The Collison Newsletter April 2014


                               SWEET  POTATO*   



The sweet potato (Ipomoea batatas) is a dicotyledonous plant that belongs to the family of Convolvulaceae. Dicotyledons are so named because the seed typically has two embryonic leaves or cotyledons. The genus Ipomoea also includes several garden flowers called morning glories.


The sweet potato is only distantly related to the potato (Solanum tuberosum) and does not belong to the nightshade family.


It is a root vegetable, with large, starchy, sweet-tasting, tuberous roots. The sweet potato plant is a herbaceous perennial vine. The edible tuberous root is long and tapered, with smooth skin whose colour ranges between yellow, orange, red, brown, purple, and beige. Its flesh ranges from beige though white, red, pink, yellow, orange, and purple. Sweet potato varieties with white or pale yellow flesh are less sweet and moist than those with red, pink, or orange flesh.


The sweet potato is also called kûmara (a Mâori term). Although the orange sweet potato is often called a "yam" (especially in parts of Northern America), the sweet potato is botanically very distinctive from a genuine yam (Dioscorea), which is native to Africa and Asia. Oca (oxalis tuberosa) is yet another different plant, and is also called a "yam" in many parts of Polynesia, including New Zealand.


The centre of origin and domestication of the sweet potato is thought to be either in Central America or South America. In Central America, sweet potatoes were domesticated at least 5,000 years ago.

Nutrient Content of Sweet Potatoes   (Nutritional Value per 100g) 

Energy359kJ (86kcal)
Dietary fibre3.0g

In addition to the macronutrients in sweet potatoes (carbohydrates, fat and protein), they are also rich in micronutrients (vitamins, minerals and trace elements and the various phytochemicals). These include vitamins A and C, vitamins B 1, 2, 3, 5, 6, and 9, iron, zinc, calcium, magnesium, potassium, and carotenoids. The amount of phytochemicals such as beta carotene varies, depending on the sweet potato variety, the dark orange flesh having more beta carotene than those with light-coloured flesh.

Carbohydrates and Sweet Potato 

A carbohydrate is a compound that contains carbon, hydrogen and oxygen. Carbohydrates are classified according to their chemical structure.


Simple Carbohydrates. These are also referred to as 'sugars'. Simple carbohydrates have a chemical structure that is composed of one or two sugars. Monosaccharides (one sugar) include fructose and glucose. Disaccharides (two sugars, ie two chemically linked monosaccharides) include sucrose, lactose and maltose.


Complex Carbohydrates. These have three or more sugars, usually linked together to form a chain. Oligosaccharides have up to 10 sugars, for example fructose-oligosaccharides are made up of short chains of fructose molecules. Polysaccharides have a large number of mono and disaccharides, generally as complex branching chains, for example starch.


Fibre and resistant starches. These are not digested in the small intestine, but are very important for health.


Starch.  Starch or amylum is a carbohydrate consisting of a large number of glucose units joined by glycoside bonds. This polysaccharide is produced by most green plants as an energy store.


Sweet potatoes contain simple sugars and are rich in complex carbohydrates, including starch and fibre. Indeed, one fifth of sweet potato is carbohydrate, more than half of which is starch.

Health Benefits of Sweet Potatoes 

Sweet potatoes are an excellent source of starch and fibre. There is also a small amount of protein and negligible amounts of fat. They are readily available and affordable, as well as being delicious.


They are high in vitamin B6, which helps reduce the chemical homocysteine in our bodies. High levels of homocysteine have been linked with degenerative diseases, including heart disease.


Vitamin C and the other vitamins contained in sweet potatoes are important in maintaining good health.


The various minerals and trace elements in sweet potatoes are also vital for healthy functioning of the body. In particular, sweet potatoes are an excellent source of potassium, one of the important elements that help regulate heartbeat and nerve signals.


The rich orange variety of sweet potato is, as indicated by the colour, high in the carotenoids, especially beta carotene, a precursor to vitamin A in the body. Thus they help strengthen the eyesight and boost our immunity to disease. They are powerful antioxidants.


The purple variety of sweet potato is rich in anthocyanin, which is responsible for the purple colour (also found in blueberries, red grapes and red cabbage). Epidemiologically, anthocyanin is associated with a reduced cancer risk.


The Glycemic Index of sweet potato (average) is 70. That of potato (boiled, white) is 82.


In 1992, the Center for Science in the Public Interest ( compared the nutritional value of sweet potato to other vegetables, and ranked it highest in nutritional value. They list it as the No. 1 of the "10 Best Foods", and claim sweet potatoes to be "A Nutritional All-Star .... one of the best vegetables you can eat."


Sweet potatoes are an ideal, some would say 'perfect', vegetable and should be a routine part of a healthy diet.


They are versatile. They can be roasted, puréed, steamed or baked.  They can be added to soups and stews, or even grilled and placed on top of leafy greens for a delicious salad.

Sweet potatoes are a healthy, nutritious and delicious food.



*Copyright 2014: The Huntly Centre.

Disclaimer: All material in the website is provided for informational or educational purposes only. Consult a health professional regarding the applicability of any opinions or recommendations expressed herein, with respect to your symptoms or medical condition.



Back to the list  Print friendly version