As a dietitian, I’ve noticed that people are confused about when to eat sweet potatoes because they’re unsure of how quickly they digest.
Sweet potato can be fast digesting or slow digesting depending on the cooking method. Baking, steaming, and roasting are linked with higher GIycemic Index scores (faster digestion) than boiling. Eating the skin also makes a difference, as it contains fiber and thus slows down digestion.
Learning how quickly sweet potato digests can be useful when you are trying to plan meals around your workouts, as it can help you decide when is the best time to consume these types of foods.
Key Takeaways
- Sweet potatoes are made up of fast-digesting starch, fiber, and small amounts of sugar, indicating that they are a complex carb. Because of the fast digesting starch, they can have a high GI rating, like white bread and white potatoes.
- Research suggests that the cooking method determines their GI rating, which ranges from low to high (44-91).
- You can make sweet potatoes a slower-digesting carb by boiling them, eating the skin, or pairing them with protein and fat, such as eggs, avocado, and nuts.
Understanding The Glycemic Index
The glycemic index (GI) is a measure used to inform people how quickly carbohydrates raise blood sugar levels by ranking foods on a scale from 0 to 100.
Foods with a low (1-55) to medium (56-69) GI cause a steady increase in blood sugar levels, as they break down and convert to glucose (energy) more slowly. This is because they contain fewer simple sugars and more fiber and starch, which take longer for the body to break down.
Foods with a high GI (70-100) cause a fast rise in blood sugar levels, as they digest and absorb more quickly. This is because they contain mostly simple sugars and/or refined carbs, which break down more easily.
Although the GI helps select appropriate carbs for maintaining stable blood sugars, other factors should be considered as well while making dietary choices, such as the portion size of a carb (and consequently the glycaemic load) and the presence of other nutrients (protein, fiber, and fat).
- Related article: What Are Fast Digesting Foods? 10 Examples & When to Eat
How Long Does It Take Sweet Potato To Digest?
It can take around 30 minutes to 3 hours for a whole sweet potato to digest, depending on how it’s prepared, and if it’s eaten alone or with food. This explains why the GI ranges from low to high, or 44-91 according to the International tables of glycemic index values.
Different cooking methods, such as boiling, baking, or roasting, will change the rate of digestion of sweet potatoes.
For example, if you boil sweet potatoes, they will digest much slower than if you bake or roast them. If you peel and boil them, they will digest faster than if you boil them with their skin on.
The rate of digestion of sweet potatoes will also change based on whether you’re eating them alone or with other macronutrients (more on this later).
Is Sweet Potato A Complex Or Simple Carb?
Sweet potatoes are root vegetables containing mostly starch, some fiber, and a small amount of simple sugars. As a large proportion of sweet potato is made up of a fast-digesting starch, it is considered a complex carb (that is fast digesting).
“The classification and measurement of nutritionally important types of starch includes its division into rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS)”
Hans N. Englyst – Food Chemistry Journal
In simple terms, this means that some complex carbs digest faster than others (like sweet potato), but even the fastest digesting complex carb will not digest as quickly as a simple carb.
Complex carbs are made up of three or more sugar molecules and are typically starches. Foods high in these carbs usually also contain some fiber, which is why complex carbs take longer to digest and convert to energy (like oat bran bread or rice).
Conversely, simple carbs are made up of one or two sugar molecules (simple sugars). This makes them easy to digest, which means they convert to energy more quickly (like soda).
So, how do sweet potatoes compare to other types of carbs?
The following table shows a few different types of carb foods with their GI score, according to the International tables of glycemic index values.
*Note: Low GI foods are 1-55, medium GI foods are 56-69, and high GI foods are 70+.
| Foods | Glycaemic Index |
|---|---|
| Baked sweet potato | 91 |
| Boiled sweet potato | 44 |
| French baguette | 95 |
| Instant flavored oats | 83 |
| Oat bran bread | 45 |
| Soda | 90 |
| Overripe banana | 70 |
| Basmati White Rice | 67 |
| Apple (with skin on) | 40 |
To put this in context, a baked sweet potato is faster digesting than a banana and flavored instant oats, but slower digesting than a french baguette.
A boiled sweet potato is slower digesting than basmati rice, but faster digesting than an apple.
Types of Sweet Potato: Ranking From Fastest To Slowest Digesting
Sweet potatoes can have different GI ratings depending on the preparation (cooking method), which means the digestion rate will be different as well.
According to the International tables of glycemic index values, sweet potatoes can have a low to high GI rating (44-91) depending on how they have been cooked and prepared.
This is likely one of the main factors that will determine how quickly or slowly a sweet potato digests.
The following table shows the GI score of sweet potatoes based on cooking methods.
*Low GI foods are 1-55, medium GI foods are 56-69, and high GI foods are 70+.
| Types of sweet potato | Glycaemic Index |
|---|---|
| Boiled | 44 |
| Boiled in water with 2 g salt | 48 |
| Sliced, deep-fried in oil for 5 min | 58 |
| Peeled, cubed, boiled in salted water for 15 min | 60 |
| Steamed in high heat for 35 min | 71 |
| Sweet potatoes, baked for 30 min | 91 |
Boiled sweet potatoes have the lowest GI, whereas baked sweet potatoes have the highest GI.
Based on these ranges, one can assume that baking likely leads to faster digestion and boiling leads to slower digestion.
Benefits of Eating A Slow/Fast Digesting Carb Like Sweet Potato
1. Versatile – Provides Quick or Slow Energy
Sweet potatoes are versatile in terms of the type of energy they provide (fast or slow acting).
If you bake, steam, or roast them, the energy will be fast-acting. If you boil them, the energy will be slow-acting.
If you peel them, the fiber will be removed, making them digest quicker.
2. Boosts Your Fiber Intake
Incorporating sweet potatoes (with the skin on as that is where the fiber is) in your diet will help you meet your daily fiber intake.
Fiber is important for gut health and promotes regular bowel movements, so it is important to consume an adequate amount. This equates to 14 g of dietary fiber per 1,000 kcal, or 25 g for adult women and 38 g for adult men per day.
Fiber also keeps you full for longer, as it slows down digestion which can be beneficial if you are trying to lose weight by potentially reducing the number of calories you consume throughout the day.
- Related Article: Is Pasta Fast Digesting? (A Dietitian Answers)
Drawbacks of Eating A Slow/Fast Digesting Carb Like Sweet Potato
1. Blood Sugar Spikes (based on the cooking method/portion)
If you have a larger portion of sweet potato (i.e. 2 medium baked sweet potatoes, ~360g), it will cause a rapid rise in blood sugar.
This can be a problem for those with poor blood sugar control like those with diabetes or insulin resistance.
2. Potential Digestive Issues
Sweet potatoes can be difficult to digest for some people when consumed in larger amounts due to their higher fiber content.
Overconsumption of fiber can lead to digestive discomfort, bloating, and gas.
If you’re sensitive to fiber or have had a low fiber intake for quite some time, it might help to have fiber-rich foods in smaller portions to allow your digestive system to adapt gradually.
When Should You Eat Sweet Potatoes?
Sweet potatoes can be eaten at any time throughout the day, but there are times when having sweet potatoes can be particularly advantageous.
- 1-2 hours before exercise, as a good source of sustained energy that can support exercise performance.
- After exercise, this type of energy supports the recovery phase by replenishing energy stores in the muscles (better if paired with a source of protein rather than eaten alone).
- Breakfast, lunch, or dinner, as a source of carbohydrates that keep you full for longer periods. They can be paired with protein, such as grilled chicken, eggs, fish, and vegetables to create a balanced meal.
Related: 14 Best Vegetables For Muscle Growth
How To Make Sweet Potato Digest Faster or Slower
1. Eat Them With Fiber, Protein, and/or Fat Sources
Eating sweet potatoes with high-fiber foods, such as leafy greens, whole grains, or legumes, and protein mixed with some fat, such as meat, fish, dairy foods, avocado, and nuts, can slow down their digestion and help to balance blood sugar levels.
2. Eat Them Alone
If you want a faster rise in blood sugar for a quick burst of energy, then have roasted sweet potato by itself (with no skin).
3. Cook Them Thoroughly (except boiling)
Cooking sweet potatoes breaks down the fiber and resistant starch, making them easier to digest. Steaming, baking, or roasting sweet potatoes can all help to break down their fibers and make them more digestible.
The exception to this is boiling sweet potatoes which actually has the opposite effect, making them digest more slowly.
About The Author
Giulia Rossetto is a qualified Dietitian and Nutritionist.
She holds a Masters in Human Nutrition (University of Sheffield, UK) and more recently graduated as a Dietitian (University of Malta).
Giulia aims to translate evidence-based science to the public through teaching and writing content. She has worked 4+ years in clinical settings and has also published articles in academic journals.
She is into running, swimming and weight lifting, and enjoys spending time in the mountains (she has a soft spot for hiking and skiing in the Italian Dolomites).