Potatoes: A complete Food

Dhiraj K. Singh[1] and Pinky Raigond[2]

“Considering the widespread under-nutrition in the country, there is a need for popularising the consumptions of potato on a larger scale.”(MS Swaminathan, Eminent Agricultural Scientist)

Potato is a major world food crop and by far the most important vegetable crop in terms of quantities produced and consumed worldwide. It is popularly known as the “Vegetable King”. It is the world’s most productive vegetable and provides a major source of nutrition and income to many population and communities, and its content in dry matter, edible energy and edible protein makes it of good nutritional quality.

Potato is a versatile, carbohydrate-rich food. When freshly harvested, it contains about 80 percent water and 20 percent dry matter content. About 60 to 80 percent of the dry matter is starch. On a dry weight basis, potato protein content is similar to cereals but very high when compared with other root and tuber crops. It is low in fat content (0.1%) but rich in several micronutrients, especially vitamin C. Potato is a moderate source of iron, and its high vitamin C content promotes iron absorption. It is a good source of vitamins like Vitamin B1, B3 and B6 and minerals such as potassium, phosphorus and magnesium. Potatoes also contain dietary antioxidants, which play a part in preventing diseases related to ageing, and dietary fibre, which benefits health.

Energy value

Potato is a low energy food. 100 g of raw potato dry matter provides about 310 kcal and a boiled potato provides about 69 kcal per 100 g consumed. The energy value of potato is less than major food crops like rice, wheat, maize and sorghum. The energy produced through potato gets stored as glycogen in muscle and liver and functions as a readily available energy during prolonged, strenuous exercise. That’s why; it is an important part of players’ diet.

Source: Technical bulletin No. 49, Central Potato Research Institute, Shimla

Carbohydrates

The major role of carbohydrates in nutrition is to provide energy. Carbohydrates in potato is mostly found in the form of starch.  On an average potato contains 14% of starch on fresh weight basis. It provides most of the energy supplied by the potato. The digestibility of potato starch is low in raw state but improves considerably after cooking or processing. Sucrose, fructose and glucose are the main sugars in potato. Sugar quantity  in potato influences the quality of processed potato products like chips and French fries. Higher the sugar level in potato, darker the color of chips or French fries. Therefore, potato varieties having low sugar content are preferred for processing purpose.

Protein

Potato is a very good source of high quality protein. Average protein content of potato is 2% on fresh weight basis. The crude protein content in potato is higher than other major root and tuber crops lke seet potato, yam and cassava. Potato protein has a very high biological value because all essential amino acids are present in good proportion in it. It is much higher than major cereals and higher than even proteins of animal origin like milk and beef. With its high lysine content, potato can supplement diets which are limiting in lysine. Potato has a clear advantage over cereals in India because of its ability to provide high quality protein. 

Fat

Many people think that eating potato may cause obesity which is not true. Potatoes contain very little quantity of fat. The average fat content of potato is 0.1% on fresh weight basis which is lower than major cereals like rice, wheat, maize and sorghum. The little fat present in potato contributes towards potato palatability. Nearly, 60-80% of the fatty acid content in potato is composed of unsaturated fatty acids and linoleic acid is the predominant among them. The high content of unsaturated fatty acids increases the nutritive value of the fat present in potato. When eaten without added fat, potato is good for weight conscious people because of its low energy density. However, when fat is added to the fried or processed potato products, it becomes rich in energy and will cause obesity.

Vitamins

Potato is one of the  rich natural source of vitamin C or ascorbic acid as it contains 30 mg or more ascorbic acid per 100 g tuber. Potatoes have high quantities of vitamin C than other vegetables like carrots, onion and pumpkin. When consumed in sufficient quantity potatoes can meet the vitamin C requirements of a person. Potato is an important source of thiamine, niacin and pyridoxine and its derivatives (vitamin B6 group). It also contains pantothenic acid (vitamin B5), riboflavin and folic acid. B-vitamins are essential for general health and growth. Since they are water soluble, so potatoes should not be washed after peeling to prevent loss of vitamins.

Minerals

Important minerals and trace elements are present in potato. It is a good source of phosphorous. The phosphorous present in potato is more assimilable than the phosphorous present in other food crops because of the relatively small percentage of phytic acid in potato. The lower phytic acid content of potatoes makes a large part of potato phosphorous available to human body and is also helpful in allowing greater availability of calcium, iron and zinc. The potassium content of potato is also relatively high. Because of high potassium content potatoes are not included in the diet of patients with renal failure. On the other hand the sodium content of potato is very low. Potatoes are a good source of iron and their iron content is comparable to most other vegetables. Potatoes provide a good source of magnesium. Zinc is an important trace element found in potato. Though zinc content of potato is not very high but its availability is high because of the low phytic acid content. Potato can supply at least part of daily requirements of trace elements like copper, manganese, molybdenum and chromium.

Dietary Fibre

Dietary fibre content in potato tuber  ranges from 1-2 g/100g fresh wt. Unpeeled potatoes contain more dietary fibres than peeled potatoes. Potato contains good quality dietary fibres that help in lowering cholesterol levels.

Glycoalkaloids

Potato contains a glycoalkaloids called solanine. It contains nearly 5 mg solanine per 100 g fresh weight which is far lesser than the safety limit of 20 mg/100 g. Thus, glycoalkaloids content of potato is so low that it is not even perceptible by taste. It is a fallacy to say that potato glycoalkaloids can be poisonous to human beings. Moreover, most of the glycoalkaloids (80%) are found in outer layer and therefore can be easily removed.

Table 1: Nutritional value of potato (100 g fresh)

Source: USDA National Nutrient Database

Health benefits of potato consumption

Potato contains a complete range of nutrients, including those necessary for growth and development of human beings. They are rich in vitamin C and thus prevent scurvy. More than half of dietary fibre in potato is in the form of pectic substances, which helps in lowering cholesterol levels in human. Moreover, the dietary fibre dilutes highly caloric components in food, stimulates peristaltic movement and improves digestion. Because of its low sodium content potatoes can be used in diets given to patients with high blood pressure. Potato is a good source of vitamin B6. Many of the building blocks of protein, amino acids, require B6 for their synthesis, as do the nucleic acids used in the creation of our DNA. Because amino and nucleic acids are such critical parts of new cell formation, vitamin B6 is essential for the formation of virtually all new cells in the body.

Raw potato juice is regarded as an excellent food remedy for rheumatism. Potato is a good source of resistant starch. Natural resistant starch helps maintain a healthy colon and a healthy digestive system via several mechanisms and prevents colorectal cancer and type 2 diabetes. Resistant starch is a valuable tool for formulators of reduced-calorie foods. Resistant starch may also help to burn fat and may lead to lower fat accumulation. Resistant starch contributes to oral rehydration solutions for the treatment of diarrhea. It is predicted to help maintain "regularity” with a mild laxative effect due to increased microbial activity in the large intestine. Consumption of natural resistant starch by humans has been shown to result in decreased glycemic response in healthy individuals, decreased glycemic response in diabetics, increased insulin sensitivity in healthy individuals, individuals with Type II diabetes as well as insulin resistant individuals. When resistant starches are included in a meal, it slows down the absorption of sugars from other foods. That means there is more gradual rise and fall in blood sugar levels after eating. That’s particularly helpful for diabetics, who need to keep their blood sugar levels steady.

Conclusion

Potato is a nourishing food. It’s low energy density is advantageous when eaten without much added fat. Potato contains high quality protein rich in essential amino acids. It is a rich source of vitamin C and is far superior in this respect to most other vegetables and cereals. Considerable quantities of some of the B group vitamins are also present in potato. Potato contains many minerals and trace elements. Potato contains very little fat. Potato is such a wholesome food that one can live by eating potatoes alone. With increasing population, potatoes are going to be very crucial for providing food and nutritional security to Indian masses.