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22.11.2014

Milk, the white ladykiller

You can't have missed it, it's all over the news media: the epidemiological study that researchers at Uppsala University in Sweden published recently in the BMJ. The study shows that every glass of milk you drink daily increases your chance of an early death and of broken bones. The culprit is thought to be the sugar galactose.

Study
The Swedes have followed a group of over sixty thousand women since the late 1980s and a group of almost fifty thousand men since the mid 1990s. The researchers got their subjects to complete questionnaires on their dairy consumption. They also recorded any broken bones and fatalities that occurred.

Results
Milk had little effect on the men. Every glass of milk they drank each day increased their chance of dying by one percent and their chance of breaking a bone by about the same amount.

Among the women the situation was different. For every glass of milk they drank each day, their chance of dying increased by 15 percent, and their chance of breaking a bone increased by 2 percent.

Women who drank three glasses of milk a day were twice as likely to die compared with women who drank less than one glass of milk a day. Milk increased the chance of developing fatal cardiovascular diseases in particular, but also increased the likelihood of developing a fatal form of cancer.

Explanation
The Swedes suspect that the simple carbohydrate galactose found in milk is the cause of the problems. Milk contains lactose, a double carbohydrate consisting of one glucose molecule and one galactose molecule.

Results
Galactose is a dextro isomer of glucose. In the human body enzymes convert lactose into galactose and glucose, and then they convert galactose into glucose.

Animal studies have shown that galactose speeds up the aging process. [J Neurosci Res. 2006 Aug 15;84(3):647-54.] In 2006 Chinese researchers published the results of an experiment in which they injected mice daily for seven weeks with 100 mg galactose per kg bodyweight, and discovered that this caused the animals' brain cells to age faster. Galactose probably boosts free radical activity.

The Chinese were actually able to reduce the harmful effects of galactose by administering R-alpha-lipoic acid. In another Chinese animal study, ECGC, a flavonoid in green tea, protected mice against galactose-induced premature aging. [Biol Pharm Bull. 2009 Jan;32(1):55-60.]

The dose that the Chinese used was not high, the Swedes say. "This is equivalent to 6-10 g in humans, corresponding to 1-2 glasses of milk. Based on a concentration of lactose in cow's milk of approximately 5%, one glass of milk comprises about 5 g of D-galactose."

The researchers tried to test the theory and measured the concentration of the inflammatory protein Interleukine-6 in the blood and of the inflammatory marker 8-iso-PGF2alpha in the urine. The more milk the study participants drank, the higher the levels of these were.

Cheese, soured milk and yoghurt
"Particularly noteworthy is that intake of fermented milk products such as yogurt and soured milk and cheese were associated with lower rates of fracture and mortality", the Swedes write.

Conclusion
"Our results may question the validity of recommendations to consume high amounts of milk to prevent fragility fractures", the researchers write. "The results should, however, be interpreted cautiously given the observational design of our study. The findings merit independent replication before they can be used for dietary recommendations."

Source:
BMJ 2014;349:g6015.

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