Capsules and other presentations of vitamin supplements are usually considered harmless and there is a certain tendency to think that, as they are vitamins, taking too much is not dangerous or that several can be combined at the same time without any problem.

But the truth is that taking several capsules of the same or different vitamin supplements can be dangerous if toxic doses are reached, because vitamins can also have toxic effects in excess. Factors such as the exact formulation of each capsule, diet or health status and medications being taken, including over-the-counter medications and medicinal preparations of any kind, influence.

CDR and vitamin supplements

The Recommended daily allowance, abbreviated RDA, called in some countries Recommended Daily Intake (RDI), is the minimum recommended amount of a nutrient to stay healthy. There are tables with the CDR of energy and of each nutrient by population groups based on age, sex and other factors. The most used tables are those of the Institute of Medicine of the National Academy of Sciences of the United States, an institution that adopted the DRI system (Dietary Reference Intake or Dietary Reference Intake) based on which the daily values ​​or RDI (Reference Daily Intake either Recommended Daily Intake). In Europe, one of the most widely used reference tables are those of the German Nutrition Society.

In the vitamin supplement labels and inserts should appear the CDR percentage covering each vitamin, mineral and any other nutrients contained in each capsule. For example, a certain vitamin supplement might say on its label that it covers 80% of the RDA of vitamin C in each capsule.

The most normal thing is that the supplements are multivitamins and that the same product combines several vitamins, as well as minerals, amino acids and other nutrients. Taking several at the same time it is easy to exceed the CDR. For example, a preparation may combine vitamin D and vitamin K; another may combine vitamin D and calcium. If you take both, you will be taking double vitamin D and you may exceed the CDR of this vitamin.

Exceed CDRs of some vitamins not necessarily a problem. It depends on the vitamins involved. Some vitamins have a very wide margin and the toxic doses are too high and difficult to reach, while others have less margin.

In general, water-soluble (water-soluble) vitamins are eliminated relatively quickly through the urine, almost daily, making it even more difficult for toxic doses to accumulate. These rapidly eliminated vitamins are usually present in vitamin supplements in amounts greater than 100% of the RDA and even then the risk of consuming toxic doses is very low. There are other vitamins, the fat-soluble ones, whose elimination is much slower and exceeding the RDA each day in a sustained way can cause toxic doses to be reached over time by cumulative effect. For example, vitamin C is water soluble and vitamins A, D and E are fat soluble.

Even so it’s hard to tell when problems will appear from taking several vitamin supplements at the same time. This is because the CDRs are still recommendations; they are considered sufficient minimum amounts to prevent some diseases in the majority of the population, such as the RDA of vitamin C and the prevention of scurvy. The exact amount of each nutrient for each person will be very different depending on many factors, such as age, sex, physical and intellectual activity, health status, drug treatments and many other factors.

The influence of diet

The foods you eat contain vitamins. For example, if you eat an orange every morning you cover the daily dose of vitamin C and you would not need any supplement of this vitamin. Therefore, it is important to consider the diet you follow as well as the composition of the vitamin capsules you take and the possible repetition of ingredients between them.

To make matters more complicated, the absorption of vitamins is influenced by various factors that can cause them to be completely absorbed or that only a small proportion of the amount ingested is absorbed. For example, vitamins A, D, and E are fat-soluble (fat-soluble) and are best absorbed if consumed with fatty foods; for this reason it is very likely that fat-soluble vitamins taken in capsules will not be fully used.

Medications, medicinal preparations and health status

Some medicines and medicinal preparations of any kind (herbal, homeopathic, etc.) can interact with the absorption of vitamins and their effect. For example, retinoids are chemically similar to vitamin A (retinol) and they are medications frequently prescribed for psoriasis and other conditions that affect mucous membranes and epithelia.

Physicians should always ask patients about other sources of this vitamin that they may be consuming, and patients should always bring to the attention of their physician any medications, medicinal preparations, or vitamin supplements they are taking, including those that are over-the-counter or prescribed. by other professionals.

Replace supplements with a balanced diet

Without a doubt, the best way to ensure that you get enough of all the nutrients your body needs is to follow a balanced diet that includes a high amount of fruits and vegetables. Nutritional supplements should never replace a varied and balanced diet and should only be taken as something exceptional at specific times when, for some reason, there is a greater need for a vitamin or nutrient or a temporary deficiency has to be made up.

In any case, nutritional supplements should always be taken under professional advice.