Purple Sweet Potato vs Purple Yam: What’s The Difference?

Purple yams and purple sweet potatoes are often mistaken for one another and are mistakenly referred to as “yams.” There are similarities and differences leading many people to ask, what’s the difference between a purple sweet potato and purple yam?

Purple sweet potatoes and purple yams are distinct types of vegetables. Purple sweet potatoes grow underground as tubers while purple yams grow underground also from a vine plant above ground. Purple yams taste sweeter than purple sweet potatoes and are more difficult to find in the United States.

This article includes a side-by-side nutrient comparison. In addition, I’ll discuss their tastes, textures, culinary differences, costs and whether one can substitute for the other. Then I’ll examine their health benefits and if one is easy to store than the other.

As a Certified Health Coach I’m asked about both foods often. In addition to coaching clients about them, I’ve purchased, researched and consumed both prior to, during and sometimes after writing this article.

Is Purple Yam and Purple Sweet Potatoes The Same?

Purple sweet potatoes and purple yams are not the same. The narrower purple yams have a brown-reddish colored skin with a light purple flesh. Purple sweet potatoes have a beige outer skin with a blue-purple flesh. Purple yams are a species of yam native to South East Asia while purple sweet potatoes are native to Polynesia and South America.

First, let’s take a look at each one individually.

Yams

Also known as ube, the purple yam is a distinct species of yam native to South East Asia. They grow as a tuber underground. Above ground the vined plant can grow rapidly and long. They have a sweet and nutty flavor with hints of vanilla and pistachio.

Ube is high in vitamin C, antioxidants, and resistant starch. A yam, in general, is a good source of beta carotene, although the purple variants contain less than orange variants. The purple yam is also relatively high in anthocyanin, an antioxidant that gives it its purple color.

Yams are actually more like cassava than sweet potatoes. We’ll discuss nutritional details and taste comparisons more in-depth later in this article.

Sweet Potato

There are many different varieties of sweet potato with purple color. Depending on the region you live in, the ones you find at your local store could be from one out of a dozen different varieties. The species most common in the United States is Ipomoea batatas, which grows in many different colors.

They are native to Polynesia and South America and are a good source of beta carotene like the purple yam. Also, the purple coloration comes from the anthocyanin content.

This type of sweet potato is high in oligosaccharides, which are prebiotics promoting healthy gut flora.

There are two main common variations.

Okinawan Sweet

Okinawan sweet originated in Central and South America but are locally grown in Hawaii. Okinawan sweet has white skin with deep purple flesh. Although they have a bluish-purple color, their texture is dry and starchy with a mildly sweet and bitter aftertaste.
The purple Okinawan sweet potato is grown underground.

Stokes Purple

Stokes purple was initially native to North Carolina but is grown commercially in Central California. This sweet potato has purple skin and flesh, a moist and starchy texture and a mildly sweet floral taste. Available year-round, these sweet potatoes have purple-tinted skin with a deep purple flesh that intensifies when cooked.

Botanical Differences

Dioscorea alata, or purple yam, grows underground like sweet potatoes. They are considered an invasive species in the southern US.

Purple yams contain the toxin dioscorine and must be thoroughly cooked to make them suitable for human consumption. Dioscorine, a neurotoxin, can cause nausea, dizziness, and vomiting in small doses, and convulsions or other serious side effects in large quantities.

Notably, many cultivars are sterile, so wild dispersal of the fruit is uncommon. Accordingly, they are indicators of ancient human migration used by evolutionary biologists and anthropologists.

On the other hand, purple sweet potatoes come in many different varieties depending on the region in which they are found. Some varieties are cultivated extensively in the US, whereas others are native to South East Asia.

The purple sweet potato gets its bright coloration from the antioxidant anthocyanin. This is the same chemical responsible for the red/purple coloration in red wine and red cabbage.

Taste and Texture: Are They Sweet?

Since they are grown differently and come from different areas of the world, one would think they taste different. Let’s examine the taste and texture of a purple sweet potato and purple yam.

Purple sweet potato has a rich taste, almost wine-like flavor with a creamy texture. Purple yam is sweeter and nuttier. Both are starchy and dry.

The purple yam has a sweet and nutty flavor with hints of vanilla and pistachio. The texture is soft like a potato when cooked. If you like your potatoes sweet, this makes a good alternative.

Purple sweet potatoes have a rich taste with a wine-like flavor. The texture is dry but slightly creamy.

Substitutions

Purple yams may be difficult to find in the supermarket. Therefore, they may be unavailable for a recipe. For this reason, many people wonder if they can substitute one for the other in a recipe.

Purple sweet potatoes and purple yams can substitute for each other in recipes due to their similar tastes and textures. They can both be boiled, steamed, baked, fried, shredded, roasted or made into chips. Substitute them with equal quantities.

How to Cook

Purple yams can be cooked similar to the way sweet potatoes are cooked and used in the same traditional recipes.

In the Philippines, they are used to make purple jam by blending it with evaporated milk, coconut milk, condensed milk and sugar. The recipe mixture is simmered for about 45 minutes. If you prefer your food fast, this will take a little while.

The mixture is added to the following recipes:

Custards
Cheesecakes
Ice cream
Parfaits
Anything to add a bright color.

Purple sweet potatoes can be cooked similar to regular sweet or white potatoes. They can be used for the following recipes:

Boiled
Baked
Steamed
Mashed
Fries

They require a longer cooking time than orange sweet potatoes so keep this in mind when preparing your recipe.

Find out how the the regular types of each compared in my article.

Costs

With the rising prices of just about everything lately, the cost of something certainly matters to most people. The price may sway your decision about which food to use. Therefore, let’s examine which one costs more.

Purple yams cost more than purple sweet potatoes. The average price for purple sweet potatoes is $0.99 per pound. The average price for purple yams is $13.73 per pound.

In the United States, it is rare to find fresh purple yams. Purple sweet potatoes, however, are readily available and cheap to acquire. In South East Asia, it may be easier and cheaper to get purple yams.

To conduct original research, I visited local supermarkets and searched online for their prices. I was only able to find purple yams on Amazon. Jams made with them were more available, and I found those in most stores.

I first visited the Shoprite supermarket:

Purple sweet potatoes
- $2.99 per pound

I also checked Walmart and only found regular sweet potatoes.

I then checked a specialty store (Friedas) and found the following price:

Purple sweet potatoes
- $4.00 per pound

I then checked Amazon and found the following price:

Purple yam
- $13.73 per pound

View the following video below and learn how to make an easy Ube recipe.

How To Store

Whichever you choose or have on hand, properly storing them is important. How you store them can affect their quality and how long they last before going bad. Therefore, let’s examine how to store each one.

Store purple yams and purple sweet potatoes in a dark, cool place away from heat and do not store either in the refrigerator. A humid basement or root cellar is the best area. They should be kept in a burlap bag or ventilated container and stored between 40°F and 60°F.

Storing them in a refrigerator can make the center hard and change the cell structure. This can diminish the flavor. If you don’t have a cool basement, store them in a ventilated place, away from heat and light.

Don’t wash either one before storing them. The moisture will promote the growth of bacteria and fungus¹.

Humid storage locations are best for them because they are 80% water and can dry out if stored in a drier place. Commercial potato storage facilities are set at 90 to 95% relative humidity².

Glycemic Index

Knowing the glycemic index is important especially if blood sugar levels are a concern. Avoiding blood sugar spikes is an important thing people should be aware of, diabetic or not.

The Glycemic Index (GI) is a scale measuring how fast a particular food raises the blood sugar in the blood³. Blood sugar spikes can lead to health complications with the kidneys, nerves, heart and eyes⁴.

Foods on the GI scale are categorized as:

Low-GI foods: 55 or under
Medium-GI foods: 56-69
High-GI foods: 70 or over

How blood sugars levels are affected:

Foods with a glycemic index 70 or more cause a quicker spike in blood sugar levels.
Foods with a glycemic index 56 to 69 cause a moderate spike in blood sugar levels.
Foods with a glycemic index 55 or less cause a slow spike in blood sugar levels.

Now we know what GI is, and how it affects blood sugar, let’s find out which of the two has a better GI score.

Purple sweet potatoes and purple yams have a moderate glycemic index depending on the cooking method used.

Find out how turnips compared in my article, Turnip vs. Potato: What’s The Difference? Let’s Compare.

Nutrition Value of Purple Sweet Potatoes and Yams

Any meaningful discussion about health benefits must start with reviewing nutritional information. Therefore, let’s quickly look at the nutrient content.

Here’s a table of the nutritional contents of a 100-gram (3.5 ounce) serving of raw purple sweet potato and purple yam.

	Purple Sweet Potato (100 g)	Purple Yam (100 g)
Calories	85	120
Protein	1.54 g	1.00 g
Carbohydrates	20.0 g	27.0 g
Fiber	3.1 g	4.0 g
Fat	0.1 g	0.1 g
Sugar	3.85 g	0 g
Vitamin C	10.9 mg	12.0 mg
Potassium	337 mg	611 mg
Iron	0.62 mg	0.36 mg
Calcium	30 mg	20 mg

Nutrient Resources Trusted Source⁵⁶⁷

Purple sweet potatoes contain fewer calories and carbohydrates. They provide more protein, iron and calcium. Purple yams provide more fiber, vitamin C and potassium.

Both have similar nutrients and are considered healthy. There’s not much of a difference between the two and most people can’t go wrong choosing either one.

Find out how white sweet potatoes compared to sweet potatoes in my article, White Sweet Potato vs. Sweet Potato: What’s The Difference?

Health Benefits

A yam, in general, is a good source of beta carotene, although the purple variants contain less than orange variants. It is also relatively high in anthocyanin, an antioxidant that gives it its deep color.

Purple sweet potatoes are rich in anthocyanins. As mentioned earlier, anthocyanins are the pigments that give red, purple, and blue fruits, plants and vegetables their rich coloring and provide anti-inflammatory benefits.

The Immune System

According to Harvard University, vitamin A is a great source to stimulate healthy white blood cells⁸. These cells have the responsibility of keeping the immune system as healthy as possible to fight viruses and illnesses effectively.

The purple sweet potato provides 10.9 mg of vitamin C compared to 12.0 mg for purple yams. The body can’t make vitamin C, so it must come from the foods ate every day. Vitamin C has been shown in studies to help with the growth and repair of tissues throughout the body⁹.

Vitamin C helps heal and repair wounds, maintain healthy bones, skin and cartilage. Vitamin C acts as an antioxidant and fights free radicals which damage the cells. Helping to prevent cell damage can help with the following:

Certain diseases like cancer.
Heart disease.
Promote healthy aging.

Heart Health and Blood Pressure

Both foods benefit the heart in several ways. One reason is due to the vitamin C. This vitamin helps lower blood pressure in individuals with elevated blood pressure levels and those without¹⁰.

Vitamin C also helps check several risk factors of heart disease, including the following:

High blood pressure.
High levels of “bad” cholesterol.
Low “good” cholesterol levels.

By reducing these risk factors, it helps reduce your chances of developing heart disease.

The effectiveness of Vitamin C in reducing the risk of heart disease is well documented in various studies. For instance, a review of 9 scientific studies with almost 300,000 participants established maintaining a daily consumption of at least 700 mg of vitamin C for ten years lowers the risk of heart disease by 25%¹¹.

They both contain the following nutrients beneficial for blood pressure:

Potassium
Magnesium
Vitamin C
Calcium

Let’s take a look at each one of these minerals and how they benefit blood pressure. Vitamin C was already discussed earlier.

Magnesium

Magnesium helps keep blood pressure levels stable and balanced. Recent scientific research examined previous studies and concluded magnesium supplementation decreased systolic and diastolic blood pressure¹².

Magnesium helps control the following:

Blood pressure
Blood sugar
Insomnia
Muscle
Nerve function

One reason many people supplement with magnesium in the evening is because it helps calm the whole body including blood vessels.

In the heart and muscles, magnesium competes with calcium to help the muscles relax after contracting. When the body is low in magnesium, calcium can over stimulate the heart muscle’s cells causing a rapid or irregular heartbeat ((National Institutes of Health: Magnesium)).

Potassium

Potassium helps the body get rid of excess sodium reducing fluid build-up. These help keep systolic and diastolic blood pressure lower ((American Heart Association: How Potassium Can Help Control High Blood Pressure)).

According to Harvard Health, a number of studies have shown a connection between low potassium levels and high blood pressure¹³.

The more potassium, the more sodium your body will lose. Consuming too much sodium or not enough potassium throws off the delicate balance the kidneys need to remove the excess water¹⁴.

Calcium

Calcium is important for the heart and blood pressure. Harvard Health reports calcium helps maintain blood pressure by helping in the controlling of the relaxing and tightening of blood vessels¹⁵.

Calcium also helps the following:

Helps nerve function.
Helps muscles function properly.
Build and maintain strong bones.

Digestion and Gut Health

Both foods contain soluble and insoluble fiber. Fiber remains in the digestive tract and provides gut related health benefits. Fiber rich diets have been linked to regular bowel movements and a lower risk of colon cancer¹⁶.

If you’re interested about how pumpkin compared for health and nutrition, check out my article here.