The sweet potato is an underground tuber. It grows on the roots of a plant known scientifically as Ipomoea batatas.
It is rich in an antioxidant called beta-carotene, which is very effective at raising blood levels of vitamin A, particularly in children (, , , ).
Sweet potatoes are nutritious, high in fiber, very filling and have a delicious sweet taste.
They can be consumed in a variety of ways, but are most commonly boiled, baked, steamed or fried.
Sweet potatoes are most commonly orange, but are also found in other colors, such as white, red, pink, violet, yellow and purple.
In some parts of the USA and Canada, sweet potatoes are called yams. This is a misnomer since yams are actually a totally different species.
Sweet potatoes are only distantly related to regular potatoes.
A raw sweet potato contains water (77%), carbohydrate (20.1%), protein (1.6%), fiber (3%) and almost no fat.
The table below contains information on the nutrients in sweet potatoes ().
Carbs in Sweet Potatoes
A medium-sized sweet potato (boiled, without skin) contains 27 grams of carbs.
The main components are complex carbohydrates called starches, which make up 53% of the carbohydrate content.
Simple sugars, such as glucose, fructose, sucrose and maltose then make up another 32% of the carb content ().
The glycemic index is a measure of how fast blood sugar values rise after a meal.
Sweet potatoes have a medium to high glycemic index, varying from 44-96 ().
Given the relatively high glycemic index of sweet potatoes, large amounts in a single meal may be unsuitable for diabetics.
Boiling seems to be associated with lower glycemic index values than baking, frying or roasting ().
Starches are often split into 3 different categories based on their characteristics during digestion ().
The starch proportions in sweet potatoes are as follows.
- Rapidly digested starch (80%) that is quickly broken down and absorbed, increasing the glycemic index value.
- Slowly digested starch (9%), which breaks down more slowly and causes a smaller rise in blood sugar levels ().
- Resistant starch (12%) that escapes digestion and acts like fiber, feeding the friendly gut bacteria. The amount of resistant starch may increase slightly by cooling the sweet potatoes after cooking (, ).
Cooked sweet potatoes are relatively high in fiber, with a medium-sized sweet potato containing 3.8 grams.
The fibers are both soluble (15-23%) in the form of pectin, and insoluble (77-85%) in the form of cellulose, hemicellulose and lignin (, , ).
Soluble fibers, such as pectin, may increase satiety, decrease food intake and reduce blood sugar spikes by slowing down the digestion of sugars and starches (, ).
Insoluble fibers have been associated with health benefits, such as reduced risk of diabetes (, , ) and improved gut health (, ).
Bottom line: Sweet potatoes are mainly composed of carbs. Most of the carbs come from starch, but sweet potatoes also contain a decent amount of fiber.
Protein in Sweet Potatoes
A medium-sized sweet potato contains 2 grams of protein, which is relatively low.
Sweet potatoes contain unique proteins, called sporamins, that account for more than 80% of the total proteins ().
The sporamins are produced in the potato whenever the plant is subjected to physical damage, to facilitate healing.
Recent research suggests that these proteins may have antioxidant properties ().
Despite being relatively low in protein, sweet potatoes are an important protein source in many developing countries (, ).
Bottom line: Sweet potatoes are relatively low in protein, but are still an important protein source in many developing countries.
Vitamins and Minerals
Sweet potatoes are rich in many vitamins and minerals, and provide an excellent source of beta-carotene, vitamin C and potassium.
Listed below are the most abundant vitamins and minerals in sweet potatoes.
- Vitamin A: Sweet potatoes are rich in beta-carotene, which is transformed into vitamin A in the body. The recommended daily amount of vitamin A can be achieved with only 100 grams of sweet potatoes.
- Vitamin C: An antioxidant, which may decrease the duration of common colds and improve skin health (, ).
- Potassium: Important for blood pressure control, this mineral may decrease the risk of heart disease ().
- Manganese: A trace mineral that is important for growth, development and metabolism ().
- Vitamin B6: Plays an important role in the conversion of food into energy.
- Vitamin B5: Also known as pantothenic acid, this vitamin is found to some extent in nearly all foods.
- Vitamin E: A powerful fat-soluble antioxidant that may help protect the body against oxidative damage ().
Bottom line: Sweet potatoes are an excellent source of vitamin A (in the form of beta-carotene), vitamin C and potassium. They are also a decent source of many other vitamins and minerals.
Other Plant Compounds
Like other whole plant foods, sweet potatoes contain a number of plant compounds that may affect our health.
The antioxidant activity of sweet potatoes increases with the color intensity of the flesh.
It is highest in colored varieties, such as purple, deep orange and red sweet potatoes (, , ).
- Beta-carotene: An antioxidant carotenoid that is transformed into vitamin A in the body. Adding fat to the meal can increase its absorption.
- Chlorogenic acid: The most abundant polyphenol antioxidant in sweet potatoes (, ).
- Anthocyanins: Purple sweet potatoes are rich in anthocyanins, which possess strong antioxidant properties ().
- Coumarins: Sweet potatoes contain small amounts of esculetin, scopoletin and umbelliferon, which may prevent blood clotting and help inhibit replication of the HIV virus in animal and cell studies (, ).
Bottom line: Sweet potatoes are rich in many plant compounds, such as beta-carotene, chlorogenic acid, anthocyanins and coumarins.
Sweet Potatoes vs. Regular Potatoes
Many people have substituted regular potatoes for sweet potatoes, believing sweet potatoes to be the healthier choice.
Let's compare the two.
The two species (boiled, without skin) contain similar amounts of water, carbohydrates, fat and protein ().
Sweet potatoes contain higher amounts of both sugars and fibers, and do sometimes have a lower glycemic index.
This is likely due to slower absorption of sugar as a result of complex starch and soluble fiber content.
Both are good sources of vitamin C and potassium, but sweet potatoes also provide excellent amounts of vitamin A.
Regular potatoes may be more satiating, but they also contain glycoalkaloids, which can be harmful in large amounts (, ).
In conclusion, sweet potatoes have a lower glycemic index, are a better source of fiber, and provide similar or slightly higher levels of vitamins and minerals (especially vitamin A) than regular potatoes.
Based on this summary, sweet potatoes are the healthier choice of the two.
Bottom line: Based on this comparison, sweet potatoes are healthier than regular potatoes. They have a lower glycemic index, more fiber, contain excellent amounts of vitamin A and do not contain any toxins.
Health Benefits of Sweet Potatoes
Consumption of sweet potatoes has been associated with good health and nutrition status ().
Sweet potatoes have mainly been studied in association with vitamin A deficiency, blood sugar regulation and antioxidant activity.
Prevention of Vitamin A Deficiency
Vitamin A plays an important role in our body, and deficiency in this essential nutrient is a major public health issue in many developing countries ().
Deficiency can cause both temporary and permanent damage to the eyes and even lead to blindness. It can also suppress immune function and increase mortality, especially among children and pregnant and lactating women (, ).
Sweet potatoes are an excellent source of highly bioavailable beta-carotene that is transformed into vitamin A in our bodies.
The intensity of the yellow or orange color of the sweet potato is directly linked to the beta-carotene content ().
Orange sweet potatoes have been shown to have a superior ability to increase blood levels of vitamin A compared to other beta-carotene sources, as they contain the "trans" variety of beta-carotene, which is highly bioavailable ().
This makes the consumption of sweet potatoes an excellent strategy against vitamin A deficiency in developing countries.
Bottom line: Orange sweet potatoes are an excellent source of beta-carotene, which is converted into vitamin A in the body. They may be valuable in the battle against vitamin A deficiency in developing countries.
Improved Blood Sugar Regulation
Imbalance in blood sugar levels and insulin secretion are the main characteristics of diabetes.
A certain type of sweet potato, with white skin and flesh (Caiapo), has been suggested to improve diabetic symptoms in individuals with type 2 diabetes.
The Caiapo sweet potato may decrease fasting blood glucose and LDL-cholesterol levels, as well as increase insulin sensitivity (, , ).
However, the current data is considered insufficient to prove the effectiveness of sweet potatoes in the treatment of type 2 diabetes ().
Further human research is needed.
Bottom line: A certain type of sweet potato (Caiapo) may help improve blood sugar regulation in individuals with type-2 diabetes.
Reduced Oxidative Damage and Cancer Risk
Oxidative damage to cells is often associated with increased risk of cancer, an adverse condition where cells grow beyond their normal boundaries and into other tissues.
Diets rich in antioxidants, such as carotenoids, have been associated with lower risk of stomach, kidney and breast cancers (, , , ).
Studies have shown that sweet potatoes contain potent antioxidants that may neutralize free radicals, harmful substances that can increase the risk of cancer. Purple potatoes have the highest antioxidant activity (, ).
The antioxidant activity of purple sweet potatoes has been found to be 3 times higher than that of a certain variety of blueberries, but blueberries are considered extremely high in antioxidants ().
Bottom line: Sweet potatoes, especially the purple varieties, contain high amounts of antioxidants. They may reduce oxidative damage and cut the risk of several types of cancer.
Adverse Effects and Individual Concerns
Sweet potatoes are well tolerated in most people.
However, they are considered fairly high in substances called oxalates, which may cause problems in people who are prone to kidney stone formation ().
Bottom line: Sweet potatoes are usually well tolerated, but they contain oxalates, which may increase the risk of kidney stone formation.
Sweet potatoes are underground tubers that are usually orange, although varieties in other colors (such as purple) exist.
They are excellent sources of vitamin A (in the form of beta-carotene), as well as many other vitamins, minerals and plant compounds.
Sweet potatoes may have several health benefits, such as improved blood sugar regulation, improved vitamin A status and reduced risk of several types of cancer.
In conclusion, sweet potatoes are nutritious, cheap, taste great and are very easy to incorporate into the diet.