Updated: Jan 28
We are sure you have all heard that sweet potatoes are healthier than regular potatoes but what most people don’t know is that in the depth of the produce section may lie an even better choice. Introducing the purple sweet potato, the orange sweet potatoes’ polyphenol packed cousin, slightly harder to find (although many shops and supermarkets now sell them)but the extra effort to find them is worth it. In this article you will find out where they come from, why they are so good and how to cook them.
What Are They?
Despite their name, purple sweet potatoes are not the same as regular potatoes. They are from a different family altogether. The potato is part of the Solanacaea, or nightshade family, whereas the purple sweet potato varieties are part of the Dioscoreaceae family. It is worth considering that some people experience side-effects when eating nightshades. (1)
Below is a list of purple sweet potato varieties:
Stokes Purple® Sweet Potato - Originating in Stokes county, North Carolina, this variety is the most likely to be found in supermarket shelves in the Western hemisphere. From the outside they look like a normal sweet potato but the flesh inside is a beautiful, deep purple. The flavour is much less sweet and has a subtle chocolate quality to it. The Stokes purple® variety also packs the biggest antioxidant and polyphenol punch than others.
Okinawan Sweet Potato - Many believe the Okinawan sweet potato was brought to Okinawa from Aztec South America via the Phillipines and China, where they were initially cultivated and later spread throughout the rest of Japan. Since then, they found their way to Hawaii where they became a staple in their diet. The skin is light in colour and the flesh is not as dark as the Stokes® variety; more of a lavender than a deep purple. Their flavour is said to be subtle and slightly sweet.
Purple Yam (Ube) - These are not sweet potatoes. They are “true yams” in that they grow on a vine, whereas Stokes Purple® and Okinawan varieties grow underground. Their skin is brown and rough and their flesh is white/violet with flecks of purple. Ube is a staple of the Filipino kitchen and difficult to find in the West. Its flavour has been described as “an amalgamation of vanilla with the nuttiness of pistachio”.
What Makes Them So Great?
Their deep purple colour is attributed to the high amounts of anthocyanins (a potent antioxidant which has been linked to a reduced risk of cancer) present in their flesh. Anthocyanins may also help reduce inflammation in the body - chronic inflammation is hypothesised to be the root cause of most common diseases.
Another important phytochemical is chlorogenic acid. Chlorogenic acid is found in purple sweet potatoes, coffee and prunes and has been shown to reduce blood pressure. Purple sweet potatoes can also help lower blood pressure due to their high potassium content.
Furthermore, they are fibrous. The average adult in the Western world does not consume enough fibre which can lead to gastrointestinal problems. Purple sweet potatoes contain adequate amounts of fibre which may improve digestion. In addition, humans can create resistant starch by cooking then cooling them before eating. Resistant starch is a prebiotic fibre which cannot be digested; it passes through to the intestines for our healthy gut bacteria to feed on.
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Stokes purple sweet potato - 100g
Calories - 155Kcal
Total Fat - 0g
Total Carbohydrate - 26g
Sugar - 4g
Fibre - 4g
Protein - 2g
Sodium - 0mg
Potassium - 297mg
Vitamin C - 18%
Iron - 5%
Calcium - 4%
Purple sweet potatoes can be steamed, baked, boiled or fried. If you choose to boil them, the water you used will contain most of the antioxidants so remember to drink or use the liquid (yes, we are being serious). We enjoy steaming them because it is the simplest option which preserves the valuable nutrients and tastes incredible, however, our favourite method of cooking is to roast them quickly under the grill with some coconut oil, pink Himalayan salt and black pepper:
1. Preheat the grill on its highest setting.
2. Wash and scrub the purple sweet potatoes, then cut them into 1cm thick slices or strips.
3. Place 1 tsp coconut oil onto a baking tray (if your coconut oil is not runny, place 1 tsp onto a baking tray and put it in the oven for a few seconds to melt).
4. Place the purple sweet potato slices face down onto a baking tray and move them around to coat both sides with coconut oil. Season with ground black pepper and pink Himalayan salt.
5. Place under the grill for 10-15 minutes until fork-tender, turning half-way through.
A note on sweet potato skins: if you are having sweet potatoes regularly (any variety), it might be a good idea to alternate between peeling them and leaving the skin on. While the skin of regular potatoes is toxic, sweet potato skins are generally considered safe to eat and research shows that the skin of purple sweet potatoes contains the most anthocyanins (1). There is a debate on pesticides and fungi/toxins found on the skins, so err on the side of caution and alternate between eating them with and without the skins.
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ABOUT THE AUTHORS
John Maitland is the co-founder of 'The Evolved Way.’ A personal trainer with over 10 years’ experience, he has worked alongside a wide range of leading CEOs, entrepreneurs and medical professionals. John is a keen athlete and holds a black belt in Shaolin Kung fu. A fan of the great outdoors, he can often be found exploring the British countryside and mountains...or breaking pine boards with his fingers.
Co-founder of 'The Evolved Way', and experienced personal trainer, Samson practices what he preaches. His own healthy lifestyle, which informs this site, is based on understanding the right way to eat and exercise, not excluding of course going out and enjoying life knowing you can still feel and look good.