Did you know that regular potatoes and sweet potatoes range from low to high glycemic depending on how they're cooked and other factors? Let's look into those factors and compare sweet potato glycemic index vs potato glycemic index, along with health benefits to see if one is healthier than the other.
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4 Myths About Potatoes
Myth: Sweet potatoes are low glycemic.
Truth: Sweet potatoes have a low GI of 46 only when they're boiled.
Myth: Sweet potatoes have a lower glycemic index than white potatoes.
Truth: Sweet potatoes and white potatoes both have an average GI of 88 when baked.
Myth: Sweet potatoes are healthier than potatoes.
Truth: Both are equally nutritious and healthy, but sweet potatoes have 100 times the amount of vitamin A as potatoes.
Myth: Sweet potatoes are better for diabetics.
Truth: The nutritional differences that influence glycemic response are too small to claim sweet potatoes are better. What matters most is the preparation method for the type of potato, but both types are part of a healthy diet.
What affects glycemic index?
Glycemic index (GI) is a measurement of how quickly a food raises blood sugar levels. On a scale of 1 to 100, foods are tested and given a value based on how quickly they raise blood sugar levels.
- Low: 0 - 55
- Medium / Moderate: 56 - 69
- High: 70+
High glycemic foods are digested quickly and rapidly raise blood glucose levels. Low glycemic foods are digested more slowly, leading to a gradual increase in blood sugar rather than a spike.
Numerous factors influence a food's GI:
- number of carbohydrates
- type of carbs
- amount of protein
- amount of fat
- fiber content
- cooking method
- how long it's cooked
- when it was harvested
- how ripe it is
- and more.
When it comes to a potato's glycemic index and a sweet potato's glycemic index, how they're prepared makes them either low or high glycemic.
Sweet Potato GI vs Potato GI
The latest published update to the International Glycemic Tables was in 2021. They report, overall, the white potato averaged high glycemic for every preparation method except cooling. All potatoes cooked, refrigerated for at least 24 hours, and served cold were low glycemic.
The same can't be said for sweet potatoes because the Tables don't show data for sweet potatoes being cooled, likely because they're almost always eaten hot. The glycemic index of sweet potato is lowered significantly only when boiled.
Cooking Method
| Potato GI | Sweet Potato GI | |
|---|---|---|
| Baked / Roasted | 88 (high) | 88 / 87 (high) |
| Boiled | 73 (high) | 46 (low) |
| Deep Fried | 65 (medium) | 71 (high) |
| Served Cold | 49 (low) | N/A |
Air Fry
The deep-fried method produced a lower GI because the potatoes were submerged in oil which allows the potato to soak up oil and create resistant-starch-5. Air frying is more like roasting or baking and will not lower the GI like deep frying.
Lowest Glycemic Potatoes
The lowest GI white potatoes were the:
- boiled Novel Clone from Canada (GI of 38)
- boiled Carisma from Australia (GI of 53)
- boiled Marfona from Britain (GI of 56)
- boiled Nicola from Australia and Britain (GI of 58).
The lowest GI sweet potatoes were the:
- boiled Chinese yam (GI of 35)
- boiled New Zealand yam (GI of 37).
Research shows that baking is the cooking method that retains the most nutrients and resistant starch in potatoes, but more resistant starch will form if they're served cold.
Lowering Potato GI & Healthy Ways to Eat Them
Aside from serving them cold, adding low glycemic foods like sour cream or butter in mashed potatoes, or cheese and meat in loaded baked potatoes is one way to lower the GI.
If you want a plain side of roasted mashed potatoes, fill your plate with low glycemic foods like broccoli and chicken. This is called low glycemic eating and it's the best way to curb blood sugar spikes.
Another scientifically proven "trick" is to eat acidic foods like vinegar or citrus fruits with starchy carbs like potatoes. Acidic foods play a special role in slowing starch digestion.
Nutritional Comparison
Both white and sweet potatoes are nutritious carb choices, but sweet potatoes have a slight edge over regular white potatoes.
To accurately compare, the following nutrition data reflects 100 grams being baked, plain.
| Sweet Potato | White Potato (with skin) | |
|---|---|---|
| Calories | 90 | 93 |
| Protein | 2 | 3 |
| Fat | 0 | 0 |
| Carbs | 21 | 21 |
| Fiber | 3 | 2 |
| Sugar | 6 | 1 |
| Starch | 7 | 17 |
| Vitamin A | 107% of the DV | 0% of the DV |
| Vitamin B6 | 17% of the DV | 18% of the DV |
| Vitamin C | 22% of the DV | 11% of the DV |
| Potassium | 10% of the DV | 11% of the DV |
| Manganese | 22% of the DV | 9% of the DV |
They're almost identical in grams of carbs, protein, and fat, and the sweet potato has just 1 more gram of fiber per serving. They're also low sodium and equal in vitamin B6 and potassium.
Where the sweet potato stands out is in its high amount of vitamin A. It's packed with beta carotene (a precursor to vitamin A) as evidenced by the orange color. It's also an excellent source of vitamin C. Vitamins A and C are antioxidants that fight free radicals.
White and purple varieties of sweet potatoes do not contain the same amount of vitamin A as the orange variety.
Conclusion
Both potatoes and sweet potatoes are equally high glycemic when baked or roasted. Boiling will lower GI for sweet potatoes, but not potatoes. To lower GI for potatoes, they must be cooked, refrigerated for 24 hours or more, and served cold.
Both potatoes have similar nutritional values, but sweet potatoes have 107% of vitamin A's daily value. Both are part of a healthy diet.
FAQs
Potatoes and sweet potatoes are nutritionally similar with the exception of an extremely high amount of vitamin A in sweet potatoes; so, either potato is suitable for a diabetic.
Both baked potato and baked sweet potato have a high glycemic index of 88.
The sweet potato's glycemic index is lower only when boiled, producing a GI of 46. A potato's glycemic index is lower when served cold, producing a GI of 49.
There are several ways to lower the GI of potatoes; foremost, serving them cold. Another way is to add acidic foods to the dish because acidic foods slow starch digestion. Fat and protein can also be added and will slow carbohydrate digestion.
boiled Novel Clone from Canada - 38
boiled Carisma from Australia - 53
boiled Marfona from Britain - 56
boiled Nicola from Australia and Britain - 58
boiled Chinese yam - 35
boiled New Zealand yam - 37
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