Milk and dairy products in general have received bad press recently, with some sources claiming that they can lead to chronic diseases. A general scepticism about the safety of this food group has ensued and it has become more common for the media and bloggers to advocate in favour of plant-based choices, citing a myriad of health benefits.
What (if any) evidence exists for the general population to cut dairy out of their diets? To address this question and other closely related issues, my colleagues and I completed a comprehensive review of studies addressing milk and dairy intake and their effect on diseases and all-cause mortality.
We had three aims in this review. First, we set out to explore the health implications of a diet that includes milk and dairy compared to a no or low-dairy one. Secondly, we checked whether there is evidence to substantiate the claim that there are health benefits of replacing milk with plant-based drinks. And finally, we looked at whether it is justified to recommend that the general lactose-tolerant population should avoid dairy altogether.
The review: “Milk and dairy products: good or bad for human health? An assessment of the totality of scientific evidence” examined observational studies and randomised controlled trials. The paper highlights the following points about milk and dairy products:
- Dairy is a protein-rich food source and helps meet nutrient recommendations
- There is no association between milk consumption and all-cause mortality
- Consumption has a neutral or slightly beneficial effect on risk of type 2 diabetes
- A high intake of milk and dairy does not increase the risk of cardiovascular diseases
- There is a positive effect on bone health in childhood and adolescence, but limited evidence exists regarding bone health and bone fractures in later stages of life
- Varying degrees of positive and negative associations exist in regard to risks for different forms of cancer
- Cow’s milk and plant-based drinks are not nutritionally comparable
A matter of life(style)
Let’s take a closer look at the primary target of negative claims around dairy products: cardiovascular disease (CVD). The evidence indicates, in fact, that a high intake of milk and dairy products, about 200–300 millilitres daily, does not increase the risk of CVD. More specifically, there seems to be an inverse association with the risk of hypertension and stroke.
For example, it is well accepted that obesity fuels a predisposition to type 2 diabetes (T2D) and to CVD. Therefore, reducing body weight in overweight or obese individuals would help them to reduce the risk of these now common lifestyle conditions. Yet, among adolescents, a meta-analysis points to dairy protecting against overweight and obesity – particularly when dairy is combined with a weight loss diet. This may be due to the satiating effect of protein in dairy, which helps to reduce overall caloric intake and prevent weight gain. Meanwhile, evidence for the effect of fermented dairy products on reducing the risk of T2D is supported by quite robust prospective evidence.
High blood levels of low-density lipoprotein (LDL)-cholesterol have also been shown to predict CVD risk due to LDL cholesterol’s artery-clogging behaviour. High-fat dairy products with ample levels of saturated fat have, therefore, received some flack as the saturated fat can, in theory, increase levels of unwanted LDL-cholesterol. Variations do, however, exist with LDL particle sizes and this naturally affects how LDL-cholesterol behaves in the body. A number of meta-analyses covered by our review indicate that full-fat cheese, for example, often has little effect on blood LDL-cholesterol levels despite its higher saturated fat content. These findings are, however, based on comparison with butter, and the types of cheese involved are limited.
Beneficial for bones
There has been a long-standing body of evidence showing that the naturally-occurring nutrients in milk are ideal for optimum bone health and maintenance. While some plant-based drinks contain added calcium, a number of the other essential nutrients for bone health are lacking. It is not simply calcium that is important for bone health – a recent study suggests that magnesium may actually play a bigger role and of course vitamin D is always important.
The evidence around dairy and positive bone health in childhood years is quite robust, yet few meta-analyses have supported a protective effect in adulthood with regards to the risk of osteoporosis and fracture, as such studies are difficult to perform and prospective in nature, since the complex interaction of nutrients and multifactorial aetiology of bone fractures make it difficult for researchers to show cause and effect.
When it comes to cancer risk, population studies reveal positive and negative health effects of dairy intake. This may be due to the range of bioactive compounds found in dairy and their effects on carcinogenesis.
The World Cancer Research Fund (WCRF), which is committed to cancer prevention research, conducts regular systematic reviews and stays up-to-date with the latest evidence in the field. In its reports addressing linkages between dairy consumption and breast, prostate and bladder cancer, evidence has usually been inconsistent or inconclusive. Yet for colorectal cancer, the WCRF and other meta-analyses point to dairy having a protective effect.
One size does not fit all
Long-term human trial evidence is not yet available about the implications of consuming plant-based drinks over milk. So making any kind of blanket statement about the benefits of removing dairy and replacing it with plant-based alternatives is not only unsubstantiated, but also an unnecessary public health risk.
That said, it is indeed appropriate for lactose-intolerant individuals or those with a diagnosed cow milk allergy to avoid milk and dairy. Yet, for the wider population, choosing to only consume plant-based drinks often means selecting options with higher sugar and oil content, fewer minerals and less protein. This choice is a particular concern for children, with some plant-based alternatives containing essentially no protein.
A safe bet
Milk and dairy products contribute to meeting nutrient recommendations and may, in fact, protect from many of the common lifestyle diseases that are rife in the Western world today. Given that our review of the evidence suggests that there are limited or no adverse effects of milk and dairy consumption, milk and dairy should be thought of as a wholesome, highly-nutritious choice.