Judging by the way they are often displayed in local markets and street corners, looking dirty and sometimes shrivelled, one may be tempted to disdain and dismiss sweet potatoes as being nutritionally deficient. This perhaps explains why, unlike other root and tuber crops, such as yam and cassava, potatoes are not regarded as staple foods in this clime. Interestingly, however, recent studies have revealed that sweet potatoes are rich in anti-cancer, anti-diabetes, beta-carotene, and other agents that reduce risk of cardiovascular diseases.
Even more interestingly, the researchers found that it is everything about the sweet that is nutritious, including the leaves. In fact, the leaves are said to be more nutritious than the tuber itself. One study found that potato leaves contain appreciable amounts of nutrients (crude protein, crude fat, crude ûbre, ash, carbohydrates, moisture contents, and energy), vitamins (vitamin A and vitamin C), mineral elements (zinc, potassium, sodium, manganese, calcium, magnesium, and iron), low levels of toxicants (phytic acid, cyanide, tannins, and total oxalate). It was also recommended to be included in diets to supplement dietary allowances of essential nutrients.
According to the study, which was published in the the Journal of Medicinal Food 17(7), and titled “Sweet Potato (Ipomoea batatas [L.] Lam) – A Valuable Medicinal Food”, it was found that eating orange-fleshed sweet potatoes would decrease the risk of breast, colorectal, gallbladder and kidney cancer. Another study, conducted by Japanese researchers, evaluated the risk factors for kidney cancer death including 47,997 males and 66,520 females aged 40 years and older. Taking into account medical history, anthropometry, dietary, and lifestyle considerations over the 10-year study, the researchers concluded that eating sweet potatoes and potatoes regularly was associated with a decreased risk of the disease.
Ipomoea batatas (L.), commonly known as sweet potato, belongs to the plant family Convolvulaceae. It is an important root vegetable which is large, starchy, and sweet tasting. The plant is a herbaceous perennial vine, bearing alternate heart-shaped or palmately-lobed leaves and medium-sized sympetalous ûowers.
The edible tuberous root is long and tapered with a smooth skin. It is valued for its short growing period of 90 to 120 days, high nutritional content, and its sweetness. L. batatas has played an important role as an energy and phytochemical source in human nutrition and animal feeding. Tuber flesh colours can be white, yellow, orange and purple; while skin colour can be red, purple or white. It is considered a major food in a few countries, but is much appreciated as alternative food in many countries.
The plant has signiûcant medicinal importance and various parts of the plant are used in traditional medicine. Ipomoea batatas (L.) is an extremely versatile and delicious vegetable that possesses high nutritional value. It is also a valuable medicinal plant having anti-cancer, antidiabetic, and anti-inûammatory activities.
Sweet potato is now considered a valuable source of unique natural products, including some that can be used in the development of medicines against various diseases and in making industrial products. Sweet potatoes pack a powerful nutritional punch. They have got over 400 per cent of your daily needs for vitamin A in one medium spud, as well as loads of fibre and potassium. They have got more grams of natural sugars than regular potato but more overall nutrients with fewer calories.
Specific nutritional contents of sweet potato
Sweet potato is one of the average calorie starch foods and provides 90 calories/100 g vs. 70 calories/100g of other types of potatoes (Solanum tuberosum). The tuber, however, contains no saturated fats or cholesterol and is a rich source of dietary ûbre, anti-oxidants, vitamins, and minerals. Its energy content mainly comes from starch, a complex carbohydrate.
Sweet potato has a higher amylose to the amylopectin ratio when compared to S. turberosum. Amylose raises the blood sugar levels slowly in comparison to simple sugars, and is recommended as a healthy food substance, even for patients with diabetes.
The tuber is an excellent source of ûavonoids, phenolic compounds such as beta-carotene, and vitamin A. A 100g tuber provides 14187 IU of vitamin A and 8509 lg of b-carotene. The value is one of the highest in the root-vegetables category. These compounds are powerful natural antioxidants. Vitamin A is also required by the body to maintain the integrity of healthy mucus membranes and skin.
Health benefits of sweet potato
While various studies have confirmed the medicinal importance of sweet potato, authorities in the field of nutrition have also validated its benefits to the human system. In a recent interview, President of the Nutrition Society of Nigeria (NSN), Professor Ngozi Mercy Nnam, substantiated the fact that sweet potatoes are loaded with essential phytochemicals to enrich the body, as well as reduce the risks of non-communicable diseases.
According to the professor of Public Health Nutrition, from the Department of Home Science, Nutrition and Dietetics, University of Nigeria, Nsukka, Nigeria, the orange-fleshed sweet potato, which was recently introduced into the market, has an added food value, which is Beta-carotene. She explained that Beta-carotene is the precursor of Vitamin A, and since the orange-fleshed potato has an avalanche of this, it has an edge over Irish potato.
She equally added that the potato has a lot of fibre, which has some therapeutic effects. “It provides bulk in the diet, and prevents constipation,” she said.
Professor Nnam listed other health benefits of the sweet potato, stating that it has substances capable of preventing cardiovascular diseases because it contains no fat, and fat is implicated in the development of these degenerative diseases.
“Since cholesterol is derived from fat, the absent of fat in sweet potato, makes it cholesterol free. The sweet potato has got a lot of flavonoids, which are powerful antioxidants- that mop up free radicals, thus it can prevent cancer, diabetes, cardiovascular diseases,” she said.
The nutritionist also explained that the leaves and flesh of the orange-fleshed sweet potato can be combined to prepare a very nutritious delicacy, adding that a little oil can be added to the combination with other spices to increase the phytochemicals content of the meal.
Specific health benefits
Sweet potatoes are considered low on the glycaemic index scale, and recent research suggests they may reduce episodes of low blood sugar and insulin resistance in people with diabetes. The fibre in sweet potatoes makes a big difference too. Studies have shown that type 1 diabetics who consume high-fibre diets have lower blood glucose levels and type 2 diabetics may have improved blood sugar, lipids and insulin levels. One medium sweet potato provides about 6 grams of fibre (skin on).
- Blood pressure
Sweet potatoes contain a large amount of vitamin B6. This vitamin is crucial in breaking down a substance called homocysteine, which contributes to hardening of the arteries and blood vessels. Vitamin B6 helps keep the walls of these important blood passageways flexible and healthy, which allows blood to flow freely.
Maintaining a low sodium intake is essential to lowering blood pressure, however increasing potassium intake may be just as important. One medium sweet potato provides about 542 milligrams of potassium. Also of note, high potassium intake is associated with a 20 per cent decreased risk of dying from all causes.
Among younger men, diets rich in Beta-carotene may play a protective role against prostate cancer, according to a study conducted by the Harvard School of Public Health’s Department of Nutrition, Beta-carotene has also been shown to have an inverse association with the development of colon cancer in the Japanese population.
- Digestion and regularity
Because of its high fibre content, sweet potatoes help to prevent constipation and promote regularity for a healthy digestive tract.
For women of childbearing age, consuming more iron from plant sources appears to promote fertility, according to Harvard Medical School’s Harvard Health Publications. The vitamin A in sweet potatoes (consumed as Beta-carotene then converted to vitamin A in the body) is also essential during pregnancy and lactation for hormone synthesis.
Plant foods like sweet potatoes that are high in both vitamin C and beta-carotene offer an immunity boost from their powerful combination of nutrients.
Choline is a very important and versatile nutrient in sweet potatoes that helps with sleep, muscle movement, learning and memory. Choline also helps to maintain the structure of cellular membranes, aids in the transmission of nerve impulses, assists in the absorption of fat and reduces chronic inflammation.
According to Duke Ophthalmologist, Jill Koury, MD, as published on medicalnewstoday , vitamin A deficiency causes the outer segments of the eye’s photoreceptors to deteriorate, damaging normal vision. Correcting vitamin A deficiencies with foods high in beta-carotene will restore vision. Also of note, the antioxidant vitamins C and E in sweet potatoes have been shown to support eye health and prevent degenerative damage.
- Great source of vitamin A
Just one 5 inches long sweet potato can provide you with over 300 per cent of your daily Vitamin A requirement. Isn’t that incredible? No other root-vegetable contains as much Vitamin A as that! It also contains significant amounts of Vitamin B-6 and other Vitamins. Most of us depend on nutritional supplements in drugs to fulfil our Vitamin requirements. Imagining how much Vitamins you get from sweet potatoes alone should make you add it to your meal schedule.
- No fat and cholesterol
If you are concerned about your intake of fats and cholesterol, then sweet potatoes should be on your menu. This is because it contains zero percent fat and zero percent cholesterol.
- A great source of manganese
Manganese is a little-discussed trace mineral that has some great health benefits. It is a pivotal component in the metabolism of carbohydrates which helps support healthy blood sugar levels. This can help stabilise the appetite for hours as opposed to the temporary satisfaction that comes with most other carbohydrates.
It also is a cofactor in enzymes that play an important role in the generation of energy as well as the efficient utilization of antioxidants. It is used for the treatment of anaemia and is useful as a treatment for several premenstrual symptoms in women as well.
- Rich in vitamins C and E
As if being one of the top vegetable sources of beta-carotene weren’t enough, sweet potatoes are also rich in vitamins C and E. These are potent antioxidant vitamins that play an important role in disease prevention and longevity.
Both vitamins also play a huge role in the health and beauty of your skin and hair, making them popular supplements. The combination of beta-carotene, vitamin E and vitamin C in one food makes the sweet potato one heck of a “beauty food”. These nutrients all contribute to a healthy, glowing complexion and vibrant hair.
- Journal of Medicinal Food 17(7) · June 2014
- Medical News today