Dr. Rhonda Patrick: Okay, so let's talk about these key biomarkers for aging. From a metabolic perspective, what do you think would be the most indicative of biological aging, and what biomarkers are good to look at?

Dr. Ben Bikman: Yeah, my first one would be fasting insulin. If I could change healthcare policy and practice in the United States, my one thing would be to have insulin be a standard measurement on every blood test. As much as the average individual is going to go in and get their annual checkup, they're going to get their glucose, their A1C, all their lipids, and uric acid. Those can be great, and there are some worth revisiting in a moment. But to me, the fact that we don't include insulin on that panel is an absolute travesty. It is, in my mind, the best overlooked marker.

So fasting insulin, if a person can get their fasting insulin measured, do it. If that measurement is six microunits per milliliter or less, it's a great sign. If it's up to about the mid-teens or high-teens, that's maybe an okay sign because insulin can be dynamic. But if it's in the high-teens to the 20s, it's a problem. That's a warning that you're metabolically off.

Let's come back to some of the common ones. The triglyceride-to-HDL ratio is a great surrogate marker for insulin resistance and cardiometabolic health. We focus so much on LDL, for example, but the triglyceride-to-HDL ratio is a way better predictor for cardiovascular risk than LDL is. You take your triglycerides, which you're always going to get on a blood test, and divide them by your HDL cholesterol, which you're always going to get on a blood test. If that number is less than 1.5, that's a great sign that you're doing well metabolically.

Maybe uric acid is another one. It's another one of those markers in a really well-done longevity study, the AMORIS study from Sweden. It found that uric acid was one of the very few predictors when they looked retrospectively at these people, measuring the same markers for decades. Their glucose control and uric acid were predictive variables for who lived the longest, healthiest lives. So lower uric acid is going to be better.

Dr. Rhonda Patrick: And just for general metabolic health, would you add some of the HbA1c and maybe ApoB? You mentioned LDL. They don't even directly measure LDL. ApoB would obviously be a more direct measure, but then looking also at particle size, which I again think is important. It's the small, dense LDL particles.

Dr. Ben Bikman: Yeah. I describe this in my book, Why We Get Sick. Why is it that we have such conflicting data across LDL? Some studies say it predicts, and some studies say it doesn't at all. Maybe it's because we're not accounting for the diameter differences. Even then, most people won't have had their diameter measured.

The triglyceride-to-HDL ratio is an awesome surrogate. There's a beautiful figure from a study. I can't remember the citation, but I can recall the figure perfectly. It looks at the difference in the population of the big, buoyant LDL versus the small, dense LDL. Right around a triglyceride-to-HDL ratio of 1.5 on the x-axis is that crossover. As the triglyceride-to-HDL ratio was higher, it reflected a higher pattern B LDL. The lower the triglyceride-to-HDL ratio was, the more it reflected pattern A, the large, buoyant, apparently less atherogenic LDL. Once again, we could come back to that pretty reliable surrogate.