Impact of intermittent fasting on micronutrient intake

This narrative review aims to evaluate the current evidence on how intermittent fasting regimens - including alternate-day fasting (ADF) and time-restricted eating (TRE) - affect micronutrient intake in adults.

Several randomized controlled trials have reported reductions in the intake of key micronutrients such as calcium, magnesium, potassium, folate, vitamin C, and various B vitamins during ADF and TRE. These deficiencies are largely driven by lower total energy intake and reduced consumption of nutrient-dense foods on fasting days. While some studies found no significant differences in micronutrient adequacy between ADF/TRE and continuous energy restriction, others observed higher prevalence of inadequate micronutrient intake with intermittent fasting regimens. Dietary supplement use varied across studies and may help mitigate deficiency risks. Variations in study design, dietary adherence, dietary patterns, baseline nutritional status and nutritional advice appear to influence outcomes substantially.

Although intermittent fasting is an effective and flexible approach to weight management, it may compromise micronutrient intake if dietary quality is not prioritized. Emphasis should be placed on nutrient-dense food choices during eating windows. Dietary supplements may be necessary in restrictive or prolonged fasting regimens to prevent deficiencies and support overall metabolic health.