7 Science-backed Ways to Lower Glycemic Index of Potatoes

1. Rinsing or Soaking - You know how the water turns cloudy when you boil potatoes? That's the starch leaching into the water from the potato, and starch is a type of carb.

Rinsing and/or soaking are ways to remove starch before cooking. Even more starch can be removed by peeling and cutting them first. Cutting potatoes into smaller pieces exposes more surface area, which allows for more starch to rinse off or leach out. The smaller the cut, the more starch exposed.¹

How much is rinsed off? It varies depending on several factors such as the type of potato, peeled vs unpeeled, how it's cut, how long it's rinsed/soaked, how much water is used, and more.

2. Boiling - Boiling potatoes lowers their glycemic index by way of starches leaching out into the water. The effect is roughly a 12-point reduction, which is great, but it stays in the high-glycemic range.

You may have heard that boiling makes potatoes low glycemic, but this is true only for sweet potatoes. White potatoes are still high-glycemic when boiled, but are low-glycemic when cooled.

3. Cooling - No matter how a potato is cooked, when it's cooled, something called retrogradation takes place. This process changes the starches into resistant starches that are fiber.²

In fact, this change is so significant that cooled potatoes have a low glycemic index; a big change from their normally high glycemic values. This is for potatoes served cold, like potato salad.

Reheating potatoes will increase their index again, but repeating the cycle of cooling and reheating increases the amount of resistant starch, thereby lowering their glycemic index.

In other words, it's okay to reheat potatoes after cooling. Their glycemic index will be lower than freshly cooked potatoes. This is why glucose levels are lower with leftovers.

4. Portioning - It's important to portion any high-carb food in blood sugar management, and potatoes are a high-carb food. Limiting how much you eat at one time will help avoid spikes.

There is no recommended amount because everyone has a different tolerance, but think of one portion as 15 grams of carbs. For a baked potato, just over ½ cup is roughly 15 carbs. This portion is NOT the same for all potatoes.

5. Pairing with Low GI Foods - First, let me explain that the reason potatoes are considered high glycemic and blood-sugar-spiking is because they have a lot of carbs, little protein and fiber, and even less fat. So when you eat potatoes by themselves, the carbs quickly enter the blood, causing blood sugar to rise fast.

If you eat potatoes with other foods that have more protein, fiber, and fat, everything becomes more balanced, and blood sugar rises gradually instead of quickly. This is what eating a low-glyemic diet means. Protein, fiber, and fat are the nutrients that slow down the digestion of carbs.

• Low-carb Proteins: low-carb soy products, eggs, animal meats.
• Low-carb Fiber Foods: the skin of the potato, green leafy vegetables, green vegetables, other non-starchy vegetables.
• Low-carb Fats: egg yolks, avocado, olives, Greek yogurt, coconut, butter, sour cream, oils, mayonnaise.

Examples:

• Potato Leek Soup
• Potato Salad with mayo, Greek yogurt, or eggs added.
• Mashed Potatoes with cream or butter added. An old-time secret is to mix in a raw egg as soon as everything is mashed, but the potatoes have to still be hot (so the egg comes to a safe temperature).
• Breakfast Burrito Casserole

6. Adding an acid - Adding acid like vinegar or citrus juice to starchy foods like potatoes chemically changes the starches, thereby lowering the glycemic index.²

This is commonly done in European potato dishes, but you can make your own version by adding a vinaigrette or using Greek yogurt in your potato salad or mashed potatoes.