The Disadvantages of Sweet Potatoes

Sweet potatoes are a low-fat source of many beneficial nutrients important to your health. Particularly rich in vitamins, especially vitamin A, fiber and antioxidants, sweet potatoes should be considered a healthy addition to your diet.

The health benefits of the sweet potato far outweigh any of the disadvantages. (Image: Diana Taliun/iStock/GettyImages)

Although there is some speculation about harmful effects of oxalates in sweet potatoes, it’s mainly a concern if you have a history of kidney stones. Overall, the health benefits of eating sweet potatoes outweigh any disadvantages.

What Are Sweet Potatoes?

It’s easy to recognize sweet potatoes. They are the root vegetable with the copper-colored skin and bright orange flesh, although among the hundreds of varieties grown worldwide, they can range in color from dark red to brown to purple to orange-yellow to white.

It's often easy to confuse sweet potatoes and yams, but they are different plants and not related at all. Sweet potatoes are root vegetables and members of the morning glory family; yams are tubers related to lilies that are native to Asia and Africa, according the Harvard T.H. Chan School of Public Health. Yams can be distinguished by their blackish-brown, bark-like skin and white or purple-toned flesh.

High Fiber and Carbohydrate Content

In addition to helping your digestive system work properly, fiber in your diet helps reduce the risk of obesity, heart disease and diabetes. Dietary Guidelines says you need between 22.4 and 33.6 grams of fiber a day, depending on your gender and age. Fiber is found in both the skin and flesh of sweet potatoes.

The flesh, which contains supplies about 10 percent DV for soluble fiber, which slows digestion and helps manage weight, containing 2.5 grams per 100 gram serving. If you leave the skin on the potato and bake it, the insoluble fiber content, which supplies roughage, increases to 3.3 grams or 13 percent DV per 100 grams.

To put a 100-gram serving into perspective, one medium-size sweet potato, 5 inches long and 2 inches in diameter, weighs about 114 grams.

Carbohydrates enable fat metabolism, provide fuel for energy and prevent protein from being used as an energy source. The USDA recommends that 45 to 65 percent of your daily caloric intake comes from carbohydrates, which is equal to about 225 to 325 grams on a 2,000-calorie diet. Sweet potatoes have a relatively high carb count, with 18 grams per serving.

Good Food for Diabetics

Although sweet potatoes have a high carbohydrate content, they have a low glycemic index (under 55). The glycemic index is a rating of different carbohydrate-rich foods based on how fast and to what level they raise blood sugar after being eaten.

Foods with a high glycemic index are rapidly digested and cause blood sugar levels to fluctuate. Foods with a low glycemic index are digested more slowly and have a more gradual effect on raising blood sugar.

A diet with a high carb to low glycemic index is helpful to maintain your energy since your blood sugar level will remain steady throughout the day. Sweet potatoes are an ideal food for people with diabetes who need to control blood sugar fluctuations or weight gain, says the American Diabetes Association.

Protein Provides Energy

You need dietary protein for energy and to build and maintain your bones, skin and muscle. On a daily basis, 10 to 30 percent of your calories should consist of protein. Boiled sweet potatoes, without the skin, contain 1.4 grams of protein per 100 gram serving. Baking the potato in its skin increases the protein content to 2 grams.

Hold the Salt

Sweet potatoes don’t contain a large amount of sodium until you sprinkle on the salt. Unsalted cooked potato contains 27 milligrams of salt or 1 percent DV per serving. However, the USDA lists boiled sweet potato, without skin but with salt, as containing 263 milligrams of salt, which is 11 percent of your daily value in just one serving.

Why Are Sweet Potatoes Sweet?

In addition to their sugar content of 5.7 grams in each serving, the sweetness of sweet potatoes is enhanced by an enzyme that, when heated, breaks down the starch into a sugar called maltose. While it's not as sweet as table sugar, maltose may satisfy your sweet tooth.

Food Revolution Network suggests that you can increase the sweetness of sweet potatoes by cooking them slowly using low heat. This allows maltose-making enzymes enough time to convert the starch to sugar. A temperature of 135 F will effectively activate the enzyme; about 170 F, will stop it.

Healthy Nutritional Profile

In addition to a high vitamin A content, boiled sweet potatoes offer a host of B vitamins, including folate, niacin, pantothenic acid, riboflavin, thiamine and B6. The B group of vitamins is important for providing energy, helping your body detoxify, and maintaining your brain function and immune system.

Sweet potatoes also contain the antioxidant vitamin C, with 21 percent DV, as well as vitamins E and K. Your body uses antioxidants to neutralize free radicals that can cause heart disease, cancer and other health problems.

Boiled sweet potato is especially rich in manganese, with 13 percent DV per serving. Manganese is an important mineral for the health of your bones. In addition, the root vegetable contains 5 percent DV for potassium and copper, 4 percent DV for iron and magnesium, and 3 percent DV for calcium and phosphorus, per 100 gram serving.

Baking sweet potatoes with the skin on increases the nutritional content of the vitamins and minerals significantly. For example, the vitamin C content increases from 12.8 milligram per 100 grams in boiled potato to 19.6 milligrams if baked with the skin on. That's 33 percent DV for vitamin C in just one serving.

Is Vitamin A Content a Concern?

Vitamin A is essential for your immune function, reproduction and cellular communication. It is probably best known for supporting good vision, but vitamin A also plays a crucial role in the normal formation and maintenance of your organs, including your heart, lungs and kidneys.

Sweet potatoes contain an extremely high amount of vitamin A with 787 milligrams per serving. Dietary Guidelines recommends a daily intake of 700 milligrams for adult women and 900 milligrams for men, so one serving of sweet potato will pretty much meet your daily value. You might be wondering if so much vitamin A can be harmful.

You need not worry. Orange-fleshed sweet potatoes are one of the top sources of beta carotene — a precursor to vitamin A — with 9,444 micrograms per 100 grams. Beta carotene is a provitamin A carotenoid. Your body converts this plant pigment into an active form of vitamin A that can be used for metabolic functions or stored in your liver. Although vitamin A from animal sources can cause toxicity with excessive intake, large amounts of beta carotene and other provitamin A carotenoids are not associated with any health risks.

If you eat a lot of sweet potatoes in addition to taking a vitamin A supplement over a long period of time, the most significant effect would be carotenodermia. This is a harmless condition that causes the skin to become yellow-orange and is reversible once you discontinue eating the beta carotene in sweet potatoes or other foods.

Are Oxalates Harmful?

There is some concern that the high amount of dietary oxalate in sweet potatoes may contribute to the development of calcium-oxalate kidney stones, the most common type of kidney stone.

Oxalates are natural substances found in many foods, including fruits and vegetables. These foods are nutrient dense and healthy, containing vitamins, minerals and fiber. According to a report in 2015 in the journal Clinical Nutrition Research, high-oxalate foods are safe for patients with diabetes, hypertension and high blood cholesterol. However, in patients that have developed kidney stones, the recommendation is to change to a diet lower in oxalate content.

Oxalates normally bind to calcium during digestion and are excreted in your stool. If oxalates are not bound to calcium in the stomach or intestines, they travel as waste to your kidneys where they can leave the body with urine. However, if there is too much oxalate and not enough liquid in the urine, the result is the creation of calcium-oxalate fragments. These fragments can stick together and form a larger crystal known as a kidney stone, according to the National Kidney Foundation (NKF).

The NKF suggests that you can reduce your risk of developing kidney stones by drinking lots of fluids and eating calcium and oxalate-rich foods together during a meal. This would help ensure that oxalate and calcium bind to one another in the stomach before being processed by the kidneys, making it less likely that stones will form. Sweet potatoes naturally contain calcium.

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