We have recently celebrated the 100th anniversary of the “discovery” of vitamins. New meta-analyses indicate the benefits of multi-vitamins in reducing inflammation and cardiovascular risk factors [10
] and the benefits of vitamin C supplementation [11
] on improved endothelial function in subjects with cardio-metabolic disorders, but no demonstrable improvement was observed in healthy subjects. However, there is heterogeneity of results among studies.
In the Heart Protection Study, 20,536 adults in United Kingdom with coronary disease, other occlusive arterial disease, and/or diabetes did not show any benefits from “antioxidant” vitamin supplementation (600 mg vitamin E, 250 mg vitamin C, and 20 mg β-carotene daily) [12
]. In addition having study-design concerns, in many of these studies with neutral outcomes, vitamins and minerals were supplemented in populace who are already sufficient with micronutrients. Thus, one would not have expected positive results from these studies. Nevertheless, based on such data, it is unfortunate that there have been recent calls for reductions in micronutrient supplementation in developed countries [13
These variations in results may occur partially due to differences in nutritional status of the test subjects, and inadequately designed studies. In his 2003 EV McCollum Award Lecture, Robert Heaney divided nutritional issues between prevention of short-latency deficiency diseases such as beriberi, pellagra, rickets, and scurvy, versus long-latency, multifactorial disorders such as the chronic diseases increasing common globally; e.g., cancer, cardiovascular disease and diabetes [14
]. The Nobel Prize-winning discoveries of the major vitamins and their ability to prevent or treat specifically caused diseases led to dramatic decline of those pathologies in the economically advanced counties. As a result, severe micro-nutritional deficiencies directly causing diseases are now found mainly in the developing economies.
A recent study in Cambodia found 50% of the women subjects in Phnom Penh and rural Cambodia were thiamine deficient (39% urban, 59% rural) [15
]. In developed countries, thiamine deficiency and beriberi are rare on a population basis, but clinical deficiencies are reported worldwide [16
]. Dealing with short-latency deficiency diseases is in principle relatively straightforward, the main difficulties usually being establishing the deficiencies at the population level. Recent, nationally representative studies in Indonesia and Malaysia reported vitamin D deficiency (using the cutoff of 50 nmol/L; 20 ng/mL) in over 60% of girls 7-12 years old [17
], which had never been measured before. Fortification has proven to be an effective way to increase intakes of selected nutrients in both developed and developing countries [9
], although sub-optimal data is often found in estimating population deficiencies and food intakes of potentially fortified foods.