloid concentrations of 2 to 5 mg/kg body weight. 3 , 9 The biological half-life of alpha-solanine has been estimated to be 10.7 hours, and 19.1 hours for alpha-chaconine. 8 , 9 A recommended acceptable level of total glycoalkaloid concentration in commercial potato cultivars is not more than 200 mg/kg fresh potato, but the safety of this level is disputed and has not been officially adopted in the United States. 3 , 10
Pregnancy/Lactation
Generally recognized as safe when used as food. Avoid excessive consumption because safety and efficacy are unproven.
The contribution of potato glycoalkaloids to neural tube defects has been explored. Animal studies have shown the ability of potato glycoalkaloids to induce spina bifida, anencephalopathy, embryo toxicity, and teratogenicity. However, studies in pregnant women whose fetuses exhibited neural tube defects had lower serum levels of glycoalkaloids compared with those of unaffected women. 3 , 28
Interactions
None well documented. 10 In experiments with rabbits, potato glycoalkaloids enhanced the neuromuscular blocking action of the anesthetic mivacurium. 3 The relevance of protease inhibitors found in potatoes is unclear. 25 , 27
Adverse Reactions
Case reports exist of anaphylaxis to cooked and raw potato. Allergic reactions include atopic dermatitis, contact dermatitis, rhinitis, and wheezing. 29 , 30
GI adverse effects (eg, abdominal pain, diarrhea, nausea, vomiting) have been reported and are generally associated with the consumption of blighted, greening, or sprouted tubers. 3 , 9 , 10
Toxicology
Acrylamide and glycoalkaloids are the two primary toxins associated with potatoes.
The highest dietary exposure to acrylamide in man comes from potatoes, cereals, and coffee. 12 Acrylamide presence in foods is a consequence of a heat-induced reaction between asparagine and reducing sugars, known as the Maillard reaction. The relative levels of these precursor chemicals, which themselves are dependent on the cultivar, growing conditions, harvest time, and storage, determine the final acrylamide concentration in the potato. 12 The heat intensity and cooking method are directly related to the formation of acrylamide. Boiled and baked potatoes generally have less acrylamide, whereas French fries and potato and tortilla chips have a higher acrylamide content. 11 , 12
A maximum acceptable exposure level has not been determined, and a direct association between dietary acrylamide and cancer has not been established, despite animal experiments demonstrating genotoxicity. 11 Epidemiological studies have found no association between acrylamide consumption and breast cancer in women, 31 , 32 and likewise no association between acrylamide intake and colorectal cancer in men. 33
Glycoalkaloids have been implicated as teratogens in animal studies. In vitro experiments have shown glycoalkaloids to inhibit human serum cholinesterases, and in case studies of toxicity related to potato consumption, effective plasma cholinesterase levels were low. 3 , 10 Symptoms associated with this effect include weak, rapid pulse; rapid and shallow breathing; delirium; and coma. Reports of death exist, especially associated with the consumption of blighted, greening, or sprouted tubers. More commonly, GI adverse effects are reported, including abdominal pain, diarrhea, nausea, and vomiting. 3 , 9 , 10 Interference by glycoalkaloids on the transport of calcium and sodium ions across cell membranes and the disruption of cholesterol-containing cell membranes has also been reported. 10 , 34
The glycoalkaloids solanine and chaconine are found in potatoes; however, the total glycoalkaloid content depends on the cultivar of the potato, as well as postharvesting exposure to light and heat and the processing methods for cooking and consumption. 3 Boiling potatoes reduces the glycoalkaloid content by approximately 3%, microwaving by 15%, and deep frying by amounts of up to 40%. Potato fries, chips, and flakes commercially available contain variable amounts of glycoalkaloids. Concern has been raised regarding frying processes, especially with regard to the frequency with which the oil used for frying is changed. The oil can become saturated with glycoalkaloids and diffusion back into the potato can occur, increasing the glycoalkaloid level. 3
Bibliography
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