Do potatoes cause diabetes? - Dr. Ronald Hoffman

There’s no question that curbing carbs can help with blood sugar regulation. Sugary foods and refined carbohydrates are major offenders. But what about potatoes?

According to the Gospel of Atkins, they were verboten. But the popular Whole30 Diet endorses them while cutting out all grains. The Autoimmune Paleo Diet (AIP) eschews them because they belong to the nightshade family, which may trigger flares in susceptible individuals.

Indeed potatoes are a starchy root vegetable, whose glycemic index is moderate relative to high GI foods like white bread or orange juice. I consume potatoes regularly, but I also don’t have elevated hemoglobin A1c or triglycerides—harbingers of blood sugar dysregulation—and I have a healthy body composition.

Try Resistant Starch

One way that I mitigate the carbohydrate impact of potatoes is via a little kitchen chemistry trick: I boil them or bake them, and then allow them to cool. I then make hashed browns out of them by frying them in a little lard or peanut oil. Once cooled, the starch in potatoes is converted to resistant starch, which takes longer to break down, blunting the glycemic impact of the potatoes’ sugar content.

The question of whether potatoes increase the risk of diabetes was addressed recently in a large and lengthy observational study. It analyzed dietary and health records of over 205,000 health professionals followed for almost 40 years.

How you consume potatoes makes a difference

Potato consumption overall modestly contributed to heightened risk of diabetes—by a mere 5%. But when researchers investigated the relationship between intake of potatoes prepared by different methods (boiled, baked, mashed versus French fries), it became apparent that fries were the main culprit. For every three weekly servings of French fries, the risk of diabetes was hiked by 20%.

Parenthetically, potatoes outperformed white rice when it comes to diabetes; replacing potatoes with white rice was associated with increased risk; on the other hand, swapping potatoes with whole grains conferred modest protection against diabetes.

First of all, it must be acknowledged that most Americans find potatoes boring. Maybe potatoes’ inherent blandness is a check on overconsumption? Unless garnished with butter, drenched in sour cream and chives, or served au gratin, most people would rather just eat French fries.

A close up of French fries and salt falling onto a table.

And who eats French fries without generous amounts of ketchup?! Plus, ketchup is a major Trojan Horse for sugar. Just one tablespoon of ketchup has four grams of sugar, mostly from high-fructose corn syrup, that delivers 19 rapidly absorbed calories. A typical 14-ounce bottle of Heinz ketchup contains over 18 teaspoons of sugar!

French fries are hyperpalatable—the perfect blend of toasty carbohydrates laden with fat and salt. Add ketchup, and you amp up mouth appeal with a dollop of sweetness.

Toxic cooking oil

Not to mention the oil that French fries are fried in. Not only does it pack a lot of additional calories, but lately questions are being raised over the wisdom of switching from traditional animal fat to industrially-processed seed oils as a frying medium.

Cooking oils are used over and over in fast-food eateries. Contact with foods and repeated exposure to high temperatures results in harmful alterations. According to a recent review:

“Repeatedly heated cooking oils (RCO) produce various byproducts, containing polycyclic aromatic hydrocarbons (PAHs) and aldehydes, well-known to be a carcinogenic, mutagenic, and tumorigenic properties.”

Acrylamide, heterocyclic amines, free radicals and trans-fats are also rife in RCO. These oils are predominantly Omega-6 fatty acids, which in contrast to Omega-3s, may tip the body toward inflammation.

Vegetable oil blends of canola, soybean and sunflower oil are now typically used in fast-food eateries. Their chemical bonds are predominantly unsaturated making them more susceptible to heat damage. Saturated fats like coconut and palm oil, lard and tallow have more stable double chemical bonds that resist thermic insults.

Why not fry the old-fashioned way?

Tallow’s high saturated fat content makes it ideal for high-heat cooking, a quality that made it a long-time favorite in fast-food restaurants before the widespread switch to vegetable oils. Why was it abandoned?

Thanks in large part to Phil Sokolof, an eccentric millionaire who virtually singlehandedly bankrolled a jihad against saturated fats in the 1980s. His campaign was amplified by the Center for Science in the Public Interest, which helped launch the low-fat/low-cholesterol craze. McDonald’s caved in the 90s, substituting a trans-fat blend for lard in their fryers, until it was revealed that those hydrogenated ersatz fats were highly toxic. They’ve switched in light of a 2015 FDA ban on trans-fats, now using unhydrogenated seed oils instead.

When eating out, it’s hard to avoid the allure of French fries, given the ubiquity of steak frites, burgers and fries, fish ‘n chips, cheesy fries, and French Canadian-style poutine.

Air-frying fries with some of those new counter-top gadgets may minimize exposure to toxic oils. Also, many restaurant chains are capitalizing on newly-minted public backlash against seed oils, offering instead traditional fries prepared in animal fat.

Beef tallow contains stearic acid, a type of saturated fat that may not raise cholesterol levels as much as other saturated fats.

But beware: The retro fries are highly satiating compared to vegetable oil-drenched versions. But that’s to the good; maybe people will just eat less of them—like they used to when Americans’ waistlines were slimmer in the mid-twentieth century.

Check out our coverage of this topic on the Intelligent Medicine podcast: