The dangers of consuming vitamins in excess

Vitamins are natural substances that humans cannot synthesize, that is to say, you must take them from external sources.

People need 13 vitamins. In the first place, the 9 water-soluble (soluble in water) that include C and those of group B (B1, B2, B3, B5, B6, B7, B9 and B12). In second place, the 4 fat-soluble (insoluble in water), which include A, E, K and D.

A balanced diet provides us with the necessary quantities since they are present in a great variety of foods, especially of vegetable origin.

An important exception is vitamin B12, which is present in foods of animal origin. For this reason, vegan diets should consume this vitamin as a nutritional supplement.

Vitamin deficiency (hypovitaminosis) is the cause of various diseases. However, the pathologies associated with hypovitaminosis are rare, since the daily requirements of vitamins are minimal (in the order of micrograms to milligrams).

First diseases due to vitamin deficiency

Scurvy It was the first disease for which its dependence on nutritional factors was known. It was the French navigator Jacques Cartier who described the disease in some indigenous people in Canada and in part of his crew.

Later, the Scottish physician James Lind published a treatise on scurvy and suggested the use of lime juice for your treatment.

We currently know that such a pathology is due to a deficiency of vitamin C, also called ascorbic acid (which means «anti scurvy»). That is why they recommended such treatments.

Since then, possibly, the study of vitamins and their role in preventing certain diseases has been the biggest milestone in biomedical nutrition research.

Apart from scurvy, there are other diseases directly associated with vitamin deficiencies.

For example, beriberi (vitamin B1), pellagra (vitamin B2), anemia (vitamin B9 or vitamin B12, independently), xerophthalemia (vitamin A, leading to blindness), and rickets in children or osteomalacia in adults (both associated with vitamin D deficiency).

Overdose can also be vitamins

Due to its nature as a natural substance and the known beneficial effect on health, many people are using large amounts of vitamins indiscriminately and vitamin complexes without a prescription.

However, this practice is not without risks. On the one hand, vitamins are highly biologically active chemical compounds that have various roles in our body.

It is well known that active substances exert their action at a certain concentration and that what can be beneficial at a physiological concentration can be toxic in greater amounts.

Some reasons why a beneficial compound can become toxic when used in excess include:

  1. The amount of the unused bioactive principle can accumulate in certain tissues – for example, lipophilic substances accumulate in adipose tissue and in the liver, and hydrophilic substances are stored in some organs such as the kidneys and the liver – causing long-term deleterious effects.
  2. It is also possible (and not exclusive with the previous explanation) that the excess of bioactive compound is metabolized to toxic substances. This is especially important in the substances that accumulate in the liver, which is the «chemical factory» of our body.
  3. The excess of bioactive compound can interact with other substances present in our body. It is well known that some vitamins interact with some drugs decreasing their activity, which can be detrimental to our health.

For these reasons, bioactive substances should always be consumed in the indicated doses, based on the scientific method.

Vitamin A and the peculiar case of the supposed vitamin D

In general, few side effects of water-soluble vitamins are known, since they are excreted relatively easily, even in the case of hypervitaminosis (with some exceptions).

On the contrary, the excess of fat-soluble vitamins produces more and more serious harmful effects. Remember that these are A, E, K and D, which we will see in detail.

Vitamin A is present in numerous fruits and vegetables and, if a balanced diet is followed, its supplementation is not necessary.

From a physiological point of view, its main function is in the process of vision. It is also known to be an immune system stimulant.

Deficiencies in vitamin A usually arise from a chronic disease that affects its absorption. It manifests itself in some symptoms related to vision problems, a higher frequency in infections of the skin, respiratory tract and mucous membranes.

But the excessive consumption of vitamin A has also been associated with certain diseases and ailments, among which we can mention headache, fatigue, nystagmus (involuntary and uncontrollable movement of the eyes), peeling of the skin, an increase in the lymph node and problems various bone.

Vitamin D, really, it is not a vitamin but a hormone. In the diet we consume precursors of vitamin D, which are transformed into it in our body through photochemical reactions, for this reason it is necessary to sunbathe to have good levels of vitamin D.

Woman walking in the sun
(Photo: GETTY IMAGES)

Currently, it is common to find, through blood tests, that the amount of vitamin D is less than the standard.

This deficiency can be caused by two factors. On the one hand, due to inadequate exposure to sunlight.

For another, for the tendency to lower your cholesterol level (either through medication or diet), since this is a precursor of vitamin D in the body.

The vitamin D deficiency has serious consequences on our health. It causes rickets in children and osteomalacia – softening of the bones – in adults.

Furthermore, vitamin D dietary supplements do not tend to alleviate this deficit, perhaps due to ineffective absorption or, more frequently, the poor quality of over-the-counter preparations.

In some situations -such as in pregnancy, lactation and in people with problems in the metabolic pathway of vitamin D- there is an increased need for vitamin D.

In these cases, you should always follow the doctors’ instructions, as you have to remember that it is a hormone and that imbalances in the endocrine system have serious health consequences.

On the one hand, some recent publications have analyzed intoxications caused by hypervitaminosis D, which have shown alarming growth for a decade.

Vitamin D has been found to cause high concentrations of calcium ions in plasma, causing excitability in the central, autonomic, and somatic nervous systems. TIt has also been associated with cognitive delay.

Other symptoms caused by excessive doses of vitamin D are headache, fatigue, growth retardation (which can be reversed with medical treatment), diarrhea and failure of various organs (kidneys, lungs, heart, blood vessels and skin).

In addition, from a biochemical and physiological point of view, hypervitaminosis can cause irreversible effects on the production of calcitonin, which is the hormone that controls the way the body uses calcium.

Vitamin D
(Photo: GETTY IMAGES)

Other fat-soluble vitamins: E and K

The physiological role of vitamin E in humans is not fully elucidated, although it does play an important role.e in blood clotting.

Its main activity is as an antioxidant. Regarding the effects caused by its deficit, there are still no results in humans.

But it does on hypervitaminosis E, and these indicate that it does not produce serious harmful effects. For this reason, also used as a food additive (E-306, E-307, E-308 and E-309).

Finally, regarding its toxicity due to overdose, the K1 type can cause some mild effects such as transient facial flushing, or a more serious one such as dyspnea, which can cause death.

For his In addition, excess vitamin K2 can lead to kernicterus (a type of cerebral palsy in newborns), hemolytic problems in children, jaundice, damage to the mucous membranes, and liver problems.

Also, due to its chemical (oxidant) characteristics, vitamin K can interfere with some antioxidants.

That is why it is necessary not to take these supplements lightly and, in case of observing any anomaly, consult with the professionals of your health center.

* Bernardo Herradón is a scientific researcher in organic chemistry and a scientific communicator at the Institute of General Organic Chemistry (IQOG – CSIC). This article appeared on The Conversation. You can read the original version here.

It may interest you:

* High doses of vitamin C can increase the risk of kidney stones
* What foods can alleviate the symptoms of vitamin B12 deficiency
* 24 foods with vitamin D that will strengthen your health


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