A recent study on dairy’s role in cardiometabolic health has added further nuance to the topic by indicating the different outcomes total dairy and individual dairy products have on biomarkers of disease.
Cardiometabolic diseases including cardiovascular disease, diabetes and chronic renal failure are now the number one cause of death in our aging population. The main cause of these diseases is an unhealthy lifestyle. A broad range of biomarkers (indicators of a disease that can be found in the blood) have been identified and can be used to determine onset. Some studies have linked dairy intake with increased risk of individuals developing cardiometabolic disease. The present study tested these associations to further understand how dairy products can influence cardiometabolic health by measuring biomarkers.
The cross-sectional study included over 35,000 women aged 50 to 79, spanning 40 clinical centres across the US. Concentrations of 20 different biomarkers were compared.
The key findings were:
Lower triglyceride (type of fat associated with cardiometabolic disease) was associated with greater intake of total dairy. This was driven by full-fat dairy products
Greater total milk and yoghurt intake were associated with lower concentrations of total cholesterol, while greater butter intake was associated with higher cholesterol concentrations
Greater total dairy, total and full-fat cheese and yoghurt were consistently associated with lower concentrations of glucose, insulin and C-reactive protein (all of which are biomarkers of cardiometabolic disease).
These findings do not support conclusions of dairy playing a role in cardiometabolic disease, and more specifically the health benefit for low-fat dairy product varieties over full-fat, as promulgated by some health authorities. The challenge in finding consistent outcomes for the role of dairy in the onset of cardiometabolic disease calls for further research in the area. What has been made obvious is the critical role that nutrition plays in the health of our populations and that individual products, rather than food groups, should be considered.
Although overnutrition continues to grow globally, undernutrition rates are decreasing. Undernutrition currently affects more than 800 million people, either as protein-energy malnutrition or micronutrient deficiencies.
The researchers used data from 1991-2013 from the FAO and the World Bank to analyse both undernutrition and related factors. The countries studied were mostly developing countries located in sub-Saharan Africa, Asia or Latin America.
Undernourishment and child mortality showed decreasing trends overall. Urban populations, GDP, food production and agricultural land had all increased over the study period. However, when grouped into regions, the Eastern Mediterranean countries (Iran, Iraq, Jordan, Tunisia and Yemen) showed a late upwards trend in undernourishment, possibly due to political unrest in this region in the latter years of the study period.
A problem noted by the authors is in equal distribution of food, both between countries and within national populations. This is a conclusion also reached by the DELTA Model, which shows that apart from a few micronutrients, the global food system in 2018 would have supplied sufficient nutrition for the world’s population, had it been equally distributed. The problems of unequal distribution are bound up in many other social, economic, political and environmental factors.
While it is reassuring to see the decreases in undernourishment and infant mortality shown by this study, it also highlights areas that remain to be improved.
For nearly 50 years it has been believed that saturated fat is linked to heart disease. However, the scientific evidence does not universally support this assertion and recommendations are being made to change dietary guidelines and public knowledge around saturated fat.
In response to increasing rates of heart disease in Western populations in the mid-20th century, the results of epidemiological studies comparing diets in different countries suggested that saturated fat intake could be a risk factor. Minimising the intake of saturated fat-containing foods such as red meat, dairy and chocolate was advised as a result. Currently, the NZ and UK dietary guidelines recommend reducing saturated fat intake, while the US and Australian Dietary Guidelines recommend the restriction of saturated fatty acids (SFAs) to less than 10% of total calorie intake in order to reduce the risk of cardiovascular disease (CVD).
Saturated fatty acids (SFA), colloquially termed saturated fat, are molecules found in many common foods, especially animal fats and certain plant oils. Saturated refers to the molecular structure of the fatty acids, which have only single bonds between the carbon atoms, which cannot bond with any more hydrogen: thus, saturated with hydrogen.
The claim that saturated fats were linked to negative health outcomes was accepted by public health institutes such as the World Health Organisation and the American Heart Association, and quickly caught on as a widespread belief. This has become so ingrained that, despite evidence to the contrary, it is proving difficult to change nutritional guidelines and the opinions of medical professionals, nutritionists, and consumers.
A recent study, published in the Journal of the American College of Cardiology (JACC), performed a meta-analysis of randomized trials and observational studies on saturated fat. It was found that there were no beneficial effects of reducing SFA intake on cardiovascular disease and total mortality. While it was found that SFAs do increase cholesterol in most individuals, they increase concentrations of large particles of low-density lipoprotein (LDL) cholesterol, which is less correlated with CVD risk than the small, dense particles.
An important finding of this study was that health effects could not be predicted from the SFA nutrient group alone; consideration of the overall macronutrient distribution and food matrix was necessary. Different SFAs have different physiological effects, which are further influenced by the foods they are found in and the carbohydrate content of the diet. Several foods relatively rich in SFAs but also rich in other nutrients, such as whole-fat dairy, dark chocolate, and unprocessed meat, were not associated with increased CVD or diabetes risk.
There are calls to examine the overall risks of foods containing SFA, rather than SFA themselves. Likewise, the replacement of SFA-containing foods with those containing other fatty acids, often recommended in nutritional guidelines, was found unlikely to reduce CVD events or mortality. The authors of this last publication warned that current recommendations to replace SFA with alternative fatty acids may hinder efforts to get people to adopt more beneficial lifestyle changes, thinking that this single dietary change may be sufficient to reduce their CVD risk.
One of the studies included in the JACC meta-analysis was the PURE (Prospective Urban Rural Epidemiological) study of 135,000 people from 18 countries on five continents. It found all types of fat (saturated, mono-unsaturated and polyunsaturated) were not associated with CVD, and saturated fat had an inverse association with stroke. Additionally, fat intake was associated with lower risk of total mortality. In contrast, a diet high in carbohydrates was associated with higher overall mortality risk.
The claims around the negative consequences of fat intake may themselves have caused health problems. Reduction of saturated fat in the diet can lead to excessive consumption of carbohydrates as a replacement. Prevalence of obesity and type 2 diabetes has exploded in recent years, as seen in the chart below. Dr James Muecke, 2020 Australian of the Year, wrote in the Canberra Times: “A flawed dietary guideline, which we have obediently and blindly followed for 40 years, is literally killing us. We’ve been encouraged to eat less fat and consume more carbs and yet we’ve never been fatter, our teeth never more rotten, and type 2 diabetes and its complications never more prevalent.” Dr Mueke makes clear the far greater need to prioritise reductions in excess carbohydrate consumption, rather than reductions in fat, to reduce the rate of non-communicable diseases in developed nations like Australia.
In addition, advice to reduce consumption of nutrient-rich foods such as dairy and meat risks limiting the intake of nutrients such as calcium, iron, zinc, riboflavin and Vitamin B12. The Global Burden of Disease study shows that in the main, global health problems are caused more by what people do not eat – either through poor choice or through lack of choice – rather than an excess of certain foods. With the exception of excess sodium, the highest association of mortality and disability-adjusted life years globally was with insufficient intake of nutrient-rich foods. The study also showed the problems of consuming excess sugars. Consuming calorie-rich but nutrient-poor foods (e.g., sugary drinks) can displace nutrient-rich foods in the diet. The Global Burden of Disease study demonstrates that diets low in nutrient-rich foods are correlated with higher mortality. Importantly, saturated fat intake did not appear with any link to higher burden of disease.
It is important for policy makers and health institutes to take all evidence into account when- designing nutritional guidelines. Arbitrary recommended intake levels for saturated fat will be less useful for the prevention of CVD or reduced mortality than targeting excess consumption, particularly of carbohydrates, and micronutrient deficiencies. Foods containing saturated fat, such as meat and dairy, can contribute to a nutritious balanced diet. They certainly should not be removed from the diet due to their saturated fat content, which has inconsistent links to modest impacts on CVD. Replacing these foods with carbohydrates will likely cause greater damage.
FAO’s latest ‘The State of The World’ report assesses progress towards achieving sustainable development goals of ensuring access to safe, nutritious food for all people all year round, and eradicating all forms of malnutrition.
Current estimates are that nearly 690 million people are malnourished. This has been on the rise since 2014, increasing by nearly 60 million in 5 years. The world is not on track to achieve zero hunger by 2030. While there are significant challenges in just accessing food, accessing healthy diets is even harder. Based on FAO’s estimations, a healthy diet is five times more expensive than diets that only meet dietary energy needs and is unaffordable for more than three billion people globally.
In order to increase availability and affordability of healthy diets, cost of nutritious foods must come down, requiring large transformations in food supply chains globally. This must begin with prioritising agricultural production towards more nutrition-sensitive food. This is supported by the DELTA Model, which shows us that nutrient-dense foods must be prioritised to give the best chances of sufficient food production to meet global nutrient requirements.
Consultative Group on International Agricultural Research (CGIAR) have been developing and implementing biofortified crops to address micro-nutrient deficiencies.
Deficiencies in micro-nutrients poses serious and widespread threats to health and economic development. This is known as ‘hidden hunger’. The conventional response has been supplementation or food fortification. However, these solutions involve high and recurrent costs, can be hard to organize in poor rural areas, and cannot always solve the problems. CGIAR scientists proposed that the same health impacts could be achieved by breeding vitamins and minerals into the staple crops that people eat every day, such as sweet potato, wheat and rice. This is known as ‘biofortification’. CGIAR have been working on this for almost 25 years and invested $900m into development and implementation. More than 290 new varieties of 12 biofortified crops have been released or are in testing. This has benefited 10 million farming households globally to date.
The DELTA model can be used to scenario test various food systems with the view of adequate sustainable nutrition for the global population. This repeatedly demonstrates that on a global scale, animal-sourced foods are needed to meet nutrient requirements. However, this is based on the fact that current conventional crops do not have the same content of bioavailable micro-nutrients and trace elements that animal-sourced foods do. There may be potential for biofortified plants to better contribute to global nourishment and reduce requirements for animal foods. However, what is still unclear is whether those micro-nutrients in biofortified plant-based foods would have the enhanced bioavailability that characterises animal-sourced foods. In addition, biofortified plant-based foods may not have the ability to enhance the uptake of micro-nutrients from plant-derived sources, in the same way animal foods do as part of a meal. For example, haem iron from meat helps with the uptake of non-haem iron from plant sources. The ability of biofortified plants to do the same needs to be determined before concluding that biofortified crops can replace the role of animal foods in the global food system.
Researchers at the University of Minnesota and Oxford University compared the environmental effects against the noncommunicable disease risk of certain food products.
It was found that foods associated with improved health outcomes; whole grain cereals, fruits, vegetables, legumes, nuts and olive oil, had amongst the lowest environmental impacts. In contrast, foods associated with the largest negative environmental impacts—unprocessed and processed red meat—were associated with the largest increases in disease risk. Chicken, dairy products, eggs, and refined grains had no significant impacts on either disease risk or environmental metrics. The report concluded that dietary transitions towards greater consumption of healthier foods would generally improve environmental sustainability.
These findings could help consumers, policy makers, and food companies to better understand the multiple health and environmental implications of food choices. However, this study looked at non-communicable disease incidence only, and did not address many other factors, not the least of which are nutrient deficiencies and the impact of nutrition on child development. For example, red meat plays a key role in the contribution to global requirements for multiple micro-nutrients such as iron, zinc and vitamin B12.
In addition, not all research agrees with the findings of this study. The Global Burden of Disease study found that a diet high in red and processed meat had very little impact on the risk of death or disability-adjusted life years. Diets low in healthy foods such as fruits and wholegrains, or high in sodium had a much higher mortality rate. Another study found that advice to eat less red meat is not backed by sufficient scientific evidence.
It is not as simple as eliminating red meat to improve both health and the environment. Many factors must be considered in conjunction when making decisions about the food system, as a thinking failure today will lead to a system failure tomorrow.
A recent report published by EpiX in The Journal of Nutrition suggests that the EAT-Lancet proposed diet has no greater impact on mortality reduction than energy consumption changes.
The EAT-Lancet reference diet promotes an increase in plant-based food, and a reduction in red meat and sugar intake. The authors claim this can reduce premature deaths caused by diet-related noncommunicable diseases (NCD) by between 10.9 and 11.6 million per year. However, EpiX has identified that the EAT-Lancet report does not meet standards for transparency and replicability. Nor does it fully account for statistical uncertainty. Once uncertainty is accounted for and calculation errors are fixed, the impact on mortality reduction is less significant. In fact, the impact is no greater than changes in energy consumption that would prevent underweight, overweight and obesity alone.
The aim of the EAT-Lancet report – to determine an optimal global diet from a sustainable food system to improve both human and planetary health – is to be commended. It asks all the right questions; the problem is the assumptions and methods used appear to have fallen short. The report has had a massive uptake in media and social media, in part by a well-managed and orchestrated campaign by the EAT movement. According to Stockholm University, in the first 2 months after the report was released in January 2019, there were 5800 articles in 118 countries with over one million shares on social media. Given the need to make the global food system more sustainable, and the concerns raised about the validity of the recommendations made in the EAT-Lancet report, this is worrisome. It is important to avoid a thinking failure today to avoid a system failure tomorrow.
If there are health benefits from eating less beef and pork, they are small, and not sufficient to tell individuals to change their meat-eating habits. Links are mostly in studies that observe groups of people, and even then, are only detectable in the largest groups.
This raises questions about the longstanding dietary guidelines urging people to eat less red meat. There have been concerns for years that red meat causes heart disease, cancer and other illnesses. However, if this is not backed by good scientific evidence it should not influence dietary guidelines. Red meat plays a key role in the contribution to multiple micro-nutrient requirements such as iron, zinc and vitamin B12. Research from the Global Burden of Disease study found that 11 million deaths and 255 million disability-adjusted life years were attributable to dietary risk factors, however the key risk factors were under-consumption of whole grains and fruits, and meat was found to have very little impact. It may be that high consumption of red meat is not inherently unhealthy, but rather a lack of choice and/or poor choice means a high level of red meat in the diet results in lower consumption of other healthy foods in the diet. In other words, is not red meat itself causing disease, but the lack of other foods as part of a balanced diet.
Therefore, it may not be in individual’s best interests to decrease red meat consumption, instead we should focus on consuming a balanced diet of healthy foods and sufficient nutrients.