The prohibition on the use of vegetable oil during the Great Fast has deep historical and religious roots connected to the ideals of asceticism and spiritual discipline, enshrined in church traditions.

Sacred Abstinence: The Role of Vegetable Oil in Lenten Discipline

The prohibition on the use of vegetable oil during the Great Fast has deep historical and religious roots connected to the ideals of asceticism and spiritual discipline, enshrined in church traditions. During the period when fasting rules were being established, the Church sought to strengthen believers' self-restraint by introducing a multi-tiered system of abstinence, in which the renunciation of vegetable oil served as one level of deprivation aimed at subduing passions and submitting the will to church canons.

According to the description of fasting levels, there are five stages of abstinence, with the fourth stage—the renunciation of vegetable oil—highlighting the strictness of the fast through the degree of deprivation of nutritional benefits. This indicates that the avoidance of oil was seen as an important element of the fasting individual's self-discipline, contributing to an enhanced spiritual experience and repentance. As noted in one source:

"For physically healthy individuals, the basis of fasting is considered to be food abstinence. Here, one can distinguish 5 levels of physical fasting: 1) the renunciation of meat, 2) the renunciation of dairy products, 3) the renunciation of fish, 4) the renunciation of vegetable oil, 5) complete abstinence from food for certain periods." (source: link txt)

In addition, special attention was given to the rules of the Great Fast, during which not only meat and dairy products but also vegetable oil were excluded, underscoring the particular strictness of this period. The prohibition on oil symbolized a rejection of refined pleasures and a commitment to a purely dry, meager diet, which promoted spiritual purification. This rule was further established in church canons as a means to humble and subordinate the human flesh, as well as to prepare for important religious events. In this context, restrictions on oil were also seen as a reminder of the need to live humbly and to control one’s passions:

"So, the fast during the Holy Forty Days, according to Church rules, consists in abstaining not only from meat and dairy products, but even from fish and vegetable oil; it consists in a dry diet (that is, without oil)..." (source: link txt)

Thus, the historically established rules of the Great Fast included the renunciation not only of certain types of food but also of the use of vegetable oil, in order to underscore the importance of self-denial and spiritual elevation through asceticism. This decision was motivated not only by sanitary and dietary concerns but, above all, by the aspiration to purify the soul by limiting bodily pleasures and intensifying prayer practices.

Supporting citation(s):
"For physically healthy individuals, the basis of fasting is considered to be food abstinence. Here, one can distinguish 5 levels of physical fasting: 1) the renunciation of meat, 2) the renunciation of dairy products, 3) the renunciation of fish, 4) the renunciation of vegetable oil, 5) complete abstinence from food for certain periods." (source: link txt)

"So, the fast during the Holy Forty Days, according to Church rules, consists in abstaining not only from meat and dairy products, but even from fish and vegetable oil; it consists in a dry diet (that is, without oil)..." (source: link txt)