Dr. Elena Cho, Head of Research at Ayurnomics, spends time reading multivitamin labels, looking past the featured numbers to the ones manufacturers leave out - the ratios between one mineral and another, or between a B vitamin and its metabolic partner. "Dose is what gets printed on the front," she says. "Ratio is what determines whether any of it reaches its target."
This interview has been edited for clarity.
Why the Dose Conversation Is the Wrong Conversation
You have a phrase: "dose is a promise, ratio is the contract." What do you mean?
A label saying 18 mg iron or 500% DV of B12 tells you what went into the capsule at the factory. It doesn't tell you what you will absorb, or whether the formula helps your body absorb it. A milligram declaration is a one-ingredient story. Absorption is a systems story. Two nutrients competing for the same gut transporter can mean that the effective dose of both is lower than either label figure suggests.
Give me a concrete example.
Iron and zinc are the clearest case. Both rely on divalent metal transporters in the small intestine. Research in The American Journal of Clinical Nutrition showed that when iron and zinc are consumed together in solution, competitive inhibition at these shared transporters reduces the absorption of each mineral in a dose-dependent fashion. That finding is over 30 years old and has been confirmed repeatedly. A later analysis confirmed that iron-zinc and calcium-iron interactions reduce mineral uptake when these nutrients are present at high ratios relative to each other in the same supplement. The practical implication: a multi-nutrient containing a generous dose of non-haem iron alongside an equally large dose of zinc may deliver less than a better-balanced version.
Why does the industry keep formulating this way if the interaction is so well-documented?
Labels are regulated by what's in the product, not by what your body actually absorbs from it. The manufacturer declares a milligram figure. Regulators check whether that figure is accurate. No one checks if mineral A actually reaches your system when mineral B is there too at those doses. So the incentive is to maximize each nutrient line individually. Ratio logic - thinking about how nutrients interact inside the body - requires planning that starts with how nutrients work together, not just what looks good on paper.
The Folate-B12 Blind Spot
Is this only a mineral problem, or do vitamins have a ratio issue too?
Vitamins do not compete for the same transporter in the way minerals do, but they are metabolically interdependent, and that creates a separate ratio problem. The clearest case is folate and vitamin B12. Both are involved in one-carbon metabolism and homocysteine regulation. A study in the European Journal of Clinical Investigation found that folate is the primary determinant of circulating homocysteine concentration in healthy adults with apparently adequate B vitamin status. That sounds reassuring - until you see the direction the ratio can tip.
Which direction is the problem?
High folate alongside low B12. Many multi-nutrient formulations load up on folic acid because it is inexpensive and the dose stands out on a panel. B12 is more costly and harder to flag in standard blood work at early stages of inadequacy. A 2009 paper in The American Journal of Clinical Nutrition found that older adults with elevated plasma folate and low serum B12 had significantly higher homocysteine and methylmalonic acid - both markers of B12 inadequacy - compared with adults whose B12 was adequate. The folate was not compensating for the B12 shortfall. It may have masked it.
Does this only matter for older adults?
The research is concentrated in older adults because B12 absorption tends to decline with age. But the biochemical mechanism - high folate can hide the signs of B12 deficiency while the problem continues - applies across the lifespan. If your multi-nutrient carries a substantial folate dose relative to a token B12 figure, that imbalance is worth examining. A formulation that works well doses them to work together through the methylation cycle, not to highlight one and hide the other. The Journal's piece on why B12 shots alone don't resolve fatigue covers this whole-complex argument in more depth.
Magnesium as a Vitamin D Co-Pilot
You have written internally about magnesium and vitamin D as a ratio pair. Where does that fit into this conversation?
Magnesium is a cofactor for the enzymes that convert vitamin D from its storage form - 25-hydroxyvitamin D - into its biologically active form, 1,25-dihydroxyvitamin D. Without adequate magnesium, those enzymatic conversions slow down. A randomized trial published in The American Journal of Clinical Nutrition found that magnesium supplementation influenced vitamin D metabolism in both directions - raising 25(OH)D concentrations in participants who were insufficient, and moderating them in participants with higher baseline levels. The trial was clear: doctors need to think about magnesium status when checking how well vitamin D supplements work.
So a multi-nutrient that includes vitamin D but carries a minimal magnesium dose may underperform on D?
That is a reasonable reading of the data, yes. Vitamin D gets the marketing spend. Magnesium does the enzymatic work and rarely makes the front panel. A multi-nutrient that pairs a clinically relevant vitamin D dose with enough magnesium lets these nutrients work together instead of separately. That is the ratio argument applied to a nutrient pair most people don't think about.
Reading a Label With Ratio Logic
Most people don't look past the front panel. Where do you actually start when you pick up a label?
The Supplement Facts panel. I look at the mineral block first and ask: what is the ratio of non-haem iron to zinc by milligrams? Competitive absorption interference becomes measurable when iron is much higher than zinc at the doses used. Then I check if B12 is balanced with folate - not just as a regulatory requirement. A 2018 review in Nutrients formalized the argument that examining dietary micronutrient ratios works better than looking at each nutrient alone when assessing metabolic outcomes. The same logic applies directly to supplement design.
What else do you look for?
Calcium's proximity to iron in the formulation - calcium can also inhibit divalent metal transporter activity and reduce iron uptake when doses are high. The presence of vitamin K2 alongside vitamin D, since K2 is involved in directing calcium toward bone tissue rather than soft tissue. Selenium and iodine together at high combined intakes. These are not exotic concerns. They're the design of the formula. A multi-nutrient that has considered these interactions is different from one put together by stacking big numbers that look good. The Journal's piece on mineral competition in multivitamins covers the absorption mechanics in more detail for readers who want to go deeper.
What a Well-Designed Formula Looks Like in Practice
Is there a formulation you point to as an example of this ratio-first thinking?
I won't name other brands. What I can say is that the principles described in this conversation were the primary design criteria when working on Ayurnomics's Nutricore-5 Multi-Nutrient - a multivitamin and mineral blend created carefully, with inter-nutrient ratios and cofactor pairings considered from the start, not as an afterthought. The goal was a Supplement Facts panel that functions as a working system, not just big numbers in one pill.
For someone already taking a multi from another brand - is this research grounds for switching, or grounds for being more informed?
More informed first, always. Look at your current Supplement Facts panel with ratio logic rather than single-number logic. If your iron dose is much higher than your zinc, ask whether that is right for you - perhaps your clinician directed a higher iron dose for a documented deficiency - or whether it is just how the label was put together. If your folate dose is much bigger than your B12 dose, that is worth discussing with a clinician, particularly if you are in an age group where B12 absorption is variable. Readers who blame afternoon energy crashes on missing nutrients will find the Journal's piece on why afternoon energy crashes outlast your multivitamin a useful complement to this conversation - it covers how timing and mineral bioavailability interact through a full day.
Supplementation is not a problem to solve once. You need to keep checking it.
If you are on prescription medication, pregnant, or breastfeeding, the mineral and B vitamin interactions described here carry additional clinical dimensions - speak with your clinician before adjusting your multi-nutrient regimen, as drug-nutrient interactions can shift the ratio picture considerably.
Browse the Vitamins and Minerals collection at Ayurnomics, or review the formulation details for Nutricore-5 Multi-Nutrient directly.
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