Why do we religiously pop multivitamins… but couldn’t actually tell you what Vitamin B12 does if our lives depended on it? Dan Koh and Neil Humphreys admit the truth: even the fittest among us might be blindly trusting the alphabet soup of nutrition.

In Part 1 of their two-part deep dive, the duo tackles the first three letters in the vitamin lineup — A, B, and C. What do these vitamins actually do? Where do we get them? And how do we know if we’re not getting enough?

From improving vision and boosting immunity to fighting fatigue and brain fog, Dan and Neil uncover why these micronutrients are anything but minor — and how simple food choices can make a big difference.