12 April 2022 – A new study comparing the nutritional differences between cow, goat, and sheep milk in the diets of older adults will soon commence. The study, hosted by Massey University’s Riddet Institute, will examine the intake of the three milks by elderly people as well as investigate any gut health consequences from consuming them.
Earlier this month a grant of $1,410,978 by High-Value Nutrition (HVN) Ko Ngā Kai Whai Painga National Science Challenge was awarded to the Riddet Institute to undertake the study, along with the Department of Human Nutrition at the University of Otago and industry partner NIG Nutritionals Limited (NIGN). The study will look at three different types of milk powder: goat milk, provided by NIGN; cow milk, provided by Miraka; and sheep milk, provided by Spring Sheep Milk Co.
Warren McNabb, Professor of Nutritional Sciences at the Riddet Institute, says the study will be the first trial of its kind and is large, involving four groups of about 30 participants aged 60 and older. The study will take place over about 14 weeks. It builds on earlier research at the Riddet Institute that indicates milk from different species have differing composition and milk structural assemblies (such as casein micelles) that could lead to differences in nutrition and digestive comfort.
“We know from the work we’ve done that compositionally they are different, and that the structural assemblies in the milks are different.”
Prof McNabb says scientists have also established that the acid reaction in the stomach results in differences to at least casein and whey gastric digestion between goat, sheep, and bovine milks.
“In the human stomach we know that cow’s milk forms a casein ‘curd’ that tends to be harder than it is with goat and sheep’s milk gastric curds.”
This means the rate the digestive system can process the milk curds and get them from the stomach to the small intestine to be further digested and absorbed is likely to differ with the different species’ milks.
Prof McNabb says the hypothesis is that blood amino acids will rise at different rates, connected to the hardness of the casein ‘curd’ forming in the stomach and how quickly it breaks down. Bovine milk is the hardest, closely followed by goat’s milk. The casein curds from sheep’s milk are much softer.
“We think the rise in amino acids in the blood will have different shapes.
“The anecdotal evidence is that goat and cow milk composition is roughly the same. But sheep’s milk is very different, with a higher protein and lipid content.”
Along with the differences with nutrient absorption, the new study aims to identify the impact on digestive comfort, nutritional status, and skeletal muscle function from adding whole milk powders to the diets of older adults.
Prof McNabb says the study is not about determining which milk is good, bad, or better, but discovering useful nutritional evidence that can help consumers decide between products, depending on what they want to achieve. The different milks may be found to be more suitable for different nutritional needs, such as those of an athlete and the elderly, for instance.
Prof McNabb says there is a lot of consumer interest in alternative milks, with anecdotal evidence that people who find cow’s milk difficult to stomach can handle goat or sheep milk.
In the clinical trials hosted by the University of Otago, human participants will consume 250mls of milk twice a day and fill in questionnaires to record experiences of gut comfort, along with a control group that does not consume the milk. Blood glucose testing, blood pressure and faecal sampling will also be undertaken.
“We will get a really good handle of the effects of older adults drinking milk in terms of their nutritional status, blood glucose, gut comfort, vitality, how they sleep, sort of thing.”
“We will also be able to figure out, are there differences between the milks.”
Once human ethics approval is confirmed, Prof McNabb says the study hopes to be recruiting human participants by the middle of the year, with the study completed by Christmas.