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.
Table of contents
What Are Purple Sweet Potatoes?
Purple sweet potatoes are a colorful root vegetable with high starch content, and they contain a broad range of nutrients.
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.
Purple sweet potatoes are sometimes confused with ‘purple yams.’ Unlike purple sweet potatoes, yams are a variety of tuber rather than a sweet potato or root vegetable.
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.
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).
|Name||Amount||% Daily Value|
- 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
- Potassium: 17% DV
- Zinc: 9% DV
- Magnesium: 7% DV
- Iron: 6% DV
- Calcium: 4% DV
- Phosphorus: 4% DV
- Sodium: 1% DV
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).
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.
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.
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.
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.
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 significantly 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.
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.
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):
|Name||Amount per 171-gram purple sweet potato||Amount per 180-gram orange-fleshed sweet potato|
|Calories||251 kcal||162 kcal|
|Vitamin A RAE||1643 mcg||1730 mcg|
|Vitamin E||1.0 mg||1.28 mg|
|Vitamin C||34.0 mg||35.28 mg|
|Thiamin (B1)||0.21 mg||0.19 mg|
|Riboflavin (B2)||0.07 mg||0.19 mg|
|Niacin (B3)||0.97 mg||2.68 mg|
|Folate||10.26 mcg||10.80 mcg|
|Vitamin B6||0.49 mg||0.51 mg|
|Vitamin B12||0 mcg||0 mg|
|Calcium||58.0 mg||68.40 mg|
|Iron||1.0 mg||1.24 mg|
|Magnesium||29.0 mg||48.60 mg|
|Phosphorus||55.0 mg||97.20 mg|
|Zinc||1.0 mg||0.58 mg|
|Potassium||812 mg||855.0 mg|
|Sodium||22.0 mg||64.80 mg|
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.
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.
For this reason, some individuals may be following medically-supervised low-oxalate diets.
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.
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.