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“Drinking just one glass of milk a day could boost your brain power,” the Daily Mail has reported today. Milk is being hailed as a memory aid, the newspaper says, with a study showing that dairy products could “help stave off mental decline”.

The study on which the story is based found that adults with higher intakes of milk and other dairy products did better in memory and other brain function tests than those who drank little or no milk.

However, the Mail’s excitement is misplaced – the study did not show that milk was responsible for better mental performance. The type of study reported cannot show cause and effect. All it showed was that, at one point in time, people who drank more milk performed better in mental tests than those who drank less. It is possible that many other things influenced people’s performance in mental function tests, including occupation, stress levels, even how well they were feeling at the time they took the tests.

Milk may be good for your bones but so far there is no good evidence that it improves mental performance.

 

Where did the story come from?

The study was carried out by researchers from the University of Maine in the US and the University of South Australia. It was published in the peer-reviewed International Dairy Journal. It was partly funded by the Maurice de Rohan International Scholarship, the University of South Australia and the National Heart, Lung and Blood Institute, the National Institute on Aging and the National Institutes of Health, all in the US.

The Mail reported the study uncritically. Its suggestion that milk could help stave off mental decline is not supported by this research. It’s worth noting that the study was released to the press by a US PR company on behalf of the National Fluid Milk Processor Promotion Board, which is an industry-funded organisation set up by the US government to promote milk. This may explain how it found its way into the Daily Mail.

 

What kind of research was this?

This was a cross-sectional analysis of nearly 1,000 participants that aimed to investigate whether dairy food intake was associated with mental functioning. This type of study can provide a “snapshot” of various lifestyle factors and people’s health at one point in time, but it cannot establish cause and effect. A cohort study that recorded people’s dairy consumption over time and then tested their mental function more than once would provide more reliable results although even this type of study cannot establish cause and effect.

The researchers say that as the whole population ages, cognitive decline and dementia place a severe strain on both families and healthcare systems. Change in diet may have a role in preventing cognitive decline, but they say little attention has so far been paid to the relationship between dairy foods and mental performance.

The researchers say there is growing evidence that dairy products may be of benefit to cardiovascular health. Many experts would dispute this. Some dairy foods are high in saturated fat, which is associated with obesity and heart disease. Most dietitians advise a restricted intake of dairy products or consumption of low-fat varieties.

 

What did the research involve?

Researchers recruited 1,049 adults of all ages who were taking part in research looking at cardiovascular health and mental functioning. They collected health and lifestyle data from the participants by various methods including self-reports, medical examination, diagnostic interviews, health records and neuropsychological testing.

After excluding those who did not fulfil eligibility criteria (for example, because dietary or cognitive data were missing or because they had suffered a stroke), they were left with 972 participants.

To measure mental functioning of the participants, the researchers used a validated series of tests measuring memory, verbal recall, visual–spatial perception, organisational and verbal skills, and abstract reasoning ability. For dietary intake, they used a recognised questionnaire that included questions about nutrition and lifestyle.

The dietary component of this questionnaire included questions about dairy products. Milk was considered separately from total dairy foods. Total dairy foods were grouped as followed:

• cheese
• yoghurt and dairy desserts
• cream and ice-cream

Participants were asked how frequently they consumed such foods, with six possible responses:

• never
• seldom
• once a week
• 2-3 times a week
• 5-6 times a week
• once or more a day

Participants were also asked which type of milk they consumed – full fat, reduced fat or skimmed.

The researchers used validated statistical methods to analyse the relationship between mental performance scores and dairy intake. They adjusted their results for other factors that might affect the results, including age, education, smoking and alcohol.

 

What were the basic results?

The researchers report that participants who consumed dairy products at least once a day had “significantly higher scores on multiple domains of cognitive function” compared with those who never or rarely consumed dairy foods. In addition, those who reported eating dairy foods between two and four times a week performed significantly better on some of the tests than those who ate dairy foods once a week. The association between greater dairy food consumption and mental performance remained significant after adjusting for a number of risk factors. There was no significant association, however, between intake of specific categories of dairy foods (such as milk, cheese or yoghurt) and results of the tests.

 

How did the researchers interpret the results?

The researchers say their results support an association between high dairy food consumption and cognitive function. Although little is known about how dairy foods might influence mental functioning, they say that one possibility is that dairy food consumption may be beneficial for mental functioning through its “favourable effect” on cardiovascular risk factors such as obesity.

 

Conclusion

Contrary to the headlines, this study does not show that dairy food consumption has benefits for mental functioning. All it can do is provide a “snapshot” of a group of people’s dairy consumption and their mental functioning at one point in time. Some limitations are that:

• It relied on people self-reporting their dairy intake, which introduces the possibility of error.
• It is possible that many other factors (known as confounders) might have affected the results, including exercise habits, alcohol and stress levels, although researchers tried to adjust their findings for some of these.
• As the authors acknowledge, the dietary questionnaire did not specify size of portions or servings, which undermines the accuracy of estimated intakes.

Dairy products contain many nutrients that are needed for good health, in particular for the development of healthy bones and teeth. However, they are also high in saturated fat, which is associated with heart disease and obesity. At present there is no good evidence that dairy foods are especially beneficial for brain functioning.

Find out how dairy fits into a healthy diet using the Eatwell Plate.

Links To The Headlines

The white stuff: Drinking just one glass of milk a day could boost your brain power. Daily Mail, January 31 2012

Links To Science

Crichton GE, Elias MF, Doreb GA, Robbins MA. Relation between dairy food intake and cognitive function: The Maine-Syracuse Longitudinal Study. International Dairy Journal 2012:22;15-23

“Drinking just one glass of milk a day could boost your brain power,” The Daily Mail has reported today. Milk is being hailed as a memory aid, the newspaper says, with a study showing that dairy products could “help stave off mental decline”.

The study on which the story is based found that adults with higher intakes of milk and other dairy products did better in memory and other brain function tests than those who drank little or no milk.

However, the Mail’s excitement is misplaced – the study did not show that milk was responsible for better mental performance. The type of study reported cannot show cause and effect. All it showed was that, at one point in time, people who drank more milk performed better in mental tests than those who drank less. It is possible that many other things influenced people’s performance in mental function tests, including occupation, stress levels, even how well they were feeling at the time they took the tests.

Milk may be good for your bones but so far there is no good evidence that it improves mental performance.

 

Where did the story come from?

The study was carried out by researchers from the University of Maine in the US and the University of South Australia. It was published in the peer-reviewed International Dairy Journal. It was partly funded by the Maurice de Rohan International Scholarship, the University of South Australia and the National Heart, Lung and Blood Institute, the National Institute on Aging and the National Institutes of Health, all in the US.
The Mail reported the study uncritically. Its suggestion that milk could help stave off mental decline is not supported by this research. It’s worth noting that the study was released to the press by a US PR company on behalf of the National Fluid Milk Processor Promotion Board, which is an industry-funded organisation set up by the US government to promote milk. This may explain how it found its way into the Daily Mail.

 

What kind of research was this?

This was a cross-sectional analysis of nearly 1,000 participants that aimed to investigate whether dairy food intake was associated with mental functioning. This type of study can provide a “snapshot” of various lifestyle factors and people’s health at one point in time, but it cannot establish cause and effect. A cohort study that recorded people’s dairy consumption over time and then tested their mental function more than once would provide more reliable results although even this type of study cannot establish cause and effect.

The researchers say that as the whole population ages, cognitive decline and dementia place a severe strain on both families and healthcare systems. Change in diet may have a role in preventing cognitive decline, but they say little attention has so far been paid to the relationship between dairy foods and mental performance.
The researchers say there is growing evidence that dairy products may be of benefit to cardiovascular health. Many experts would dispute this. Some dairy foods are high in saturated fat, which is associated with obesity and heart disease. Most dietitians advise a restricted intake of dairy products or consumption of low-fat varieties.

 

What did the research involve?

Researchers recruited 1,049 adults of all ages who were taking part in research looking at cardiovascular health and mental functioning. They collected health and lifestyle data from the participants by various methods including self-reports, medical examination, diagnostic interviews, health records and neuropsychological testing.

After excluding those who did not fulfil eligibility criteria (for example, because dietary or cognitive data were missing or because they had suffered a stroke), they were left with 972 participants.

To measure mental functioning of the participants, the researchers used a validated series of tests measuring memory, verbal recall, visual–spatial perception, organisational and verbal skills, and abstract reasoning ability. For dietary intake, they used a recognised questionnaire that included questions about nutrition and lifestyle.

The dietary component of this questionnaire included questions about dairy products. Milk was considered separately from total dairy foods. Total dairy foods were grouped as followed:

• cheese
• yoghurt and dairy desserts
• cream and ice-cream

Participants were asked how frequently they consumed such foods, with six possible responses:

• never
• seldom
• once a week
• 2-3 times a week
• 5-6 times a week
• once or more a day

Participants were also asked which type of milk they consumed – full fat, reduced fat or skimmed.
They used validated statistical methods to analyse the relationship between mental performance scores and dairy intake. They adjusted their results for other factors that might affect the results, including age, education, smoking and alcohol.

 

What were the basic results?

The researchers report that participants who consumed dairy products at least once a day had “significantly higher scores on multiple domains of cognitive function” compared with those who never or rarely consumed dairy foods. In addition, those who reported eating dairy foods between two and four times a week performed significantly better on some of the tests than those who ate dairy foods once a week. The association between greater dairy food consumption and mental performance remained significant after adjusting for a number of risk factors. There was no significant association, however, between intake of specific categories of dairy foods (such as milk, cheese or yoghurt) and results of the tests.

 

How did the researchers interpret the results?

The researchers say their results support an association between high dairy food consumption and cognitive function. Although little is known about how dairy foods might influence mental functioning, they say that one possibility is that dairy food consumption may be beneficial for mental functioning through its “favourable effect” on cardiovascular risk factors such as obesity.

 

Conclusion

Contrary to the headlines, this study does not show that dairy food consumption has benefits for mental functioning. All it can do is provide a “snapshot” of a group of people’s dairy consumption and their mental functioning at one point in time. Some limitations are that:

• It relied on people self-reporting their dairy intake, which introduces the possibility of error.
• It is possible that many other factors (known as confounders) might have affected the results, including exercise habits, alcohol and stress levels, although researchers tried to adjust their findings for some of these.
• As the authors acknowledge, the dietary questionnaire did not specify size of portions or servings, which undermines the accuracy of estimated intakes.

Dairy products contain many nutrients that are needed for good health, in particular for the development of healthy bones and teeth. However, they are also high in saturated fat, which is associated with heart disease and obesity. At present there is no good evidence that dairy foods are especially beneficial for brain functioning.

Find out how dairy fits into a healthy diet by checking out the Eatwell Plate.

Links To The Headlines

The white stuff: Drinking just one glass of milk a day could boost your brain power. Daily Mail, January 31 2012

Links To Science

Crichton GE, Elias MF, Doreb GA, Robbins MA. Relation between dairy food intake and cognitive function: The Maine-Syracuse Longitudinal Study. International Dairy Journal 2012:22;15-23

A “sunny break may be alternative to IVF” the Daily Mail has reported. The newspaper said that sunlight can increase levels of vitamin D, which balances sex hormones in women and improves sperm count in men. It added that a study found some couples ‘may be undergoing unnecessary and costly fertility treatment when spending time in the sun could be the answer’.

The news is based on a systematic review of any kind of scientific study that was related to vitamin D and fertility. The review found that there was a lack of human studies, particularly controlled human studies, which had looked at the effect of vitamin D on fertility. This review therefore mostly reviewed animal laboratory and observational studies and it is not clear what the implications of this basic research is for infertile couples without further follow up with human studies. The basic research showed that vitamin D plays a role in biological processes in sperm and ovary cells and may affect levels of sex hormones.

There are many reasons why a couple may be infertile. The cause of a couple’s infertility is usually determined prior to IVF or other fertility treatments. It is not possible to say, as the Daily Mail has suggested, whether some time in the sun would prevent the need for fertility treatments, without assessing the cause.

 

Where did the story come from?

The study was carried out by researchers from The Medical University of Graz in Austria and was funded by two Austrian governmental agencies and the Styrian Business Promotion Agency 
It was published in the peer-reviewed medical journal the European Journal of Endocrinology.

The Daily Mail accurately reported some of the findings of this review but overemphasised the relevance to infertile couples. Without human controlled trials it is not possible to say whether spending time in the sun could reduce the need for fertility treatments, though the advice does present an attractive option.

 

What kind of research was this?

This was a systematic review that looked at all of the available scientific papers on vitamin D and fertility. Many factors can cause infertility. The researchers said that in approximately 30 to 40% of infertile couples the underlying cause is problems with the men’s sperm. In women, there are various factors that can mean that they don’t release an egg or make it difficult for a fertilised egg to attach to and grow in the uterus. The researchers say that one major cause of female infertility is polycystic ovary syndrome (PCOS), a condition that affects their sex hormones.

This systematic review took a broad sweep approach to look at the evidence for a link between vitamin D and any aspect of fertility. Although systematic reviews are a good way of comprehensively looking at all of the evidence in an area, there can sometimes be limitations to pooling data if the included studies differ in design. In this systematic review, the researchers included both human and animal studies and care has to be taken in reporting which of the included studies have relevance to humans.

 

What did the research involve?

The researchers looked in one medical database for English language publications up to October 2011. They searched the terms and phrases: vitamin D, fertility, vitamin D and reproduction, vitamin D and PCOS. They also searched for alternative names for vitamin D and looked at the reference lists from the studies their search had found.

In most systematic reviews, the researchers list their criteria for including or excluding studies. They may, for example. only include some study designs and not others. However, in this review the researchers did not say how they decided to include studies. The researchers said that they did not find many human studies and have included animal and laboratory studies that can give information about the basic biology of vitamin D but don’t tell us whether vitamin D can help infertile couples.

 

What were the basic results?

The researchers said that studies have shown that:

• The vitamin D receptor has been found in human testes and sperm in men and in the ovaries and placenta in women.
• Removing the vitamin D receptor in genetically modified mice, leads to decreased sperm count and motility and affects the structure of the testes. In female genetically modified mice, removing this receptor causes changes to the structure of the ovaries and uterus.
• One study reported that in high latitude countries  there is a large difference in the amount sunlight in the summer and winter and there is decreased conception rates in the winter months and peak conception rates in the summer months.
• One study suggested that women’s ovulation rates and the receptiveness of their uterus for a fertilised egg is reduced during long dark winters in high latitude countries.
• Studies investigating the association of vitamin D status with IVF had inconsistent results. One study found no association; one found that higher vitamin D levels had a positive effect, and one found that women with sufficient vitamin D had poorer outcomes then women with insufficient vitamin D.
• Three studies found a correlation between low vitamin D and some, but not all of the symptoms of PCOS.
• Studies looking at the effects of vitamin D on fertility in healthy women are sparse. One study of 101 young women found that higher vitamin D levels were associated with lower sex hormone levels. A small study found that a course of vitamin D supplementation had no statistically significant effect on sex hormone levels.
• One study of 300 men found that there was an association between higher vitamin D levels and higher sperm motility, but another study found no association between vitamin D and sperm count and the proportions of normal sperm.
• One study of 2299 men found an association between vitamin D levels and male sex hormone levels.

 

How did the researchers interpret the results?

The researchers said that evidence based largely on animal work and observation studies rather than controlled trials has suggested that vitamin D deficiency might be important for hormone disturbances including fertility in women as well as men. They say that these findings deserve further investigation.

 

Conclusion

This systematic review looked for all available studies prior to October 2011 that had looked at fertility and vitamin D. Besides this very broad search, the review included animal, laboratory and observational studies, which means that it’s difficult to draw conclusions on the implications of this data for people. The researchers noted that there was a real lack of human controlled studies. As a result, it is not possible to say that fertility problems in men and women could be helped by vitamin D supplementation, increasing vitamin D through diet or spending time in the sun.

Vitamin D and its human effects is currently a topic of immense interest to the public and to policy makers. This research looks at another angle, that of fertility, and is useful in giving a broad overview of the basic biology of vitamin D and a range of biological processes involved in infertility. It highlights where there has been a lack of studies and where more work could be done. Future assessments into the role of vitamin D in fertility should as a minimum involve controlled human trials.

Links To The Headlines

Sunny break may be alternative to IVF: How the sunshine vitamin can help boost fertility. Daily Mail, January 30 2012

Links To Science

Lerchbaum E, Obermayer-Pietsch BM. Vitamin D and fertility – a systematic review. European Journal of Endocrinology. Puiblished online January 24 2012