Your Smartwatch Can Now Tell You How Well You Eat

Samsung just added something wild to its Galaxy Watch 8. The gadget can now check how many antioxidants are floating around in your body. All it takes is a quick thumb scan that lasts about five seconds. The watch spits out a number between 0 and 100. Higher scores mean your body has more of those helpful plant pigments that come from colorful fruits and veggies.

But here is the deal. The watch does not measure every single antioxidant bouncing around inside you. It focuses specifically on carotenoids, which are basically the yellow, orange and green pigments found in produce. These little guys can build up in your skin over time. Samsung admits that sunlight, boozing and stress can also mess with the final number. So it is really just giving you a rough estimate of how many fruits and vegetables you are eating.

The actual scan works like this. You take off the watch, dig into the Samsung Health app, find Antioxidant Index and hit Measure. Then you press your thumb firmly against the BioActive Sensor on the back. The sensor shoots out different colored LED lights, including yellow, blue, purple and green. Your skin absorbs some of that light while the rest bounces back. Carotenoids soak up blue light especially well, and photodiodes pick up whatever reflects. Samsung runs those reflection patterns through calculations to estimate your carotenoid concentration and give you that score.

Samsung picked the thumb for solid reasons. Dark pigment in your skin, called melanin, can throw off optical readings. Finger skin happens to have less melanin than most other body parts. Plus, pressing your thumb down temporarily slows blood flow. That reduces interference from hemoglobin, another substance that can mess with the measurements.

The company validated this whole system against Raman spectroscopy, which is a lab technique scientists use to measure skin carotenoids. They also compared results with blood tests, food diaries and clinical data from hundreds of people. A 2023 study with Samsung researchers showed a strong link between reflection spectroscopy and Raman spectroscopy when tracking these pigments.

Here is the important part though. Samsung never published a clear accuracy percentage or error margin for regular customers. The company also says this feature should not diagnose or treat any medical conditions. Treat it like a fun health trend to watch, not a replacement for actual medical tests.

Engadget tested it and found the number does not change super fast. Reviewer Amy Skorheim switched up her diet for a day and her score only dropped by two points. On other days, her readings bounced between 56 and 60. Samsung also notes that carotenoids from food typically need two to three weeks to accumulate in your skin to detectable levels. So do not expect instant results after eating a single salad.