In an effort to do as much as possible for our health, we often turn to all sorts of combinations of capsules and vitamins. Although the intention is good, our body does not function like a container into which we can simply pour anything at any time. Many vitamins use the same absorption pathways, bind to the same receptors or directly alter the metabolism of others.
An inappropriate combination can completely negate the effects of the supplements; in the worst case, it can cause problems or put a strain on the body.
The battle over absorption
Minerals are among the most common culprits when it comes to mutual inhibition. This is due to competitive inhibition, as the body has a limited capacity to absorb certain substances in the intestinal wall.
Calcium and iron: One of the best-known and most common mistakes. Calcium directly blocks the DMT1 transporter, through which non-haem iron is absorbed. If you take an iron tablet and wash it down with milk or combine it with calcium, iron absorption can drop by as much as 50–60 per cent.
Zinc and Copper: High doses of zinc stimulate the production of the protein metallothionein in the gut. This protein binds to minerals, and has an even greater affinity for copper than for zinc. Paradoxically, long-term, unsupervised use of zinc alone often results in a severe copper deficiency, manifesting as anaemia and neurological problems.
Calcium and magnesium (in high doses): Although they are often sold together in pharmacies, at high concentrations (above 250 mg) they compete with one another for absorption. At normal doses from a varied diet, the body has no problem, but it is better to take high, one-off doses from supplements separately.
Chemical blockers and unsuitable solvents
Some substances inactivate one another through a chemical reaction, or require a completely different environment for the body to be able to process them at all.
Vitamin C and Vitamin B12: High doses of ascorbic acid (vitamin C) taken at the same time as vitamin B12 may break down the B12 in the digestive tract into inactive forms. If you need to take supplements of both, leave at least a 2-hour gap between doses.
Fat-soluble (A, D, E, K) – taken on an empty stomach or with water: Vitamins A, D, E and K require the presence of fats in the diet for absorption. Taking them with water alone in the morning on an empty stomach means that most of the active ingredient passes through the body without being utilised. Furthermore, excessive doses of vitamin E can negatively affect vitamin K-dependent blood clotting.
Whilst the body usually excretes excess water-soluble vitamins (B complex, C) in the urine, fat-soluble vitamins and minerals are stored in the tissues.
Combining multivitamins and single-ingredient supplements: It is common to take a multivitamin to boost immunity, and to add separate supplements containing zinc, vitamin D and ‘something for the joints’. This can very quickly lead to safe daily limits being exceeded, which puts a strain on the liver and kidneys.
Bleeding and blood thinning: High doses of vitamin E, when taken in combination with ginkgo biloba, omega-3 fatty acids or garlic extracts, may reduce blood clotting, which could pose a risk in the event of injuries or planned surgical procedures.
The basic rule for safe supplementation is simple. You simply need to divide several specific substances into two or three daily doses (morning, afternoon, evening) according to their solubility and how they interact with one another.
