Plant-based diets are considered healthier than many omnivorous diets. However, it is unclear that restriction of animal products necessarily motivates increased consumption of nutrient- and fibre-rich plant-based foods as opposed to energy-dense but nutrient-poor plant-based foods containing refined grains and added sugars and fats. The present study examined FFQ and food record data from ninety-nine individuals in the USA with varying degrees of adherence to the Orthodox Christian tradition of restricting meat, dairy and egg (MDE) products for 48 d prior to Easter to investigate whether restricting MDE products in the absence of explicit nutritional guidance would lead to increased consumption of healthy plant-based foods and greater likelihood of meeting dietary recommendations. Multiple linear regression models assessed changes in major food groups, energy and nutrients in relation to the degree of reduction in MDE consumption. Logistic regression analyses tested the odds of meeting 2015–2020 Dietary Guidelines for Americans on plant-based foods in relation to MDE restriction. Each serving reduction in MDE products was associated with small (approximately 0·1–0·7 serving) increases in legumes, soya products and nuts/seeds (all P values < 0·005). MDE restriction was not associated with higher odds of meeting recommendations on vegetable, fruit or whole-grain intake. Consumption of refined grains and added sugars did not change in relation to MDE restriction but remained above recommended thresholds, on average. These findings demonstrate that a reduction of MDE products for spiritual purposes may result in increases in some nutrient-rich plant-based foods but may not uniformly lead to a healthier dietary composition.

The Orthodox Christian diet is unique in regularly interchanging from an omnivore to a vegetarian-type diet, and no study to date has focused on the impact of this on Fe status. Thirty-five Greek Orthodox Christian strict fasters (n 17 male, n 18 female; mean age 43·6±13·2 years) and twenty-four controls (n 11 male, n 13 female; mean age 39·8±7·6 years) were studied before (pre) and near completion (end) of the Christmas fasting (CF) period (40 d), during which meat and dairy products are prohibited. Fe status was assessed using standard haematological parameters, and Fe deficiency was determined via serum ferritin levels (<12 ng/ml) and the tri-index model. While fasters had marginally poorer pre haematological indicators, values were well above the cut-off levels, suggesting that intermittent fasting for a mean of 22·5±15·5 years did not have any substantial adverse effects on Fe status. During the CF period the changes in Fe status indices were more beneficial for fasters than for control subjects. In particular, fasters increased their ferritin levels (P=0·02) and decreased their total Fe-binding capacity (P<0·001). Compared with males, the effect of CF was more pronounced in female fasters. No subjects were detected with Fe deficiency at the end of the CF period. End dietary Fe and fibre intake were significantly higher in the fasters as compared with the control group (P=0·038 and P=0·001, respectively). Adherence to the Orthodox Christian dietary guidelines does not have a major impact on Fe status and is not associated with a significantly greater degree of Fe deficiency.

The longevity and excellent health status of the population of Crete has been attributed to its lifestyle and dietary habits. The impact of Greek Orthodox Christian Church fasting on these dietary habits has never been studied. One hundred and twenty Greek Orthodox Christians living in Crete participated in a 1-year prospective study. One half of the subjects, who fasted regularly (fasters), and sixty non-faster controls were followed longitudinally for the three main fasting periods over 1 year; Christmas (40 d), Lent (48 d) and the Assumption (15 d). Pre- and end-holy days measurements were performed in each fasting period including: 24 h dietary recall, blood collection and anthropometric measurements. Based on the 24 h recall, fasters as compared with controls had lower intakes of end-holy days dietary cholesterol, total fat, saturated fatty acids, trans-fatty acids and protein (P>0·001). Fasters presented a decrease of 753 kJ (180 kcal) in end-holy days energy intake (P>0·05) compared with an increase of 573 kJ (137 kcal) in the controls (P>0·05). Fasters had a decrease in end-holy days Ca intake (P>0·001) and an increase in end-holy days total dietary fibre (P>0·001) and folate (P>0·05), attributed to their higher consumption of fruit and vegetables in end-holy periods (P>0·001). There were no differences for other vitamins or minerals between pre- and end-holy periods in both groups except for vitamin B2. The Orthodox Christian dietary regulations are an important component of the Mediterranean diet of Crete characterised by low levels of dietary saturated fatty acids, high levels of fibre and folate, and a high consumption of fruit, vegetables and legumes.