Is slaughter-free ‘cultured meat’ possible without using genetic modification?

Cultured meat is frequently mentioned in popular media. The option to enjoy meat with minimal animal suffering is appealing.

Cultured meat can be produced by taking a tiny tissue sample from a living animal and growing the harvested cells into large numbers in the laboratory or factory. One important detail that often isn’t clarified is how meat cells are cultured. The question is particularly relevant to vegans who not only avoid animal slaughter but also do not want to consume foods produced with genetic modification (GM).

I’ve grown millions of mammalian cells, mostly human cancer cell lines, in my lab days. One essential ingredient of the culture media at the time was fetal bovine serum (FBS) which provides a mixture of bovine growth factors that supports the proliferation of many mammalian cell lines. FBS production involves slaughtering pregnant cows, so any cultured meat production process that uses FBS can hardly be considered vegan.

Nowadays, more than twenty years since I harvested my last cell culture, FBS is still being used. However, for some applications FBS has been replaced by growth factors produced by genetic modification (GM), in which a gene encoding a growth factor is introduced into host cells and the resulting growth factors are purified.

At NutrEvent 2022 I asked the representative of a well-known cultured meat producer whether their FBS-free culture medium contained GM-derived growth factors, which he denied. He never sent the supporting article he promised, so I tried to find evidence for such ‘miracle’ medium. I have not been able to find any. I found the article he referred to (I think) but as I suspected, their FBS-free culture medium contains several growth factors that were produced by genetic modification. Essential components such as insulin-like growth factor 1 have not been found in plants, after all.

As far as I know it is currently not possible to produce cultured meat without using either animal-derived or GM-derived growth medium. I’m curious whether cultured meat producers will try the ‘vegetarian’ route by using growth factors derived from milk.

I wouldn’t mind consuming genetically modified foods that have passed adequate safety assessments, especially when the modification introduces a benefit to the consumer. But many people have a different opinion, which underlines the need for cultured meat producers to be transparent about their production processes.

Potential severe restrictions on PFAS use in Europe

On 15th July 2021, five European countries submitted a proposal that could lead to a prohibition on the use of per- and polyfluoroalkyl substances (PFAS) in the European Union.

PFAS are a large family of thousands of synthetic chemicals that are widely used throughout society as they have desirable properties such as heat stability and repulsion of grease and water. PFAS are found in fast food containers such as pizza boxes and candy wrappers, non-stick pans and kitchen utensils, water resistant clothing and many other products. Through migration, wear and tear micro- and nanosized fragments of these products enter the air, dust, food, soil and water. Most PFAS are either non-degradable or transform ultimately into stable terminal transformation products which are still PFAS.

Potential adverse health effects associated with PFAS exposure include liver damage, thyroid disease, decreased fertility, fetal development, hormone suppression and cancer.

Therefore Denmark, Germany, The Netherlands, Sweden and non-EU member Norway have notified the European Chemicals Agency (ECHA) of their intention to prepare a restriction dossier for the manufacturing, placing on the market and use of PFAS in the European Union.

Such announcement is a legal requirement for a Member State to notify ECHA of its intention to prepare a restriction dossier. The advance notice enables interested parties to plan and prepare for commenting later on.

Stakeholders are encouraged to submit any relevant information to the dossier submitters during the preparation of the restriction proposal and during the consultations. Information to motivate any exemptions to the scope described in the intention is particularly useful to receive in the preparatory phase of the dossier. If justified based on robust risk and socio-economic information the dossier submitters may propose derogations from the proposed restriction. If a derogation is not proposed by the dossier submitters, then it will be up to the relevant stakeholders to do so during any consultation process with a full risk and socio-economic justification accompanying it.

The five countries expect to formally submit their restriction proposal on 15th July 2022.

It is interesting to note this development in the context of other EU member activities on restricting or discouraging the use of certain chemicals. Notably, France plans to introduce a Toxi-Score label on household products in 2022. Toxi-Score is expected to be based on the suspected, presumed or proven presence of an endocrine disruptor in the household product. Such national initiatives might well be followed by wider implementation throughout the European Union later on.

Risk communication

Risk assessment is fairly well harmonized globally. Sometimes there are small differences in daily intake (such as ADI and TDI) recommendations from national and international expert groups, but mostly they are the same.

In contrast, risk management decisions sometimes differ considerably between countries, e.g. on genetically modified organisms. These are sometimes driven by local circumstances such as unavoidable contaminants in foods. More often, divergent risk management decisions originate from different societal values regarding the appreciation of scientific progress, risk perception and trust in regulators, industry and activist NGOs.

In this varied societal landscape it can be hard to adapt risk communication to the country and sub-populations concerned. I’ve summarized some general guidelines for risk communication in a presentation at the Conference on Food and Nutrition Safety in Baku (AZ), 25 November 2019. Hope you’ll find it useful.

Gut microbes modify drugs

There is a saying that a drug is beneficial in one third of patients, ineffective in another third, and detrimental in the remaining third. This variability is partly due to genetic differences between individuals. A new study suggests that gut microbes play a big part as well: about two thirds of oral drugs may be chemically modified by gut microbes.

Zimmermann and coworkers found that two thirds of 271 oral drugs were metabolized by at least one of 76 bacterial strains that represent the majority of gut microbes. They identified 30 microbial enzymes that collectively converted 20 drugs to 59 candidate metabolites. These results complement previous observations that drugs influence the composition of the gut microbiome.

These finding should encourage the deep-pocketed pharma sector to put more efforts into elucidating the composition and role of the microbial communities hosted in our gut. If so, this could boost probiotics research as well.

Zimmermann et al. 2019

ILSI and the funding of science

Early June 2019, I was surprised to see familiar names in the Dutch mainstream media. Not only the International Life Sciences Institute, but also the names of its founder and a former Executive Director of the Washington-based global center.

Less surprisingly, ILSI was being lambasted for being a scientific lobby group for the food industry. Never mind ILSI’s transparency about its funding and policies like having a Board majority of public trustees; for some people, all industry funding is suspect.

I do have a stake here. I’ve been Executive Director of ILSI Europe for nine years and was responsible for ILSI Europe’s scientific credibility from May 2003 until April 2012. I have never jeopardized it, nor have I ever been asked to let industry interests prevail over science.

Many years ago, when being criticized for taking industry money, I asked what source of funding of science would be acceptable. “Well, government money, of course” – what else would you expect UN staff to say?

There is not a single food company in the world that obliges me to buy their products, or forcefully separates me from my money. What does government do? They send me to jail if I don’t pay tax. They allocate part of my money to build things I appreciate like roads and (of even greater value, since I’m living below sea level) dikes. However, they also spend some of my money in ways that are scientifically unsound and in my view morally wrong, like subsidizing religion and overpopulation. So let’s not glorify government and their money.

Although most scientific publications are not influenced by their source of income, industry and government sporadically try to shape the conclusions of science they fund. This is wrong, and it can be prevented. Many safeguards are in place such as pre-registration of clinical trials. Moreover, peer review and the quest for reproducibility are strong forces ensuring that ultimately scientific truth will prevail, regardless of funding source.

The carbon fallacy    -    Cows are not cars   (pdf)

In discussions about global warming and climate change, often all carbon emissions are seen as equally bad. It is saddening to observe that even a quality journal like Nature (1) includes cattle-produced methane when calculating greenhouse gas emissions from food and compares these to those of electrical appliances that are powered by fossil fuels.

Carbon released by livestock, mostly methane and carbon dioxide, is derived from plants. This “surface carbon” will be incorporated from the atmosphere back into plants and other photosynthetic organisms within days, years or centuries. However, the “deep carbon” released from oil, coal and gas by power plants and combustion engines will not be put back in its original form (buried deeply under earth's surface, inaccessible to the atmosphere) for millions of years.

Cycling of “surface carbon” by herbivores and plants has been part of life almost since its inception. Large ruminants, such as the bison herds roaming US prairies in the past, have been belching methane into the atmosphere for millions of years as part of the natural carbon cycle. This cycle has only been broken since humans started releasing “deep carbon” into the atmosphere by combusting fossil fuels. We wouldn’t be discussing the carbon footprint of livestock if the fossil fuel industry hadn’t been invented.

Those arguing that a methane molecule is a methane molecule regardless of source may want to note that the IPCC includes biofuels (derived from ‘surface carbon’ just like livestock feed) among net-zero CO2 energy systems (2). Another analogy is the water footprint calculation that distinguishes between blue, green and gray water (3).

1. Camilleri et al. (2019) Nature Climate Change 9:53

2. IPCC_AR6_WGIII_SummaryForPolicymakers.pdf


Potential breakthrough in crop yield and carbon capture

Photosynthesis is the key process enabling plant growth and life on earth. It is also a great way to capture carbon dioxide from the atmosphere into biomaterial. However, the efficiency of photosynthesis is limited by photorespiration, which helps plants to reduce the buildup of oxygen gas in their leaves without losing moisture.

South and colleagues engineered more efficient photorespiratory pathways into tobacco plants while inhibiting the native pathway. This increased photosynthetic efficiency and vegetative biomass by up to 40%. The authors are optimistic that similar engineering of crops may improve their yield, which would help nourish the increasing human population. They don’t mention it, but I would assume it would increase carbon capture by plants as well, helping to reduce the buildup of fossil fuel-derived carbon dioxide in the atmosphere.

South et al. (2019) Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field. Science 363:45.

Trouble brewing in our gut?

Researchers estimate that bacteria in the human intestine contain over 6000 genes that encode antimicrobial resistance (AMR). AMR is a health concern because it can make treatment with antibiotics ineffective.

The good news is, transfer of AMR genes from gut microbiota to pathogens is probably a very rare event. This makes sense. Antimicrobial resistance is a weapon in the never-ending war between bacteria, and it is good practice to stick to your guns rather than share them with others.

The bad news may appear to be the large number of antimicrobial resistance genes in our gut microbiota. However, initial results indicate that this is not the result of antibiotic use, as treatment of patients with antibiotics reduced the variety of AMR genes.

Antimicrobial resistance genes have been present for millions of years in the environment and may likewise have protected human gut microbiota from natural antibiotics long before we discovered penicillin. While we need to more deeply investigate gut-dwelling AMR genes to better understand the safeguards against their transmission to pathogens, at the moment I’m not losing sleep over them.

Ruppé et al. (2019) Prediction of the intestinal resistome by a threedimensional structure-based method. Nature Microbiol. 4:112.


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