Reference to synthetic vitamins is in fact a misnomer, because all vitamins are synthesised and therefore synthetic. To clarify terminologies, it should be stated that plants generally synthesise vitamins using enzymes in metabolic pathways, whereas man synthesises vitamins using chemical reactions. What the term synthetic vitamins is really referring to then is the artificially synthesised man made vitamins created in laboratories that are ultimately destined to be added to vitamin supplements. As more individuals consume such supplements, increasingly it is repeated that synthetic vitamins are not well absorbed or are not utilised by the body as readily as ‘natural’ vitamins in foods. As with all good lies, this is based on an ounce of truth, but twisted and distorted to tell a different story and paint a different picture. True, some plant derived vitamins are more bioavailable than man made alternatives. The all-rac-α-tocopherol synthesised in the laboratory is for example about 74 % as bioavailable as the RRR-α-tocopherol synthesised by plants (here).
However, such trivialities can easily be overcome by consumption of larger quantities of the man made alternative. In fact, man made vitamin E is considerably cheaper than the plant derived alternative and so compensation for reduce affinity for the tocopherol transfer protein can be overcome without undue cost. In fact, apart from a limited few example, such as vitamin E and β-carotene, there is little scientific data to show that man made ‘synthetic vitamins’ are any less well absorbed or utilised in man that plant derived alternatives. For example, in the case of vitamin C and folate, researchers have made direct comparisons between man made and plant derived versions of the vitamins1. In the study, man made vitamins in the form of vitamin supplements were directly compared with plant derived versions in orange juice. Absorption across the jejunum in human volunteers was not significantly different between the various vitamin preparations. Therefore synthetic vitamins are just as readily absorbed as those present in food.
If ‘synthetic vitamins’ are as well absorbed as plant derived food based vitamins, it suggest that supplements may be beneficial when food is vitamin deficient. This contention is supported by metabolic studies in the nutritional literature whereby synthetic vitamin C is able to correct physiological changes brought about by scorbutic diets. For example, in one study2 researcher investigated the ability of synthetic vitamin C to improve erythrocyte concentrations of glutathione following a vitamin C deficient diet. Under double-blind placebo controlled conditions healthy subject consumed a vitamin C deficient diet for 2 weeks, and were then supplemented with 500 mg vitamin C for a further 2 to 3 week period. Following the vitamin C supplemental period, mean red blood cell glutathione concentrations rose nearly 50 %, although no further improvements were seen at vitamin C intakes of 2000 mg per day. Synthetic vitamins are therefore effective at redressing vitamin deficient diets which supports a role for synthetic vitamin in health.