This is one of the most-asked questions about supplementation, and the honest answer is: probably, yes — even if your diet is genuinely good. That's not a sales pitch. It's a reflection of how hard it actually is to hit every micronutrient target through food alone, consistently, every single day.
"Eating well" and "nutritionally complete" aren't the same thing
A diet can be well-balanced by every reasonable standard — lean protein, vegetables, whole grains, healthy fats — and still fall short on specific nutrients, for reasons that have nothing to do with willpower or effort:
Modern soil has measurably lower mineral content than it did decades ago, which means the same vegetable today often contains less magnesium, zinc, and iron than it used to. Cooking and storage degrade water-soluble vitamins like C and several B-vitamins. And some nutrients — vitamin D being the clearest example — are genuinely difficult to get from food at all; most of it is meant to come from sun exposure, which a lot of people simply don't get enough of.
Where gaps show up most often
A few nutrients are common shortfalls even in generally healthy eaters: vitamin D, magnesium, and — depending on diet pattern — vitamin B12 and iron (particularly relevant for anyone eating a largely plant-based diet). None of these are exotic; they're just easy to under-hit without noticing, because the symptoms of a mild, chronic shortfall (low energy, poor sleep, slower recovery) are easy to attribute to something else.
Think of it as a baseline, not a replacement
A multivitamin isn't meant to replace real food, and it can't compensate for a genuinely poor diet. What it's actually good for is closing the gap between what your diet provides on an average day and what your body needs on every day — a floor, not a strategy. If your diet is strong, a multivitamin is insurance. If it's inconsistent, it's closer to a necessity.
The most useful way to figure out whether you personally need one isn't guessing — it's tracking what you're actually taking against your body's needs, and watching for patterns in how you feel. That's the whole premise behind Re's Insights tab: not telling you what to take, but helping you see, from your own data, whether what you're doing is actually working.
