Is there an issue [transgressing the Mishna Avos (Avos 3:8) of causing oneself to forget his learning] to eat olives seeing that Horayos (13b) writes olives eaten frequently will cause one to forget his learning? If there is an issue, is there a way to remove the forgetfulness?
In a personal letter Rav Chaim Kanievsky wrote to me that one should wait thirty days between one "eating" of olives and the next "eating" so that one shouldn't be "ragil ba'zeisim." He said however that dipping the olives in olive oil is sufficient to remove the problem of eating olives altogether.
This point was recently discussed in Rav Chaim Bleier shlita's Chukei Chaim series, no. 299
Firstly, by way of introduction, some further information on the potential problem:
The Gemara (הוריות י''ג ע''ב) lists "הרגיל בזיתים" ("one who is accustomed to eating olives") among the things that cause one to forget his learning; this is quoted in the words of several poskim (ארחות חיים הל' ת"ת אות כ"ה, של"ה שבועות פ' נר מצוה אות ק"ה, רע"א או"ח סי' ב', ערוה"ש או"ח סי' ב' ס"ה, סי' ק"ע סט"ו ) Some say this has a natural cause (רבינו בחיי, בראשית לד:א); others say it is supernatural .(חסד לאלפים או"ח סי' קנ"ז סק"ו, הגרשז"א, הליכות שלמה תפלה פ"ב הע' ק"ג)
Interestingly he points to a couple of heteirim:
- Whilst the Gemara in Horayos talks against regular consumption of olives it is clear that Tannaim ate olives (Yevamos 15b) implying there are permitted ways to eat them.
- Chovos HaLevavos (Shaar HaPrishus 5) - one should refrain from eating foods which require great efforts to prepare, and instead, one should suffice with side dishes that don’t take any effort to prepare, such as olives, cheese, figs, grapes, etc.
In terms of understanding what is deemed "הרגיל" - "regular" he cites the differing views:
- DAILY - e.g. Siach Yitzchok on Horayos, or every meal (Birurei HaMiddos Maharil, Likkutim 78). Therefore having them every other day would be fine (BaTzeil HaChochma on Horayos).
- EATING A LITTLE - Only an issue if you eat loads of them. Therefore, ok to eat occasionally or even every day if eaten sparingly (Mayim Chaim, Orach Chaim 190).
- WEEKLY - Once a week is not called "הרגיל" (Halichos Even Yisrael, Moadim - cheilek 2, 52, note 11).
- EVERY 30 DAYS - As per Rav Chaim Kanievsky zt"l (Sefer Zikaron, cheilek 2, ois 11, s.v. "V'Hinei"). Therefore, in such a case, one can have many olives at least in one meal (She'eilas Rav, cheilek 1 21:4).
Finally he also reviews if the colour of the olives is an issue:
Specifically black - i.e. green colour do not cause forgetting (Rav Avraham Palagi, Sefer Avraham Ezkor 7:36)
By not explicitly differentiating, poskim hold that green are also an issue (Pri Chaim 24).
As to your point:
Is there a way to remove the forgetfulness
The Gemara in Horayos 13b notes that olive oil restores forgotten Torah learning. Accordingly, some poskim hold that it is okay to eat olives along with olive oil (See Halichos Shlomo, Tefillah, perek 2, he'arah 103). Indeed, this was the custom of many in Yerushalayim (e.g. Sha'arei Hora'ah, cheilek 4 p.17 letter hei). However, not all poskim agree with this.
Also if one maintains certain kavanos whilst eating the olivesit also can reverse the forgetfulness (see Chukei Chaim there for greater detail)