Whether vitamin supplements are good for you or not is a question to which there is no simple yes or no answer – the best answer is the rather vague “it depends”. In order to increase our understanding around vitamins and when supplements are called for, we need to dig deeper.

Vitamins can be divided into fat-soluble ones and water-soluble ones. A, D, E and K are fat-soluble and there are nine different B vitamins and vitamin C that are water-soluble. The role of vitamins in the body includes aiding the metabolism and growth as well as maintaining body tissue, which makes them essential. If you eat a varied diet, which provides you with enough energy, you will normally get all the vitamins you need. Since vitamins affect health, we are often fooled into thinking that an increased dose = improved health, when the truth is that both a deficiency and overdosing may have negative effects on the body. The margin of error for what is a healthy amount for the body and what is a harmful one varies widely from one vitamin to another. Overdosing on vitamin A and vitamin D can have serious consequences, while vitamins B and C can be consumed in large doses, more or less without any risks, provided that you are fit and well. The reason for this is that vitamin A is fat-soluble, and the surplus is stored in the liver, which eventually puts a strain on the liver and may cause damage. Overdosing on vitamin D can cause elevated calcium levels in the blood, which in turn can lead to kidney damage. Vitamins B and C, on the other hand, cannot be stored in the body since they are water-soluble and any surplus which the body cannot absorb is expelled in the urine.

There is no evidence that vitamin supplements in general are good for healthy individuals who eat a varied diet. However, supplements may benefit certain individuals who eat a less balanced diet, e.g. if you choose to eliminate animal products partly or completely. This is because some vitamins can only, or mostly be found in animal products, e.g. vitamin D and B12 (cobalamin). Other target groups who may need supplements due to a change in their nutritional needs are those who are pregnant, breastfeeding or unwell.


B12 or cobalamin, as it is also known, is only found in animal produce, such as meat, fish, shellfish, egg, liver, cheese and milk. Certain plant-based dairy substitutes, such as oats/ soya/ rice/ almond/ coconut/ cashew drinks tend to be enriched with B12. B12 is essential for things like cell metabolism, the formation of blood cells and for a functioning nervous system. Low consumption may consequently lead to anaemia and neurological symptoms. It is therefore very important to take supplements if you are vegan or are suffering from an illness which inhibits B12 absorption. Lacto-ovo vegetarians may also not get enough, even if they eat meat and eggs. The ability to absorb B12 decreases with advancing age and, as a result, the risk of a deficiency increases in older individuals.

Those who have undergone intestinal surgery, gastric bypass or gastric sleeve, are at increased risk of suffering from a vitamin B12 deficiency, which is why these patients often need to take supplements for the rest of their lives, following their gastric surgery. The reason for the increased risk of deficiency is that when the stomach is bypassed or reduced in size during the operation, it means that the amount of hydrochloric acid in the stomach is restricted. The hydrochloric acid of the stomach contains a protein called intrinsic factor (IF), which is needed in order to “activate” B12 so that the vitamin to be absorbed. Following gastric surgery, only a small amount of IF remains in the stomach, which is why high doses of vitamin B12 are recommended to those who have undergone gastric surgery.

Vitamin D

Vitamin D is unique in that it is made in the skin, and across the world the sun is the most common source of vitamin D. That means that those of us in northern hemisphere are at greater risk of deficiency since we have fewer hours of sunshine in a year. The sun is only strong enough to enable vitamin D synthesis through radiation for a limited time of the year and time of day. Those who wear clothing that covers the entire body, those with a darker skin tone and those who, for any reason do not spend much time outdoors are therefore particularly at risk. Overweight people are also at increased risk of deficiency, since vitamin D is stored in fatty tissue and a smaller quantity of the vitamin is accessible to the body. Vitamin D deficiency may affect the bone structure in that bones lose density and become weak.

In terms of food, we mainly get vitamin D from oily fish, such as salmon, herring, mackerel and tilapia, but also dairy products with added vitamin D, as well as egg and meat. Again, these are mainly animal products, hence the recommendation of supplements for those eating a completely plant-based diet. All children under two are recommended vitamin D supplements and anyone who is pregnant should ask their midwife for advice on supplements.

How do I know if I need supplements?

If you suspect that you have a vitamin deficiency, you would be advised to contact your GP surgery. They can arrange blood tests for you in order to establish if you have any deficiencies and what these might be. The first piece of advice is to review your food intake, since a low vitamin intake can often be improved simply by eating a better diet. If, on the other hand, you have a diagnosed deficiency and your doctor thinks that you need supplements of some kind, these will be prescribed to you. Do not attempt to “treat” what you think is a vitamin deficiency on your own but find out WHETHER you are deficient and WHAT that deficiency might be. Avoid multivitamins since they often contain a dose far above the RDI (recommended daily intake). They may not cause any harm, but nor will they provide any benefits to your health if you already eat a balanced diet.

By Sandra Nilsson

Sources: Swedish food agency, Näringslära för högskolan