What Are Water-Soluble Vitamins?

What Are Water-Soluble Vitamins?

Water-soluble vitamins, as the name suggests, are those that dissolve in water. But what does this actually mean in practice?

Fat-soluble vitamins like vitamin D can be stored in the fat cells of the body, ready for use at a later date. In contrast, water-soluble vitamins tend not to be stored for when they are needed. Instead, any excess is typically excreted.

Note, however, that unless you have been consuming a diet that is seriously deficient in a certain water-soluble vitamin for some time, your body will still maintain a “reservoir” that it is working through. Over time this level will drop progressively if not replenished through supplementation or the diet.

This lack of storage in the body has two knock-on effects for long-term health. Firstly, water-soluble vitamins must be regularly consumed in the diet to maintain optimal levels. This is in contrast to fat-soluble vitamins which may be consumed only occasionally, then drawn from storage when needed.

The second important aspect of water-soluble vitamins is that excess vitamins tend to be easily flushed from the body through normal daily excretion. This means that a toxic build-up of water-soluble vitamins is more unlikely.

Which Vitamins Are Water Soluble?

Surprisingly, most of the vitamins our bodies need are actually fat soluble. For a full list of the fat-soluble vitamins please click here. The water-soluble vitamins are vitamin C (ascorbic acid) and the eight B vitamins that make up the “vitamin B complex”. These are:

  • B1 / Thiamine
  • B2 / Riboflavin
  • B3 / Niacin
  • B5 / Pantothenic Acid
  • B6 / Pyridoxine
  • B7 / Biotin
  • B8 / Folate
  • B12 / Cobalamin

Functions & Deficiencies of Water-Soluble Vitamins

We now know that we need to regularly consume water-soluble vitamins in suitable quantities because they tend not to be stored in the body. The next obvious question is exactly what each of these vitamins really does for you, how much you need, and which foods are rich in water-soluble vitamins?

Vitamin B1 / Thiamine

Thiamine is considered to be an “essential” vitamin because it cannot be made by the human body. Instead, it must be consumed in the diet and is required by every cell of the human body, including the brain. Vitamin B1 plays an important role in all manner of chemical processes in the body, including the creation of neurotransmitters in the brain.

It is also crucial for many metabolic processes including the breakdown of glucose and amino acids into their composite molecules, which are then used in a range of bodily processes.

Thiamine is only needed in very small quantities by the body; a level which is easily reached with a balanced diet that is rich in whole foods. In reality, thiamine deficiencies are most commonly experienced by heavy drinkers, because ethanol (alcohol) interferes with the absorption of vitamin B1 from the gut. Consequently, even if consumed in a suitable volume, many alcoholics are prone to vitamin B1 deficiencies.

One of the most severe signs of thiamine deficiency is known as “Wernicke–Korsakoff syndrome” which can lead to irritability, insomnia, hallucinations and memory loss, among other symptoms. Vitamin B1 deficiency is also associated with an increased prevalence of heart disease in some sufferers, often as a result of incorrect blood chemistry and, therefore, blood flow velocity.

Vitamin B1 is found in asparagus.How Much Vitamin B1 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 1.1mg of thiamine per day. In most cases this should be easy enough to accomplish through a balanced diet.

Foods Rich in Vitamin B1

Avoiding a deficiency in thiamine is reasonably simple, as it is found in a wide range of foods. Fish, pork, nuts, seeds, bread, peas, beans and asparagus are all great sources of vitamin B1.

Vitamin B2 / Riboflavin

Like thiamine, riboflavin exerts its impacts in a multitude of different ways. Principally it functions as a “coenzyme”, being required for a wealth of different enzymatic processes in the body. A deficiency in vitamin B2 has been shown to impact the body's ability to absorb and use iron in the body, meaning that low levels can result in cases of anaemia, with all the issues this brings with it such as fatigue, dizziness and muscle cramps.

Alongside this, vitamin B2 has been observed to operate in tandem with other B vitamins - namely vitamin B6 and B7 - and a deficiency can concurrently cause issues with the metabolism of these nutrients too. Children that are given a diet deficient in riboflavin have been observed to suffer from stunted growth, heart defects and deformities.

How Much Vitamin B2 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 1.4mg of riboflavin per day.

Foods Rich in Vitamin B2

As with vitamin B1, a diet that is rich in natural foods like meat, dairy and vegetables will normally ensure you're getting enough riboflavin in your diet. Lamb, milk, yoghurt, mushrooms, spinach, almonds, eggs and salmon are all great sources of vitamin B2.

Vitamin B3 / Niacin

Niacin is involved in more than 200 different recognised chemical reactions in the body, though arguably the most important of these is the role it plays in the metabolism of adenosine triphosphate (ATP) - the unit of energy used by every cell in the body. It should be no surprise, therefore, that mild deficiencies tend to be associated with fatigue and a slow metabolic rate which can lead to sufferers feeling cold all the time.

Niacin is probably best known for what happens in the case of deficiency; namely the complaint known to experts as “pellagra”. Pellagra is famous for its symptoms which are typically described as the “four D's” - diarrhoea, dementia, dermatitis and death.

Once again, niacin deficiency is quite uncommon on a balanced, Western diet, but is more commonly found in poverty-stricken areas, especially where dietary choices are few. Niacin is also one of the few water-soluble vitamins that seems to show serious potential complications in cases of overdose.

Sadly, the scientific journals are awash with stories that patients (erroneously) believe consuming high levels of niacin can help them pass drug tests. This has led to many people overdosing on niacin. The end result can be unpleasant, sometimes leading to serious multi-organ failure if left untreated.

Peanuts are a great source of vitamin B3.How Much Vitamin B3 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 16 mg of niacin per day.

Foods Rich in Vitamin B3

Turkey breast, chicken breast, peanuts, mushrooms, tuna and peas are all great sources of vitamin B3.

Vitamin B5 / Pantothenic Acid

Pantothenic acid's main impact on the body is as an ingredient in the production of “coenzyme A”. A chemical process in the body combines vitamin B5, an amino acid known as cysteine and ATP to create this all-important coenzyme. Coenzyme A, in turn, plays a role in nervous system function, the production of the sleep hormone melatonin, vitamin D synthesis and energy-yielding metabolism, among others.

Common symptoms of pantothenic acid deficiency include fatigue, irritability and insomnia. At the same time, scientists found that animals fed on a diet deficient in vitamin B5 experienced weight loss and visual complications like conjunctivitis. Once again, therefore, you'll want to ensure that you're getting sufficient pantothenic acid in your diet either through the consumption of whole foods or a high-quality supplement.

To learn more about pantothenic acid please consult our full guide at: https://www.simplysupplements.co.uk/healthylife/supplements/vitamin-b5-benefits

How Much Vitamin B5 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 6 mg of pantothenic acid per day.

Foods Rich in Vitamin B5

Sunflower seeds, salmon, avocado, corn, broccoli and mushrooms are all great sources of vitamin B5.

Vitamin B6 / Pyridoxine

Vitamin B6, also known as pyridoxine, is involved in the production of serotonin and norepinephrine, which help to transmit signals in the brain. It benefits a range of physical and psychological conditions, including nerve function, protein metabolism, and the production of antibodies and healthy haemoglobin. It also helps to regulate hormonal balance and is a central part of the storage and breakdown of glycogen in the muscle cells and liver.

Interestingly, a study of 85,557 different women also found that the consumption of vitamin B6 was inversely associated with kidney stones, with the experts concluding higher amounts of vitamin B6 may protect against the incidence of kidney stone formation.

As with other B complex vitamins, the symptoms of vitamin B6 deficiency can be far-ranging. For example, one study observed that women taking a combined oestrogen and progesterone oral contraceptive were more likely to suffer from such deficiencies. The study found that such deficiencies were also linked to cases of depression, and that study participants supplemented with additional pyridoxine often made a full recovery.

This is another water-soluble vitamin where toxicities are possible, but are also highly unlikely, with one study finding that toxicities occur when vitamin B6 intake is roughly 1,000 times the recommended therapeutic intake; something nearly impossible to achieve through diet alone.

To learn more about pyridoxine please consult our full guide at: https://www.simplysupplements.co.uk/healthylife/supplements/vitamin-b6-benefits

Avocados are a rich source of biotin.How Much Vitamin B6 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 1.4mg of pyridoxine per day.

Foods Rich in Vitamin B6

Turkey breast, beef, chicken breast, tuna, pistachios, pinto beans, avocado and sunflower seeds are all great sources of vitamin B6.

Vitamin B7 / Biotin

Biotin is possibly best-known as the “beauty vitamin”, with numerous topical creams and supplements including it to aid skin health and elasticity. Biotin helps to break down fatty acids, which are then distributed to vital organs around the body, including the skin. These fatty acids protect the skin's cells against damage and water loss, and so help to retain moisture and prevent dry, itchy skin.

It also offers similar benefits to the hair and nails, helping to strengthen and protect them against breakage. Biotin deficiencies can, understandably, therefore lead to hair loss or discolouration, skin rashes and weak nails. Alongside these symptoms, however, a biotin deficiency can also result in tingling in the extremities and lethargy.

To learn more about biotin please consult our full guide at: https://www.simplysupplements.co.uk/healthylife/supplements/biotin-benefits

How Much Vitamin B7 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 50 mcg of biotin per day.

Foods Rich in Vitamin B7

Eggs, almonds, fish, meats, cheese, cauliflower and avocado are all great sources of vitamin B7.

Vitamin B8 / Folate

Folate, also known as folic acid, is crucial for cell replication and division. It is also an “essential” nutrient as it cannot be made in the body. While all of us should ensure that we're getting enough vitamin B8 in our diet, this is particularly important for pregnant women, where such an intake helps to reduce the risk of neural tube birth defects. In adults, the signs of folate deficiency can include lethargy, heart palpitations or skin sores.

Citrus fruits are a great source of vitamin B8.How Much Vitamin B8 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 200 mcg of folate per day.

Foods Rich in Vitamin B8

Dark leafy greens, asparagus, broccoli, citrus fruits, avocado, nuts and legumes are all great sources of vitamin B8.

Vitamin B12 / Cobalamin

Like the term “vitamin E”, the word “cobalamin” actually refers to a group of compounds we know together under this umbrella term. Vitamin B12 plays an important role in the body's production of energy and the maintenance of the nervous system. B12 is also essential for the proper development and function of red blood cells, nerve cells and neurotransmitters.

As vitamin B12 is only found in animal-derived foods, vitamin B12 deficiencies are particularly likely in vegetarians and vegans who have chosen to omit these food items from their diet. Indeed, one study in Germany found that 28% of vegans were deficient in this important vitamin. Clinical signs of a cobalamin deficiency in adults include anaemia and neurological problems, while children may also suffer from growth problems or developmental difficulties.

To learn more about vitamin B12 please consult our full guide at: https://www.simplysupplements.co.uk/healthylife/supplements/vitamin-b12-benefits

How Much Vitamin B12 Do I Need?

According to the European Food Safety Authority, adults are advised to consume 2.5mcg of cobalamin per day.

Foods Rich in Vitamin B12

Great sources of vitamin B12 tend to be restricted to meat and dairy, with eggs, milk, cheese and fish all being great dietary sources.

Vitamin C / Ascorbic Acid

Like vitamin B1, ascorbic acid is considered an “essential” vitamin in humans, as we are one of the few species unable to create our own in the body. Most people are familiar with the concept of taking vitamin C to help protect you from colds, even if the scientific evidence on this matter is a long way from conclusive at present.

What we do know, however, is that vitamin C is crucial for the formation of collagen in the body, helping to keep structural elements such as teeth, gums, bones, joints and skin in optimal condition.

It also plays other roles. For example, vitamin C has been found to possess antioxidant properties, and a higher intake of ascorbic acid is therefore associated with a lower risk of suffering from a range of potentially serious health conditions. One study examining the effect of vitamin C on illness concluded that a “50g per day increase in fruit and vegetable intake was associated with about a 20% reduction in risk of all-cause mortality”.

A vitamin C deficiency is associated with scurvy. In laboratory experiments in which volunteers were fed a diet deliberately lacking in suitable vitamin C, symptoms included skin problems, swollen gums, sore joints, muscular pain and “conjunctival haemorrhages”.

Fortunately, as with other water-soluble vitamins, a number of foods are rich sources. Additionally, reasonably-priced vitamin C supplements are a great alternative.

Citrus fruits are a great source of vitamin C.How Much Vitamin C Do I Need?

According to the European Food Safety Authority, adults are advised to consume 90mg of ascorbic acid per day.

Foods Rich in Vitamin C

Citrus fruits, dark leafy greens, tomatoes, peppers and winter squash are all great sources of vitamin C.


Depending on your point of view there are either two water-soluble vitamins - vitamin B complex and vitamin C - or nine if you consider each of the B vitamins individually. Fortunately, while we need a regular supply of such vitamins, it is not difficult to achieve on a varied diet that includes a range of wholefoods.

Prioritizing fruits, vegetables and lean meats with a suitable proportion of dairy in your diet will help to ensure sufficient levels in your body.

Alternatively, if you're concerned about the health risks of not meeting your daily vitamin requirements it is simple enough to buy vitamin B complex supplements and vitamin C tablets.

Indeed, such supplements can also be ideal for individuals who are particularly at risk of deficiencies - such as vegans - to ensure they are receiving all the nutrients their body needs.