Journal of Evidence-Based Integrative Medicine

Thiamine (vitamin B ₁) was the first B vitamin to have been identified. It serves as a cofactor for several enzymes involved in energy metabolism. The thiamine-dependent enzymes are important for the biosynthesis of neurotransmitters and for the production of reducing substances used in oxidant stress defenses, as well as for the synthesis of pentoses used as nucleic acid precursors. Thiamine plays a central role in cerebral metabolism. Its deficiency results in dry beriberi, a peripheral neuropathy, wet beriberi, a cardiomyopathy with edema and lactic acidosis, and Wernicke—Korsakoff syndrome, whose manifestations consist of nystagmus, ophthalmoplegia, and ataxia evolving into confusion, retrograde amnesia, cognitive impairment, and confabulation. Patients on a strict thiamine-deficient diet display a state of severe depletion within 18 days. The most common cause of thiamine deficiency in affluent countries is either alcoholism or malnutrition in nonalcoholic patients. Treatment by thiamine supplementation is beneficial for diagnostic and therapeutic purposes.

The current increase in cardiovascular and cerebrovascular morbidity is a growing burden for society. Consideration must therefore be given to compounds capable of slowing down these pathological processes without significant adverse effects. The natural vitamins pantetheine/pantothenic acid are major precursors of coenzyme A and acyl carrier protein, which are essential for fatty acid oxidation and participate in the metabolism of cholesterol and carbohydrates and in at least 70 other enzymatic processes. Following a number of theoretical considerations and clinical observations, various clinical studies have revealed that they possess significant beneficial effects. In particular, they demonstrate useful moderating effects on vascular pathological processes, lowering lipid levels, and inhibiting platelet functions and lipid peroxidation. Although they are natural, well-tolerated therapeutic agents, few controlled clinical trials have been conducted. The available data suggest the need for larger clinical trials and possible use of pantetheine/pantothenic acid as adjuvant therapy.

There is good agreement concerning average requirements and reference intakes for vitamin B₆ but less agreement over safe upper levels from supplements. High-dose supplements cause sensory nerve damage. Supplements of vitamin B₆ have been advocated for treatment of the premenstrual syndrome, with little evidence of efficacy. There are plausible mechanisms for an antidepressant action and protection against steroid hormone—dependent cancers but no evidence from clinical trials. Pyridoxamine reduces the glycation of proteins and so could be beneficial in preventing the adverse effects of poor glycemic control in diabetes. There are plausible mechanisms for an antihypertensive action but only suggestive evidence from small intervention trials. There is no evidence that supplements of vitamin B₆ have any beneficial effect in hyperhomocysteinemia. There is neither a plausible mechanism nor any evidence from controlled trials for any effect of supplements of vitamin B₆ in preventing a decline in cognitive function with aging, amelioration of dementia or autism, or improvement of the carpal tunnel syndrome.

Understanding the molecular mechanisms of vitamins has opened new perspectives regarding the relationship between nutritional signals and biological functions, which, in turn, has led to the development of new therapeutic agents. Although little is known about water-soluble vitamins as genetic modulators, evidence about their effects on gene expression has grown. In the case of biotin, besides its role as a carboxylase prosthetic group, it also affects gene expression and has a wide repertoire of effects on biological functions. Only recently, the role of pharmacological concentrations of biotin on systemic functions has attracted attention, and it is now being reconsidered with the help of new technologies. This novel approach could lead to new perspectives in its use as a therapeutic agent. The present review is focused on the effects of pharmacological concentrations of biotin on several biological functions and on the biotin signaling pathways that participate in gene expression.

Vitamin C functions in enzyme activation, oxidative stress reduction, and immune function. There is considerable evidence that vitamin C protects against respiratory tract infections and reduces risk for cardiovascular disease and some cancers. Current trials are examining the efficacy of intravenous vitamin C as cancer therapy. Many experts believe that the recommended intakes for vitamin C (45 to 90 mg daily) are several orders of magnitude too low to support optimal vitamin C functionality. Also, there is a misperception that vitamin C deficiency disease (scurvy) is largely historical and rarely observed in developed nations. Physical symptoms of scurvy include swelling of the lower extremities, bleeding gums, fatigue, and hemorrhaging, as well as psychological problems, including depression, hysteria, and social introversion. The long-term safety of vitamin C supplementation seems evident as large investigations have noted reduced risk of mortality in vitamin C supplementing populations and in those with elevated plasma vitamin C concentrations.

Vitamin D deficiency is pandemic, spanning many continents and including all ages, genders and racial/ethnic groups. Currently, world-wide attention is focused on the importance of vitamin D in optimizing health and preventing disease. This focus is largely the result of the scientific discovery that vitamin D receptors are present in nearly every tissue and cell in the body and that adequate vitamin D status is essential for optimal functioning of these tissues and cells. An impressive body of research has accumulated over the past two decades providing new information about the role of vitamin D in prevention of a broad range of diseases. The purpose of this paper is to provide a review of this new information.

Vitamin K is traditionally recognized for its role in blood clotting. More recently, new roles for vitamin K have emerged. The current evidence for the role of vitamin K in bone, cardiovascular, and reproductive health will be discussed. There will be a particular focus on populations who could be at risk for vitamin K deficiency.