In this article, we will look closer at water-soluble and fat-soluble vitamins that we need in varying quantities daily from different food sources. We will start our discussion with the fat-soluble vitamins (Vitamin A, D, E, K), and then we will move to water-soluble (Vitamin C, B group). I will try to give a more detailed explanation of each vitamin and the amount we need every day. So, fat-soluble vitamins are A, D, E and K, and they are found chiefly in foods that contain fats and oils. They have an essential part to play in our health, from helping us to see in the dark to regulating our immune system. When our intake of fats is restricted for any reason, the intake of fat-soluble vitamins is also reduced. This can lead to many physical conditions that reduce fat digestion and absorption. So, all in all, fat-soluble vitamins have critical roles in our bodies.
Vitamin A
Vitamin A is a fat-soluble vitamin that is essential for vision in dim light. It also helps to maintain the mucous membranes that protect areas of our body, such as the respiratory tract. Finally, it retains our skin and is essential for growth. Vitamin A is normally produced in the body from its precursors: retinol, retinal, retinoic acid, and ß-carotene. Vitamin A deficiency can have some nasty consequences. We can end up with reduced night vision and eventually loss of sight due to damage to our corneas. Our resistance to infection may also be lowered, as vitamin A helps to regulate our immune systems.
Luckily, vitamin A occurs in many common foods. Good sources are liver, carrots, dairy products and spinach. If we only consume vitamin A from natural sources, we are unlikely to get too much of it to become harmful. However, taking vitamin A supplements can lead to excess amounts being stored in the liver, where it may eventually become toxic. That’s why pregnant women should seek professional advice before taking any vitamin A supplement, otherwise they may end up consuming high enough levels to harm their foetus. The dietary reference value for vitamin A is 600 μg/day for females and 700 μg/day for males.
Vitamin D
Vitamin D promotes the absorption of calcium and phosphate from food and is, therefore, essential for healthy bones and teeth. This vitamin is also thought to have functions in the brain, the nervous system, cellular growth, and immunoregulation. The primary source of vitamin D is synthesis by exposing the skin to UV radiation in sunlight, and we are unlikely to obtain all the vitamin D we need from our diets.
Our ability to synthesise vitamin D is affected by our skin pigment – the darker it is, the less we can produce. There are three other sorts of people who may have difficulty synthesising enough vitamin D. Older people, especially those who are bedridden or unable to go out easily, and those who live in regions with limited sunlight, such as Northern Europe, find it hard to get enough sunlight. The same goes for people whose clothing completely covers their skin, either for protection against the weather or cultural or religious reasons.
Although, as we have seen, we cannot obtain all the vitamin D we require from our diets, it is still possible to get some of it. The best dietary sources of vitamin D are cod liver oil, oily fish such as salmon or mackerel, eggs, and fortified foods. As our body stores vitamin D, it does not need to be consumed daily. Most people should be able to meet their vitamin D requirements through sun exposure and a balanced diet. However, the Department of Health recommends that the following people take daily vitamin D supplements:
- All children aged six months to five years old
- All pregnant and breastfeeding women
- All people aged 65 and over
- People who are not exposed to much sun
- People with darker skin such as people of African-Caribbean and South Asian origin
Although it is unlikely that we will consume too much vitamin D through natural food sources, there is a danger if we take additional supplements when we don’t need them. Because it is a fat-soluble vitamin stored in the liver, too much of vitamin D can be toxic. Taking 25microg (0.025mg) or less of vitamin D supplements daily is unlikely to cause any harm.
Vitamin E
Vitamin E’s main role is as an antioxidant protecting the cell membranes from damage by oxidation. This vitamin is the most important of a group of antioxidants. The most common cause of vitamin E deficiency is malabsorption. This is usually related to a disruption of fat absorption or poor absorption of the vitamin and may lead to the development of a condition affecting the nervous system. Although vitamin E is fat-soluble, high intake levels don’t appear harmful.
Vegetable oils, avocados, nuts, and seeds are the best dietary sources of vitamin E. No dietary reference value has been set for vitamin E because it is so closely related to the intake of polyunsaturated oils in the diet, which varies considerably throughout the UK. However, an intake of 4–8mg daily is considered adequate.
Vitamin K
Vitamin K is essential in the formation of blood-clotting proteins, in particular prothrombin. It is mainly synthesised in the gut by the resident bacteria. Suppose you have a healthy gut flora and no problems with fat absorption. In that case, you are very unlikely to experience a deficiency of vitamin K. Vitamin K is an essential component in your body’s normal blood-clotting process. Our diet’s primary sources of vitamin K include dark green leafy vegetables such as broccoli, sprouts, kale, and spinach.
The dietary reference value for vitamin K is set at between 0.5 and 1.0 μg/kg/day. This is based on our body weight. This means that if your weight is 80 kg, you would require up to 80μg/day of vitamin K. If you consume natural vitamin K orally in milligram quantities, it is remarkably free from any toxic side effects. The same cannot be said if the same amount is taken as a synthetic preparation. Excessive amounts of synthetic vitamin K have been linked to the breaking down of red blood cells, known as haemolysis, and liver damage.
Vitamin K supplements could benefit newborn babies with no gut flora to produce vitamin K and who may be unable to make blood clots. This condition is known as “haemorrhagic disease of the newborn” and is treated by an injection of vitamin K when they are born. Older people who have undergone a long course of antibiotics are at risk of vitamin K deficiency. This is because the antibiotics kill off our gut flora, preventing them from producing vitamin K.
Water soluble vitamins.
Now, let’s discuss water-soluble vitamins. These are the vitamins C and B-complex groups. For the most part, water-soluble vitamins cannot be stored in the body (B12 is the exception). Normally, any excess water-soluble vitamins we consume are excreted via urine as the body has limited storage capability. That’s why we will need a continuous supply of them in our diets, so we must consume these vitamins regularly.
Also, we must bear in mind that water-soluble vitamins are easily destroyed. They are susceptible to heat and are soluble in water, so they are easily destroyed when heated in water. Also, exposure to light and air will reduce the level of these vitamins in food. To reduce vitamin loss, we should refrigerate fresh produce, keep milk and grains away from intense light and use the cooking water from vegetables to prepare soups. Now, let’s take a closer look at the individual water-soluble vitamins.
Vitamin C
Vitamin C is involved in the formation of collagen, a protein used in the structure of connective tissue and bone to help hold them together. It also aids wound healing and iron absorption and has strong antioxidant properties. Vitamin C is needed for the growth and repair of tissues in all parts of the body. Any prolonged vitamin C deficiency can lead to poor wound healing, bone weakening, and scurvy.
Because vitamin C decomposes so quickly, our consumption amount may be questionable. For example, if we leave fruit juice to stand, it quickly loses its vitamin C content. That’s why we should consider keeping fruit juice in an airtight container in the dark and at a cool temperature in the fridge. Also, the more we can reduce the handling and processing of foods containing vitamin C, the better. We must also consider our cooking and preparation methods. Boiling vegetables to a pulp destroys most of the vitamin qualities, and excessive heating is also bad for the food. The best techniques are stir-frying, steaming, and microwaving. Good sources of vitamin C include fruits (especially citrus fruits, blackcurrants, strawberries, papaya and kiwi), green vegetables, peppers and tomatoes.
The RNI for vitamin C is 40 mg per day. If consumed in high quantities, being water soluble, any excess vitamin C is removed from the body in the urine because the body cannot store it. Very high doses, such as 1 g or 1,000 mg taken as a supplement, can lead to some uncomfortable symptoms, including diarrhoea and kidney stones. Another important fact is that smoking increases the rate at which the body uses vitamin C, increasing the body’s intake requirement. A smoker should consider increasing their intake of vitamin C-rich foods such as oranges, green vegetables, tomatoes, and other fruits, including kiwis and strawberries.
Vitamin B1 (Thiamine)
As with all the B vitamins, their function is intimately linked to all the energy pathways in the body. Thiamine is involved in the release of energy from carbohydrates. It is essential for the brain and nerves to utilise glucose for all their energy needs and helps support proper heart function. However, thiamine is the most unstable vitamin, as it is easily destroyed by cooking and storage, with up to 20% of its value lost in food preparation.
The symptoms of a deficiency of vitamin B1 may initially include poor appetite, fatigue, and weight loss. These symptoms can appear within ten days of insufficient B1 intake and progress to include muscle weakness, nerve damage affecting the hands and feet, heavy legs, and headaches. An advanced form of B1 deficiency, known as beriberi, can cause problems with the nervous system, heart, and lungs. Alcoholics will sometimes develop a deficiency because excessive alcohol intake significantly reduces the body’s ability to absorb this vitamin from food.
Thiamine requirements will be based on our energy intake. The RNI has been set at 0.4 mg/1000 kcal. So, if you consume 2000 kcal daily, you will need 0.8 mg/day. Very high intakes of 3g/day or more have been linked with symptoms including headaches, irritability, insomnia, a rapid pulse, and weakness. Thiamine is found in various foods, with pork and yeast being excellent sources. Other good sources include green vegetables, root vegetables, seeds, mushrooms, tuna, and fortified cereals.
Vitamin B2 (Riboflavin)
The following water-soluble vitamin is riboflavin – vitamin B2. As with all the B vitamins, riboflavin function is involved with all the energy pathways in the body, particularly in energy release from fat and protein. A riboflavin deficiency can cause changes to the mucous membrane and skin around the mouth and nose. Rich sources of vitamin B2 include liver, cheese, eggs, yeast extract, milk, yoghurt, green vegetables, and fortified cereals. Milk exposed to the sun loses 10% of its riboflavin content per hour. The dietary reference value for riboflavin is set at 1.1 mg/day for females and 1.3 mg/day for males. The body will excrete an excess of riboflavin and toxicity is rare even in high intakes.
Vitamin B3 (Niacin)
Vitamin B3 or niacin is also known as nicotinic acid or nicotinamide. It is involved with energy production, particularly from the breakdown of glucose, amino acids, fatty acids and the metabolism of folate and vitamin C. Niacin is also required for the development, maintenance and function of skin, the digestive system and nervous system and is vital in the manufacture of DNA.
A deficiency in niacin can lead to a condition known as pellagra. Early symptoms include fatigue, loss of appetite, muscle weakness and anxiety. The lining of the mouth and tongue become inflamed, and more advanced symptoms include diarrhoea, skin rashes and delirium. Pellagra can be fatal. Deficiency is extremely rare in developed countries. People who drink excessive amounts of alcohol are at an increased risk of niacin deficiency as alcohol significantly reduces the ability of the body to absorb vitamin B3 from food. Rich sources of vitamin B3 include liver, beef, pork, mutton and other meats, fish, yeast extract, fortified cereals. The recommended niacin intake for optimal health is 6.6 mg/1000 kcal or 12-18 mg per day. Very high intakes, where doses are around 3-6 g per day, can cause liver damage.
Vitamin B6
Vitamin B6 is a mixture of pyridoxine, pyridoxal and pyridoxamine and is involved in many biological reactions. It is particularly associated with amino acid metabolism. B6 also plays a role in fat metabolism and is involved in glycogen metabolism in the muscle. Vitamin B6 protects the body against infection and plays a vital role in producing haemoglobin, a protein which transports oxygen around the body.
A severe clinical deficiency of B6 is rare. Still, symptoms may include anaemia, a smooth tongue, cracks at the corners of the mouth, dermatitis, muscular system problems, and an increased need for vitamin B6. Ageing can cause a B6 deficiency as there is a decline in vitamin B6 status due to changes in the absorption and metabolism of the vitamin. Alcoholism can also cause a B6 deficiency. Excessive intake of alcohol can reduce the body’s ability to absorb and utilise vitamin B6. Also, some medical conditions may decrease the levels of B6 in the blood, including asthma, kidney disease, Hodgkin’s disease, sickle-cell anaemia, and diabetes.
Rich sources of vitamin B6 include liver, meat, whole cereals, walnuts, peanuts, bananas, and salmon. The RNI for vitamin B6 is 1.2–1.4 mg/day. Excessive intakes of vitamin B6 have been associated with disturbances in the sensory nervous pathways at doses from 50–500 mg/day. Vitamin B6 is one of the most popular supplements in the UK, probably due to a widespread belief that it is effective in treating pre-menstrual syndrome. A review of the studies that have been conducted concluded that high dose supplements of 50–100 mg appear to be effective. However, since none of the reviewed studies were randomised controlled trials, the gold standard of clinical testing, the review could not definitively conclude that vitamin B6 effectively treated PMS.
Vitamin B12
Vitamin B12 is required for normal growth and development and so is especially important for babies, young children, and teenagers. It also plays a vital role with folate to produce normal red blood cells. Vitamin B12 is important in the protection and function of nerve cells, the manufacture of DNA and metabolism of fats and carbohydrates.
It can take up to 30 years to develop a deficiency of vitamin B12, and although it is water soluble, we are able to store it in the liver. A deficiency of vitamin B12 in the diet can lead to a condition called megaloblastic anaemia, where red blood cells are abnormally large and inefficient at carrying oxygen. As the primary sources of B12 are meat and offal, a person who turns vegetarian or vegan at a young age may not have sufficient vitamin stores. In this situation, dietitians or other registered health professionals may decide to supplement a person’s diet with supplements.
Basically, the foods containing vitamin B12 are meat, fish, eggs, and dairy products. A range of meats and offal, as well as fish such as cod, salmon, haddock, and halibut, along with clams and shrimp, are the major sources of vitamin B12. Other useful sources include milk, fortified breakfast cereals, and yeast extracts such as Marmite. Plant foods do not contain vitamin B12, so green vegetables and fruit are not good sources. The RNI for vitamin B12 is 1.5 μg/day.
Biotin
Biotin is another member of the B-complex vitamins and has a widespread role in the body. Its functions include being used as a co-enzyme for the carboxylase enzyme that carries carbon dioxide (CO2) units in the metabolic pathways. It also plays a central role in lipogenesis, the synthesis of fatty acids in the cell, and gluconeogenesis, the formation of glucose from other sources such as amino acids. Biotin is involved in the catabolism (breakdown) of branched-chain amino acids.
Biotin deficiency is a rare nutritional disorder. This extremely low prevalence of biotin deficiency is probably because all foods contain significant quantities, and many widely consumed foods are relatively rich in biotin. Symptoms of biotin deficiency include a loss of hair or fine scaly dermatitis. One primary source of biotin is its synthesis in the gut flora. Other good sources include egg yolk, liver, legumes, oats and grains, almonds and walnuts, chickpeas (canned), yellow split peas, green split peas, brown lentils, lima beans (canned).
There was insufficient evidence to set an RNI for between 10–200 μg/day, which is considered safe and adequate. The removal of biotin via faeces means that 3–6 times more biotin can be removed from the body than can be ingested. This means no known toxicity exists, as any excess intake would be excreted in the faeces.
Pantothenic acid
Pantothenic acid, or vitamin B5, is from the Greek word pantos, meaning ‘everywhere’, and this accurately describes this vitamin’s role in the body. It is vital to transforming energy in the cells by assuring adequate production of healthy fat in our cells. Pantothenic acid helps to break down and change the shape and function of proteins and their acids. It also has a pivotal role in energy production, creating fats and turning fats and carbohydrates into usable energy.
A deficiency of pantothenic acid can cause low energy-related symptoms, including an abnormal sensation in the lower legs and feet of malnourished patients, fatigue, dizziness, headaches, and muscle weakness. Good sources of pantothenic acid include meat—especially calf’s liver—cereals, vegetables—mushrooms, cauliflower, broccoli, tomatoes, corn, sunflower seeds, low-fat yoghurt, eggs, strawberries, and grapefruit.
As there is no accepted biochemical method of establishing pantothenate status in humans, no dietary reference value is set. For guidance, the mean intake of pantothenic acid in the UK is 5.4 μg /day. No known problems are caused by excessive intake of this vitamin.
Folate (folic acid)
Folic acid is the parent molecule for a group of derivatives collectively known as folates. Folate plays a vital role in the manufacture of DNA and proteins. It is essential for normal growth and development and in producing new cells. It also works with vitamin B12 in the production of haemoglobin in red blood cells. A deficiency of folate can lead to a condition known as megaloblastic anaemia, where red blood cells are too large and make carrying oxygen inefficient. The metabolism of folate is closely linked with B12 and B6 status. Good sources of folic acid include liver, dark green vegetables – spinach, broccoli, greens and asparagus, nuts and beans, beets and lentils, wholemeal bread.
Some breakfast cereals are also fortified with folic acid and are, therefore, a useful source. The liver is a good source of folate, but pregnant women and those looking to conceive should avoid this as a food source. Liver, you may recall, is also a rich source of vitamin A, and vitamin A at high levels can cause malformations and birth defects in the foetus. The RNI for folate for healthy adults is 200 μg/day. For the first 12 weeks of pregnancy, an additional 400 μgis recommended. High intakes may reduce zinc absorption, but on the whole, as this vitamin is also water-soluble, the danger of toxicity is low.
Folate is one of the few examples where there is strong evidence to support supplementing for a specific group of individuals. The Department of Health recommends that pregnant women supplement their diet with 400μg of folic acid. There is conclusive evidence that shows these levels of intake can significantly reduce the risk of neural tube defects (NTD) like spina bifida, where the spinal cord is incompletely formed during the first three months of foetal development.
That’s it about main vitamins that our body needs. Don’t forget that we also need minerals. Information about them you can find here: “All you need to know about minerals“.
