Issue No. 039 · Sweet Potato

The “Healthy” Potato That Spiked Me 62 Points

I baked a sweet potato and watched my glucose monitor. Then I boiled one.

I trusted the sweet potato.

For years it was my “good” carb. My doctor told me to trade white potatoes for orange ones, and I did it for ten years without a single question. It was my side dish at every restaurant and my answer whenever someone asked how I ate to stay healthy.

So last Sunday I baked one. It went in the oven for an hour at 400 degrees, with the skin on and a pat of butter on top. I ate that sweet potato alone and watched my glucose monitor.

That baked sweet potato raised my blood sugar 62 points.

For the “healthy” potato, that number felt like a betrayal.

+62

Points from one baked sweet potato

Personal CGM readings from one person. Responses vary. This is not medical advice, so talk with your doctor before changing how you manage blood sugar.

The number shocked me... until I read the research.

A sweet potato does not have one glycemic index. In a 2011 study, researchers tested ten sweet potato varieties on ten people each, using the standard GI method. The baked versions scored between 82 and 94. Boiled, those same potatoes scored between 41 and 50.

In other words, the oven nearly doubled the score.

The reason is heat and time. A slow, dry bake gives the potato’s own enzymes time to turn starch into a sugar called maltose. That’s why a baked sweet potato tastes like candy... and why my blood sugar treated it like candy too.

Boiling works the other way. A 2023 lab study found that starch from boiled sweet potato broke down more slowly in a model of digestion than starch from baked sweet potato.

My doctor never mentioned this. He told me which potato to buy, but not how to cook it.

And I’m angry about that for you, because you probably got the same advice.

Meanwhile... The Hack

So I ran the test again three days later... with one change.

I cut a sweet potato of the same size into chunks, left the skin on, and boiled it for 30 minutes. Then I added the same pat of butter and ate it alone again.

My blood sugar rose 30 points.

That’s less than half the spike from the exact same food. Boiling time seems to matter too. In published tests, sweet potato boiled for 30 minutes scored about 46, while 8 minutes of boiling scored 61.

By the way, the butter was in both tests on purpose. A little fat may slow how fast starch reaches your blood, so I kept it the same each time.

One woman with one monitor is not a clinical trial, and your number may be different. Bodies vary, and the variety and size of a sweet potato can shift the result. But my result points the same way as the lab data.

Anyway, the fix costs nothing. It takes one pot of water, about 30 minutes, and a fork to test it.

You never had to quit sweet potatoes.

★ Welcome to the revolution

Jackie