Murasaki from Japan
Given that the Japanese have a well earned reputation for longevity, it is always interesting to take a look at their diets. When compared with the traditional Western and American diet, the Japanese people have much less fondness for all things sweet. And let’s face it, we do tend to overdo it in the sugar stakes.
For example, these days it is nigh on impossible to get hold of a dried berry in American grocery stores that has not been sweetened further with unnecessary sugar. Even products which are marketed as ‘healthy’ like protein bars have more often than not been sweetened with the addition of some type of sugar.
Having said that, the Japanese diet is not always as healthy as we would assume and they are not immune to the curse of the sweet tooth. They also have a tendency to peel their fruit which also cuts off much of the nutritional value and plenty of the antioxidant potential.
Of course, this article has nothing to do with fruit but a Japanese variety of sweet potato called murasaki. While considerably healthier than the traditional western spud, it may offer further proof that the Japanese diet is not quite the picture of perfect health that we have been told.
What is Murasaki?
Murasaki is a white variety of sweet potato grown in Japan. In order to evaluate its health benefits, it is necessary to compare murasaki sweet potatoes with the traditional orange yams that you are used to eating and also the purple Okinawan variety.
You have probably heard of Okinawa before. It is famed for the longevity of its inhabitants and is one of only five so called Blue Zones in the world where a third or more of the population survive into their 90s.
Okinawa is not a part of mainland Japan but an island some 600 kilometers south. Up until very recently, Okinawa could boast the highest life expectancy in the entire world. A fascinating fact here is that a whopping 70% of the former Okinawan diet consisted of the Okinawan purple sweet potato.
Those figures likely tell you without going any further that those purple yams are more than a little bit good for you. So how does the murasaki potato compare?
Murasaki Nutritional Value
When it comes to the white fleshed variety of sweet potato like murasaki, they vary very little in terms of appearance and taste and their nutritional value is nearly identical. Being that we are more familiar with the orange fleshed variety of sweet potato in the West, let us use that as a marker to compare the two.
For the Comparison, one serving equates to 130 grams or one medium sized potato.
- Calories are almost identical with the murasaki containing 120 calories compared to the orange sweet potato’s 112.
- Both have four grams of dietary fiber representing 16% of your recommended daily value.
- Both contain near identical amounts of carbohydrates with 26 grams and 25 grams respectively.
- The murasaki contains considerably more potassium. (620 mg compared with 438
- Murasaki is higher in both vitamin A and vitamin C. In fact, murasaki contains 40% vitamin C compared to 5% in the regular orange variety.
How do Murasaki Sweet Potatoes Taste?
The murasaki sweet potato has a very different flavor, texture and appearance compared with the regular orange yam. The taste of the murasaki is very different to the orange variety and has been compared with the taste of chestnuts.
The murasaki has a much creamier texture and less noticeable fibrous strings. The murasaki is pure white on the inside despite having a much darker purple or brown colored skin.
By comparison, the Okinawa sweet potato is less creamy but has a sweeter, fruitier taste.
Antioxidant Value Compared
When it comes to the antioxidant value of various sweet potatoes, the murasaki does not fare well at all. It appears that purple colored potatoes contain far more antioxidants than the pure white variety like the murasaki.
In a comparative study conducted by Sydney University between the murasaki, purple fleshed sweet potatoes and the regular orange variety, the purple kind comes out on top by a country mile. That is because the more purple the flesh, the more cyanidin and peonidin the food possesses. These compounds are a type of anthocyanin which are a very powerful class of antioxidant.
Because of the absence of pigments in the flesh, the murasaki contains very few antioxidants. While raw purple sweet potatoes are valued at 2720 on the ORAC scale, the murasaki only rates a 272. Even the regular orange sweet potato that we all know and love comes in several fold higher at 902.
While ORAC values are not the be all and end all, this is pretty good evidence that the murasaki is far from your healthiest choice of sweet potato.
Glycemic Index Compared
When it comes to another important health consideration, the glycemic impact, the murasaki does not fare especially well again even when set against other types of sweet potato.
According to research, the murasaki contains a whopping 60% or so more sugar than a regular orange fleshed sweet potato. The fact that murasaki has such a creamy, smooth consistency would make one suspicious that it is absorbed faster thus having a much greater impact on blood glucose levels.
The testing done by Australia’s Sydney University certainly confirms this.
The glycemic index results from the research are based on a serving of 150 grams of sweet potato. Which was prepared by boiling them for some 8 minutes.
Orange sweet potatoes have a glycemic index of 61 and a glycemic load of 11 while murasaki has a higher glycemic index of 75 and a significantly higher glycemic load of 22.
The way in which the sweet potatoes are prepared has a significant impact on these figures. If you were to bake them instead of boiling, you could expect to see a glycemic index for the murasaki of around 90. To put that in perspective, it is higher even than instant mashed spuds which have a GI of 87.
Although a food’s glycemic index is valuable to be aware of, it is the glycemic load which is regarded by experts as the best indicator of blood glucose impact. As you can see from the figures above, the murasaki has double the glycemic load of the regular orange type even when the vegetables were boiled.
To Sum Things Up
Despite the fact that the murasaki contains a very good amount of vitamin A and vitamin C as well as being a good source of potassium and dietary fiber, they are certainly not the best choice of sweet potato.
Of course, your choice of food does not always depend on ORAC values and other health considerations. The murasaki has a delicious, nutty flavor and a creaminess lacking in other varieties. It is also a much healthier option than your common spud and you will probably enjoy its flavor.
Nevertheless, if you are choosing between various sweet potatoes and are indeed concerned about their impact on your health, it is impossible to recommend the murasaki. You are better off going with a purple fleshed sweet potato which contains far more antioxidants and is far less likely to send your blood sugar spiralling out of control.