Purple Sweet Potatoes: Nutrition Facts and Benefits

Last Updated on March 13, 2022 by Michael Joseph

Purple sweet potatoes are a type of root vegetable.

Although they share many similarities with regular sweet potatoes, this purple variety has unique characteristics.

This article examines purple sweet potatoes, their nutritional values, and potential benefits.

What Are Purple Sweet Potatoes?

Purple Sweet Potatoes - Whole and Cut Open Showing Their Flesh.

Purple sweet potatoes are a colorful root vegetable with high starch content, and they contain a broad range of nutrients.

This purple-hued vegetable shares the same scientific name as orange sweet potatoes (Ipomoea batatas L.), and it is part of the morning glory family of plants (1).

Purple sweet potatoes may also be known as ‘Okinawan sweet potatoes’ or ‘Hawaiian sweet potatoes.’

The above picture shows that purple sweet potatoes have intensely purple-colored flesh.

Aside from this, their outer skin, shape, and overall appearance look relatively similar to orange-fleshed sweet potatoes.

How Do They Taste?

The texture of purple sweet potatoes is a bit drier than other sweet potatoes, likely due to their slightly higher starch content.

Regarding the taste, it is slightly sweeter than regular sweet potato varieties.

While the flavor is not entirely different from orange sweet potatoes, the purple variety has a unique taste.

Key Point: Purple sweet potatoes are a popular root vegetable with a purple flesh. They also have some difference taste and nutritional characteristics from regular sweet potatoes.

Nutrition Facts

Unfortunately, the primary nutritional databases, such as the USDA’s FoodData Central database and the NCC Food and Nutrient Database, do not have an entry for purple sweet potatoes.

However, published nutrient analysis by the University of Hawaiʻi at Manoa shows the nutritional values.

Based on this data, the full nutritional values per medium (171g) cooked purple sweet potato are below (2). All daily values have been calculated using this data and the FDA’s published daily values (3).

NameAmount% Daily Value
Calories251 kcal
Carbohydrates61.0g22% DV
Fiber6.0g21% DV
Fat0g0% DV
Saturated0g0% DV
Monounsaturated0g
Polyunsaturated0g
Protein1.0g2% DV
Table 1: Nutrition facts per medium (171-gram) cooked purple sweet potato

Vitamins

  • Vitamin A RAE: 183% of the daily value
  • Vitamin C: 38% DV
  • Vitamin B6: 29% DV
  • Thiamin (B1): 18% DV
  • Vitamin E: 7% DV
  • Niacin (B3): 6% DV
  • Riboflavin (B2): 5% DV
  • Folate: 3% DV

RAE = retinol activity equivalents

Minerals

  • Potassium: 17% DV
  • Zinc: 9% DV
  • Magnesium: 7% DV
  • Iron: 6% DV
  • Calcium: 4% DV
  • Phosphorus: 4% DV
  • Sodium: 1% DV
Key Point: Like other root vegetables, purple sweet potatoes are mainly a source of carbohydrates. Among their vitamin and mineral content, they contain high levels of potassium, vitamin A, vitamin C, and B vitamins.

Benefits

Here is a summary of the potential benefits of purple sweet potatoes, based on their nutritional values and peer-reviewed scientific research.

Purple Sweet Potatoes Contain Anthocyanins

Unlike regular sweet potatoes, purple sweet potatoes contain high levels of anthocyanins.

Anthocyanins are purple-colored pigments found within certain plant foods, such as blueberries and raspberries. They are a type of polyphenol sometimes referred to as “antioxidants,” and evidence suggests they may have protective benefits for human health (4).

On this note, a large 2021 meta-analysis of large observational trials found that regular consumption of anthocyanin-rich foods was associated with a 9% lower risk of coronary heart disease (5).

Interestingly, a 2006 study published in the Journal of Agricultural and Food Chemistry investigated the estimated intake of anthocyanins from everyday foods. Based on the results of this study, the average daily intake of anthocyanins was 12.5 mg per day per person in the United States (6).

Meanwhile, it has been demonstrated that fresh purple sweet potatoes can contain 519 mg of anthocyanins per 100 grams (7).

For an idea of how this compares to other foods, studies have shown that blueberries contained 25-495 mg and red cabbage had 250-322 mg of anthocyanins per 100 grams (8).

Key Point: Purple sweet potatoes contain significant amounts of anthocyanins, a type of polyphenol that may confer health benefits.

An Excellent Source of Vitamin A

Purple sweet potatoes are one of the best sources of vitamin A.

While they don’t quite match the levels of orange-fleshed sweet potatoes, they still contain substantial amounts.

In this regard, a medium-sized cooked sweet potato contains 1643 mcg of retinol activity equivalent vitamin A. This amount is equal to 183% of the daily value for the vitamin (2, 3).

Vitamin A is an essential micronutrient that, among other functions, plays a critical role in the immune system and visual health (9).

Good Source of Vitamin C

Purple sweet potatoes also provide moderate amounts of vitamin C, another essential micronutrient.

With 34 mg of vitamin C per medium-sized cooked purple sweet potato, this represents 38% of the recommended daily value (2, 3).

Vitamin C is essential for the immune system and its antioxidant activity (10).

On this note, it is worth pointing out that regular white potatoes are an under-recognized and surprisingly rich source of vitamin C.

May Lower Blood Pressure

Research has shown that purple sweet potato intake may help lower blood pressure.

In this regard, a 2016 trial that enrolled 20 participants with elevated blood pressure examined the effect of a purple-fleshed sweet potato beverage on blood pressure (11).

Each participant consumed two purple sweet potato beverages per day for 28 days. This intake level was equivalent to 234 mg of anthocyanin per day.

Interestingly, blood pressure increasingly fell across the participants as the study progressed:

  • Day 15 blood pressure was significantly lower than pre-study.
  • Day 29 blood pressure was lower than day 15.
  • Day 43 blood pressure (two weeks after the trial finished) was significantly higher than day 15 and day 29.

However, it is important to note that this trial had some clear limitations.

Firstly, a sample size of only 20 people makes it difficult to generalize the results to the entire population. Secondly, the study was not a randomized controlled trial, so there was no ‘placebo’ control group to compare the intervention.

That said, some mechanisms explain why purple sweet potato may potentially lower blood pressure.

For instance, research has consistently demonstrated that potassium can have a beneficial blood-pressure-lowering effect (12, 13).

Additionally, cell and animal studies support the ability of anthocyanins to lower blood pressure. However, this has yet to be confirmed in humans, and the existing research provides mixed outcomes (14).

Longer, high-quality randomized controlled trials in this area are necessary to provide more clarity.

Key Point: Purple sweet potatoes may lower blood pressure, potentially due to their potassium and anthocyanin content.

May Have Benefits For the Liver

There has been some research into the potential benefits of purple sweet potato for liver health.

Firstly, a 2007 Japanese randomized, double-blind, placebo-controlled study examined the effect of two purple sweet potato beverages per day on markers of liver health. Forty-eight participants consumed two of these drinks daily (200.3 mg anthocyanins per drink) for eight weeks (15).

Notably, compared to placebo, the intervention group consuming the drinks had statistically significant lower levels of several liver enzymes associated with liver damage.

However, a 2016 double-blind, placebo-controlled pilot trial had a less certain outcome. This study also examined the effect of an anthocyanin-rich purple sweet potato beverage on markers of liver health (15).

The study recruited 40 Caucasian participants aged 40 and 70 who were otherwise healthy aside from having ‘borderline hepatitis.’ Each participant was asked to consume a purple sweet potato beverage (177 mg anthocyanins) three times per day for eight weeks.

However, the study found “no clinically relevant changes in blood and clinical parameters” (15).

Why the difference in results? The researchers involved in the 2016 study noted that further research was necessary and that there may be racial differences between Caucasians and Japanese.

Also, notably, the 2016 study did not record alcohol consumption, which is a potentially significant confounder. In contrast, the Japanese research calculated and adjusted for alcohol intake.

Key Point: Purple sweet potatoes and their anthocyanin content may potentially have benefits for liver health. However, the existing research is mixed, and more high-quality studies are necessary for clarity in this area.

What Are the Differences Between Purple Sweet Potatoes and Regular Sweet Potatoes?

As previously mentioned, purple sweet potatoes and orange-fleshed regular sweet potatoes are not entirely different nutritionally.

However, there are also some apparent differences between the two.

Based on data from the USDA’s FoodData Central nutrition database and the University of Hawaiʻi at Manoa’s nutrient analysis, here follows a summary of those differences (2, 16).

Note: the USDA entry has nutritional data for orange-fleshed sweet potatoes per 180-gram ‘medium’ sweet potato (16). In contrast, the University of Hawai’i at Manoa has available nutritional data for a 171-gram medium sweet potato (2). Therefore, it is essential to bear these weight differences in mind when reviewing the differences in nutrient profile (the orange-fleshed sweet potato is approximately 5% larger):

NameAmount per 171-gram purple sweet potatoAmount per 180-gram orange-fleshed sweet potato
Calories251 kcal162 kcal
Carbohydrates61.0g37.28g
Fiber6.0g3.78g
Fat0g0.2g
Protein1.0g2.07g
Vitamin A RAE1643 mcg1730 mcg
Vitamin E1.0 mg1.28 mg
Vitamin C34.0 mg35.28 mg
Thiamin (B1)0.21 mg0.19 mg
Riboflavin (B2)0.07 mg0.19 mg
Niacin (B3)0.97 mg2.68 mg
Folate10.26 mcg10.80 mcg
Vitamin B60.49 mg0.51 mg
Vitamin B120 mcg0 mg
Calcium58.0 mg68.40 mg
Iron1.0 mg1.24 mg
Magnesium29.0 mg48.60 mg
Phosphorus55.0 mg97.20 mg
Zinc1.0 mg0.58 mg
Potassium812 mg855.0 mg
Sodium22.0 mg64.80 mg
Table 2: Nutritional comparison table of purple sweet potatoes and regular sweet potatoes

The Main Differences

Adjusting for the 5% difference in weight, purple sweet potatoes have more calories, carbohydrates, fiber, and zinc.

As previously discussed, purple sweet potatoes also contain high levels of anthocyanins, whereas orange-fleshed sweet potatoes contain zero anthocyanins.

In contrast, orange-fleshed sweet potatoes have more protein, riboflavin, niacin, magnesium, phosphorus, and sodium.

Orange sweet potatoes also contain high levels of carotenoids, which influence the color of their orange flesh (17, 18).

Key Point: Purple sweet potatoes contain more carbohydrates and anthocyanins than regular sweet potatoes. However, they are slightly lower in several vitamins and minerals.

Potential Downsides

There are no downsides to purple sweet potatoes when consumed in normal amounts for most healthy people.

However, regardless of color, all sweet potatoes are high in oxalic acid.

Oxalic acid (also known as oxalate) is thought to increase the risk of kidney stones in individuals susceptible to developing them (19, 20).

For this reason, some individuals may be following medically-supervised low-oxalate diets.

Purple sweet potatoes are not compatible with a low-oxalate diet (21, 22, 23).

How To Use Purple Sweet Potatoes

Purple sweet potatoes are versatile, and like regular sweet potatoes they can be used in various ways:

  • Mash them and use as a side
  • Boil them
  • Bake them within their skin
  • Use them in soups and stews
  • Chop them into pieces, cover in oil and roast

There are a variety of recipes here that provide some unique ideas alongside simple ones, both savory and sweet.

The more adventurous recipes include everything from cakes, smoothies, and latte to purple sweet potato fries, chips, and even bread.

Final thoughts

Purple sweet potatoes have a unique, deep purple color, and they share several differences with regular sweet potatoes.

Most notable among these differences are their higher starch content and the presence of anthocyanins.

Purple sweet potatoes are a great-tasting, nutrient-rich vegetable, and they are very versatile for cooking purposes.

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