The use of dietary supplements fuels a multibillion-dollar industry, with the figure estimated to reach $60 billion by 2020.1 The use of vitamin and mineral supplements increases in people with a history of anxiety and/or depression, among other health challenges.2 Women are 50% more susceptible to depression, generalized anxiety disorder, panic disorder, phobias and insomnia compared to men due to a variety of factors, including conflicting societal and family roles and limited free time.3-5 Stressed, anxious and time poor women may therefore be particularly susceptible to self-diagnosis, and therefore be especially vulnerable to the lure of dietary supplement advertisements and labeling targeting a reduction in these mood states. Indeed, a number of surveys have found that dietary supplement usage is more prevalent among women than men, lending support to this hypothesis.6,7 In addition, complementary or alternative therapies, which include dietary supplements, are estimated to be used by over half of the individuals who are diagnosed with anxiety or mood disorders.8 This estimate is likely to be higher if one includes those who self-diagnose, using the advice of friends and family to guide both purchasing and usage decisions. Unfortunately, these acquisitions are based largely on personal hope and media hype regarding supplement use, as evidenced by the systematic review published in this issue of the JBI Database of Systematic Reviews and Implementation Reports that highlights a lack of research-based evidence to support their use for anxiety and stress reduction in the general female population.9
The comprehensive search identified 14 eligible studies, all of which investigated the effectiveness of specific nutrients on female anxiety or stress, with 80 percent of these studies investigating these mood states during a hormonal phase, such as pregnancy, premenstrual tension (PMT), peri-menopause or menopause.9 The effectiveness of specific nutrient interventions on the reduction of anxiety or stress was evident in a number of studies where a specific hormonal phase was present, but not in other studies where no hormonal phase was present. In addition, during similar hormonal phases, combining nutrients led to a reduction in anxiety in one group, while another group using them separately did not experience a similar reduction. These mixed results, among others in our review, have limited usefulness for women attempting the use of dietary supplementation to manage anxiety or stress.9 In addition, intervention duration may be an important factor to take into account in determining the effects of specific nutrients, the idea of which is supported in a number of studies in our review.9 The need for increased intervention duration and possible effectiveness using nutrient combination may therefore need to be communicated to women who are aiming to manage these mood states with supplements during specific hormonal phases. Unfortunately, dietary supplementation labeling does not communicate these concepts adequately, and medical practitioners, along with allied health care providers, may also be remiss in explaining them sufficiently, leaving supplement users vulnerable to the opinion and advice of friends and family to guide supplement use. Another factor, which was not discussed in any of our selected papers, is whether nutrient dosage should be adjusted according to body weight. To date, only one essential fatty acid (EFA) dietary supplement suggests intake based on body weight.10 Evidence on the effectiveness of combination-nutrient dietary supplementation addressing female anxiety and stress, regardless of hormonal phase, is also sparse, with results from a number of studies yielding mixed results, 85% of which were partly funded by commercial supplement manufacturers introducing a possible risk of bias.9
There is clear biochemical evidence to indicate that nutrients play a critically important role in central nervous system (CNS) functioning.11 In addition, subclinical deficiencies in nutrients may influence psychological wellbeing before physical ailments are noted.12 There is also evidence to suggest that there is widespread prevalence of nutrient deficiencies in developing and developed countries, due to both poor dietary choices and soil nutrient deficiencies.13,14 Stress is likely to exacerbate these deficiencies due to increased nutrient requirements during periods of chronic stress, leading to a cascade of negative physical and mental sequelae such as cardiovascular disease, lifestyle-related diabetes, metabolic and immune dysfunction along with cognitive decline and depression, which has been linked to chronic stress.15-17 Self-diagnosis coupled with experiencing a lack of effectiveness from the use of supplementation may lead to a worsening of stress and anxiety-induced symptoms. Dietary supplementation may therefore play an important role in managing female anxiety and stress, but, as evidenced by the heterogeneity of the studies in our systematic review, and the mixed results, future studies examining the effectiveness of specific nutrient intervention on female anxiety and stress, regardless of hormonal phase, are warranted and sorely needed. However, future studies should take into account the relationship between nutrient intake and status at baseline, intervention duration, the combination of specific nutrients, dosage and individual differences, such as body weight, while controlling for hormonal phase. Unless studies address these relationships, any resulting systematic reviews will be afflicted by the same limitations from which our review suffered. Therefore, at this point in time, the majority of women may not experience the full benefit of specific dietary supplementation for anxiety or stress management.
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