My glucose monitor barely moved.

All week I tested diet drinks. Coke Zero raised my blood sugar by about 2 or 3 points — basically nothing. Diet Coke: the same. Sparkling water: flat. If you’re asking whether a can of Coke Zero raises blood sugar the way a regular Coke does… no. Not even close.

But the question filling my inbox wasn’t that one.

It was: are artificial sweeteners safe?

That’s a messier question.

The blood sugar answer is boring. The more interesting question is what these sweeteners do over months and years. And there, the research is divided.

Saccharin and sucralose — two of the most studied sweeteners — have been shown in some studies to shift gut bacteria in ways that may reduce how well the body handles sugar over time. In other words: these sweeteners don’t raise blood sugar while you’re drinking them, but some research suggests they could change the environment in your gut in ways that make blood sugar control worse in the long run. A 2025 review in Frontiers in Microbiology confirmed that saccharin and sucralose had measurable effects on gut microbiota composition.

The evidence is still inconsistent, though.

A 2025 randomized controlled trial published in Nature Metabolism found that people who used sweeteners as part of an otherwise healthy diet lost more weight than a sugar group, and showed beneficial shifts in gut bacteria. So this isn’t a clean “sweeteners are bad” story. It’s more complicated.

Here’s a distinction worth knowing.

Acesulfame potassium — the sweetener that makes Coke Zero sweet — just went through a full re-evaluation by Europe’s food safety authority in April 2025. They raised the acceptable daily limit and gave it a clean bill of health. Aspartame — the sweetener in regular Diet Coke — is in a different position. The World Health Organization flagged aspartame as “possibly carcinogenic” in 2023.

Not banned. Not proven to cause cancer at normal drinking amounts.

But it’s on a different shelf.

So if you’re choosing between them… Coke Zero’s sweetener just got cleared. Diet Coke’s has a question mark.

And if you want to skip the debate entirely, sparkling water with a squeeze of lemon is the cleanest option. Same fizz. Nothing to argue about.

● This Week’s Rules

● The Scoreboard

Here’s how the week’s drinks ranked on my glucose monitor. The gap between regular Coke and everything else is the whole story.

This is one person’s experiment, not medical advice — everyone’s body responds differently.

● Reader Mail

● Next Week

Next week we’re putting bread on trial. Specifically: is real sourdough different from the loaf at the supermarket, and does toast-and-cool actually work?

— Stay steady

In less than 30 minutes, my blood sugar shot from 85 to 180 mg/dL. A spike of 95 points. And then it crashed hard back down to 72 within the hour.

It's revealing.

A banana seems like a healthy choice. We've been told it's a good source of potassium and fiber. And it is. But here's the thing… a banana on an empty stomach is basically a sugar bomb with good PR.

In other words, without fat or protein to slow things down, the sugar floods your bloodstream like water through a burst pipe.

The crash that follows is what makes you reach for a muffin at 10am. It's the reason you feel tired and foggy before lunch. And it's the thing that, done day after day, nudges your body toward insulin resistance.

A terrible cycle.

● Meanwhile, The Hack

If I'd eaten two eggs first, and then had the banana, the story would have been completely different.

Protein and fat act like a dam. They slow the rush of sugar into your blood. The spike shrinks. The crash softens. And you stay full until lunch.

I tested this the next day. Same banana. But this time, after two scrambled eggs.

Look at the difference…

Same banana. One small change. 65% lower spike.

● The Bigger Picture

I walk around these days with a glucose monitor stuck to the back of my arm. My wife thinks it makes me look like a cyborg. The kids think it's cool.

What the monitor has shown me, over and over, is that the foods we think of as "healthy" are often the biggest spikers.

Here are three more surprises from my monitor…

We've been told to fear fat and worship fruit. But our blood sugar tells a different story.

This is something we should all keep an eye on.

If you're feeling adventurous… try eating two eggs before your fruit tomorrow morning. Then notice how you feel at 10am. I think you'll be surprised.

That's it for today. Small change. Big difference.

To flatter curves and fewer crashes 🍳