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The importance of Greek Orthodox fasting for health

Fasting is defined as partial or total abstinence from all foods or selective abstinence from certain foods. Fasting is mainly imposed for religious reasons, but because it is a non-pharmacological intervention to improve health and increase longevity, fasting has been the subject of scientific research.

Fasting periods

There are three main periods of fasting for Greek-Orthodox Christians. During Nativity Fast (40 days, November 15 to December 24), believers abstain from dairy products, eggs, and meat daily. They also stay away from fish and olive oil on Wednesdays and Fridays. During Lent (48 days, Shrove Monday to Easter), believers abstain from dairy, eggs, and meat daily. In addition, they avoid olive oil on weekdays during this period and from fish every day except March 25 and Palm Sunday. During the Dormition of the Mother of God (15 days, 1 to 14 August), the Christian believers avoid dairy products, eggs, and meat. They also avoid olive oil on weekdays and fish every day, except on August 6th.

Apart from these 3 important periods of fasting, every Wednesday and Friday believers abstain from eating cheese, eggs, fish, meat, milk, and olive oil. Exceptions to these prohibitions appear the week after Christmas, Easter, and Pentecost. In total, fasting periods range from 180 to 200 days each year. The Greek-Orthodox Christian diet consists mainly of bread, fruits, legumes, nuts, seafood, and vegetables during fasting periods. This diet can be considered a variation of vegetarianism as well as a form of dietary restriction. The restrictive diet is one of the 3 best-studied diets. The other two are the caloric restriction diet and the alternate-day fasting.

Nutrient intake

During Greek-Orthodox fasting, the daily calorie intake may decrease or remain constant (compared to the non-fasting days). Regarding the percentage of intake of carbohydrates - fats - proteins, during fasting, the intake of carbohydrates increases, and the intake of fat decreases. Also, the amount of protein intake in relation to the intake of carbohydrates and fats may be reduced during fasting, but this is not always the case. When expressed as absolute amounts, total fat and total protein intake decrease during fasting periods, while total carbohydrate intake does not change. During fasting periods the consumption of saturated fats and trans-fatty acids decreases while the consumption of monounsaturated fats does not change. In addition, the consumption of polyunsaturated fats (Ω3 and Ω6) can be reduced during fasting, but this is not the norm.

In terms of intake of vitamins and inorganic elements (minerals and trace elements), both riboflavin intake (vitamin B2) and calcium intake decrease during fasting periods while, on the contrary, magnesium intake increases. Intake of the following vitamins and minerals does not appear to change significantly during fasting periods: vitamin A, thiamine (vitamin B1), niacin (vitamin B3), vitamin C, vitamin E, phosphorus, potassium, and zinc. Some studies indicate that folic acid intake increases during fasting, while others have found no difference. Sodium intake has been found to either decrease or not change significantly during fasting. Also, vitamin B12 may be or may not be reduced during the Greek Orthodox fasting.

Anthropometric Data

In terms of anthropometric results, body mass index (BMI) may decrease or remain unchanged during fasting periods. Another observation concerns the average body mass that seems to decrease during fasting in a statistically significant manner.

Biochemical Changes

In terms of biochemical test results, levels of total cholesterol and "bad" LDL cholesterol decrease during fasting periods. One study reported a decrease in "good" HDL cholesterol levels but other studies reported no change in HDL. The LDL / HDL ratio does not change during fasting. Regarding triglyceride levels, one study found an increase during fasting periods, while other studies showed no change. In addition to blood lipids, fasting can lower blood glucose levels, and several studies have reported an increase in fiber intake.

Other changes that have been observed during fasting are an increase in ferritin levels and a decrease in MCHC levels in the complete blood count, while no change in hemoglobin, iron, and transferrin serum levels is observed. Another observation concerns the hematocrit. The hematocrit of those who do not fast may decrease more than that of those who fast. Despite this decrease, the final hematocrit values ​​of those who are not fasting are actually higher than the final hematocrit values ​​of those who are fasting, but both hematocrit final values ​​in both groups are within normal limits.

Blood pressure

There are conflicting data about the effects of Greek Orthodox fasting on blood pressure. One study found that systolic blood pressure increased during fasting periods, while another study found no change in blood pressure when fasting and non-fasting individuals were compared. The same conflicting findings existed for diastolic pressure. One study found that diastolic blood pressure of non-fasting individuals decreased significantly during fasting periods compared to changes in fasting individuals, while another study reported that diastolic blood pressure between the two groups did not change during fasting periods.

Although so far no study has examined oxidative stress in detail in response to fasting, a recent study measured serum levels of antioxidant vitamins before and after fasting and found that the antioxidant vitamins retinol (vitamin A) and alpha-tocopherol (vitamin E) decreased after fasting.


In conclusion, Greek Orthodox fasting seems to reduce body mass. Carbohydrate intake appears to increase, while protein, total fat, saturated fat, and trans-fatty acid intake decrease during fasting periods. Both total and LDL cholesterol are reduced, although the LDL / HDL cholesterol ratio does not appear to change significantly. Fiber intake increases during fasting periods, which may partly explain the change in serum lipids. Intake of most vitamins and minerals does not appear to change during these periods, although riboflavin and calcium intake seem to decrease while magnesium intake appears to increase.

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