Can Diabetics Eat Potatoes?

Dr Jedha, Host

Hello and welcome to another episode of Type 2 Diabetes Talk.

Today’s topic is one that sparks a lot of questions and a fair bit of confusion among people managing their blood sugar, and that is: Are potatoes diabetes-friendly?

If you go and surf the wild west web, you’re going to read all sorts of conflicting advice about potatoes, glycemic index, resistant starch and whether cooling potatoes after cooking can make them a better choice for blood sugar control.

I get it—potatoes have been a staple food for many, and they come in so many forms: mashed, roasted, baked and boiled; and even as sneaky additions in recipes that are labeled ‘diabetes-friendly.’ And of course, they can be made into French fries, chips, crisps are other snack foods. But the question we’re investigating today is whether it’s okay for you to embrace potatoes or is it better to just skip them altogether?

We’re going to dig into the nutrition facts of potatoes, specifically today we’re talking about white potatoes, not sweet potatoes, which is a whole topic in and of itself. We’ll explore the confusion around the glycemic index of potatoes, the research behind resistant starch, the truth about different potato cooking methods, and whether any of it actually makes a difference to your blood sugar levels.

02:31

Let’s start with the basics: what are potatoes nutritionally? While they may be considered a vegetable in the culinary world, nutritionally speaking, potatoes belong in the starch category. This is because they’re packed with carbohydrates that can significantly impact blood sugar levels.

A medium potato contains about 32 to 37 grams of carbohydrates. Now, to put that into perspective, that’s roughly half to one-third of the daily carb intake we recommend for people trying to manage blood sugar. And while potatoes do have some fiber—about 4 to 5 grams per medium potato—it’s not nearly enough to offset the rise in blood sugar that follows eating them.

Then there’s the glycemic index, or GI, which measures how quickly a food raises your blood sugar. Most potatoes have a GI between 60 and 95, which is considered high. For comparison, a low-GI food would be something below 55, like non-starchy vegetables such as spinach or broccoli, spinach being close to zero, broccoli being around 10. The higher the GI, the faster it raises your blood sugar—and that’s not what we’re aiming for when treating type 2 diabetes or prediabetes. We want quite the opposite, foods that have a low impact on blood sugar.

Potatoes do provide some nutritional benefits. For example, they’re a good source of potassium, vitamin C, and vitamin B6. But here’s the reality: while these nutrients are helpful, there are plenty of other, more blood sugar-friendly foods that can provide similar or even better nutritional benefits without the carb load.

So, the takeaway here is that while potatoes may have some good qualities, their high carbohydrate content and high glycemic index make them a challenging choice for managing blood sugar effectively.

04:40

Now let’s tackle the glycemic index, or GI, because it’s a term that gets thrown around a lot, especially in discussions about potatoes. As I mentioned earlier, the GI measures how quickly a food raises blood sugar after eating.

Potatoes generally rank high on the glycemic index—anywhere from 60 to 95 depending on the variety and preparation. But what makes this confusing is that different types of potatoes and how they’re cooked can significantly alter their GI.

For example, a baked russet potato has a GI of around 85, which is very high. Meanwhile, boiled and cooled potatoes, like those used in a potato salad, can have a GI closer to 55, which is technically considered low.

So, does this mean that cooling your potatoes magically transforms them into a diabetes-friendly food? Not exactly.

Here’s why. The glycemic index is a useful tool, but it doesn’t tell the whole story. It only measures the speed of blood sugar rise, not the overall amount of sugar your body has to process—this is where glycemic load, or GL, comes in. A GL of 10 is considered low, while 20 is high. Most potatoes, regardless of their GI, still have a high GL due to their large carbohydrate content, ranging from 16 to 26 GL.

There are two types of waxy potatoes that are considered low GL and they are Carisma and Nicola, which both have a low GI and GL, Carisma being the best at 53 GI, 8 GL. Unfortunately though, these are not available everywhere and can be hard to find in the US. For our listeners in Canada, Australia, the UK o Europe, you can probably find these more readily available. Though they have become more readily available in the US.

If you’re one of our members, we’ll have a full nutrition facts chart for you alongside today’s episode, along with the various types of potatoes that are the best options and where to source them depending on where you live.

But here’s the thing, even a low-GI potato like Carisma or Nicola still delivers around 20 grams of carbs per serving, which can add up quickly. So let’s not forget portion size is a critical factor. A medium potato might look manageable on paper, but let’s be honest—how often do we stop at one medium potato? Most people consume two or three, especially in the form of mashed potatoes or fries, turning what could be a reasonable carb load into a blood sugar spike waiting to happen. For reference, a half cup scoop of mashed potatoes contains around 19 grams of carbs, half a cup isn’t that much so it’s definitely a matter of portions as well.

The bottom line here is that while cooling or choosing lower-GI potatoes can slightly reduce their impact on blood sugar, it doesn’t erase the challenges they pose for you, when you need to be particular conscious on blood glucose control. It’s important to look at the bigger picture, including the total carbohydrate content and how it fits into your overall meal plan.

So, before you fall into the GI trap, remember: low GI doesn’t always mean low carb, and both factors are crucial for managing blood sugar effectively.

08:57

So, we’ve looked at how potatoes are high in carbohydrates and why their glycemic index can be a challenge for blood sugar management. But what about all the buzz around cooking methods and resistant starch? Could the way you prepare your potatoes make them more blood sugar-friendly?

Let’s explore what the research tells us.

First, what is resistant starch? It’s a type of carbohydrate that behaves a bit like fiber—it resists digestion in the small intestine and ferments in the colon instead, which can have potential benefits for gut health and even insulin sensitivity.

There are five types of resistant starch, and when we talk about potatoes, we’re mainly looking at type 3, or retrograded starch. This forms when cooked starches like potatoes are cooled, which alters their structure and makes them harder to digest. Sounds promising, right?

But here’s where it gets interesting. While resistant starch can reduce the insulin response to some foods, the research on cooked and cooled potatoes specifically is mixed.

Let’s look at what the studies say:

In one study, 8 healthy participants ate either freshly cooked mashed potatoes or mashed potatoes that had been cooked, cooled, and reheated. While there was no significant difference in post-meal blood sugar levels, the insulin response was about 24% lower with the cooled potatoes. That suggests some potential impact on insulin sensitivity.

Another study in 25 overweight healthy women who ate russet potatoes that were either boiled or baked then chilled. This study also found there was no difference in post-meal blood sugar levels but there were lower insulin spikes when people ate the baked then chilled potatoes.

Another study in 9 men with varied insulin sensitivity found that eating hot vs cooled potatoes reduced their digestibility by about 10%, which could slightly blunt the blood sugar spike. But, again, the carbohydrate content remains largely intact.

These studies have been mainly done in healthy participants and they suggest that while cooling potatoes after cooking may lower the insulin response or reduce their digestibility, the overall impact on blood sugar levels remains minimal, if exerting any influence at all. The reality is overall, there have been few human studies on the effects of resistant on glycemic control and hormonal responses.

In people with type 2 diabetes, studies are even fewer and the few studies that exist haven’t found consistent improvements in post-meal blood sugar levels or other outcomes when cooled potatoes are consumed versus freshly cooked ones.

One study in 24 people with T2Diabetes, compared boiled, roasted, or boiled and cooled potatoes. Similar to the studies we already mentioned with healthy participants, there was no difference in post-meal glucose. The only outcome was that there was a lower spike in insulin after eating the cooled potatoes.

In a review of 31 studies of all the different resistant starches 1-5 in T2Diabetes, the authors clearly concluded that resistant starch type 3 does not lower postprandial blood sugar levels. Remember, type 3, or retrograded starch, is the form of resistant starch that occurs when cooked starches like potatoes are cooled. So, this review pretty clearly states the fact: resistant starch type 3 does not lower postprandial blood sugar levels.

I just want to clarify that people do use potato resistant starch supplementation, which is frequently RS1 and RS2 and perhaps this is an area that gets confused out there on the wild west web. Various types of resistant starch are now manufactured and added to foods or taken as supplements and that’s a whole other story when we look at the results, which we may dive into in another episode. Point being: we’re not talking about supplementation with resistant starch today, we’re talking about eating potatoes themselves.

13:32

So, does this mean cooling your potatoes is pointless? Well, not entirely. It is certainly going to be better to cook and cool potatoes, or cook, cool and then reheat them. The studies have demonstrated a lower insulin spike and that’s certainly beneficial, but it’s not a magic fix to go and eat potatoes like lots of places make out.

When it comes to cooking methods, baking potatoes tends to retain more resistant starch compared to boiling. Microwaving cooled and reheated potatoes has been shown to further enhance resistant starch levels. And interestingly, one study did mention that shorter boiling times and slightly undercooking potatoes can increase RS2 content, RS2 being a more beneficial type of resistant starch. But overall there isn’t any research to confirm that or to test the impact on glucose control.

So when we bring all this together, the practical reality is: even with these techniques, you’re still consuming a food that is predominantly starch and carbohydrate. So, while cooking and cooling might slightly reduce the glycemic impact, unfortunately, it doesn’t turn potatoes into a diabetes-friendly food.

15:35

Okay, the final thing we’re going to do today is unpack and clarify or reclarifying some myths and truths about potatoes in a rapid Q&A. Let’s tackle some of the common myths and truths about potatoes. This is where a lot of confusion sets in, especially with all the conflicting advice out there.

Myth 1: Sweet potatoes are better for blood sugar than white potatoes.

This is one of the most common misconceptions and while I said we won’t cover sweet potatoes in detail today, I will touch on this very briefly. While sweet potatoes may seem healthier because they’re rich in antioxidants like beta-carotene, nutritionally speaking, they’re quite similar to white potatoes. They contain roughly the same amount of carbohydrates and have a similar glycemic impact. So, while sweet potatoes may have some additional benefits like anti-inflammatory properties, they’re not a better choice when it comes to managing blood sugar.

Myth 2: Potatoes are fine as long as they contain resistant starch.

We just discussed resistant starch, and while it can lower the glycemic index and slightly lower the insulin response, it doesn’t eliminate the problem of high carbohydrate content. Even cooled potatoes still have a substantial amount of carbs that your body needs to content with. So, while resistant starch might help reduce some of the glycemic impact, it doesn’t transform potatoes into a low carb food.

Myth 3: All potatoes are the same when it comes to blood sugar.

This one’s partially true. Most potato varieties—whether russet, Yukon Gold, or red—have similar amounts of carbohydrates and glycemic impact. But there are exceptions, like Carisma or Nicola potatoes, which have a lower glycemic index and glycemic load. Researchers are also exploring the potential impact of other varieties, such as Huckleberry Gold, Muru, Multa, and Green Mountain potatoes.These varieties might be a better choice if you’re determined to include potatoes in your meals.

Myth 4: Potatoes are no different from bread or pasta.

This one’s a bit more nuanced. Studies have shown that potatoes often result in higher blood sugar spikes compared to bread or pasta when matched for the same amount of carbohydrates. This is likely because of the way our bodies digest the starch in potatoes. So, while none of these foods are ideal for blood sugar management, potatoes can sometimes have a more significant impact.

So, we’ve covered a lot of ground today, from the nutrition facts of potatoes to the research on glycemic index, resistant starch, and cooking methods. We’ve also busted some common myths about potatoes and their impact on blood sugar.

The bottom line is this: potatoes are a high-carb food that can significantly impact blood sugar levels, regardless of how you slice, dice, or cook them. While cooking and cooling potatoes or choosing low-GI varieties like Carisma or Nicola may help reduce some of the glycemic impact, these approaches don’t turn potatoes into a low-carb or diabetes-friendly food. If you want to focus on lowering your blood sugar and A1c, it’s best to avoid potatoes or approach them with caution.

But if you decide to include potatoes in your meals, on occasion, here are a few practical tips to keep in mind:

Strictly control your portions, sticking to small servings of about half a cup or less, and be mindful of how often you include them in your diet.

Choose low-GI varieties when possible. If you can find Carisma or Nicola potatoes, they’re a better choice for managing blood sugar.

Consider your cooking methods. Baking and cooling does increase the resistant starch and reduces the glycemic index of in the potatoes, which although it makes no difference to blood sugar, it can have health benefits and does decrease insulin spikes. Cooled potatoes can then be reheated for other purposes such as mashing etc.

And remember, there are plenty of tasty, lower-carb alternatives to potatoes. If you’re one of our members, we’ve got more detailed potato nutrition facts, more details on low GI potatoes and where you can purchase them, plus, many delicious alternative options for potatoes and recipes too. Find all those in the members library alongside this episode.

Thank you for joining me today and I’ll see you in the next episode.

Dr Jedha, over and out.