Milk: too many fake news, it's time to reevaluate it

It is one of the most debated topics in recent years, according to some it is a complete food due to its macro and micronutrient content, it is used to grow healthy and strong and in the elderly it prevents osteoporosis. Others argue that it's very bad because after weaning its intake becomes useless and harmful: it causes different types of tumors it is responsible for many food allergies and makes the bones lose calcium by taking away their strength!

The media chaos, in the alleged attempt to enrich the baggage of knowledge, very often obtains the opposite effect of disorientation of the consumer who, not possessing scientific training, does not have the ability, nor often the will, to verify what is stated by the aforementioned channels of spread. The information produced by the mass media mainly refers to observational studies, in vitro, and on animal models, while very little derives from studies conducted on humans. Furthermore, reference is rarely made to milk in its entirety, but only its individual components are often examined.

Andrea Ghiselli, research manager of CREA - Food and Nutrition in Rome, already in 2013 defined a "worrying disinformation campaign that is creating alarm among Italian consumers”, "in the media and on the web we read about everything, but without any scientific basis”. Correct information on the part of the consumer is essential for taking a position given the multiplication of sources and dissemination systems, whose scientific reliability, however, should be evaluated.

Disinformation is not without side effects, damage to health and the economy represent the main risks associated with "fake news". In the case of the campaign that demonizes milk, we have had a reduction in milk sales and a growing consumption of products “reduced or lactose-free” and vegetable drinks, regardless of verified lactose intolerances or vegan choices.

As reported in the latest ISMEA/Nielsen 2017 report, in the last five years there has been a reduction of 7% in the purchase of drinking milk by Italian families. The greatest decline in milk purchases is recorded in families with a higher income (-15,8%); therefore, it is not the economic factor that influences milk purchases which, on the other hand, seem more linked to the emergence of new food models.

Bucking purchases of highly digestible milk (lactose-free) increased by 47% mainly motivated by health reasons. Furthermore, the vegetable bases for the production of cow's milk substitute beverages have multiplied – rice, almonds, etc.; among the first and most widespread there are soy-based beverages that saw purchases increase by 108%. Since it is unlikely that there has been a parallel increase in lactose intolerance, this variation in consumer choices is more likely to be attributable to changes in perceptions of the healthiness of milk.

Among the most frequent declarations, according to which the consumption of cow's milk should be discouraged for the whole population, there is the one which states: after weaning, the consumption of milk from other mammals is harmful as it is "unnatural", a declaration supported by the natural progressive reduction of the activity of the enzyme lactase, essential for its digestion, in two thirds of the human population.

Milk sugar is lactose, to be able to digest it we need an enzyme called lactase, its activity in the human body tends to decrease with age: it is highest in infants and decreases over the years. The impossibility of digesting this disaccharide is the basis of lactose intolerance to which various intestinal disorders are associated (diarrhoea, abdominal pain and swelling) which effectively prevent the consumption of milk. Undigested lactose does not necessarily lead to gastrointestinal phenomena.

An interesting hypothesis that explains where this difference originated is the one based on genetic mutations. The advent of animal milk as food for humans was made possible at the beginning of the Neolithic, about 10.000 years ago, with the transition from the nomadic life of our hunter-gatherer ancestor to the more sedentary life based on breeding and agriculture. It is very probable that initially the milk was only transformed to produce yoghurt and cheese, thus providing a means of conservation that facilitated its transport.

Then a random genetic mutation, which appeared in that period, made it possible for some of our ancestors to feed themselves with milk and not only with cheeses that contain a lower quantity of lactose than milk. The ability to digest milk even as adults has allowed our ancestors to have an evolutionary advantage allowing them to survive and pass on the genetic mutation to their children and therefore to pass on that mutation to a greater extent than those who did not possess it. We now know that lactase persistence is typical of populations where milk consumption is high and where the milk is seen as a symbol of a healthy and nutritious diet, like the populations of Northern Europe.

The degree of lactose intolerance varies between individuals and is influenced by numerous factors that can modify gastrointestinal symptoms, such as: dose, food matrix, intestinal transit time, fermentative capacity of the intestinal microbiota. According to EFSA, the European Food Safety Agency, most people who digest lactose poorly can tolerate up to 12 g of lactose (equivalent to 2 portions of milk, equal to 250 ml) in a single intake and up to 20-24 g distributed throughout the day, without experiencing gastrointestinal symptoms. EFSA declares: ”…milk is such an important food in the diet, that a low-lactose diet excluding the consumption of milk should not be recommended, before having confirmed the intolerance through one of the recommended tests…”.

Anyone with mild lactose intolerance can still drink milk, accompanying it with other foods (bread, biscuits or baked goods) to slow down its absorption. Those who, on the other hand, show severe lactose intolerance can choose to consume milk or other lactose-free products such as yogurt, kefir or many aged cheeses, as the fermentation and aging processes determine the hydrolysis of most of the lactose .

A other news “fake” applicant is that the consumption of milk and its derivatives causes a loss of calcium from the bones following acidification of the blood, thus contributing to osteoporosis.

Milk proteins contain sulfur amino acids which give rise in their metabolism to sulfuric acid which acidifies the blood. In the body, to buffer the increase in acid load after the consumption of milk and derivatives, calcium is mobilized from the bones and subsequently eliminated in the urine. A study conducted by US researchers compared two groups of menopausal women, one group was provided with a diet with a high protein content and high renal acid potential, and the other group with a lower protein diet with a low renal acid potential. The researchers observed that the dietary treatments did not influence bone metabolism as an increased loss of calcium from the bones corresponded to an increased absorption of the same mineral in the intestine. In conclusion, a high-protein diet did not show adverse effects on bone health.

Speaking of milk consumption and the onset of cancer, to the question: “Is it true that, based on the China Study, there is scientific evidence to support a vegan diet to reduce the risk of cancer?” responds the AIRC, the Italian Association for Cancer Research, which says: "No, the China Study was deemed unreliable by the scientific community and there are no studies in favor of a diet that totally eliminates proteins of animal origin, in particular dairy products”. Researchers argue that the China Study it has no scientific reliability: its results have never been published in a scientific journal, but gathered in 2005 in a book signed by nutritionist T. Colin Campbell and his son Thomas. The essay had worldwide echo, it is argued that cardiovascular pathologies, diabetes, osteoporosis and some types of cancer would be linked to even the minimum consumption of dairy products, as well as meat and animal fats. In particular, Campbell wrote that casein, one of the proteins in milk, functions as a tumor fertilizer. The China Study, however, is considered unreliable by the scientific community for a number of reasons, starting with the method based more on ideology than rigor: the author only takes into consideration the parameters useful for demonstrating his theses and discards the others.

The studies of the are of a different opinion World Cancer Research Fund on the consumption of milk and derivatives and the incidence of cancer: the researchers indicate a reduction of the risk for colorectal cancer which represents the most common neoplasm in Western countries for daily consumption of 200 ml of milk and 50 g of cheeses. The merit would be of calcium, capable of binding the inflammatory factors of bile acids and reducing cell proliferation. Similar considerations appear to apply to protection from bladder cancer as well.

As far as prostate cancer is concerned, there is moderate scientific evidence on the correlation between the daily consumption of more than 400 g of milk and dairy products and the increased risk of developing it. It remains to be established whether a diet high in calcium is contraindicated for the prevention of this cancer. The results of some research, collected in 2014 in a meta-analysis published in the American Journal of Clinical Nutrition, correlate high calcium consumption with the risk of getting prostate cancer. The reason? The mineral affects the metabolism of vitamin D, to which prostate cells are sensitive, which respond by stimulating their growth. But we are talking about excesses: it absolutely cannot be said that drinking a cup of milk at breakfast causes cancer, as also confirmed by the CAPSURE study, a large US study in 2017, which examining skimmed milk found no associations with male gland cancer.

Scientific evidence represents facts and not the opinions of individuals or groups and tells us that milk not only does not pose a danger to our health, but on the contrary is a food we cannot and must do without. If the consumption of milk and its derivatives is done in compliance with the recommendations, we are able to obtain that load of essential nutrients throughout the life span, especially in childhood and adolescence when bone mass and density increase. Milk calcium but also magnesium and phosphorus, due to their high bioavailability, are crucial nutrients for bone metabolism. As for the fanciful hypotheses that hypothesize a cause-effect relationship between the acid load of the diet and bone health, studies confirm that the calcium balance is not affected: if urinary excretion increases, calcium absorption increases . And finally, at present there is strong evidence of a protective effect of milk and dairy products for colorectal cancer, while there is moderate evidence for the association between their high consumption and the increased risk of developing cancer of the prostate.