Introduction

Today I’m going to give you a general overview of what vitamins are, their main functions and which ones are the most important. In future posts, we’ll look at them one by one to get to know them better and find out which foods contain them.

Vitamins are complex organic molecules with no structural relation to one another. They are micronutrients, meaning the body requires them in very small amounts. They have no energetic value.

They are essential, meaning the body cannot synthesise them. However, there are three exceptions that can be synthesised:

– Vitamin D₃ in the skin, although it is often not sufficient.

– Vitamin K, synthesised by intestinal bacterial flora.

– Nicotinic acid, synthesised in the liver through the conversion of tryptophan.

Plants do not produce vitamin D or B₁₂; the rest of the vitamins they do.

When vitamins are ingested but not absorbed, we speak of a shortage, and when they are not ingested at all, we speak of a deficiency.

Types of Vitamins

Their solubility in water or fat determines their means of transport, excretion and storage potential. They are classified as either water-soluble or fat-soluble.

Water-soluble Vitamins

These are relatively harmless, although high doses can alter metabolism. They are not stored in the body; excess amounts are excreted in urine and they are generally distributed in extracellular and intracellular fluids.

They include:

• Thiamine (B₁)
• Riboflavin (B₂)
• Niacin (B₃)
• Pantothenic acid (B₅)
• Pyridoxine (B₆)
• Biotin (B₈)
• Folic acid (B₉)
• Cyanocobalamin (B₁₂)
• Ascorbic acid (C)

They act as coenzymes, activating a large number of enzymes. A lack of coenzymes generally interrupts the reaction chain; the substance that should be transformed is not, and it accumulates. As a result, the product of the reaction decreases and energy from food is not released, preventing the cell from obtaining energy.

The most immediate consequence of a vitamin deficiency is a biochemical alteration, although the link between biochemical damage and clinical symptoms is not well understood.

Secondary deficiencies can appear even with sufficient vitamin intake, due to several factors:

• Disruption in digestive utilisation and absorption of the vitamin.
• Vitamins bound in a way that prevents absorption, e.g., niacin in maize.
• Egg whites contain avidin, which binds to biotin and blocks its absorption.
• Destruction of vitamins, such as thiamine in raw fish, which contains thiaminases—enzymes that break down thiamine.
• Vitamins with similar chemical structures, such as vitamin K: in its vitamin K form it promotes clotting, but in the form of dicoumarol, it increases bleeding.
• Some medications can also cause secondary deficiencies, such as antibiotics and contraceptives.

Fat-soluble Vitamins

These vitamins are heat-stable and are transported in the fats of the foods that contain them. They can be stored and are not excreted in urine, which makes them potentially toxic in excess.

• Retinol A (stored in the liver)
• Calciferol D3 (stored in adipose tissue and the liver)
• Tocopherol E (found in cell membranes)
• Menadione K (synthetic, stored in the liver)

Now that you have a general understanding of what vitamins are, let’s delve a bit deeper into the topic of vitamin supplements, which have become very popular in recent times.

Do Vitamin Supplements Actually Work?

Nowadays, there is a growing trend of taking vitamin supplements to boost energy during times of stress, nervousness or fatigue. I’ve even seen many people take them simply as a preventative measure. In Spain, spending on vitamin and dietary supplements keeps increasing (around 259 million euros last year, according to Euromonitor), and this is concerning, as it has yet to be proven that they are a cure-all for better health.

In my opinion, taking supplements is unnecessary, as a balanced diet and healthy lifestyle habits should provide all the vitamins we need through food.

If there is truly a shortage or deficiency in the diet, the solution should be to improve eating habits, including all the foods that we know support good health.

There are cases where, due to illness, surgery or trauma, a doctor may recommend supplementing the diet with vitamins, because in such cases the deficiency cannot be corrected otherwise.

So now you know—if you were about to buy a vitamin supplement or already have one at home, bear in mind that your body will most likely eliminate anything it doesn’t need. That’s basically money down the drain.

Plan your diet better and tailor it to your needs throughout the year—you’ll eat better, enjoy it far more, and it’ll be much more affordable.