How many of us have been told how kids drink our milk, because it will give us strong bones?
The idea has a certain meaning. Milk contains calcium. Calcium is known to improve the mineral density of bones.
However, the demonstration of the final relationship between milk use and strong bones is harder than it seems. The ideal study will take two large groups of people and randomly assign each member of the same group to drink a lot of milk daily for several decades, while the other group will instead drink some milk to the placebo. Obviously, this is too difficult to do in practice.
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Instead, we can take many thousands of people to ask them how much milk they have been drinking over the years and then stick to them for at least ten years to make sure that People who regularly have milk are less likely to suffer from broken bones in their lives
This was in a study published in 1
When the team did a similar study of 330,000 male male health workers, milk again did not seem to affect the frequency of fractures.
Randomized trials were conducted, in which the diet was deliberately strengthened with calcium, sometimes through drinking milk. In 2015, the New Zealand team reviewed, merged and re-analyzed 15 of these studies. They found that over two years there was an increase in the mineral density of the bone tissue, but after that time the growth stopped. Drinking a glass of milk on the day was found to be associated with more bone damage and early death
An alternative is to take calcium supplements. After fears of long-term side effects of taking additive, the same team in New Zealand combined data from 51 randomized controlled trials to assess whether the benefits outweigh any risks. Again, they found that increasing the strength of bones is stopped in a year or two, and that calcium supplements can only slow down, rather than stop – the loss of mineral density of bone tissue in old age. They came to the conclusion that this would probably only lead to a slight reduction in the rates of the fracture.
When different countries studied the same data, they came up with very different conclusions about their recommended daily calcium intake. The United States, for example, recommends that the UK or India is almost twice as large. In the United States, people were given three glasses of 8 ounces (227 ml) per day.
To confuse things further, in 2014, results from two large Swedish studies that resulted in headlines that drank more than three glasses of milk a day – the larger number that most people drink will not help your bones and can even harm you.
To this end, researchers from Uppsala University and the Carolyn Institute gave people a questionnaire on milk consumption in 1987 and again the levels of mortality were reviewed in 2010. People were worried when they heard that drinking a glass of milk on the day was found to be associated with more bruised bones and with early deaths.
Milk, apparently, has good health for bones, although benefits less than you might have hoped.
But before we drop milk, there are some great caveats.
In Swedish studies, participants have been evaluating their milk consumption in previous years, which is not an easy task. It's hard to know how much you eat with cereals, either in tea or in cooking.
The research also throws up a long-standing problem of correlation or causality. Perhaps women who knew having osteoporosis deliberately drank more milk in hopes of strengthening their bones. The study did not show that drinking milk definitely caused fractures. To complicate the picture, the Swedish team found that consumption of cheese and yogurt was associated with a lower rate of fractures.
The researchers themselves have made it clear that their research will need to be repeated before it is used to provide dietary advice. Others believe that the public should be careful about changing their consumption based on these results. Therefore, until we learn more, the present weight of evidence suggests that you can still continue to drink milk if you like it. This probably has the benefit of healthy bones, although the benefit is less than you could have hoped.
It is also worth keeping your bones strong by other methods, such as physical exercise and getting enough vitamin D from your diet, from the sun or (depending on where you live in the world) from the supplements in the winter. (Learn more about whether everyone should take vitamin D supplements).
All content in this column is provided only with general information and should not be interpreted as a substitute for the medical advice of your own doctor or any other medical specialist. The BBC is not responsible for any diagnosis made by the user based on the content of this site. The BBC is not responsible for the content of any external internet sites listed and does not support any commercial product or service mentioned or recommended on any of the sites. Always consult your doctor if you are in any way worried about your health.
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