Safety and nutritional claims for raw milk

In the UK, “raw” in relation to milk means milk produced by the secretion of the mammary glands of one or more cows, ewes, goats or buffaloes, which has not been heated beyond 40° C or undergone any treatment which has an equivalent effect”. Heat-treatments, including pasteurisation are used for food quality, safety and for extended shelf-life. RDM pasteurisation uses temperatures below 100°C since casein micelles irreversibly aggregate or curdle at above boiling point.

In the UK, the two main types of pasteurisation used are High Temperature/Short Time (HTST, most commonly used for pasteurising milk) and Extended Shelf Life (ESL) treatment. ESL milk has a microbial filtration step and lower temperatures than HTST, and both are considered as a fresh food product. HTST milk is heated for 15-20 secs to 71.7 °C to inactivate vegetative microbial cells. Longer shelf-life dairy products include Ultra-High Temperature milk (UHT or ultra-heat treated), skimmed milk powders or cheese. For UHT processing, pasteurised milk is heated for a fraction of a second at 138°C, to inactivate vegetative and most sporulating cells. In cheese making, thermised milk is used where RDM is heated for at 10-20 secs at between 57-68°C to reduce microbes.

In the USA, most RDM is pasteurised by a minimum 15 secs above 161°F (72°C) for but the exact temperature and time can vary (D’Amico, D. quoted here). World-wide it is generally accepted that commercial pasteurisation of milk combined with better farm practice greatly reduced zoonotic pathogens that cause diseases like brucellosis (Brucella sp.), diphtheria (Corynebacterium diphtheriae) and tuberculosis (Mycobacterium tuberculosis), as well as foodborne illness from Shiga toxin-producing E. coli (STEC), Salmonella, Campylobacter and Listeria spp. 

The regulatory environment

In the UK, consumption of RDM is legal in England, Wales and Northern Ireland, from registered production farms. A 2018 Risk Assessment on raw dairy milk (RDM) by the Food Standards Authority (FSA) Advisory Committee on the Microbiological Safety of Food (ACMSF) concluded that the RDM risk was not so bad as to ban drinking it. However, to protect public health and balance consumer choice and business growth, improvements to the controls applied by Food Business Operators (FBOs) were required and implemented. Sales are banned in Scotland, although some English and Welsh farms offer deliveries there. UK enforcement of milk hygiene regulations involves making FBOs aware of their legal duties, providing guidance on compliance and implementing controls such as inspections, audits of the supply chain, and testing.

Within the UK, the Food Standards Agency is the Central Competent Authority for implementing the Food Hygiene Regulations. In Scotland, Food Standards Scotland (FSS) and in Northern Ireland, DAERA Agri-food Inspection Branch (AfIB) carry out this work for the Food Standards Agency. In Eire the situation required cross-border collaboration. The Food Safety Promotion Board or Safefood covers 6 North/South Implementation Bodies (Belfast Good Friday Agreement) and was given legislative effect by the North/South Cooperation (Implementation Bodies, Northern Ireland) Order 1999, and the British-Irish Agreement Act, 1999. Funding is provided by the Irish Parliament (70% funding from the Department of Health) and by the Northern Ireland Assembly (30 % from the Department of Health, NI).

In the EU, the sale of raw drinking milk is permitted in some Member States and consumed on-farm or sold directly from farm shops or by local delivery. Vending machines on-farm or in retail stores are used by some countries (e.g. Italy), but consumers are usually instructed to boil the milk before consumption. In the USA, some states e.g. California allow raw milk sales in stores, while other states allow consumers to purchase direct from farms. Interestingly the federal government prohibits the sale of raw milk across state lines.

Implementation of the regulatory stances on RDM incurs considerable effort and tax payers’ money, raising questions for some about the need. RDM has been gaining popularity among especially UK shoppers, with sales increasing five times in the past five years as trends for eating unprocessed foods have grown. RDM is often perceived or touted with benefits compared to pasteurised milk, for boosting key nutrients levels or decreasing health conditions including allergies in children. But how many RDM advocates have attended the bedsides of consumers sickened by RDM ingestion?

So is raw milk safe to drink? Is it more nutritious? Does it reduce allergies?

Safe or not?

The location of dairy animals’ udders and proximity to their anuses mean that they are readily colonised by microbes found in faeces, faecal-contaminated straw, manure, puddles and pastures (Lucey, J.A. quoted here). A major challenge in diagnosing carriage of foodborne pathogens (FBP) on the animals is because they don’t (normally) succumb to disease for FBP.

Yet, sampling of farm environments can yield pathogens including pathogenic E. coli, Campylobacter, Salmonella or Listeria, some of which can colonise the bovine anal glands. Potential pathogens in RDM can be especially dangerous for children, older adults, pregnant people and those with compromised immune systems. In serious cases, such bacteria can lead to kidney failure, Guillain-Barré syndrome and death.

In part, it comes down to a personal risk-benefit assessment: while RDM consumers don’t always get sick, consumption increases the risk of contracting a foodborne disease (Martin, D. quoted here, and here).

In the UK, consumption of raw milk was responsible for 26 outbreaks of intestinal infectious disease in England and Wales between 1992 and 2017. These involved 343 people and resulted in 41 hospitalisations. The advisory committee, ACMSF, noted that seven occurred between 2014 and 2017, with none between 2003 and 2013. During the same 25-year timeframe, milk sold as pasteurised was the cause of 12 outbreaks: 10 due to pasteurisation failures and two to post-pasteurisation contamination. The Food Standards Agency (FSA) advises “raw or unpasteurised milk and cream may contain harmful bacteria that cause food poisoning”. They state that infants and small children, the elderly, pregnant women and those with a compromised immune system are among those “particularly vulnerable to food poisoning and should not consume it”. Despite this advice, children made up almost a third of outbreak patients in 2017.

In the EU: In their scientific opinion on public health risks associated with raw milk, experts from EFSA’s Panel on Biological Hazards (BIOHAZ) conclude that RDM can be a source of FBP, mainly Campylobacter and Salmonella spp., and Shiga-toxin Escherichia coli (STEC). The BIOHAZ panel were unable to quantify the public health risks associated with drinking RDM in the EU because of data gaps. However, from Member State data on food-borne disease outbreaks, 27 outbreaks between 2007 and 2013 were due to RDM consumption. Most of them were caused by Campylobacter, one by Salmonella, two by STEC and three by foodborne tick-borne encephalitis virus (TBEV). A large majority of the outbreaks were due to raw cow’s milk, while a few of them originated from raw goat’s milk.

In the USA, it was reported that between 2013 and 2018, greater access to unpasteurised milk was associated with more outbreaks of illness. Most recently, in Pennsylvania, official warnings were issued after illnesses were reported. Milk samples yielded Campylobacter and officials warned that a particular RDM brand should be discarded. The milk was purchased on farm and in retail stores.

Nutritional aspects

UK Parliamentary questioning revealed a paucity of data regarding the health benefits of RDM and its products in that there has been no assessment to date (2023) of the health benefits of consuming raw cow’s milk, cheddar cheese or whey butter made from raw cow’s milk. Elsewhere it has been shown that there are no meaningful difference in the nutritional value of pasteurised milk c.f. RDM. Although the pasteurisation process causes milk to lose some vitamin C initial levels are very low begin with. The enzymes found in raw milk are not useful for human digestion, and any potentially probiotic bacteria found in raw milk are present in very low levels that are not beneficial to the gut microbiota (Martin, N. quoted here). Moreover, no health claim relating to raw milk has, as yet, been approved under the EU health and nutrition claims regulation.

Advocates for raw milk also say it tastes richer than pasteurised milk. But the richer taste consumers report is probably because raw milk often has more fat than other store-bought milk, which is usually standardised to a certain percentage of fat content. Raw milk also tends to be consumed closer to its production site and it isn’t usually homogenized.

Some people drink raw milk because they believe it contains beneficial bacteria and that pasteurisation destroys good bacteria as well as bad. A review found numbers of probiotic bacteria in RDM to be too low for heating to have a deleterious effect. But given that most probiotic bacteria are gut-associated, it may be that some act as indicators of faecal contamination. In one meta-analysis, the effect of pasteurisation on milk’s nutritional value was minimal with the exception of vitamin B2, because milk is relatively low in heat-sensitive vitamins relative to adult daily intake. The heat effect upon B2 deserved further investigation. In the GABRIELA study, raw milk consumption started early in life was inversely associated to asthma but not atopy with a protective effect possibly associated with the whey protein fraction of milk. This effect was reported to be independent of concomitant farm exposures, although anaerobes and some probiotic strains were not examined for. The suggestion was raw milk contains proteins and compounds that keep the immune system from over-reacting to allergens. However, the authors stated that most studies were based on farm families, whose exposure to a diverse range of microbes and allergens meant the reason for their lower allergy rates was unclear (also here). Subsequently it was shown that early life consumption of RDM lowered the risk of respiratory tract infections by approximately 30 % (compared with UHT milk) with reduced rates of rhinitis and otitis. Further, RDM consumption was linked to a reduced asthma risk by virtue of ω-3 polyunsaturated FAs, which are precursors of anti-inflammatory mediators. microRNAs (miRNA) are also immune regulators implicated in the RDM reduced asthma effect. A prominent gene targeted by miRNA is prostaglandin-endoperoxide synthase 2S (PTGS2), which is involved in the synthesis of pro-inflammatory eicosanoids which are potent mediators of allergic inflammation. Eicosanoid metabolism is also influenced by ingestion of v-3 polyunsaturated fatty acids, which may partly explain the effect of milk fat content on asthma. Significantly the same researchers have highlighted the microbiological risks associated with RDM ingestion. There has been a call for a less heat intensive–treatment of RDM to produce a microbiologically safe product but with components involved in anti-inflammatory processes, e.g. the ω-3 polyunsaturated FAs and the miRNAs, left intact or at sufficiently high levels.  The subsequent MARTHA double-blind randomisation study compared two types of cows milk: minimally processed but microbiologically safe milk (the intervention; 20 seconds at 72oC) versus UHT milk (the comparator), and involved 6-36 month old infants with a family history of atopy. Here the intervention was proven to be safe and efficacious. However the long term effects of ingestion of minimally processed milk are not known. The situation for adults with allergies needs further investigation.

What about raw cheese?

Cheese made from raw milk has been the cause of some high-profile foodborne disease outbreaks. In November 2023, the UK national gastrointestinal infections surveillance identified an outbreak of STEC O145:H28 in England and Scotland. Overall, of the 36 reported cases, 65 % reported bloody diarrhoea, 58 % were hospitalized, and one developed Haemolytic Uremic Syndrome (HUS) and died. The source was detected through an unusual association with domestic travel. An investigation identified unpasteurised cheese produced by a Lancashire dairy. Two cattle faecal samples were positive for the outbreak strain. The product was recalled in December 2023. Clearer labelling of unpasteurised cheese to cite the risks posed to vulnerable groups was called for.

In France, STEC O26 paediatric haemolytic uraemic syndrome (HUS) cases were associated with soft raw cow’s milk cheeses between March-May 2019. This was the third such raw milk cheese outbreak in France in 2019. It had 18 confirmed cases, one possible, 17 with HUS and eight with neurological complications. Notably, the median case age was 22 months highlighting the need for increased awareness of the risk of consuming raw milk cheese for certain populations, notably young children.

Harder cheeses such as Parmigiano-Reggiano are safer to eat, despite the use of raw milk, because the combination of acid, salt and low levels of moisture creates a stressful environment for bacteria to survive. These cheeses are often aged for several months resulting in die-off of potential pathogens. But softer, high-moisture raw milk cheeses often have lower acidity, providing conditions for foodborne pathogens to survive or even grow. Some hard cheeses with a shorter maturity stage, which are made from raw milk have been associated with foodborne illness, e.g. a cheddar in 2024 in the USA.

In an interesting zoonotic twist to the view from RFK Jr., questions have been raised about the potential risk of bird flu infection in humans who drink RDM from bird flu-infected cows, while his favoured RDM brand faced voluntary recalls after several batches of RDM tested positive for H5N1 (the causative agent of bird flu). Pasteurisation has been shown to inactivate the virus in milk, and the Centres for Disease Control (CDC) continues to support pasteurisation for consumption of milk and dairy products.

Conclusion

For regulators, RDM remains an inherently risky product that poses particular dangers to specific groups of people: namely children, pregnant women, older people, those who are unwell or have chronic illness. Gold-standard evidence supporting nutritional claims is scarce but an understanding of which RDM components that may help reduce allergies are emerging. The potential for an even more beneficial product that is safe, may be a combined treatment that maintain properties of favourable components and removes harmful pathogens.

This article is written from the perspective of microbiologists with long-standing experience in food production systems and food science. 

Nicola Holden is a Professor at Scotland’s Rural College (nicola.holden@sruc.ac.uk).

Gil Domingue runs a data analysis consultancy and offers farm to fork hygiene assessments. (gildomingue@yahoo.co.uk; Bluesky: @pagd.17.bsky.social).