Are we running out of milk?

Supplies of fresh cow's milk are getting scarcer by the day. Many local supermarkets have very little fresh milk for sale and there are fewer milk brands on the shelves than before.

When one of my clients asked me to check the labels of fresh milk he intends importing from China, alarm bells started ringing in my head. It would seem that South Africa is running out of milk fast.

According to Prof Lourens Erasmus from the Department of Animal and Wildlife Sciences at the University of Pretoria, the number of dairy producers in South Africa has declined from 7077 in December 1997 to 4039 in October 2006.

He also states that more and more dairy producers are leaving the industry and that supplies of fresh milk are no longer guaranteed in our supermarkets. This means that South Africans may soon have to either rely on long-life milk or milk powder for their milk supplies and that most of our milk will have to be imported from other countries.

Why we need milk

Cow's milk is one of the most nutritious foods available. The protein in milk and dairy products is used as a 'gold standard' when measuring the protein quality of other foods.

Milk protein is a 'complete protein', because it contains all the essential amino acids we need for the growth of new tissues and the repair of damaged ones. These amino acids are classified as 'essential' because the human body is not able to manufacture them and we are thus dependent on our food to supply them in adequate quantities. Milk made from soya does not contain all these essential amino acids.

In addition, milk and dairy products are excellent sources of certain B vitamins, especially vitamin B2 or riboflavin, vitamin B12, pantothenic acid and biotin. One cup of milk (250ml) will supply 31% of the RDA for vitamin B2, 42% of the RDA for vitamin B12, and 16% of the RDAs for pantothenic acid and biotin for adults.

Probably the most important contribution that milk makes to our daily diet is its high calcium value. The calcium in milk is readily bioavailable, which means that the human body is able to absorb this calcium easily and fully.

It is much more efficient to use milk rather than plant foods to obtain our daily calcium requirement, because the calcium in grains, cereals and vegetables is usually tightly bound to compounds called phytates that make it very difficult for the body to absorb this calcium.

One 250ml cup of milk provides 30% of our daily calcium requirement, so if you drink the 3 cups of milk a day recommended by nutrition experts, you will probably achieve the recommended intake of 1000mg of calcium a day.

It is particularly important for teenagers and young adults to ensure that they ingest 1000mg of calcium a day to lay the foundation for a healthy store of bone calcium to prevent osteoporosis in later life.

So, by drinking milk or eating yoghurt (which contains as much, if not more, of the above mentioned vital nutrients as milk) you can be sure that you are getting sufficient essential amino acids, B vitamins and calcium. Take our milk supplies away and we will be hard pressed to replace these nutrients from other foods.

Hormones in milk

"But," I hear you say, "milk and dairy products are loaded with dangerous hormones. Drinking milk is a health risk!"

In view of the public's perception that cow's milk is laced with dangerous hormones, I was pleased to read the article published by Prof Lourens Erasmus in a recent edition of the Food Review that sets the record straight about the use of hormones in milk production.

There is no doubt that most commercial dairy farmers use recombinant bovine somatotropin (r-BST) to increase milk production. The use of this growth hormone in dairy cattle was approved as safe by the USA FDA as early as 1994 and dairy farmers all over the world, including South Africa, use bovine somatotropin to boost milk production.

However, Prof Erasmus points out that bovine somatotropin is "a naturally-occurring protein hormone produced in the pituitary gland, which directs nutrients to the mammary gland [in cows] for increased milk production."

Traces of bovine somatotropin are found in all milk, even milk from cows that are not treated with r-BST. When humans ingest any form of BST , we digest the hormone, just like any other protein.

It is very important to differentiate between a hormone like BST, which consists of digestible amino acids and other hormones like oestrogen, progesterone and anabolic steroids which are directly absorbed into the human body and will cause hormone-related effects in our bodies.

Keep in mind that the hormone BST in cow's milk will be digested and thus made harmless to humans.

The tumour scare

Media reports have added another bogeyman to make consumers even more scared of milk.

According to newspaper reports, the increased levels of a hormone-like compound called IGF-1 increases in cow's milk when the cows have been treated with bovine somatotropin to increase milk production. The media claim that increased levels of IGF-1 will trigger increased cell division and cause tumours in humans who drink the milk.

Prof Erasmus also lays this scare story to rest. He admits that injecting cows with bovine somatotropin (BST) will increase the levels of IGF-1 in milk, but stresses that IGF-1 is a natural compound that occurs in the milk of human mothers (up to 10 ng/ml) and is a normal component of our gastric juices (up to 180 ng/ml). The normal level of IGF-1 in human blood is 120-460 ng/ml, while milk produced by BST-treated cows is approx. 5.9 ng/ml.

Consequently, the IGF-1 content of cow's milk is much lower than the level normally found in human milk and in our digestive tract. A joint FAO/WHO expert committee on food additives has concluded that 'any increase in IGF-1 from milk from r-BST treated cows is orders of magnitude lower than the physiological amounts produced in humans.' The tiny amount of IGF-1 which we may ingest as a result of drinking milk will not increase the risk of tumour growth.

As a consumer you can, therefore, be sure that the milk you drink is not laced with dangerous hormones (you will digest the BST and thus inactivate it), and that it will not cause tumours. What we do need to be concerned about is that our supplies of this precious food source may soon run dry.

Text copyright: Dr I.V. van Heerden
2 July 2007

References:
(Erasmus, L. (2007). The Truth on r-BST. Food Review, May 2007, p. 16-18)

Read more:
IGF-1: what we know