Eating potatoes occasionally probably won't cause harm, but if you have an abundance of potatoes in your diet, side effects may occur. They likely won't be serious, unless you're allergic to potatoes, but can include bloating, constipation and stomach pain.
If your diet includes lots of potatoes, as well as other rapidly digesting carbohydrates, you may also develop high blood pressure or insulin resistance, which is connected to Type 2 diabetes. Of course, this typically happens only after years of eating a high-carbohydrate diet and isn't usually a direct result of eating potatoes.
High Blood Pressure
With so many uses of potatoes, from French fries to mashed to baked, they're one of America's favorite vegetables. On average, each person consumes around 116 pounds of potatoes per year, according to the National Potato Council. That's a lot of spuds; and that quantity could be the reason you find yourself experiencing some negative side effects. Potatoes aren't inherently bad for you, but if you overdo it, you may develop some problems.
One study published in the BMJ in May 2016 compared the health effects of consuming four or more servings of potatoes per week with eating less than one serving a month. They also looked at different preparations of potatoes, including baked, boiled, french fries and chips to see if that made a difference. Researchers found that a higher, long-term intake of all types of potatoes, except chips, was associated with an increased risk of high blood pressure.
Although the exact mechanism behind the increased blood pressure wasn't clear, researchers speculated that it could be connected to two major underlying causes. The first was that a high intake of potatoes was also associated with weight gain, which is a risk factor for high blood pressure.
The second was that, due to high-carbohydrate content, they're considered high-glycemic foods. A high-glycemic carbohydrate diet increases your risk of high blood pressure. In other words, the potatoes may not be directly to blame.
Imbalanced Blood Sugar
To piggyback on what researchers from the BMJ described, one of the disadvantages of potato consumption is that the root vegetable is considered high-glycemic. The term "high-glycemic" describes carbohydrates that digest quickly, causing rapid spikes in both blood sugar and insulin followed by dips in both as well. Over time, these fluctuations in blood sugar can lead to insulin resistance and, eventually, Type 2 diabetes.
Eating a diet that contains too many high-glycemic carbohydrates can also contribute to weight gain. But potatoes on their own may not be a problem. It's likely a combination of eating too many potatoes as well as too many other high-glycemic foods like white rice, white bread and instant oatmeal.
It's also important to note that many of the carbohydrates in potatoes come from resistant starch, which is a type of carbohydrate that your body can't digest. Because of this, they might not have as significant an effect on blood sugar and insulin levels as other high-glycemic foods. According to the Mayo Clinic, this is one of the downfalls of judging a food based solely on its glycemic index. It doesn't take into account which carbohydrates a food contains or the other nutrients those carbohydrates are coupled with.
Read more: 9 Better-for-You Potato Chip Swaps
Other Disadvantages of Potatoes
If you eat potatoes with the skin on, they become a decent source of fiber as well as resistant starch. A medium-size potato contains approximately 3.6 grams of fiber, which is around 9 to 17 percent of what you need for the entire day, depending on your age and whether you're a man or a woman. While this fiber is largely beneficial, and isn't one of the direct disadvantages of potatoes, if you eat a lot of potatoes, gas may develop, especially if you're not used to eating fiber.
If you're eating too much fiber, or you've incorporated it into your diet too quickly after following a low-fiber diet for some time, it can cause uncomfortable side effects like bloating, gas, cramping, diarrhea, decrease in appetite, feelings of fullness after eating only a small amount and unintended weight loss. Fiber can also inhibit the absorption of some nutrients, like zinc, iron, magnesium and calcium, which can lead to nutrient deficiencies.
It's not likely that eating a few potatoes here and there would cause a problem, but if you eat them in conjunction with a lot of other high-fiber foods, or you eat way too many, it's possible. When you're eating a lot of fiber, it's also important to make sure you're drinking enough water. As fiber moves through the digestive system, it soaks up water like a sponge. If there's not enough water in the digestive tract for it, fiber can cause nausea and constipation.
A Word of Caution
If you eat a potato and serious side effects occur immediately after, it's possible that you have a potato allergy. Although an April 2017 report in the Journal of Allergy and Clinical Immunology notes that potato allergies are rare, you should still watch for the signs, which may include:
- Itchy eyes and nose
- Stomach cramps
- Swelling of the tongue and face
- Throat closing
- Chest tightness
- Loss of breath
Most allergic reactions start with skin symptoms, like hives, rashes and itching, but this isn't true for all cases. If you're experiencing one, or a combination, of these allergy symptoms within minutes to up to two hours after eating a potato, it's likely that you're allergic and you need to seek immediate medical attention. If you're allergic, even a small amount of potato will cause a future reaction, so you'll need to avoid the root vegetable for good.
If you experience side effects like gas, bloating and upset stomach after eating a potato without any skin reactions, it's also possible that you have a potato intolerance, instead of a true allergy. Unlike allergies, which involve a rapid immune response, food intolerances involve only the digestive system. If you have any of the symptoms of an allergy or an intolerance, check with your doctor who can give you a proper diagnosis. Allergies are serious and should be handled with caution.
- BMJ: "Potato Intake and Incidence of Hypertension: Results From Three Prospective U.S. Cohort Studies"
- National Potato Council: "U.S. Per Capita Utilization of Potatoes, by Category: 1970-2017"
- Journal of Allergy and Clinical Immunology: "Prevalence of Sensitization and Allergy to Potato in a Large Population"
- Asthma and Allergy Foundation of America: "What Are the Symptoms of an Allergy?"
- Food Allergy Research and Education: "Food Allergies: Frequently Asked Questions"
- Mayo Clinic: "Glycemic Index Diet: What's Behind the Claims"
- Harvard T.H. Chan School of Public Health: "The Problem With Potatoes"
- Harvard Health Publishing: "Choosing Good Carbs With the Glycemic Index"
- Nutrients: "Starchy Carbohydrates in a Healthy Diet: The Role of the Humble Potato"
- USDA National Nutrient Database for Standard Reference: "Potatoes, White, Flesh and Skin, Baked"
- Duke Student Health Nutrition Services: "Fiber - How"
- Academy of Nutrition and Dietetics: "Easy Ways to Boost Fiber in Your Daily Diet"