– Author: Rav Joel Kenigsberg

In 2013, when Dutch scientist Mark Post unveiled the world’s first lab-grown hamburger, many began to ask whether we might be approaching the age of a kosher cheeseburger. The new entity was touted to have the same appearance, texture, and taste of regular meat, but it had been grown in a completely revolutionary way – prompting some to speculate that there might be a new form of kosher “meat” that could be pareve, and perhaps even sourced from a non-kosher animal!

At the time, the discussion was purely speculative. The cost of the burger had been an astronomical $330,000 and the entire event had been somewhat of a media stunt.[1] However, six years later, at the time of writing of this article, many entrepreneurs, investors and scientists around the world now agree that it is a question of “when” rather than “if” lab-grown meat will hit the shelves. In December 2018, it was named by Scientific American as one of the top ten emerging technologies of the year and with several dozen companies around the world working on it, the cost is bound to come down, too.

As the concept of cultured meat (also known by many other names: “Clean” meat, cell-based meat, slaughter-free meat, cultivated meat) moves from the realm of science fiction to the world of fact, so too the question of its halachic status has moved from being a theoretical to a practical one that needs to be answered with increasing urgency. Before the technology has been perfected and the product is being sold, poskim will need to evaluate the process to determine whether the product will be kosher or not and whether it will have meaty status.

To date, several articles have been published regarding the kosher status of a cultured meat product and there has been much media speculation as well, but an authoritative halachic ruling has yet to emerge. Part of the reason for this is that any pesak must be grounded in a thorough understanding of the technology involved. At present this is difficult for two reasons. First, much of the method behind the development is being closely guarded by the companies involved, as they race to be the first to market the new product. Second, much of the exact specification of how the final product will look is still unknown to the companies themselves! As a nascent product still under development, it remains possible that methods of extraction, culturing and production of the cells that ultimately grow into meat may change, and with it the halachic status of the soon-to-hit-the-shelves cultivated meat.

This essay does not purport to give a conclusive ruling, but will aim to explore some of the issues involved and the general principles which will ultimately guide the poskim through this complex matter.

How is It Made?

The importance of understanding reality in order to determine halacha can be seen from the following Gemara:[2]

והאמר רב: שמונה עשר חדשים גדלתי אצל רועה בהמה לידע איזה מום קבוע ואיזה מום עובר!

But didn’t Rav say: I apprenticed with a shepherd for eighteen months in order to be able to know which blemish is a permanent blemish, and which is a temporary blemish?

Rav, the great Sage, spent a year and a half apprenticing with a shepherd in order to become proficient in the various types of blemishes so that he could determine the resultant halachot. In a similar vein, before beginning our halachic discussion we require at least a basic knowledge of the technology involved. As mentioned previously, much of the information behind this is not yet accessible – but we will attempt to provide a general framework, bearing in mind that even slight nuances may affect the final outcome.[3]

Firstly, stem cells are extracted from an animal. Different types of stem cells exist and there are advantages and disadvantages to using the various types. What is common to all stem cells is that they have an enormous potential for proliferation – so what begins as a handful of cells will eventually become millions or billions. For the hamburger mentioned at the beginning of this essay, cells by the name of myosatellites were used – adult stem cells found in muscle tissue. Halachically this is a crucial point as it means that the cells originated in the muscle fiber of the animal i.e., they began as edible meat. As we will see later on, cells that originate from other parts of an animal that may not halachically be classified as meaty or even edible may lead to a different conclusion.

Once the cells have been extracted they are placed in a growth medium. This is a liquid solution that provides all the nutrients the cells need in order to multiply. Once a sufficient quantity of cells has been produced, the medium is replaced so that the cells cease multiplying and begin to differentiate – to join together and to develop into primitive muscle fibers that ultimately form the basis for a juicy hamburger.

Not all companies are using identical methods. Some are producing a co-culture of different types of cells that form a 3D structure,[4] rather than isolated strands that would need to be minced together.

Finally, flavorants, colorants and binding agents may be added – but this is not inherently different to anything else that takes place in the modern food industry.

Unconventional Meat

As with many modern questions of halacha and technology, the first and perhaps most challenging question is where to look for a precedent for this complex matter. As we are dealing with a new invention that could not have been fathomed even just a few years ago, we lack a clear and defining precedent. Among the Talmud and commentaries of the Rishonim, there is certainly no clear-cut case which resembles our question exactly. However, there is a source that deals explicitly with a case of meat procured in an unconventional manner.

The Gemara in Sanhedrin[5] discusses the fact that before the time of Noach, mankind was not sanctioned to kill animals and eat them for food. This statement-of-fact is then challenged with another – that in Gan Eden, Adam HaRishon was fed meat by the ministering angels. The Gemara recounts that this was not ordinary meat but rather meat that “fell from Heaven.” The Gemara then tells the following story:

מי איכא בשר היורד מן השמים? אין, כי הא דר”ש בן חלפתא הוה קאזיל באורחא פגעו בו הנך אריותא דהוו קא נהמי לאפיה אמר (תהילים קד, כא) הכפירים שואגים לטרף נחיתו ליה תרתי אטמתא חדא אכלוה וחדא שבקוה אייתיה ואתא לבי מדרשא בעי עלה דבר טמא הוא זה או דבר טהור? א”ל אין דבר טמא יורד מן השמים.

The Gemara asks: Is there such a thing as meat that descends from heaven? The Gemara answers: Yes, it is like this incident: As Rabbi Shimon ben Chalafta was walking along the way, he encountered those lions that were roaring at him, intending to eat him. He said: “The young lions roar after their prey, and seek their food from God” (Tehillim 104:21), and they deserve to receive food. Two thighs of an animal descended from heaven for him. The lions ate one of these thighs, and they left the other one. He took it and entered the study hall, and inquired about it: Is this thigh a kosher item or a non-kosher item? The Sages said to him: Certainly it is kosher, as a non-kosher item does not descend from heaven.

The Gemara subsequently[6] also discusses the case of two sages who would create a calf using Sefer Yetzira (Kabbalistic techniques), which was then permitted for consumption.

While these cases of miracle meat or meat that fell from Heaven are certainly not directly analogous to our case of cultured meat – the common factor among both cases is that we are dealing with meat not produced in the conventional way (like a cut procured from a slaughtered animal). It is this similarity that has led some writers to conclude (among other factors) that the product in question would per force be kosher and permitted without slaughter of the original animal. In his 2014 article in Techumin, R. Tzvi Ryzman writes:[7]

לענייננו, יצירת בשר במעבדה מתא גזע אינה “נס”, אך ברור שהבשר לא נוצר בדרך הרגילה, שבה נבראו כל בעלי החיים. זו מציאות חדשה של “יצירה” הנעשית על ידי התערבות ידי אדם, ויש לדמותה לבריאה ע”י ספר יצירה. מעתה, עלה בידינו טעם נוסף להתיר את אכילת הבשר המשובט, אף אם התא נלקח מבהמה אסורה באכילה, שכן איסורי התורה חלים על בהמות רגילות, ולא על בהמות ש”נבראו” מתאי גזע במעבדה.

Stem-cell meat created in a lab is not miraculous, however it is certainly not meat produced in the conventional way, in which all animals were created. This is a new reality of a “creation” which came about through human intervention, and should be compared to meat created through Sefer Yetzira. This would therefore be another reason to permit consumption of [cloned meat], even if the original cell was taken from a non-kosher animal.

However, it seems that the analogy falls short. As Rav Yaakov Ariel and others have argued,[8] the process in question is not in any way miraculous or supernatural – it is simply a newfound technology that science has allowed. Indeed, the entire aim of the process is to mimic the natural growth process which takes place inside the body of the animal as closely as possible in a laboratory setting,. Furthermore, if such technology were to become widespread and emerge as a conventional form of meat production (as many have predicted) the argument that we are dealing with an unusual method would no longer be valid.

Aside from the above, many have rejected the comparison to this particular source altogether. The piece of Gemara is not halachic in nature and many authorities are of the opinion that practical halachic rulings cannot rest on such sources.[9] It is only because of the completely novel nature of the problem that poskim have invoked such a passage as a source for discussion. Nonetheless, it seems far more appropriate to go back to traditional halachic principles of kashrut and begin our analysis from there.

Broadly speaking, we can divide the question into two. First, what is the status of the original cells that are extracted? Do they retain the status of the animal from which they emerged (Kosher/Non-Kosher, Meaty, etc.)? Second, even if the original cells were judged to be problematic, could the process have an effect such that the final product might still be permitted for consumption?

The Original Cells

How do we view the original cells from which the meat is produced? There seem to be three general possibilities:

  1. It could be seen as meat.
  2. It could be seen as a meaty or non-meat “derivative”.
  3. It could be seen as insignificant.

1.     The Cell as Meat

If the starter cells are classified as “meat,” it seems they would be subject to the prohibition of eating a limb or flesh from a living animal (eiver min hachai and basar min hachai). The source for this is the Gemara in Chullin:[10]

אמר ר’ יוחנן, לא תאכל הנפש עם הבשר (דברים יב,כג) זה אבר מן החי, ובשר בשדה טרפה לא תאכלו (שמות כב, ל), זה בשר מן החי ובשר מן הטרפה.

ור”ש בן לקיש אמר לא תאכל הנפש עם הבשר זה אבר מן החי ובשר מן החי ובשר בשדה טרפה לא תאכלו זה בשר מן הטרפה.

The Gemara discusses the source of the prohibition of eating a limb from a living animal. Rabbi Yochanan says: “You shall not eat the life with the flesh” (Devarim 12:23); this is the source for the prohibition of eating a limb from a living animal. And the verse: “And you shall not eat any flesh that is torn in the field” (Shemot 22:30); this is the source for the prohibition of eating flesh severed from the living and flesh severed from a tereifa, even if it is not an entire limb.

And Rabbi Shimon ben Lakish says: “You shall not eat the life with the flesh”; this is the source for the prohibitions of eating a limb from a living animal and of eating flesh severed from the living. And the verse: “And you shall not eat any flesh that is torn in the field”; this is the source for the prohibition of eating flesh severed from a tereifa.

While Rav Yochanan and Reish Lakish disagree as to the exact derivation from the pesukim, both agree that there are two prohibitions, namely concerning both a limb from a living animal and flesh from a living animal. This is significant because a stem cell certainly does not comprise a full limb from an animal. However, assuming it originates from muscle tissue it could be said to be considered “flesh.”

Another point raised counter to this argument is the fact that there is a minimum shiur for which one is punished for the prohibition of eating a live limb or flesh. As the Rambam writes,[11] only one who eats a kezayit (olive’s bulk) of flesh from a living animal would be subject to the Torah’s punishment. A microscopic cell is certainly many times smaller than this measure. However, as pointed out by the Beit Yosef,[12] a kezayit is only the minimum measure for which one is liable to punishment. Less than that would still be subject to a prohibition, according to the principle that “a half-measure is prohibited by Torah law” (chatzi shiur assur min haTorah).[13]

Accordingly, there is room to argue that the starting position of cells taken from a living animal would be of forbidden status under the prohibition of “flesh from a living animal.” All would agree that if the cells were taken from a kosher species that had undergone kosher shechita then the cells themselves would pose no problem. However, to date the standard practice has been to extract cells from living animals. The reasons for this include concern for animal welfare and the desire to create a slaughter-free product, as well as increased viability for creating cell lines when cells are taken from a living animal.

We note as well that all this may be limited to cells taken from muscle tissue. Cells extracted from non-meaty parts may well be subject to different considerations. The hamburger described above was produced based on cells from pre-existing muscle tissue (myosatellite cells) but cultured meat based on cells from other non-meaty or perhaps inedible parts of the animal (such as feathers, hair or hooves) may be classed in a different category altogether.

2.     The Cell as a (Non-Meat) Derivative

Another important principle which may have bearing on our discussion is the statement of the Talmud,[14] “that which derives (yotzei) from an impure species is similarly considered impure.” There are several examples brought for the application of this principle[15] and significantly they include both non-meat derivatives such as milk and eggs, as well as a complete animal (of a kosher species) born to a non-kosher parent. Thus, irrelevant of whether it is meaty or not – taking a cell from a non-kosher animal would appear to be a non-starter.

3.     The Cell as Insignificant

There is another possibility whereby the cell would not be judged by the aforementioned principles of yotzei or eiver/basar min hachai and might rather be considered kosher, no matter what its source. This would be based on the idea that the Torah does not give credence to that which is not discernible with natural senses. An example of this point is found in the Aruch HaShulchan regarding the question of consumption of microorganisms. Bacteria, prevalent in water and in the air do not have the necessary signs for kosher creatures. As such, after their discovery the question was posed as to how their consumption is permitted. The answer is as follows:[16]

ובילדותי שמעתי מפי אחד שהיה במרחקים וראה דרך זכוכית המגדלת עד מאד כרבבות פעמים במים כל המיני ברואים ולפ”ז איך אנו שותים מים… דלא אסרה תורה במה שאין העין שולטת בו דלא ניתנה תורה למלאכים.

In my youth I heard of one who witnessed many thousands of times all sorts of creatures in water through a microscope, and according to this how is water permitted?… The Torah did not forbid that which the eye cannot see, since the Torah was not given to angels.

Accordingly, the idea has been posited that microscopic cells would not be subject to general kosher laws and automatically be permitted for consumption. The resultant entity could thus be considered kosher even if it derived from a living animal or a non-kosher species![17]

Rav Yaakov Ariel[18] has categorically rejected this argument as untenable. It is true that generally microorganisms are not subject to the general prohibitions of the Torah, but our case might be different. In order to demonstrate why, Rav Ariel quotes a passage from Rav Shlomo Zalman Auerbach dealing with genetic modification of microorganisms. In that context, Rav Auerbach argued that the principle of not giving credence to microscopic entities would not apply:

כיון שאנשים מטפלים בחלקיקים האלה ומעבירים אותם ממין אחד לשני הרי זה חשיב ממש כנראה לעינים ולא דמי כלל לתולעים שאינם נראים.

[Regarding your question concerning genetic modification…] Since people are dealing with these particles and transferring them from one species to another, it is considered precisely as if they are visible to the naked eye.[19]

According to Rav Shlomo Zalman, It would seem that the Torah’s disregard for microscopic entities would be limited to other cases – where one is unaware and perhaps would prefer for them not to be there. When it comes to laboratory endeavors where the microscopic organisms play a significant role of which all are aware – it is hard to discount their existence. It may well be that the subjective importance given to the cells through the process of manipulating them in a lab may be enough to render them significant despite their microscopic size.

The Process

Even if we reject the “microscopic” argument and view the original cells as problematic (based on their origin from a non-slaughtered animal or non-kosher species) that may not be the bottom line. The laws of Kashrut and the modern food industry abound with examples of items that change from their original status, and what begins as forbidden may end up as a permitted product. A fully nuanced and authoritative ruling on this will only emerge alongside an in-depth and transparent understanding as to the exact production method. Suffice it for the purposes of this essay to list just two examples which might bear relevance to the topic at hand.

1.     Bittul beShishim (Nullification in a Mixture)

A well-established principle of Kashrut is that when a forbidden substance is inadvertently mixed with a permitted substance, the resultant mixture may still be permitted, so long as the forbidden substance is unrecognizable in appearance or taste. The ratio required for this for most forbidden substances is 60:1. An argument has been put forward to suggest that even if the original cell derives from a problematic source, it is “nullified” by a ratio of many billions to one by the resultant mass of cells that is produced. Alternatively, one might claim that the cell along with the growth medium forms a mixture which nullifies the original cells.

2.     Panim Chadashot (A New Substance)

Another principle that might be pertinent is the question of “panim chadashot.” When a substance undergoes a significant change, its original halachic status may be uprooted as well. This question was central to the controversy surrounding gelatin deriving from non-kosher animals about which some poskim were stringent while  others were lenient. One possible reason for leniency is given by Rav Ovadia Yosef:[20]

הואיל ובתהליך התוצרת של הג’לאטין מן העור והעצמות לאחר שנתייבשו היטב בשמש, במשך כמה חדשים, מערבים בהם מלחים כימיים וטוחנים אותם הדק היטב עד שנהפך הכל לאבק דק, ופנים חדשות באו לכאן.

Since in the production of gelatin from skin and bones after they have been dried out for several months, they are mixed with chemicals and finely ground until they turn into fine powder, a new substance has emerged (panim chadashot).

The Implications for Cultivated Meat

Where does all of this leave us? Based on a combination of the arguments above, R. Tzvi Ryzman suggested (in his article cited above in Techumin from 2014) that cultured meat might be kosher (and pareve) regardless of the cell source. He writes:

אולם באמת נראה לומר שגם האוסרים לאכול ג’לטין המופק מעצמות בהמות טמאות, יודו שתא הגזע אינו אוסר את התערובת. שכן בג’לטין – אותו החומר שהופק מהעצמות המיובשות, חוזר להיות ראוי לאכילה; אולם בבשר המשובט – התא נותר בלתי-ראוי לאכילה כמו שהוא, ורק לאחר השרשתו באצת הים ולאחר שנותנים בו חומרים השונים שנועדו לקיומו ולהתרבותו, הוא הופך ראוי לאכילה. התא עצמו לא הפך ראוי לאכילה, והוא הרי בטל בשישים בשאר החומרים שמעורבים בו, אלא פנים חדשות באו לכאן, ועל כן נראה שהתא אינו אוסר את התערובת.

It seems that even those who are stringent regarding gelatin from an unkosher animal would agree that the stem cells would not forbid the mixture here. For [unlike gelatin] regarding cloned meat the cell remains inedible in its present state… and only after nutrients are added does it become edible. The cell itself has not become edible, and it is nullified in a ratio of 60:1 with the other materials mixed with it; rather a new substance has formed (panim chadashot), therefore it seems that the cell does not forbid the mixture.

This line of reasoning is far from indisputable. A heated debate ensued in the following volumes of Techumin with eminent authority Rav Yaakov Ariel weighing in, among others. He rejected the argument on several counts.

First, it seems inaccurate to claim that the cell itself is not edible. True, it could not be eaten by itself due to its microscopic size, but there is nothing inherent about the cell that makes it unfit for consumption. Indeed, the final product is simply an outgrowth of millions of identical cells, which en masse form an edible product. Second, the mixture argument is rejected on similar grounds. Nullification only applies in a mixture of prohibited and permitted substances. In our case we are dealing with one substance, the original cell culture, which simply proliferates itself.[21] As Rav Ariel writes:

לענ”ד כל הדיון של ביטול ברוב לא רלבנטי לענייננו, כי האיסור עצמו מתרבה וכל היוצא ממנו אסור כמוהו ואין כאן ביטול בדבר אחר.

In my opinion, the entire discussion of nullification is not relevant to this matter. The forbidden substance itself is increasing and anything which emerges from it is likewise forbidden. There is no nullification here in another substance.[22]


Rav Asher Weiss also recently addressed the question of what the kosher status of a cultured meat product will be. His response is particularly significant in that it marks the first time a posek has addressed this issue both through a deep understanding of the science involved, and as a matter of practical relevance[23]. His unequivocal conclusion was that the final product would have to be considered meaty. Since under the microscope a cultured meat product will be identical to the meat produced from an animal, it is regarded as meat – irrespective of how it came into the world. Regarding the other issues addressed relating to the source of the cells, the issue remains inconclusive but there certainly are concerns to be noted (and which may be prohibitive) if the cells are not taken from a kosher, slaughtered animal.

As with any developing technology, time will tell as to whether new developments may alleviate some of the questions raised and pave the way for kosher cultured meat. We are faced with a reality that has never existed before, and it remains to the poskim to determine precisely how to apply to it the eternal principles of our Torah. As science marches on, halacha will continue to seek out and provide answers and provide the expression of Torah in our daily lives in ways that were previously unimagined.

[1] See https://www.bbc.co.uk/news/science-environment-23576143

[2] Sanhedrin 5b

[3] This analysis will focus primarily on the methods used by Mark Post to create the world’s first lab-grown burger in 2013. For more information see: https://www.new-harvest.org/mark_post_cultured_beef. For a peer-reviewed academic discussion of the methods used see: Post, M. J. (2014), Cultured beef: medical technology to produce food, Journal of the Science of Food and Agriculture, 94(6), 1039-1041.

[4] See, for example, https://www.aleph-farms.com/

[5] 59b

[6] 65b, 67b

[7] Meat from Stem Cells, Techumin 34

[8] See Techumin Volumes 35 and 36

[9] And they certainly cannot rest on such sources alone.

[10] 102b

[11] Hilchot Ma’achalot Assurot 4:10

[12] Yoreh De’ah, siman 62

[13] See Yoma 73b

[14] Bechorot 5b

[15] For example, see Rambam, Ma’achalot Assurot 3:6

[16] Aruch Hashulchan, Yoreh De’ah 84:36

[17] For an elaboration on this point, see Tzvi Ryzman’s article in Techumin 34 cited above.

[18] “Cultured Meat,” Techumin 35-36

[19] Minchat Shlomo, Tanyana (2-3) 100:7

[20] Yabia Omer, Volume 8, Yoreh De’ah 11

[21] Rav Ariel invokes a fascinating precedent to prove this point from the story of Chanukah:

“The Kli Chemda asked… regarding the miracle of oil [on Chanukah] why was it kosher for the menorah, since the Torah commanded to use olive oil, and “miracle oil” is not olive oil? He answers that the additional oil that was miraculously generated retained the status of the original oil (of olive oil sealed with stamp of the Kohen Gadol)… So too in our case, the other materials and nutrients which allow the growth of the meat do not nullify the original cells, which are the substance that is proliferating. The meat in question is a multiplication of small cells in a way that is similar to the natural process and therefore it is considered like regular meat.”

[22] Although Rav Ariel does not address the argument of panim chadashot, Rav Yehuda Spitz does address it in his rejoinder to R.Tzvi Ryzman’s article (Techumin Vol.35, p.196; transinto English in the Journal of Halacha and Contemorary Society, Fall 2016). He first argues that many great poskim, including Rav Moshe Feinstein and Rav Aharon Kotler, forbade gelatin, in which case they very well may have forbidden this case as well. He then adds that even if our case would be permitted based on panim chadashot, the cells may still have the status of a davar hama’amid, a forbidden substance used to form a product in a manner that is critical for the production, which renders the product forbidden, even if the substance is technically batel (an argument that R.Tzvi Ryzman does not accept in his article). However, the subject of davar hama’amid is a complex one and beyond the purview of this article. In addition to the articles referenced here, see also in English: Rav J. David Bleich, “Stem-cell Burgers,” Tradition, Winter 2013 (available at http://traditionarchive.org/news/_pdfs/0048-0062.pdf and Rav Moshe D. Tendler, Dr. John Loike, and Rav Dr. Ira Bedzow, Pareve Cloned Beef Burgers: Health and Halakhic Considerations, Hakirah, Spring 2018 (available at http://www.hakirah.org/Vol24Loike.pdf).

[23] Although other poskim have addressed the issue, including Rav Yaakov Ariel and the other authors mentioned in the previous footnote, much of that was theoritcal or speculative in nature, as opposed to Rav Asher Weiss’ view which was formulated in response to queries from both companies involved in the manufacture of cultured meat and kashrut agencies with a view to future certification of such a product.

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