The Best is the Enemy of the Good: Why You Shouldn’t Take All Vitamins at Once

No matter how well and healthily we eat, we usually take additional vitamins (essentially, we take pills to avoid taking pills later for illnesses). Vitamins interact with each other, enhancing or, conversely, hindering each other's absorption. That’s why the same complex can have different effects on different people — and it’s not about the quality of the supplement, but rather the biochemistry of the combinations. Sometimes even truly beneficial substances, taken together and not at the right time, start to suppress each other's functions and yield zero or completely different results than expected. Nutritionist Elena Mukhina shared the details.

Calcium Interferes with the Absorption of Iron and Zinc

This mineral literally competes with iron and zinc for the same transport pathways in the intestine. If taken together, the body will choose calcium, and iron and zinc will be absorbed significantly worse. "That’s why iron supplements are recommended to be taken separately from dairy products and calcium supplements. The ideal option is to space them out by at least two to three hours. And coffee interferes with the absorption of everything, particularly iron, so it should only be consumed separately," emphasizes the doctor.

Vitamins A, D, E, and K Compete for Absorption

All these vitamins are fat-soluble. This means that fats and the action of bile acids are needed for their absorption. If you swallow them all at once in large doses, they will start to interfere with each other because the body cannot effectively process such a volume at once. It’s better to either choose balanced complexes with well-thought-out dosages or take them at different meals throughout the day.

Vitamin C May Reduce the Effect of Vitamin B12

Ascorbic acid in large doses can destroy some B12 molecules in the stomach and small intestine. "If these vitamins are taken together, the absorption of B12 may decrease. That’s why it’s advisable to maintain an interval of at least two hours between them. This is especially important for people with anemia and B12 deficiency. However, it pairs wonderfully with iron and copper," explains the nutritionist.

Magnesium and Calcium Should Not Be Taken Together in High Doses

Although both minerals are important for bones and the nervous system, they work differently and even oppositely in the body. Calcium is responsible for muscle contraction, while magnesium is responsible for relaxation. In large doses, they can neutralize each other's effects. If both are needed, it makes sense to take them at different times of the day, for example, calcium in the morning and magnesium in the evening. However, potassium can and should be combined with magnesium; together they can help alleviate tachycardia, for example.

Some Combinations, on the Contrary, Enhance the Effect

There are also combinations that work much better together than separately. Iron is better absorbed with vitamin C, and vitamin D enhances the absorption of calcium and phosphorus. Vitamins B6, B9, and B12 together support the nervous system and participate in regulating homocysteine levels, while omega-3 improves the absorption of vitamin D and is beneficial for cell membranes. That’s why it’s important not only to avoid conflicting combinations but also to consciously choose the right duos.