Vitamin supplements: what they are and when to use them

Vitamins are essential nutrients, i.e. substances that are essential for the development and proper functioning of the body. More precisely, vitamins, together with minerals, form the group of micronutrients, i.e. substances that the body needs only in small quantities, unlike macronutrients, i.e. carbohydrates, proteins, fats, fibre and water, which the body needs in larger quantities. Micronutrients play a key role in the production of enzymes, hormones and other substances needed to regulate metabolism, tissue development and growth, and the functioning of the body’s organs, apparatuses and systems.


Vitamin-based supplements contain different types of vitamins, and can be taken as a support when a person’s diet, which is the main source of vitamin intake for the body, does not provide the daily requirement. Vitamins, together with some substances important for the functioning of organic processes, such as certain fatty acids and amino acids, must necessarily be introduced from outside through the diet.

Vitamins are present in varying amounts in different types of food: foods of plant origin, especially fresh fruit and vegetables, but also meat, fish, milk and eggs. The best way to ensure that the body has a sufficient supply of all vitamins is to follow a varied and balanced diet. There are, however, situations in which the vitamin intake with the nutritional regime adopted is not sufficient to meet the requirements. This is known as vitamin deficiency or hypovitaminosis, when a vitamin is present in the body in insufficient quantities. Avitaminosis is the term used in much rarer cases in which a vitamin is completely absent.

The cause of vitamin deficiency can be, as mentioned, an insufficient intake of these essential nutrients through the diet, when the diet is not varied and balanced enough or otherwise incorrect. There are also situations of increased vitamin requirement, for example pregnancy and breastfeeding in women or the growth of children, but also conditions of prolonged stress or intense physical activity, in which dietary intake may be insufficient.

Some gastrointestinal pathological conditions may also interfere with the absorption of vitamins, and therefore represent risk factors for a deficiency of these micronutrients.

The elderly and alcoholics are more at risk of hypovitaminosis, both because of their tendency to have an unbalanced diet and because they are more likely to have an intestinal alteration, a possible cause of malabsorption. Finally, some drug therapies can also interfere with the absorption or production of vitamins, reducing their level in the body, especially if they are continued for long periods of time.

In the cases listed above, where there is an increased risk of hypovitaminosis, supplementation with specific products to correct the deficiency of one or more vitamins may be considered on the advice of a doctor or pharmacist.

Vitamin supplements act by providing the correct intake of one or more vitamins, thus counteracting or preventing the effects of deficiency, which vary depending on the vitamin present in insufficient quantity.

Fatigue, tiredness and lack of energy, difficulty concentrating and memory problems, and digestive disorders can all be red flags.

The benefits of adequate vitamin intake include, for example, maintaining healthy teeth, skin and hair and protecting cells from oxidative stress. For athletes, vitamin supplements can be useful for maintaining muscle function and for faster recovery as they counteract fatigue and tiredness.

Let’s take a more detailed look at the consequences of insufficient intake of the different types of vitamins.

Vitamins are classified into two categories:

  • Fat-soluble vitamins, which enter the body along with dietary fat and accumulate in the liver
  • Water-soluble vitamins, which are not stored in the body and therefore require daily intake through nutrients

Fat-soluble vitamins are:

  • Vitamin A or retinol: Important for the visual system, the immune system and the skin
  • Vitamin D or calciferol: can be produced directly by the body through the action of sunlight, or absorbed through food. It contributes to the normal function of the immune system, calcium absorption and maintenance of healthy bones
  • Vitamin E or tocopherol, a substance with known antioxidant power
  • Vitamin K, which contributes to regular blood clotting

Water-soluble vitamins are:

  • B vitamins (vitamin B1 or thiamine, vitamin B2 or riboflavin, vitamin B5 or pantothenic acid, vitamin B6 or pyridoxine, vitamin B9 or folic acid, vitamin B12 or cobalamin): they have various functions, such as contributing to normal energy metabolism
  • Vitamin C or ascorbic acid: it has various tasks to keep the body in shape, including its functions as an antioxidant
  • Vitamin H or biotin: generally present in sufficient quantities in the body, because it can not only be introduced with food, but is also synthesised by the intestinal flora
  • Vitamin PP or niacin: contributes to energy metabolism and normal functioning of the nervous system

The deficiency of a particular vitamin can be ascertained through specific examinations recommended by your doctor, who will consider whether a food supplement needs to be taken.

For a correct intake of vitamin supplements, firstly avoid deciding for yourself and always consult your doctor before taking a dietary supplement to assess the actual need, following their instructions regarding the mode, dosage and duration of intake. In fact, vitamin supplements may interfere with the absorption of some medicines or cause side effects, e.g. stomach upset, diarrhoea or constipation. For those with allergies, or who are pregnant or breastfeeding, as well as for children, vitamin supplements, if necessary, should only be taken under medical supervision.

Vitamin supplements are available in different formats: tablets, effervescent tablets, capsules (including extended-release capsules), powders (often in single-dose sachets), solutions (in vials or small bottles), gumdrops or orodispersible films, i.e. to be dissolved in the mouth.

The time of day when it’s best to take them depends on the specific vitamin: in the case of fat-soluble vitamins, in general, it’s advisable to take them immediately after meals, on a full stomach, as these vitamins are absorbed more effectively in the presence of fat.

Vitamin D deficiency

Vitamin D and sunshine

Vitamin D excess

Vitamin D and bones

find out more about vitamin d3 ibsa