What are vitamins and should I supplement?

Vitamins and minerals help keep our bodies functioning properly. But how do you know if you are getting enough? And are supplements (ever) the answer?

Vitamins and minerals are important micronutrients that keep your body running smoothly. So, when your body is not getting enough, you may start to experience unwanted symptoms - such as brain fog and fatigue.  

How many vitamins are there? 

There are currently 13 recognised vitamins [1]. These are: 

Vitamins are broken down into fat-soluble or water-soluble, depending on whether they dissolve better in water or lipids (fats). 

Fat-soluble vitamins:  

  1. Vitamin A 
  2. Vitamin D 
  3. Vitamin E 
  4. Vitamin K 

When there are excess levels of fat-soluble vitamins in the body, they are stored in fat cells. These vitamins require fat to be absorbed from foods, which is why it is important to have a healthy amount of unsaturated fat as part of your diet.  

Fat-soluble vitamins  

Vitamin E

Vitamin E is an antioxidant - a substance that prevents or slows damage to cells caused by free radicals.  

Free radicals include: 

  • Cigarette smoke 
  • Sunlight 
  • Pollution 
  • Chemical reactions in the body 

Vitamin E is also important in the formation of red blood cells and in keeping the immune system healthy.

It is rare in the UK to experience a deficiency in vitamin E. If you are deficient, it is usually either down to a poor diet or a digestive condition (as you may not be able to absorb nutrients as well), such as pancreatic, coeliac, and Crohn’s disease. 

Symptoms of a vitamin E deficiency include [2]: 

  • Muscle weakness 
  • Deterioration of muscle mass 
  • Vision problems  
  • Anaemia  

To avoid a vitamin E deficiency, eat plenty of vitamin E-rich foods. 

Good sources of vitamin E include: 

  • Vegetable oils 
  • Eggs 
  • Nuts  
  • Seeds  
  • Whole grains  
  • Leafy green vegetables  

The amount of vitamin E you need is quite low (4mg a day for men, 3mg a day for women), but your body does not immediately store it, so you need it in your diet every day. 

Vitamin A

Vitamin A is an antioxidant that helps to fight inflammation and reduces the risk of age-related macular degeneration (AMD), which is the leading cause of age-related blindness.  

It also helps to keep the integrity of all surface tissues, including the: 

  • Respiratory tract 
  • Bladder 
  • Gut  
  • Eyes 

There are two main forms of vitamin A [3]: 

  • Active vitamin A (also known as retinol) – comes from animal-derived foods and can be used directly by the body. 
  • Beta-carotene – from fruits and vegetables in the form of carotenoids, which the body converts to retinol after food is eaten. 

Good sources of active vitamin A include: 

  • Cheese 
  • Eggs 
  • Lamb 
  • Beef liver 
  • Oily fish 

Good sources of beta-carotene include:  

  • Spinach  
  • Carrots 
  • Sweet potatoes  
  • Mango  
  • Papaya 
  • Apricots 

The NHS’ recommendations for vitamin A for adults are [4]: 

  • 0.7mg per day for men  
  • 0.6mg per day for women 

Though uncommon, a vitamin A deficiency is possible.  

Symptoms of a vitamin A deficiency include: 

  • Weight loss  
  • Dry skin and hair 
  • Frequent respiratory infections 
  • Vision loss  

To avoid a vitamin A deficiency, ensure you eat plenty of vitamin A-rich foods as part of a healthy and balanced diet.  

Vitamin K

Vitamin K refers to a group of fat-soluble vitamins that play a role in blood clotting, as well as regulating blood calcium levels and bone metabolism. In the liver, vitamin K is needed to produce four clotting factors that are necessary for blood to properly clot.  

The four clotting factors of vitamin K are [5]: 

  • Prothrombin 
  • Factor VII 
  • Factor IX 
  • Factor X 

Most people can get enough vitamin K by eating a varied and balanced diet. As vitamin K is a fat-soluble vitamin, any vitamin K in the body that is not needed immediately is stored in the liver for future use. And the healthy bacteria that live in the digestive system can produce vitamin K. 

Vitamin K deficiencies are most common in newborns (occurring during the first few weeks of infancy) due to low clotting factor levels, and low vitamin K content of breast milk. Because of this, a dose of vitamin K is given to newborns as standard in the UK as a deficiency can cause problematic blood clotting and increased bleeding.  

In adults, vitamin K deficiencies are rare but can lead to problematic blood clotting and increased bleeding.  

Symptoms of a vitamin K deficiency include [6]: 

  • Bleeding from the nose and gums 
  • Heavy periods 
  • Slow wound healing  
  • Easy bruising 

To reduce your chances of getting a vitamin K deficiency, you should include vitamin K-rich foods as part of a healthy and balanced diet.  

Sources of vitamin K include: 

  • Broccoli 
  • Spinach 
  • Vegetable oils 
  • Fortified breakfast cereals 

Lesser amounts can also be found in chicken and dairy products. If you are considering vitamin K supplements, it is recommended to speak to your GP first, as too much can be harmful.  

Vitamin D

Vitamin D is a fat-soluble vitamin produced in the skin in response to sunlight and is important for maintaining healthy muscles and bones. Unlike most other fat-soluble vitamins, a deficiency in vitamin D is common in the UK (due to the lack of sunlight in winter).  


vitamin D blood test product banner

Symptoms of vitamin D deficiency include: 

  • Tiredness 
  • Low mood  
  • Brain fog 
  • Weight gain  
  • Joint and bone pain 

To prevent a deficiency in vitamin D, Public Health England recommends that adults, and children over the age of one, should supplement with 10 micrograms per day.  

Because vitamin D deficiency is a common cause of unwanted symptoms, we have put together a guide on everything you need to know about vitamin D and vitamin D deficiency.  

You can also check your vitamin D levels from the comfort of your own home with our Vitamin D (25 OH) Blood Test.  

Water-soluble vitamins 

In contrast to fat-soluble vitamins, most water-soluble vitamins are not stored by the body. Vitamin C and B vitamins are both water-soluble, meaning they are absorbed best in water.  

Vitamin C

Vitamin C (also known as ascorbic acid) is a powerful antioxidant that is also needed for the biosynthesis of collagen.  

Collagen helps the body form and maintain connective tissue, including: 

  • Bones 
  • Blood vessels 
  • The skin  

Vitamin C also helps to strengthen the immune system and aid the absorption in the body. As it is a water-soluble vitamin, the body is unable to make or store vitamin C, so we get it through the foods we eat.  

The best sources of vitamin C include: 

  • Guava 
  • Strawberries  
  • Tomatoes  
  • Broccoli  
  • Oranges 
  • Grapefruits  
  • Peppers 
  • Kiwis 

Not getting enough vitamin C can lead to a deficiency that can cause a range of symptoms in the body. 

Symptoms of a vitamin C deficiency include [7]: 

  • Inflammation 
  • Bleeding of the gums 
  • Dry hair and skin 
  • Slow wound healing  

A long-term insufficiency of vitamin C can lead to a condition called scurvy. In modern-day society, scurvy is rare (historically, it was common in men at sea), but people with gastrointestinal conditions are more susceptible.  

B vitamins

Altogether there are eight B vitamins, each with its purpose and role within the body.  

B vitamins are crucial for: 

  • Cell metabolism  
  • Normal functioning of the central nervous system  
  • Formation of red blood cells 
  • Converting food into fuel  
  • Metabolising fats and proteins

All the B vitamins should be readily available through a healthy balanced diet.  

Sources of the B vitamins include: 

  • Wholegrains 
  • Legumes 
  • Nuts and seeds 
  • Eggs 
  • Spinach 
  • Milk  
  • Lentils 
  • Yeast extract (such as marmite or yeast flakes) 

Two of the most common B-vitamin deficiencies are B9 (folic acid) and B12. During pregnancy, your body will need more B9 as it is vital for the development of the baby’s nervous system and can reduce the risk of the baby developing spina bifida.  

Therefore, when trying to conceive and during the first 12 weeks of pregnancy, you should supplement the recommended amount of folic acid

A B12 deficiency is more common in people who have an autoimmune disease which prevents the absorption of nutrients (such as coeliac disease, or Crohn’s disease), but can also be found in people who restrict dairy in their diet (such as vegans). 

Symptoms of a B12 deficiency include [8]: 

  • Fatigue 
  • Feeling faint  
  • Pale skin  
  • Headaches 
  • Breathlessness 

Should I supplement any vitamins?   

People take dietary supplements for all kinds of reasons, whether to improve health, boost vitality, limit the signs of ageing, or try and reduce the risk of chronic disease. 

Dietary supplements aim to supply added nutrients that may not be consumed in large enough quantities from diet alone. 

Most people do not need to take supplements as they get all the vitamins and minerals, they need through eating a healthy, balanced diet.  

Vitamin D is the exception here though, as although a small amount can be obtained through diet, most of this vitamin is made under the skin when it is exposed to sunlight. Most people in the UK are deficient in vitamin D so may benefit from taking a supplement.  

When considering a supplement, you may come across two types of vitamin D – D2 and D3. D3 is considered the better supplement, however, both work. You can read more about the differences between D2 and D3 in our everything you need to know about vitamin D guide. 

There are certain situations and groups of people who are recommended to take oral vitamin supplements as they cannot get all the nutrients, they need from diet alone. 

The NHS recommends the following for supplement use [9]:

  • 10ug of vitamin D daily for pregnant and breastfeeding women 
  • Women trying to conceive and women in the first 12 weeks of their pregnancy are recommended to take 400 micrograms of folic acid supplements, which reduces their child’s risk of neural tube defects such as spina bifida 
  • 10ug of vitamin D daily for those aged 65 and over 
  • During the autumn and winter months, the sun is not strong enough for the body to make vitamin D. Everyone should consider taking a daily supplement containing 10ug of vitamin D during the autumn and winter. 
  • People with darker skin and those who are not exposed to much sun should take vitamin D supplements. 
  • Supplementing vitamin B12 is recommended for those who follow a vegan diet, as they will struggle to get enough vitamin B12 through food alone as B12 is found (almost) exclusively in animal-based products. 

There is no straightforward yes or no answer to the question of whether you should be taking supplements - everyone’s circumstances are unique.  

The need for supplementation depends on the levels of vitamins and minerals in your body. Remember, it is also important not to over supplement as this can have negative health effects. 

To make it simple to establish and monitor your levels, we have created our Nutrition Blood Test, to help you see whether you are getting the nutrients you need from your diet and if you could benefit from taking a dietary supplement.


  1. National Institute on Aging. 2022. Vitamins and Minerals for Older Adults. [online] Available at: <https://www.nia.nih.gov/health/vitamins-and-minerals-older-adults#:~:text=There%20are%2013%20essential%20vitamins,keep%20the%20body%20working%20properly.> [Accessed 19 May 2022]. 
  2. Ods.od.nih.gov. 2022. Office of Dietary Supplements - Vitamin E. [online] Available at: <https://ods.od.nih.gov/factsheets/VitaminE-Consumer/> [Accessed 19 May 2022]. 
  3. Ods.od.nih.gov. 2022. Office of Dietary Supplements - Vitamin A and Carotenoids. [online] Available at: <https://ods.od.nih.gov/factsheets/VitaminA-Consumer/> [Accessed 19 May 2022]. 
  4. nhs.uk. 2022. Vitamins and minerals - Vitamin A. [online] Available at: <https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-a/#:~:text=The%20amount%20of%20vitamin%20A,%C2%B5g%20a%20day%20for%20women> [Accessed 19 May 2022]. 
  5. Girolami, A., Ferrari, S., Cosi, E., Santarossa, C. and Randi, M., 2018. Vitamin K-Dependent Coagulation Factors That May be Responsible for Both Bleeding and Thrombosis (FII, FVII, and FIX). Clinical and Applied Thrombosis/Hemostasis, 24(9_suppl), pp.42S-47S. 
  6. Labtestsonline.org.uk. 2022. Vitamin K Deficiency. [online] Available at: <https://labtestsonline.org.uk/conditions/vitamin-k-deficiency> [Accessed 19 May 2022]. 
  7. Harding, D., 2022. Vitamin C Deficiency. [online] Patient.info. Available at: <https://patient.info/healthy-living/vitamin-c-deficiency-leaflet> [Accessed 19 May 2022]. 
  8. nhs.uk. 2022. Vitamin B12 or folate deficiency anaemia - Symptoms. [online] Available at: <https://www.nhs.uk/conditions/vitamin-b12-or-folate-deficiency-anaemia/symptoms/> [Accessed 19 May 2022]. 
  9. nhs.uk. 2022. Do I need vitamin supplements? [online] Available at: <https://www.nhs.uk/common-health-questions/food-and-diet/do-i-need-vitamin-supplements/> [Accessed 19 May 2022]. 

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