8.2 What are the nutritional issues around meat and dairy?
8.2.1 What does mainstream nutritional advice have to say about meat and dairy in the context of a healthy diet?
Where do meat and dairy products sit in the context of national food based dietary guidelines?
Food-based dietary guidelines (FBDG) are short, science-based, practical and accessible messages produced by national governments with the goal of guiding people on healthy eating and associated healthy lifestyles. Unlike recommended nutrient intakes – which are standards that apply worldwide – FBDG are tailored to the specific nutritional, geographical, economic and cultural conditions within which they operate. In many cases, the messages provided in dietary guidelines are illustrated with the aid of visual representations such as pyramids, plates or other diagrams – also known as Food Guides. These show the recommended relative contributions of different food groups to the diet.
About 85 countries (of 215 countries in total) have official food-based dietary guidelines, although the numbers are gradually rising. Most of them are developed or more affluent countries.
These guidelines provide broadly similar messages: that diets should be diverse, in energy balance, low in sugary and high fat foods, rich in whole grains, fruits and vegetables and that they should contain some meat and dairy products. However, there are differences in the level of detail and emphasis, and the format in which advice is presented.
What do food based dietary guidelines advise on meat and dairy products?
- All include advice to consume animal products, often recommending ‘moderate’ quantities
- Often no specific quantities are recommended but general advice is given, e.g. to eat meat in moderation or that white meat is healthier than red, or to choose low fat versions
- Where specific advice on quantities is given it can vary by country (e.g. US and Sweden have different advice on how much dairy to consume)
- Only ~25% recommend reducing or limiting meat intakes, with some guidance distinguishing between red and processed meat.
- Sometimes average daily quantities are recommended
- E.g. Chinese guidelines on animal products (meat & poultry 50-100 g, fish & shrimp 50 g, eggs 25-50 g, milk & milk products 100 g)
- Sometimes there is guidance on a recommended maximum (e.g. Sweden and the UK recommend a maximum of 500 g red/processed meat a week)
- Dietary advice for vegetarians and vegans may or may not be available
- Currently only four formal government-approved national guidelines explicitly include sustainability within their guidelines (Sweden, Germany, Qatar and Brazil) – see http://www.fao.org/nutrition/education/food-based-dietary-guidelines/reg... for dietary guidelines by country and as part of this advice recommend moderating meat intakes. Advice on dairy products in relation to sustainability is less in evidence.
- The UK’s new dietary guidelines do not explicitly mention sustainability (except in the context of meat). However they place emphasis on pulses and beans as good sources of protein and recommend less dairy consumption than the previous guidelines, suggesting that sustainability as well as health concerns have been taken on board.
Why is it difficult to be very specific about how much meat and dairy is needed in the diet?
- The nutritional importance of any particular food in the diet will depend upon what else is or is not eaten – i.e. the overall quality and diversity of the diet
- The context of consumption is critical too (i.e. factors such as sanitation, pre existing health status, an individual’s particular nutritional needs etc. – see Chapter 7)
- An individual’s lifestyle also affects nutritional requirements (e.g. how physically active they are, and other lifestyle impacts upon health (smoking, alcohol consumption etc.).
- There is variability between societies and between individuals as regards the acceptability and importance of and need for particular foods based on culture, genetics and geography
- Humans are adaptable – the biological response to scarcity is to utilise nutrients (including those found in animal products) more efficiently. We are successful as a species because we are adaptable
- Sometimes recommendations focus on specific nutrients (calcium, iron) rather than the foods containing these nutrients – meat and dairy products may be rich sources of these nutrients but not the only sources.
- Variations in recommended intake between countries may be based on different population needs or judgements about what is optimal or realistic, by perceptions of risk, and may also be shaped by industry influence.
8.2.2 How do different stakeholders use the evidence available to argue for/against meat and dairy consumption in high income/consuming countries?
How are the nutritional arguments for and against meat and dairy in high income/consuming countries played out?
Since the livestock issue is so contested, stakeholders may use evidence from particular studies selectively to support their positions
Stakeholders form different conclusions on whether the link between animal product consumption and a given health outcome is causative or associative (i.e. with confounding factors) based on their ideological positions and beliefs.
Meat: some argued pathways
Many studies show an association between high processed and sometimes high red meat intakes, and various negative health outcomes including heart disease, strokes, diabetes and all cause mortality. But establishing a causal link is difficult: it is hard to randomise people to consume low meat diets over a long enough period to measure health outcomes. For example, vegetarians and vegans are often ‘different’ in so many ways that there are many confounding factors to consider when isolating the specific effect of low meat consumption. All evidence presented below is based on observational studies, so it is all associational. But when it is supported by other evidence (e.g. plausible biological pathways) and when experimental data is unlikely to emerge, then sometimes experts take a leap and call it causal.
Four main ‘pathways’ linking red and processed meat consumption to particular health outcomes have been proposed, at least three of which are contested:
- Meat and the unhealthy diet package
- Meat and saturated fat
- Meat and excess energy intakes
- (Red and) processed meat and particular health problems (colorectal cancer, diabetes, ischaemic heart disease)
Each of the pathways has its arguments, and counter-arguments, and this are discussed in greater detail below.
Pathway 1: ‘Unhealthy package’ pathway
Neutral fact: People who eat a lot of meat often eat a lot of unhealthy foods. Unhealthy diets are risk factor for many non communicable diseases and obesity.
The ‘anti-meat’ argument: “People who eat meat have higher rates of heart disease, diabetes and so forth”
- This is because their diets overall are unhealthy, and not because of the meat in the diet
- ‘Traditional’ diets containing meat offer the opportunity to eat a range of healthy foods (e.g. the Sunday roast with potatoes and two veg) e.g. www.beefnutrition.org
Question: Are high meat intakes a ‘marker’ of unhealthy diets and lifestyles or do they actually make a causal contribution?
- The answer is hard to discern because:
- Vegetarians more health conscious anyway, making comparisons hard
- One major UK study (the EPIC-Oxford study) compared vegetarians with health conscious meat eaters and found the incidence of ill health similar in both groups. But intakes of meat were lower than the UK average among the meat eaters
- Two conclusions are possible:
- Anti-meat conclusion: meat is part of unhealthy lifestyles, eaten at expense of healthy food
- Pro-meat conclusion: meat per se should be disassociated from unhealthy lifestyles and as such can be part of a healthy diet
Pathway 2: Saturated fat pathway
Neutral fact: Animal products are the main source of saturated fat in the Western diet. Saturated fat has been linked to heart disease and strokes.
The ‘anti-meat’ argument:
- Meat is high in saturated fat and consumption therefore increases the risk of heart disease and strokes
- Some studies challenge the association between saturated fat and ill health.
- It is pointed out that substituting saturated fat with refined carbohydrate could be worse.
- It is possible to choose low fat meat and dairy options: dietary guidelines often advise people to choose leaner cuts and lower fat products.
- There are differences between production systems: some environmental groups emphasise the benefits of grass-fed meat in terms of ‘good fats’, meaning a higher ratio of omega 3 compared to omega 6 fatty acids (e.g. Soil Association).
- There is evidence to suggest that not all saturated fats are equal – dairy fat is associated with lower risks of heart disease, strokes and some cancers (more on dairy later)
Pathway 3: Energy density pathway
Neutral fact: Meat eaters on average consume more energy than vegetarians and vegans, and meat eaters on average have a higher body mass index than vegetarians or vegans
The ‘anti-meat’ argument:
- Meat is energy dense because it can be high in energy dense fat and so ‘contributes to’ obesity .
- Meat is often eaten ‘instead of’ healthy and lower energy density veg etc.
- Meat is not a particularly energy dense food.
- It is necessary to distinguish between meat per se and the overall dietary patterns that may accompany meat eating.
- Meat’s high protein content means it offers satiety: meat can therefore form part of a weight loss approach (NB: The counter counter-argument: plant based high protein foods have also been found to offer similar satiety).
Pathway 4: Specific links pathway to cancer and other diseases
Neutral fact: a growing body of evidence links:
- Red meat to colorectal cancer & diabetes.
- Processed meat to colorectal cancer, ischaemic heart disease and diabetes.
The WHO concludes that there is a:
- Causal link between processed meat and colorectal cancer. An association with stomach cancer also seen.
- Probable causal link between red meat and colorectal cancer and evidence of links with pancreatic cancer and prostate cancer.
Advocates of meat consumption argue:
- That the red meat argument is purely associational and red meat has many essential beneficial nutrients (e.g. protein, iron).
- As to processed meat: is this a problem with the meat per se? Or with the additives used to process it? E.g. Salt? N-nitroso compounds? – and if alternatives were developed, would the risk go away?
Other diseases: Evidence here is currently associational (see ‘Unhealthy package pathway’ above).
What about white meat, especially chicken?
- Poultry production is a focal point for much criticism by animal welfare and environmental groups.
- But poultry consumption is positively associated with healthy outcomes (although as with all associations, the problems of confounding factors also apply).
- Critics of chicken consumption sometimes adopt a different approach, emphasising health concerns of intensive poultry production (E. coli, zoonotic diseases, broiler meat being more ‘fatty’ than free-range etc.).
Can any conclusions be drawn?
- As with all dietary factors, establishing a causal link between meat and dairy and health outcomes is difficult.
- All the data that links meat and dairy with disease incidence or mortality is collected from observational studies, where it is not possible to rule out the chance of confounding.
- Since the livestock issue is so contested, stakeholders may use evidence from individually selected studies to support their positions.
- Meta-analyses of observational studies have shown associations between red meat and processed meat consumption and coronary heart disease, type 2 diabetes and colorectal cancer.
- Most recently, after reviewing all of the epidemiological evidence, experts at the International Agency for Research on Cancer (IARC) of the World Health Organisation classified processed meat as a group 1 carcinogen (‘carcinogenic to humans’) and red meat as a group 2A carcinogen (‘probably carcinogenic to humans’).
Dairy and bone health
Neutral fact: Dairy products are rich in calcium and other nutrients. Calcium is essential to maintain bone strength and for other functions.
- Vegan groups highlight the alleged ‘calcium paradox’ – prevalence of osteoporosis is highest in high milk consuming countries. In fact:
- Some evidence that milk has positive impacts on bone health in children, but inconclusive evidence for adults.
- Bone fracture rates 30% higher among vegans but not among vegans who consume sufficient calcium.
- No evidence to support acid load theory sometimes promoted by vegans.
- Dairy positively associated with reduced risk of colorectal cancer and increased risk of prostate cancer.
- So the question arises: is dairy ‘essential’ or is it just that calcium and other contributors to bone health (e.g. phosphorus, magnesium and Vit D) are ‘essential’?
8.2.3 What about consumption in low income/consuming countries?
Meat and dairy in the context of developing countries
In developing countries, arguments relate to the need for nutritional improvement in diets via both production and consumption pathways.
- Argued production pathways
a. More livestock production leads to more animal source food consumption
b. Livestock production is a marker of higher socio-economic status (and higher SES people have better health)
c. Livestock production leads to income generation which can be good for health
- Argued consumption pathways
a. Animal products (consumption) = energy dense
b. Animal products (consumption) = nutrient dense
c. Animal products (consumption) = marker of dietary diversity
Arguments for meat and dairy consumption in developing countries focus on both production and consumption pathways
Reference: Garnett, T. (2015) unpublished
These pathways are explained in more detail below.
Pathway 1: More production leads to more consumption
There are not many studies and not much hard evidence but such as there is probably suggests that livestock production leads to increased consumption of animal products and positive impacts on health
BUT is this intrinsic to animal products or to greater / more diverse agricultural production per se?
- e.g. India’s Operation Flood: milk production heavily supported by government led to increased milk production and health benefits. But would similar health benefits have been achieved by government intervention focused on vegetables? In other words, would government interventions to promote dietary diversity in general be just as effective as focusing on dairy in particular?
Pathway 2: Meat production and consumption is marker for higher socio-economic status (SES)
- People who keep livestock/buy animal production are generally healthier
- But they may keep livestock / buy animal products because they are richer and they may be healthier because they are richer.
- In other words it could be argued that causation runs from SES to livestock and from SES to health – in other words, that livestock keeping is not causally linked to better health
Pathway 3: Livestock production as income generation
- Livestock production generates income.
- Earnings can be spent on medicines, better sanitation, better food etc. … but also on sweets, alcohol, cigarettes.
- Causation runs from livestock →higher SES → better health
- Pro-animal product conclusion: livestock is an important part of sustainable livelihoods
- Anti-animal product conclusion: rural development and income generation per se is important– other rural development approaches could achieve same outcomes without necessarily a need to boost livestock production
Pathways 4 and 5: Animal products are energy and nutrient dense
- This route is consumption/nutrition rather than production/livelihood focused.
- There have been studied interventions where children are given one of the following: meals containing meat; meals containing milk; or meals with added vegetable oil, all designed to be iso-caloric.
- In all cases there were difficulties with the study design and practical implementation (interventions were in some of the world’s poorest villages).
- Impacts were inconclusive but some positive findings.
- Pro-animal product conclusion: Animal products provide a unique package of essential nutrients and energy.
- Anti-animal product conclusion: the additional energy provided by the animal products is a significant part of the story (and other products could substitute); the nutritional role of animal products is only significant in contrast with the lack of overall diversity of the diet.
Pathway 6: Animal products as a marker for dietary diversity
Greater dietary diversity leads to increased chance of meeting nutritional needs.
Animal products can have an important role in this diversity.
- Pro-animal product conclusion: Animal products add to dietary diversity which leads to good health
- Anti-animal product conclusion: People who eat animal products tend to have more diverse diets and it isn’t ‘meat’ per se we should be encouraging but dietary diversity – and predominantly a greater range of plant foods