The Honest Supplement Audit

The thing in your multi that might be working against you

Most people in the serious-amateur-athlete category either take nothing or take everything. I fell into the "take everything" camp — a comprehensive multivitamin, an endurance stack, planning to add omega-3 and creatine back in. Reasonable, right?

Except here's what I didn't know: high-dose Vitamin E — the kind that shows up in most comprehensive multivitamins at 800–900% of daily value — has solid peer-reviewed evidence suggesting it blunts the mitochondrial adaptations you're literally training to create.

The 2009 Ristow et al. study in PNAS, replicated by Paulsen et al. in the Journal of Physiology in 2014, showed that high antioxidant supplementation can suppress the reactive oxygen species signaling that tells your mitochondria to multiply. ROS aren't just cellular damage — they're the trigger for aerobic adaptation. Suppress them too aggressively and you've paid the training tax without collecting the dividend.

The fix isn't to quit supplementing. It's to be precise about what you actually need.

What actually matters for endurance athletes

• D3 — Most athletes run deficient. Dietary sources are nowhere near sufficient at training volume. Target 40–60 ng/mL in serum — get tested before you just start dosing.
• Magnesium — Depleted through sweat at rates most people don't compensate for. Use bisglycinate or malate form — oxide is barely absorbed.
• Iron — Foot-strike hemolysis is real. Running literally destroys red blood cells through ground impact. Worth monitoring, not just assuming you're fine.
• Omega-3 (EPA/DHA) — Anti-inflammatory, reduces triglycerides, and does not blunt training adaptations the way Vitamin E does.
• Creatine — Most studied ergogenic supplement in existence. Relevant for both strength work and high-intensity interval quality. Daily supplementation beats periodic.

That's a much shorter, more targeted list than what most supplement companies want to sell you. And whether it's the right list for you depends heavily on something most supplement conversations skip entirely: what your diet is actually already covering.

Your diet changes the entire supplement equation

The reason that shorter list makes sense for me is because I eat pretty well — multiple lean protein sources, varied vegetables daily, quality fats, no alcohol, home-cooked most of the time. If your diet looks remotely similar, a comprehensive multivitamin is largely redundant for most micronutrients. The B vitamins, selenium, zinc, Vitamin A, calcium — your food handles it.

But even eating well, there are real gaps at training volume. Vitamin D is almost impossible to get from food alone. Magnesium losses through sweat are significant — the RDA was set for sedentary adults, not people doing daily doubles. And iron monitoring matters specifically for runners because of hemolysis, regardless of how much red meat you eat.

One gap nobody talks about: If you've switched from iodized table salt to Himalayan or sea salt — which is a common move among people eating this way — you may have quietly eliminated your only reliable iodine source. Himalayan salt contains negligible iodine. This matters for thyroid function, which drives your metabolic rate and energy availability. Easy fix: a standalone iodine supplement at ~150mcg/day, or just use iodized salt for some of your cooking.