The challenge of studying dietary supplements
Vitamin E acts as powerful oxygen radical scavenger particularly in the lipid bilayer of the cell membrane. Human vitamin E deficiency symptoms include anemia and peripheral neuropathy.
Dairy foods play a central role in most dietary guidance recommendations as they provide a package of essential nutrients for health that are difficult to obtain in diets with no or limited use of dairy products.
Exercise may increase the formation of reactive oxygen species in the body which may cause cellular damage, impair skeletal muscle function and pain and thereby affect exercise performance.
The main function of vitamin E is to protect against damage of reactive oxygen species. It also has non-antioxidant functions in cell signaling, gene expression and regulation.
Skin aging is determined by environmental factors, lifestyle and genetic aspects. Metabolic processes, solar UV radiation, smoking, alcohol consumption and illness can induce the formation of free radicals in human skin, which can destroy cells and cell components such as collagen and elastin fibers, if their concentration exceeds a critical threshold.
Aging is a complex biological phenomenon in which the deficiency of the nutritional state combined with the presence of chronic inflammation and oxidative stress contribute to the development of many age-related diseases.
Up until this point, the methods of evidence-based medicine developed specifically for drugs (e.g., using randomized controlled trials) have been applied to nutrient research without apparent attention to important differences between drugs and nutrients.
The use of nutritional supplements is increasingly common in the developed world, with multivitamins – containing at least three vitamins and one mineral – being the most popular type of dietary supplement.
Vitamin B12 is a key nutrient associated with one-carbon metabolic pathways related to substrate metabolism, synthesis, stability of nucleic acids and methylation of DNA which regulates gene expression.