Thoughts on Micronutrient Intake During Calorie Restriction

Despite the considerable attention given to calorie restriction and intermittent fasting in the research community, there is very little formalism applied to the practice in humans. The few clinical trials conducted to date have had to pick their own protocols, and it is only comparatively recently that the fasting mimicking diet was developed to plant a flag on one specific implementation. The challenge here is that it is difficult to monetize calorie restriction and fasting, and thus there is no push towards standardization or more detailed assessment of variant protocols from any of the usual parties who might otherwise be doing so. It is unlikely that the fasting mimicking diet or any of the existing fasting and calorie restriction trial protocols happen to be the best approach, and also unlikely that much work will be done to improve on this situation.

Caloric restriction (CR) or energy restriction, when carefully designed, monitored, and implemented in self-motivated and compliant individuals, proves to be a viable non-pharmacologic strategy for human weight control and obesity management. Beyond its role in weight management, CR has the potential to impede responses involved not only in the pathogenesis of various diseases but also in the aging process in adults, thereby being proposed to promote a healthier and longer life. The core objective of implementing caloric restriction is to establish a balance between energy intake and expenditure, typically involving a reduction in intake and an increase in expenditure - a negative balance at least initially. It may transition toward and maintain a more desired equilibrium over time.

However, it is essential to note that CR may lead to a proportional reduction in micronutrient intake unless corresponding supplementation is provided. Historical human case reports on CR have consistently maintained adequate intakes (AI) or recommended dietary allowances (RDA) for essential micronutrients, including vitamins and minerals. Similarly, longevity studies involving non-human primates have upheld micronutrient consumption levels comparable to control groups or baseline measures. Recent randomized controlled trials (RCTs) have also endorsed daily supplementation of multivitamins and minerals to meet micronutrient needs. However, aside from these human case reports, limited human trials, and primate experiments, there remains a notable gap in human research specifically addressing precise micronutrient requirements during CR.

While adhering to AI or RDA for minerals and vitamins appears sensible in the current practice, it's important to recognize that these guidelines are formulated for generally healthy populations under standard circumstances. The adequacy of these guidelines in the setting of prolonged and profound negative energy balance remains unclear. From perspectives of evidence-based medicine and precision nutrition, this field necessitates comprehensive exploration to uncover the intricacies of absorption, utilization, and metabolism and the requirement of each hydrophilic and lipophilic vitamin and mineral during these special periods. Such investigations are crucial to determine whether existing daily dietary recommendations for micronutrients are quantitatively inadequate, excessive, or appropriate when energy balance remains negative over extended durations.


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