World Milk Day on 1 June is an international day established by the Food and Agriculture Organisation of the United Nations to recognise the importance of milk as a global food.

Scientific evidence supports the importance of milk and dairy products as part of a healthy eating pattern. Dairy foods are excellent sources of calcium, vitamins B2 and B12, high-quality protein and carbohydrates in the form of lactose, and are rich in magnesium, potassium and various fatty acids generally associated with several health benefits.

Consumers are mostly aware of the health benefits of milk and other dairy foods for bone and dental health, but more recently a large body of evidence has linked dairy intake to other health benefits. This may have to do with the unique combination of nutrients in dairy – the so-called dairy matrix – as the collective metabolic effects of whole dairy seem to be stronger than that of individual nutrients. This supports the notion of a whole-food approach being more beneficial than parts thereof.

One of the 11 messages of the Department of Health’s South African Food-based Dietary Guidelines for South African adults and children aged five years and older focuses specifically on dairy products. “Have milk, maas or yoghurt every day,” reads the guideline, which refers to milk, either fresh or powdered; the traditional fermented milk product maas (also known as amasi); and unsweetened yoghurt. Not all dairy products are included, such as highly processed dairy products, to prevent an increase in the intake of saturated fatty acids, sodium and sugar. Blends and non-dairy creamers are explicitly omitted.

Milk (and some dairy products) has a low sodium-to-potassium ratio as well as bioactive peptides, which may protect against the development of noncommunicable diseases. Milk in particular has a high nutrient-to-energy ratio. There is some evidence that the calcium in milk and dairy plays an important role in the regulation of body weight and bone mineral content in children. It is a good source of high-quality protein and contains useful amounts of all the indispensable (essential) amino acids. Milk, maas or yoghurt can be used to complement foods that are low in lysine (an essential amino acid) content, such as maize and wheat. Adding dairy products to these foods results in a meal with all the amino acids and is beneficial to many in South Africa, where maize and bread are staple foods.

The two cups of low-fat milk per day recommended for adults provide 600mg calcium, which is about 60% of the dietary reference intake for calcium. The same amount of low-fat milk provides 760mg potassium, about 40% of the recommended adequate intake of potassium per day. The substantial contribution of milk to potassium intake is important for the nutrient adequacy of populations that do not meet the vegetable and fruit intake recommendations. The vegetable and fruit intake of South Africans is much lower than recommended, with an average intake of 192g/day – the World Health Organisation’s recommended intake is 400g of vegetables and fruit per day for adults (the equivalent of five servings of 80g each).

Available data shows that milk intake among South Africans is also low, with mean intake of 124g, far below the 500ml per day recommended for adults. The perceived negative effects of milk and dairy are often reported as barriers to adequate consumption. These barriers include culturally determined food preferences and dietary practices learned early in life, perceived lactose intolerance, affordability, culture and religious taboos and practices. Dairy isn’t necessary in the diet for optimal health, but most individuals who avoid milk do not consume the recommended levels of calcium, potassium and other nutrients.

Research shows that regular intake of dairy can help to reduce the risk of several lifestyle diseases that are prevalent among South Africans, such as high blood pressure, heart disease, obesity and diabetes. Also, regular dairy intake can help to combat nutritional deficiencies seen in the diets of many South Africans.

The specific proteins found in dairy products are associated with important health benefits.  Casein and whey are high-quality proteins found in dairy that have unique metabolic traits yet act synergistically to increase protein synthesis and suppress protein breakdown more effectively than other proteins. In addition to these whole proteins, milk-protein-derived peptides have been identified, and have demonstrated favourable effects on blood pressure, arterial stiffness and low-density lipoproteins cholesterol.

The health benefits associated with dairy product intake are likely due to a combination of the nutrients acting synergistically as well as the unique biological functions of each individual nutrient. Beyond the macro- and micronutrients found in dairy, emerging literature suggests there are other bioactive components of dairy that may play an important role in human health. Examples of these are conjugated linoleic acid, peptides and sphingolipids. Also, some peptides in milk have been shown to have bioactive properties, with some evidence of beneficial effects on the immune and digestive systems.  

Including milk and milk products in our diet is generally associated with better dietary quality. Milk and dairy products are thus regarded as an important component of a prudent diet and continuous research is required on this diverse product.

In 2015, the Department of Agriculture, Forestry and Fisheries published an updated version of the Regulations Relating to the Classification, Packing and Marking of Dairy Products and Imitations. These new regulations introduced a new system for the classification of cow’s milk, and includes five different class designations for milk based on the fat content compared to the three-class designation stipulated by the previous regulation. It is vital that continuous updated nutritional analyses are performed to inform researchers, nutritionists, health care professionals and industry on the role of milk as part of a healthy and balanced diet to ultimately inform the consumer. Updated techniques of analysis can improve the accuracy of analyses and allow researchers to improve recommendations in terms of the nutritious quality of dairy products.

Bibliography

FAO, 2020. FAO Food Based Dietay Guidelines. [Online]
Available at: http://www.fao.org/nutrition/education/food-dietary-guidelines/home/en/
[Accessed 21 April 2020].

Naude, C. E., 2013. Food-based dietary guidelines for South Africa: The “eat plenty of vegetables and fruit every day”. South African Journal of Clinical Nutrition, 26(3), pp. 46-56.

Pretorius, B. & Schönfeldt, H. C., 2018. Calcium in Nutrition and Health. [Online]
Available at: https://foodfacts.org.za/calcium-in-nutrition-and-health/
[Accessed 14 May 2020].

Vorster, H., Badham, J. & Venter, C., 2013. An introduction to the revised food-based dietary guidelines for South Africa. South African Journal of Clinical Nutrition, 26(3), pp. S1-S164.

Vorster, H. H. et al., 2013. "Have milk, mass or yoghurt every day": a food-based dietary guideline for South Africa. South African Journal of Clinical Nutrition, 26(3), pp. S57-S65.

Professor Hettie Schönfeldt is Director of the ARUA Centre of Excellence in Food Security and holds the DST/NRF/NDP South African Research Chair in Nutrition and Food Security. World Milk Day is commemorated annually on 1 June.

- Author Professor Hettie Schönfeldt