When I was a kid growing up in British Columbia, my kale and turnip-loving parents didn’t feed us processed sugar of any kind.
But once in a while, on a special occasion, we’d have sweet potatoes. When they were baking in the oven, our tiny cabin would fill with warmth (which was its own special treat, especially in the Canadian winter!) and the exquisite smell of sweet-potatoey goodness.
Clearly, I’m extremely fond of sweet potatoes. So when I decided to write an article about them, I had to check all my happy memories at the keyboard and look at the evidence.
Are sweet potatoes good for you? Are there any sweet potato health benefits? Where do they come from?
How can we prepare them, aside from in holiday casseroles and pies? And most confusing of all (to almost everyone), what’s the difference between sweet potatoes and yams?
Meet the Sweet Potato
Sweet potatoes (Ipomoea batatas) are large, starchy, sweet-tasting vegetables. They actually belong to the morning glory family.
Despite the shared name, sweet potatoes are only distantly related to the potatoes used to make French fries or potato chips. Non-sweet potatoes (including red, white, and Yukon gold varieties) are part of the edible nightshade family. Other members include tomatoes, tomatillos, eggplants, peppers, pimentos, and Goji berries.
Sweet potatoes are root tubers. Other root tubers include beets, carrots, parsnips, celeriac, and turnips. Root tubers store water and energy, like starch and other carbohydrates, underground. They draw upon these resources to feed the aboveground parts of the plant.
The Origin of the Sweet Potato
Sweet potatoes are some of the oldest foods known to humanity.
They are native to Central and South America. We have fossil evidence that sweet potatoes were growing in the Americas 35 million years ago. But very recently, scientists discovered 57-million-year-old leaf fossils in India that appear to be ancient morning glory leaves. This could beat the American claim as the point of origin of the sweet potato family by about 22 million years.
Wherever and whenever they originated, and however they have traveled the globe, I’m incredibly thankful that most of us have sweet potatoes in our lives today.
What’s the Difference Between a Sweet Potato and a Yam?
People often mistakenly refer to sweet potatoes as “yams.” But these two plants aren’t actually related at all.
Yams are related to grasses and lilies and native to Africa and Asia. They’re usually cylindrical with black or brown, rough, bark-like skin, and white, purple, or red flesh. Sweet potatoes have characteristic tapered ends with smoother skin.
You can find sweet potatoes at just about any grocery store. However, in North America and Europe, you will only find true yams stocked at international and specialty markets.
You might be thinking, “but I see yams at my grocery store all the time” — and you’d be right that they’re labeled that way. But this label is deceiving.
There are actually two types of sweet potatoes in most mainstream produce sections: firm and soft. Grocers needed a way to differentiate between the two types. The soft kind, which includes the Garnet and Jewel varieties, resemble yams. This is how they picked up the false name.
How Many Sweet Potato Varieties Exist?
While most supermarkets carry one or two different types of sweet potatoes, about 25 varieties are available in the United States. And I was amazed to discover that this represents only a tiny fraction of the total diversity of sweet potatoes.
The sweet potato geeks of the world may be fascinated to know that the International Potato Center in Peru maintains a gene bank consisting of over 6,500 varieties of sweet potato. I don’t know about you, but personally, I wish I could try them all!
Sweet potato varieties range in color from dark red to brown to purple to orange-yellow to white. They also have different tastes, sizes, shapes, and textures.
Here are Just a Few of the Most Popular Types of Sweet Potatoes:
- Garnet, Jewel, and Beauregard sweet potatoes have reddish-orange skin and deep orange flesh. These are often the ones masquerading as yams at mainstream grocery stores. Who knew sweet potatoes could be so sneaky?
- White sweet potatoes are crumbly, with white flesh and golden brown skin. They don’t contain as many antioxidants as orange varieties.
- Okinawan sweet potatoes are also known as purple sweet potatoes because of their high anthocyanin content. Anthocyanins are the pigments that give red, blue, and violet plant foods their beautiful colors. Anthocyanins are also what give Okinawan potatoes 150% more antioxidant power than blueberries.Despite their name, Okinawan potatoes are actually native to the Americas. They were brought over to Japan sometime in the 16th century, where they grow well and have become a staple in Japanese dishes. In North America, you will most likely find true purple sweet potatoes in an Asian supermarket.
- Japanese or Satsumaimo sweet potatoes are known for being sweeter than most other types. This is especially true when they start caramelizing in the oven.
Sweet potatoes are very hardy vegetables. They’re able to grow at many altitudes, in many climates, and under compromised soil conditions. Even if you don’t have the greenest of thumbs, sweet potatoes are pretty forgiving with just a little TLC.
What Makes a Sweet Potato Sweet?
Have you ever smelled a sweet potato caramelize in the oven or used them to make a pie or a cake?
If so, you know that even though they aren’t related to what we think of as potatoes, at least the “sweet” part of their name is entirely appropriate.
When you heat sweet potatoes, an enzyme starts breaking down their starch into a sugar called maltose. Maltose isn’t as sweet as table sugar. But it’s enough to satisfy a sweet tooth that hasn’t been entirely overwhelmed by M&M’s and Hershey’s Kisses.
You can control the sweetness of sweet potatoes somewhat by how you cook them. Cooking sweet potatoes quickly (for instance, by steaming them or cutting them into smaller pieces before roasting) can reduce their ultimate sweetness.
On the other hand, cooking sweet potatoes slowly on low heat will allow that maltose-making enzyme more time to convert the starch into sugar — giving you sweeter sweet potatoes.
Looking for even more control over the sweetness? The sweet potato enzyme is activated once they reach around 135°F and stops working at around 170°F. (That’s 57° to 77°C). So the more time they spend in that range, the sweeter they’ll be.
Are Sweet Potatoes Good for You?
The people of Okinawa, Japan have traditionally enjoyed one of the highest life expectancies in the world. I discovered this when my dad was researching his book Healthy at 100: The Scientifically Proven Secrets of the World’s Healthiest and Longest-Lived Peoples.
One of those secrets, it turns out, is lots and lots of sweet potatoes. The traditional Okinawan diet consists of minimal meat, dairy, eggs, and processed foods. Instead, they eat mostly whole plant foods. And they get a remarkable 60% of their calories from sweet potatoes alone.
It’s partly because of this high-fiber and antioxidant-rich dietary pattern that Okinawans enjoy such a long lifespan. Living to be one hundred years or older is not uncommon in Okinawa. Okinawans also experience less chronic disease than Americans do — with significantly fewer deaths from heart disease and cancers of the colon, breast, and prostate.
Traditional Papua New Guinea Highlanders have also been known to eat a lot of sweet potatoes. In fact, tubers like sweet potatoes and yams provide 90% of their calories!
They don’t eat much, if any, meat either. How has a sweet potato-based diet affected their health?
A study published in the Journal of Internal Medicine in 1994 found that, when these native groups still followed this traditional way of eating, they enjoyed lower blood pressure and weight than Westerners. And they almost never experienced heart disease, strokes, or other modern chronic diseases.
So are sweet potatoes good for you? Yes, they are!
What makes them so good for you?
Sweet Potato Nutrition
Sweet potatoes are high in fiber, vitamin C, potassium, pantothenic acid (vitamin B5), niacin (vitamin B3), vitamin B6, manganese, magnesium, and copper.
When compared to white potatoes, sweet potatoes offer more vitamins and antioxidants. Surprisingly, considering their sweeter taste, they also have a mildly lower glycemic index score. This makes them slower to digest.
But the greatest sweet potato nutritional glory of all may be its rich supply of vitamin A. A single sweet potato offers over double the daily value for vitamin A.
Sweet Potatoes Are Remarkably High in Vitamin A
Worldwide, vitamin A deficiency is the leading cause of preventable blindness in children. An estimated 250,000 to 500,000 children become blind every year due to a lack of this critical nutrient. Half of these children die within a year of losing their sight.
Hoping to solve this problem (and with perhaps a few other less noble motives in the mix), over the last several decades, biotechnology companies, governments, foundations, and scientists have spent hundreds of millions of dollars attempting to develop and popularize “golden rice.”
This is a form of rice that’s been genetically engineered to provide beta-carotene (a precursor to vitamin A). Despite decades of effort, the product still hasn’t reached the market.
How ironic that this same effort could have gotten sweet potatoes and the means to grow them into the hands of most of the impoverished families now suffering from vitamin A deficiency. Of course, that wouldn’t have made biotech company, Syngenta, any money. But it would have helped a whole lot more people than golden rice ever has, and most likely, ever will.
News flash: The biotech industry and its supporters have long promoted GMO golden rice as an urgently needed solution to vitamin A deficiency. But in late 2018, in a surprising twist, the US Food and Drug Administration (FDA) concluded its consultation process on golden rice by informing the current developers, the International Rice Research Institute (IRRI), that golden rice does not meet the nutritional requirements to make a health claim.
In effect, the FDA was saying that GMO golden rice offers no meaningful nutritional benefits.
Which again raises the question: How much better off would people be if the hundreds of millions of dollars spent on developing golden rice had instead been used to support the growth of sweet potatoes, carrots, and other vitamin A-rich vegetables in parts of the world where vitamin A deficiencies are a problem?
10 Incredible Sweet Potato Health Benefits
The unique nutritional profile of sweet potatoes makes them powerful allies in preventing disease and supporting overall health.
Here are some health benefits of adding sweet potatoes to your diet.
Sweet Potato Health Benefit #1: They Support Digestive Health
Sweet Potato Health Benefit #2: They Keep Your Heart Healthy
The high fiber content of sweet potatoes can lower LDL (bad) cholesterol levels, helping to prevent cardiovascular disease.
Sweet potatoes are also high in potassium, which works in balance with sodium in your body to maintain healthy blood pressure.
They’re also high in copper, an essential metal for making red blood cells and keeping your heart healthy. Low levels of copper have been linked to dangerously high homocysteine, blood pressure, and LDL cholesterol levels.
Sweet Potato Health Benefit #3: They Help Stabilize Blood Sugar
The fiber and complex carbohydrates in sweet potatoes can help keep your blood sugar stable. And it can help you feel full longer. Sweet potato varieties also contain other substances that benefit stable blood sugar.
A 2004 study published in Diabetes Care successfully used Caiapo, an extract from white sweet potatoes, to naturally reduce and manage blood glucose in people with type 2 diabetes.
The 30 participants who were given 4 grams of Caiapo every day for 12 weeks saw a decrease in their HbA(1c) (going from 7.21 to 6.68), fasting blood glucose (143.7 vs. 128.5), and two-hour blood glucose (193.3 vs.162.8). The 31 participants who were given a placebo instead saw no such results.
Sweet Potato Health Benefit #4: They Can Boost Your Immunity
Sweet potatoes are rich in antioxidants that prevent free radical damage in your body.
One cup of baked sweet potato contains 52% of your daily value for vitamin C, which is important for wound healing and tissue repair.
Sweet Potato Health Benefit #5: They Are Good for Your Eyes
Sweet potatoes contain several nutrients that have been linked to improved eye health and vision. Some of the most powerful are the carotenoids. They include alpha-carotene, beta-carotene, lutein, and zeaxanthin.
Beta-carotene, when taken as a supplement in isolation from the other carotenoids, can cause imbalances. But when eaten in foods, where it is always accompanied by, and in balance with, an entire suite of carotenoids, it’s been shown to have powerful anti-cancer and vision-enhancing properties.
Orange sweet potatoes (as well as other orange plants, including carrots) have particularly high concentrations of carotenoids.
It’s not just the orange sweet potatoes that are good for your vision, though. A class of anthocyanins called PSPA, derived from purple sweet potato roots, might also benefit your eyes.
A study published in Food & Nutrition Research in 2015 looked at whether PSPA could influence the health and growth of human retinal pigment epithelial (RPE) cells.
Why does this matter? The RPE is responsible for helping your eyes absorb light. It also directs immune response when faced with a threat to eye health. The researchers found that PSPA promoted DNA synthesis and healthy RPE cell growth and survival. They concluded that PSPA could potentially find use as a supplement for maintaining healthy vision.
Sweet Potato Health Benefit #6: They Fuel Your Brain
Sweet potatoes also contain compounds that help your brain function at its best, including choline and manganese.
Choline is an essential nutrient for brain growth and development, as well as the synthesis of the neurotransmitter acetylcholine that sends messages between cells.
Manganese is also important for brain health. It binds to neurotransmitters and helps move electrical impulses through your body faster. You can find 43% of your daily value of manganese in one cup of baked sweet potato.
The anthocyanins unique to purple sweet potatoes may also have memory-enhancing properties.
Sweet Potato Health Benefit #7: They Can Help Ease Stress and Anxiety
Sweet potatoes may help you relax. They’re high in magnesium, which has been shown to play a role in calming the brain. Magnesium deficiency has been linked to depression, mood disturbances, and headaches.
Other good sources of magnesium include avocados, legumes, tofu, nuts, seeds, and leafy greens.
(I’m dreaming right now of a loaded baked sweet potato piled high with a soft nut cheeze, avocado, a drizzle of flax oil, and a sprinkle of seasoning. It’s also accompanied by some freshly steamed and piping hot leafy greens for a delicious, magnesium-rich meal.)
Sweet Potato Health Benefit #8: They Can Help Boost Fertility
Vitamin A is an essential nutrient for healthy reproduction. And as we know, sweet potatoes are a fantastic source.
Sweet potatoes also offer a rich supply of iron, which has also been shown to be important in supporting fertility.
Sweet Potato Health Benefit #9: They Can Help Fight Cancer
Sweet potatoes are a rich source of cancer-fighting antioxidants, especially in their skin. They have other anti-cancer properties, too.
Up to 80% of the protein in sweet potatoes is a type of storage protein known as sporamin. This unique protein has been studied for anti-cancer ability and found to be effective in several disease types.
Research has been promising in the use of sporamin to inhibit tongue, gallbladder, and colorectal cancers. It has also been shown capable of slowing cancer cell growth and reducing cell migration and invasion in metastatic cancers.
Sweet potato peels, particularly those of the purple varieties, may be especially powerful when it comes to cancer prevention.
A study published in Nutrition and Cancer in 2016 looked at the antioxidant and anti-cancer effects of an extract from sweet potato peels. They found promising anti-cancer activity for cancers of the breast, colon, ovary, lung, and head/neck.
Sweet Potato Health Benefit #10: They Have Anti-Inflammatory Effects
Eating sweet potatoes may also help reduce inflammation.
This is chiefly due to their high levels of beta-carotene, vitamin C, and magnesium. Their abundance of antioxidants doesn’t hurt here, either.
One of the particular antioxidants that’s found most abundantly in purple sweet potato flesh is cyanidin. Cyanidin has been linked to reducing inflammation, especially in the digestive tract.
Sweeten Your Health with Sweet Potatoes
Fiber, complex carbohydrates, vitamins, and minerals are essential for good health. And sweet potatoes are a fantastic way to add them to your diet.
Many of us have ancestors who reaped their benefits for a very long time, and there’s certainly no need to stop now. Luckily, sweet potatoes are affordable, easy to use and store, and available in many parts of the world all year long.
Sounds pretty sweet to me!
Tell us in the comments:
Did any of the sweet potato health benefits surprise you?
Will you eat more sweet potatoes now?
What’s your favorite way to enjoy sweet potatoes?
Featured Image: iStock.com/zeleno