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Vitamins and Supplements

Our ultimate A-Z guide to vitamins

Phil Day: Superintendent Pharmacist | minute read

To function properly, our bodies need various nutrients that support them to successfully carry out different processes and keep us healthy. Most of these nutrients are found in the food we eat as part of a balanced diet, but sometimes additional supplements may be needed.

This article explores the 13 essential vitamins our bodies need, why they’re needed, and how much we need each day. We also look at the sources of each vitamin to help you ensure you’re naturally including it in your diet, and what you can do if you follow a diet that doesn’t include these sources.

When we talk about the RDA for each vitamin, the units of measurement vary. A microgram is one thousandth of a milligram (mg). Throughout this article, we reference micrograms using the written word and milligrams as mg.

You might also see the measurement for micrograms using the Latin symbol for micro (µ) followed by the letter g. For example, 1mg could be labelled on product packaging as 1000 µg.

Vitamin A

What do I need it for?

You might have also heard vitamin A referred to as retinol. Vitamin A supports several processes in the body, including protection against illness by bolstering the immune system, aiding your eyesight in poor light, and promoting healthy skin and hair.

Sources of vitamin A

Various food products offer good sources of vitamin A, including dairy products such as cheese, milk, and yoghurt. Liver products provide a concentrated source of vitamin A and should be consumed in moderation. If you’re pregnant, the NHS recommends avoiding liver products as too much vitamin A can pose a risk to your unborn baby. If you’re expecting a baby and want advice about what nutrients to take, this NHS article outlines what vitamins and supplements you should consider.

Vitamin A can also be sourced indirectly from foods like leafy green vegetables, red peppers, carrots, and fruits including apples, blueberries, grapefruit, and mangoes. These foods are rich in a nutrient called beta-carotene, which our bodies can turn into vitamin A.

How much vitamin A do I need?

The NHS recommends a daily intake for adults (aged 19-64) of 600 micrograms for women and 700 micrograms for men. Too much vitamin A can cause potential health complications, so it’s advised not to exceed 1500 micrograms daily.

B vitamins

What are the different B vitamins?

Vitamin B1 (thiamine) supports the body’s nervous system and helps to convert the food we eat into energy. We can get our daily supply of thiamine from foods including bananas, oranges, nuts, certain breakfast cereals, liver, and peas. Because the body cannot store thiamine, it’s important to include these food sources in your daily diet. Adults’ recommended daily intake (RDI) is 1mg for men and 0.8mg for women.

Vitamin B2 (riboflavin) performs similar functions to vitamin B1 and supports healthy skin and eyes. It’s found in eggs, mushrooms, yogurt, and milk. We don’t store riboflavin in our bodies so again, these sources should be factored into a varied diet daily. The RDI for adult males is 1.3mg and 1.1mg for females.

Vitamin B3 (niacin) serves a similar function to thiamine and riboflavin in supporting healthy skin and nerve function, as well as releasing energy from food. The adult RDI is 13.2mg for women and 16.5mg for men. Natural sources of niacin include animal sources such as meat, fish, and eggs. Non-animal sources include peanuts, mushrooms, and avocados. Possible side effects of too much B3 include skin flushes and in rarer cases liver damage, so the NHS advises not to exceed 17mg daily.

Vitamin B5 (pantothenic acid) helps our bodies make and break down fats and supports the creation of red blood cells. It’s found in various foods including most vegetables, and meats such as beef and chicken. If you follow a vegetarian diet, mushrooms and avocado are particularly good sources of pantothenic acid. There isn’t a set RDI for adults, but eating a balanced diet with plenty of fresh vegetables should ensure your body receives the quantity it needs to function properly.

Vitamin B6 (pyridoxine) performs similar functions to vitamin B5 including helping to convert proteins & carbohydrates into energy and oxygenating the blood. Good sources of pyridoxine include meats such as pork, chicken, and turkey, as well as bananas, peanuts, and soya beans. It’s advised that adult men aim for a daily intake of 1.4mg, and for women the RDI is 1.2mg. Too much of this vitamin can cause temporary issues with the nervous system that affect feeling in the arms and legs known as peripheral neuropathy. The NHS recommends sticking to the RDI to reduce the risk of any side effects.

Vitamin B7 (biotin) is part of the B vitamin family that supports the body to make fatty acids. As well as being found in some foods, it’s also produced by our small bowel. As only a very small amount of biotin is needed to help our bodies function, there is no set RDI.

Vitamin B9 (folate) is the naturally occurring form of folic acid. Its role in the body is to help produce red blood cells. It is also vital in supporting healthy foetal development in pregnant women. Green vegetables such as broccoli, spinach, and kale are excellent natural sources of folate. Pulses like chickpeas and kidney beans also provide a good source of folate. The RDI for all adults is 200 micrograms. However, if you’re planning to get pregnant or are in the first trimester of pregnancy, the NHS recommends taking a 400-microgram folic acid supplement to support your baby’s healthy development. Speak to your GP or healthcare specialist for more information on supplements during pregnancy. The NHS advises against taking a dose higher than 1mg as this can mask the symptoms of a vitamin B12 deficiency.

Vitamin B12 (Cyanocobalamin) plays a role in ensuring vitamin B9 (folate) performs the functions it needs to in the body. It also supports the nervous system and healthy red blood cell production. B12 is predominantly found in animal products such as meat, fish, and dairy. If you follow a vegan diet, you might want to consider a supplement or a food/drink fortified with B12 to ensure your body gets enough of this vitamin. The RDI for adults is 1.5 micrograms.

Vitamin C

What do I need it for?

Vitamin C (also called ascorbic acid) performs a variety of roles in the body. It helps to keep our skin and bones healthy, as well as our blood vessels and cells. Vitamin C also helps to promote the healing and regeneration of wounded tissue.

Sources of vitamin C

Many different fruits and vegetables provide a rich source of vitamin C. Citrus fruits such as oranges and grapefruits are particularly high in vitamin C, as well as kiwis, strawberries, and blackcurrants. Green vegetables including sprouts and broccoli also offer a good source of vitamin C, along with potatoes and peppers.

How much vitamin C do I need?

The RDI for adults up to the age of 64 is 40mg per day. Our bodies can’t store excess supplies of vitamin C, so it needs to be incorporated into our daily diets. Taking more than the RDI can lead to digestive discomfort in some people. If you experience tummy pain or cramps, diarrhoea, or excess wind while taking a vitamin C supplement, these symptoms should ease when you stop taking it.

Vitamin D

What do I need it for?

Vitamin D helps to maintain healthy bones, muscles, and teeth by supporting the body’s calcium and phosphate absorption. These two minerals are crucial to building and supporting healthy bone structure and muscle function.

Sources of vitamin D

Most people receive their daily vitamin D requirements from sunlight in the spring and summer months. From October to March, alternative vitamin D sources include animal products such as red meat, oily fish, and egg yolks. If you follow a vegetarian or vegan diet, a vitamin D supplement can provide your RDI.   

How much vitamin D do I need?

The recommended daily intake for everyone over the age of one is 10 micrograms. Because it’s difficult to get all the vitamin D we need from diet alone during the winter months, the NHS recommends that everyone considers taking a vitamin D supplement between October and March. Speak to your pharmacist or GP if your circumstances mean you don’t get the opportunity to spend time outdoors throughout the year as they may advise taking a supplement year-round. Taking too much vitamin D can increase the risk of calcium build-up in the body. Excess calcium can cause issues with bone health and potentially harm the heart and kidneys. The NHS recommends sticking to the RDI unless advised otherwise by a healthcare professional.

Vitamin E

What do I need it for?

Vitamin E is an antioxidant, encouraging healthy skin and eye function, and supporting the immune system to protect against infection and disease.

Sources of vitamin E

Vitamin E is present in different foods including vegetable and olive oils, peanuts, sunflower seeds, and some wheat-based cereals.

How much vitamin E do I need?

The RDI for adult males is 4mg and 3mg for adult females. Any excess vitamin E can be stored by the body for future use when needed. If you’re taking vitamin E supplements, the NHS recommends not exceeding a dose of 540mg per day.  

Vitamin K

What do I need it for?

Our bodies use vitamin K to help with blood clotting and encourage wound healing. The NHS also notes that some evidence suggests it can help support healthy bones.

Sources of vitamin K

Green vegetables such as broccoli and spinach offer good sources of vitamin K along with vegetable oils and some cereals.

How much vitamin K do I need?

The RDI of vitamin K is directly related to a person’s weight. You need approximately 1 microgram for each kilogram you weigh. For example, if you weigh 70kg, your RDI would be 70 micrograms of vitamin K. A daily intake of less than 1mg is unlikely to pose a risk to your health according to the NHS.

Where can I buy vitamin supplements?

Our online shop offers a range of vitamins and supplements from trusted brands at affordable prices. If you’re considering taking supplements to help ensure you’re getting a sufficient daily intake, read the dosage instructions and don’t exceed the RDI unless you’ve been advised to do so by a healthcare professional.

In addition to these 13 vitamins, the body also needs several minerals to perform a variety of functions in the body. You can learn about the minerals our bodies need in our minerals A-Z guide.