The statement that vitamins and minerals do not combine with each other — is an oversimplification and, in some cases, indeed an outdated notion formed in the mid-20th century.
Interactions between nutrients exist, but they are not always critical and not always harmful.
Biochemistry of Nutrient Interactions
Antagonisms between minerals. Some minerals compete with each other for absorption in the small intestine, as they use the same transport proteins:
- Zinc and copper — excess zinc reduces copper absorption (through the protein metallothionein);
- Calcium and magnesium — high doses of calcium can reduce magnesium absorption;
- Iron and zinc — taking iron in high doses can inhibit zinc absorption and vice versa.
However, when taking regular multivitamins and adequate dosages, these effects are mitigated — the body adapts by using different transport and regulatory mechanisms.
Synergies: vitamins that enhance each other's effects. Some vitamins work better in pairs:
- Vitamin D and calcium — D increases calcium absorption in the intestine.
- Vitamin C and iron — C converts iron from the non-absorbable form Fe³⁺ to the easily absorbable Fe²⁺.
- Vitamins B6, B9 (folate), and B12 — work together in methylation and hematopoiesis.
Solubility and food. Fat-soluble vitamins (A, D, E, K) are absorbed only in the presence of fats. Water-soluble vitamins (B group, C) — do not require fats but are quickly excreted.
Conclusion
When it comes to the simultaneous intake of vitamins and minerals, especially in the form of multivitamin complexes or with food, — the body usually manages their absorption thanks to a fine regulatory system: it regulates transport, binds excesses, temporarily slows down absorption, etc. In the real biochemistry of the body, "conflicts" almost never occur, especially if nutrients are supplied in physiological or moderately therapeutic doses.
However, the risk of competition (antagonism) does indeed increase, but not with combinations, rather — with isolated and high-dose intake of individual nutrients, as is sometimes done with supplements (for example, only iron, only zinc, only calcium — and in large doses). Especially with prolonged use — this can disrupt balance, displace other elements, and deplete cofactors.
That is:
- Taking nutrients together — is not a problem.
- It is the separate intake of high doses — that can be a problem.
