Basics of vitamins
Vitamins do not exist in any single form, for example, vitamin D exists in 5 forms and vitamin E exists in 8 forms (4 types of tocopherol and 4 types of tocotreinol). Only vitamin C exists in a single form (ascorbic acid), but even then there are various metabolic stages in which in can be found in. In reality, the term ‘vitamin’ refers to a group of similar nutrients as opposed to a single nutrients. There are 6 known vitamins, most of which have a number of sub-groups, which are listed below:
- Vitamin A
- Carotinods (such as beta-carotene and gamma carotene)
- Vitamin B
- Vitamin B1 (Thiamine)
- Vitamin B2 (Riboflavin)
- Vitamin B3 (Niacin)
- Vitamin B5 (Pantothenic Acid)
- Vitamin B6 (Pyridoxine)
- Vitamin B7 (Biotin)
- Vitamin B9 (Folate)
- Vitamin B12 (Cobalamin)
- Vitamin C (ascorbic acid)
- Vitamin D
- Vitamin D1
- Vitamin D2 (ergocalciferol)
- Vitamin D3 (cholecalciferol)
- Vitamin D4 (22-dihydroergocalciferol)
- Vitamin D5 (sitocalciferol)
- Vitamin E
- 4 types of tocopherols
- 4 types of tocotreinols
- Vitamin K
- Vitamin K1 (phylloquinone)
- Vitamin D2 (various types of menaquinones)
Retinol is the form in which vitamin A is found in animals (including humans), and is considered to be ‘true’ vitamin A. It is the most biologically active form in humans, and the body can readily utilize it. Retinol is fat soluble, and is is found naturally in abundance in cod liver oils, which are the only supplement source or retinol. Absorption of retinol is relatively slow due to its fat solubility, as fats take a relatively long time to break down in the digestive system.
Carotinoids such as beta-carotene from carrots, are considered to be the plant form of vitamin A, but are not true vitamin A. Carotinoids must be converted into retinol before they can be utilized in the body, and this conversion is made in a 2:1 ratio. The fact that an inefficient conversion is needed to use carotinoids shows animal forms of vitamin A are more valuable to the body than plant forms. Carotinoids can be sourced naturally from vegetables or synthesized in a lab, and investigations on their absorption/ retention in the body is inconsistent and inconclusive. Common forms in which retinol (animal form) can be artificially synthesized in are vitamin A palmitate and vitamin A acetete, both of which are ester salts of retinol.
Palmitate is derived from palmitic acid, which is a common fatty acid in many animals, and acetete is common in biology as the salt acetic acid. These are often in a powder form, but can be dissolved in an oil solution, and are sometimes added to fish oils. Absorption of these forms is very inconsistent, and some studies have shown that there is no absorption (no trace of vitamin A in the blood of participants), and other trials have demonstrated rapid absorption, which, may lead to toxic levels present in the blood. As a result of the variable and potentially high potency and absorption of synthetic forms of vitamin A and potential health risks, synthetic forms are heavily regulated in a number of countries. Due to its potential toxicity, vitamin A as a standalone vitamin supplement is very uncommon. However, synthetic forms such as the two discussed are often found in multivitamins tablets and some cod liver oil.
Each B vitamin is actually a distinct vitamins in their own right, however, because they are often found together in nature they were originally thought to be different forms of the same vitamin. All naturally occurring B vitamins, With the exception of vitamin B9 (found in vegetables only) and vitamin B12 (animal sources only) can often be found together in both plants and animal sources. These vitamins are water soluble and non-toxic, and can be rapidly absorbed in the small intestine, however, due to their water solubility the body cannot easily store them. As they are often found together it is thought that they aid with the absorption of each other in the digestive system. Synthetic B vitamins are in the form of ester salts, similar to that of synthetic vitamin A, whereas in nature they are found in what is called ‘B-complexes’.
Comparisons with absorption and retention between synthetic B vitamins and naturally occurring B vitamin has shown that naturally occurring B vitamins are absorbed between 2-3 times more than their synthetic counterparts, and were retained in the body 1-2 times longer than their synthetic counterparts. The only exception to this is vitamin B9 (folate), in which the synthetic form was absorbed more than the natural form. Interestingly, synthetic niacin (vitamin B3) also demonstrated anti-vitamin properties (inhibits absorption of other nutrients), where as the natural form didn’t. These figures clearly shown that natural B vitamins are more biologically valuable than synthetic vitamins.
Synthetic vitamin C vs Natural vitamin C
Natural vitamin C is only found in nature as ascorbic acid, and is a water soluble vitamin which is absorbed very easily by the body. Although found in many fruits and vegetables, it is rare to find it in very high concentrations in foods. In nature it is found along side other nutrients, such as bioflavinoids (an example of this is oranges), as well as various stages of its metabolism.
Studies have shown that when ascorbic acid is given in a natural citrus extract containing bioflavonoids, proteins, and carbohydrates, is more slowly absorbed by the digestive system and 35% more bioavailable than synthetic ascorbic acids alone. This highlights the value of the natural components of food, and indicates that no nutrient works in isolation. This is likely to be because one of the mechanisms by which vitamin C is absorbed in the digestive system is sugar facilitated active transport, which means simple carbohydrates are needed for the absorption of vitamin C.
Synthetic vitamin C is structurally identical to natural vitamin C, but often has additional molecules bonded to if for various reasons. Minerals are regularly bonded with ascorbic acid, to make minerals ascorbates. Examples of these are sodium ascorbate, calcium ascorbate, zinc ascorbate and potassium ascorbate. With these forms it is important to understand how much vitamin C is contained in one dose – if the label states for example, 1000mg of sodium ascorbate, this is approximately 100mg sodium and 900mg of ascorbic acid, not 1000mg of ascorbic acid. These mineral ascorbates do have an advantage in that they are less acidic than natural vitamin C, and for this reason may be more desirable to those who have stomach acidity problems. They also do provide the body with additional minerals, which can be of benefit (in the case of calcium or potassium ascorbates), but sodium ascorbates may dangerously increase sodium levels, and so sound be avoided. Another common form of synthetic vitamin C is Ester-C, which is primarily calcium ascorbate (calcium bonded with vitamin C) with a number of metabolites of vitamin C. In theory these metabolites should aid with absorption of vitamin C, but there is actually no evidence to confirm this. [is_logged_in] is another synthetic form of vitamin C which is claimed to be fat soluble, however, when taken orally the ascorbic acid and palmitic acid are separated, and the vitamin C is no longer fat soluble, and behaves similarly to other synthetic forms of vitamin C.
It would appear that the most important factor with vitamin C products is that it is taken alongside other nutrients (such as bioflavinoids and carbohydrates) to ensure that you absorb as much as possible. There currently are no studies comparing true food form vitamin C (such as eating an orange) with synthetic vitamin C with added nutrients.
Vitamin D is a fat soluble vitamin which exists in 5 forms, but there are only 2 forms which we encounter in any real quantity in the food and supplement world – vitamin D2 and D3. Vitamin D3 is the animal form, and is abundant in oily fish and dairy, which are our main dietary source of the vitamin. We are also able to synthesise vitamin D3 in our skin when exposed to sunlight.
There are no plants abundant in vitamin D2, and as it needs to undergo chemical conversion before it can be used by humans, plant sources of the vitamin do not have much nutritional value. Vitamin D3 has been shown to be nearly 90% more biological active in humans that vitamin D2 in clinical trials, which highlights how much better D3 is than D2. Vitamin D is rarely synthesized in a lab, but instead is extracted from plants/ fungi, which gives the D2 form of the vitamin. This means that although synthetic forms are rarely consumed, many vitamin D supplements will contain vitamin D2 and not vitamin D3, which makes them much less potent that dietary vitamin D3.
With vitamin D supplements, always check the label to ensure you are consuming vitamin D3.
In nature, vitamin E exists in 8 different forms; 4 types of tocopherols and 4 types of tocotreinols. They are most abundant in plants, especially nuts and seeds, but can also be found in animal sources such as eggs. As with B vitamins, the different types of vitamin E are often found together in food, and so get a broad spectrum of them from our diet. Their primary role of vitamin E is to protect cells from oxidative damage, and they are able to embed themselves in our cell membranes. Tocotrienols are most abundant in nerve cells, such as the brain, and are recognized for their neuro-protective properties. All 8 forms of vitamin E are needed to maintain good health.
Synthesizing vitamin E in a lab is extremely difficult, and only focuses on synthesizing one tocopherol (alpha-tocopherol). Synthetic vitamin E actually only contains a small amount of alpha-tocopherol, and various partial forms of alpha-tocopherol, none of which our body can easily utilize. As a result of this, synthetic vitamin E is only 50% as absorbable as natural vitamin E, and doesn’t contain any tocotreinols, making it a very poor substitute for natural vitamin E.
Vitamin K is a fat soluble vitamin which exists in 2 natural forms; vitamin K1 and K2. Vitamin K1 is the plant form of the vitamin, and can be found in dark leafy green plants such as kale. Vitamin K2 is the animal form, but can only be found in any significant quantities in fermented foods such as cheese, fermented soy, and some fermented fish oil products where the bacteria produce the vitamin.
Our probiotic population are able to synthesize vitamin K1 and K2, which we can then absorb, and so our dietary requirements are relatively low compared to other vitamins. Vitamin K is a co-factors in a number of biological reactions, but is of particular importance for bone and blood health. Synthetic vitamin K is known as vitamin K3, which is a very potent form of vitamin K and has resulted in a large number of cases of toxicity. As a result if this, vitamin K3 is banned in many countries, and is not readily available. Instead, supplements often contain vitamin K1 which is the plant form. Although this is a more natural alternative to the synthetic form, our body must convert vitamin K1 in to K2 before our body can utlise it. The efficiency of this conversion varies greatly from person to person, and there are no consistent trials which give an accurate figure. However, it is clear that vitamin K2 is a more beneficial form thank K1.
There is concern that the synthesizing of some vitamins can leave traces of heavy metals which are detectable in the final product. Over the last decade a number of supplements, from individual vitamins to whey proteins have been tested, and traces of a number of heavy metals have been detected. As mandatory product testing is not enforced it is impossible to determine which vitamins may contain these heavy metals, and which don’t. It is for this reason that many people do not recommend synthetic forms of vitamins, as heavy metals are linked to neuro-degeneration, liver toxicity and genetic mutations.
Synthetic VS Natural Vitamins – Summary
Vitamins in nature exist in a number of forms, and do not work in isolation in the body. Many vitamins can be found in plant form, animal form and can be artificially synthesised in a lab. If natural plant forms are consumed, the vitamins must be converted by our body into there animal form before they can be utilised, which reduces their potency, but are often very safe. Natural animal forms of vitamins, such as retinol from cod liver oil or vitamin K2 from fermented soy, are the ideal form for our body to use, so often exert more health benefits and pose no health risks. Synthetic vitamins are often absorbed/ retained poorly by the body and so offer less benefits to the body. There have been cases where synthetic vitamins are made in high concentrations (such as vitamin A and K) which has resulted in toxicity, and so synthetic vitamins do pose a potential health risk. Other synthetic forms, as we see with synthetic vitamin E do not contain all forms of vitamin E, and so your body will not get the full benefit of the vitamin.In order to reduce health risk, and maintain true health, vitamins should be obtained in their natural state alongside nutrients they are naturally found with.
Main image courtesy of Gharness