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last updated: Wed, 01 Apr 2015 07:06:29 GMT

 Tue, 31 Mar 2015 12:44:00 GMT Healthy diet could cut risk of Alzheimer's disease

"A new diet could more than halve a person's risk of developing Alzheimer's disease," the Mail Online reports.

In a new study, researchers looked at the effects of three diets on the risk of developing Alzheimer's disease. These were:

  • a standard Mediterranean-type diet
  • the Dietary Approach to Stop Hypertension diet (DASH) – designed to reduce blood pressure
  • Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) – this combines elements of the Mediterranean diet and the DASH diet

The study found older people whose usual diet was close to any one of these three healthy diets were less likely to develop Alzheimer's disease than those eating less healthily.

The researchers say they found the greatest effect from the MIND diet, which is rich in green leafy vegetables, wholegrains, nuts and berries, even if people didn't follow it closely. Participants who did stick rigorously to the MIND diet were 52% less likely to be diagnosed with Alzheimer's disease.

This large observational study can't show that the diets protected against Alzheimer's, only that there seems to be a link between eating a healthy diet and a lower risk of getting Alzheimer's disease. The three diets weren't compared directly, so we can't be sure which one is best.

The study provides further evidence that eating a healthy diet may reduce the chances of developing Alzheimer's disease

Where did the story come from?

The study was carried out by researchers from Rush University Medical Center in Chicago and Harvard School of Public Health in Boston, and was funded by grants from the US National Institute on Aging.

It was published in the peer-reviewed medical journal Alzheimer's & Dementia.

The Mail Online reported the study accurately for the most part, although it did not say that this type of study cannot prove causation. Strangely, it repeatedly said that the MIND diet called for a daily salad, although salad was not mentioned specifically in the study.  

What kind of research was this?

This was a large prospective cohort study of older people who were taking part in a long-running study of memory and ageing. It aimed to see whether people whose food consumption was closest to one of three types of healthy diet were less likely to be diagnosed with Alzheimer's disease during the course of the study.

As this was an observational study, it cannot prove that the diet protected against Alzheimer's disease or other types of dementia. A randomised controlled trial would be needed for that.  

What did the research involve?

Researchers worked with volunteers living in retirement communities and public housing in Chicago. They were asked to complete a questionnaire to assess their diet. They all had annual neurological examinations for an average of four to five years, which checked for Alzheimer's disease.

Researchers adjusted the results to take account of other factors that can affect Alzheimer's risk. They then looked for links between Alzheimer's diagnosis and people's diets.

At the start of the study, the researchers decided to assess three types of diet:

  • The Dietary Approach to Stop Hypertension (DASH) has been used to reduce blood pressure and stroke risk. It includes total grains and wholegrains, fruit, vegetables, dairy products, meat and fish, nuts and legumes, but restricts fat, sweets and salt.
  • The Mediterranean diet (MEDdiet) is often recommended for heart health. It includes olive oil, wholegrains, vegetables, potatoes, fruit, fish, nuts and legumes, and moderate wine, but restricts full-fat dairy products and red meat.
  • The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet is a new diet developed by the researchers with elements from the DASH and MEDdiet, and also includes foods thought to protect the brain. It includes olive oil, wholegrains, green leafy vegetables, other vegetables, berries, fish, poultry, beans and nuts, and a daily glass of wine, but restricts red meat and meat products, fast or fried food, cheese, butter, pastries and sweets.

Using questionnaires from 923 volunteers, the researchers assessed how well each of them scored on each diet. They divided people into three groups showing high, moderate or low scores for each diet.

They then looked at whether people in the high-scoring groups for each diet were less likely to be diagnosed with Alzheimer's disease during the average 4.5 years of follow-up, compared with people in the low-scoring groups.

People diagnosed with other types of dementia, such as dementia with Lewy bodies or vascular dementia, were not included as Alzheimer's cases.

The researchers did a good job of checking for other factors that could affect Alzheimer's risk. This included testing for a type of gene (APOE) that raises the risk of Alzheimer's, as well as asking about people's education level, whether they took part in cognitively stimulating activities such as playing games and reading, how much physical activity they got, their body mass index (BMI), whether they had symptoms of depression, and their medical history.  

What were the basic results?

During the study, there were 144 cases of Alzheimer's disease among the 923 people taking part.

People with the highest scores in all three diets were less likely to be diagnosed with Alzheimer's disease than people with the lowest scores.

The link was slightly stronger for the MIND and MEDdiet than the DASH diet. People who had the highest scores on the MIND diet were 52% less likely to be diagnosed with Alzheimer's disease (hazard ratio [HR] 0.48, 95% confidence interval [CI] 0.29 to 0.79).

People who had moderate scores for the MIND diet were also less likely to be diagnosed with Alzheimer's than those with the lowest scores, but the link was not as strong (HR 0.64, 95% CI 0.42 to 0.97). Moderate scores on the DASH and MEDdiet did not show a statistically significant reduction in risk.  

How did the researchers interpret the results?

The researchers said their results showed that "even modest adherence" to the MIND diet "may have substantial benefits" for preventing Alzheimer's disease.

They say that while the DASH and MEDdiet also showed positive results, "only the highest concordance" with those diets was linked to the prevention of Alzheimer's disease.

They go on to speculate that the dairy and low-salt recommendations in DASH, while useful for reducing blood pressure, may not be particularly relevant to brain health.

They concluded that, "High-quality diets such as the Mediterranean and DASH diets can be modified ... to provide better protection against dementia." 

Conclusion

The study found people who ate a healthy diet – with plenty of green vegetables, wholegrains, legumes and less red meat – may be less likely to get Alzheimer's disease. However, we should be wary of saying that their diet actually protected them from Alzheimer's, as it is a complex disease with many potential causes.

The main limitation is that observational studies cannot prove causation, even when researchers take care, as they did here, to include factors that we know affect disease risk. It's also notable that the researchers excluded dementia, other than Alzheimer's disease, from their calculations.

It would be interesting to see the effect of these diets on other types of dementia, too, especially as the DASH diet protects against hypertension, which can be a cause of vascular dementia. This was not taken into consideration when the authors concluded that low dairy and salt may not be needed for brain health (though they still remain part of a healthy, balanced diet).

Another limitation is that the food frequency questionnaire may not have completely captured people's adherence to the three diets. For example, people were asked about how often they ate strawberries, not about other types of berries. This could underestimate the effect of berry consumption in the diet.

Experts already think a healthy lifestyle can help lower the risk of getting dementia. Recommendations include eating a healthy diet, keeping to a healthy weight, exercising regularly, not smoking, drinking in moderation, and keeping blood pressure healthy. The question is: what type of healthy diet is best?

This study suggests the MIND diet may be better at lowering the risk of Alzheimer's disease than two other healthy diets. However, the study did not compare the effect of the diets directly.

We also don't know which foods in the diets might make the difference. The best advice may be to follow a healthy balanced diet, without worrying too much about exactly which foods might protect your brain.

Analysis by Bazian. Edited by NHS ChoicesFollow Behind the Headlines on TwitterJoin the Healthy Evidence forum.

Links To The Headlines

The 10 foods that HALVE the risk of Alzheimer's and the 5 that harm the brain: Stock up on berries, salad and wine - but avoid cheese, pastries and sweets. Mail Online, March 30 2015

Links To Science

Morris MC, Tangney CC, Wang Y, et al. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimer's & Dementia. Published online February 11 2015

 Tue, 31 Mar 2015 10:31:00 GMT Sperm quality pesticides claim 'should be treated with caution'

"Pesticides on fruit and vegetables may be damaging sperm counts and men should consider going organic if they want to have children," The Daily Telegraph reports.

A study found men who ate the highest amount of fruit and vegetables with high levels of pesticides had a 49% lower sperm count, as well as a 32% lower count of normally formed sperm, than men who consumed the least amount. Sperm can sometimes be an abnormal shape, making it harder for them to move and fertilise an egg.

The results of this study should be viewed with caution. Researchers did not assess individual diets for pesticide residues. They also did not know if the food the men ate was grown organically or conventionally (a failing The Telegraph overlooked). 

So it is possible the men's dietary exposure to pesticides was misclassified. The men in the study were all attending fertility clinics, so the results may not apply to the general population.

The study certainly should not be seen as an invitation to avoid eating fruit and vegetables. Aside from the general health harms a fruit and veg-free diet would hold, this could also negatively impact your sperm quality.

Many factors can affect men's sperm count and quality, including whether they smoke or drink alcohol, as well as how much exercise they take and their weight. Whether or not pesticide residue found in our diet is another factor that affects sperm quality is an important topic that needs further study. 

Where did the story come from?

The study was carried out by researchers from the Harvard T H Chan School of Public Health, Massachusetts General Hospital, Brigham and Women's Hospital, and Harvard Medical School in the US.

It was funded by the National Institute for Environmental Health Sciences, the National Institutes of Health, and the Ruth L Kirschstein National Research Service Award.

The study was published in the peer-reviewed journal Human Reproduction on an open-access basis, so it is free to read online.

The study was covered uncritically by most of the UK media. The Telegraph's assertion that, "Men who eat fruit and vegetables with high pesticide residues could double their sperm count by switching to organic food" was highly misleading.

The study did not compare the effects of organic and non-organic food on sperm count. However, both The Telegraph and the Mail Online included comments from UK experts. 

What kind of research was this?

This was a cohort study exploring whether the consumption of fruits and vegetables with high levels of pesticide residues is linked to lower semen quality.

This type of study cannot prove cause and effect, as other factors could be causing any effects seen. However, in studies of this type, researchers try to take account of other factors that can affect a health outcome.

In this case, for example, male fertility is known to be affected by lifestyle factors such as smoking and weight, which were taken into account in the statistical analyses.

The researchers say in nearly one-third of couples seeking help with conception the problem is one of male infertility.

They say occupational exposure to pesticides has been linked to lower sperm counts, and argue that pesticide exposure may explain a general decline in semen quality. Whether pesticide exposure through diet could affect male fertility is unknown. 

What did the research involve?

Men attending a fertility clinic filled out food frequency questionnaires from which the researchers estimated their intake of pesticides from fruit and vegetables. The results were then analysed to look for an association between higher pesticide consumption and lower sperm counts.

Researchers used an ongoing study of couples attending a US fertility clinic. The men in the study had to be aged between 18 and 55 without any history of vasectomy, and be in a couple seeking fertility treatment with their own eggs and sperm.

Between 2007 and 2012, the male partners in sub-fertile couples (couples who require medical assistance to conceive) completed a food frequency questionnaire. They were asked how often on average they consumed specified amounts of fruit and vegetables over the previous year using standard portion sizes.

The fruit and vegetables were categorised as being high, moderate or low in pesticide residues based on data from the annual United States Department of Agriculture Pesticide Data Program.

Fruit or vegetables low in pesticide residues included peas, beans, grapefruit and onions. Those with high residues included peppers, spinach, strawberries, apples and pears. This data takes account of how food has been prepared, such as whether it has to be peeled.

By this criteria, 14 of the fruits and vegetables in the questionnaire were categorised as high in pesticide residues and 21 as low-to-moderate in pesticide residues.

The researchers divided the men into four groups, ranging from those who ate the greatest amount of fruit and vegetables high in pesticide residues (1.5 servings or more per day), to those who ate the least amount (less than half a serving per day).

They also categorised whether men ate a "prudent" diet – consisting of high intakes of fish, chicken, fruit, vegetables and wholegrains – or a "Western pattern" – high intakes of red and processed meat, butter, high-fat dairy, refined grains, snacks, high-energy drinks, mayonnaise and sweets.

Semen samples were also collected from the men over an 18-month period following their dietary assessment. Both sperm count and the size and shape of the sperm and whether they moved normally were evaluated by computer-aided semen analysis (CASA).

A total of 338 semen samples collected from 155 men between 2007 and 2012 were used in the analysis. Fifty-seven men contributed one sample, 51 men provided two samples, and 47 provided three or more semen samples.

Using statistical methods, the researchers analysed the association between pesticide intake from fruit and vegetables with sperm count and quality.

They adjusted their findings for other factors known to affect male fertility, such as age, smoking status, weight, periods of sexual abstinence, exercise, dietary patterns, and history of varicose veins (variocele) in the testicles.

What were the basic results?

The researchers found that:

  • the men's total fruit and vegetable intake was unrelated to their semen quality
  • high pesticide residue fruit and vegetable intake was associated with poorer semen quality
  • on average, men in the highest quartile of high pesticide residue fruit and vegetable intake, with 1.5 or more servings a day, had a 49% (95% confidence interval [CI] 31 to 63) lower total sperm count and a 32% (95% CI 7 to 58) lower percentage of normally shaped sperm than men in the lowest quartile of intake (0.5 servings a day)

How did the researchers interpret the results?

The researchers say their findings suggest that exposure to pesticides used in agriculture through diet may be sufficient to affect the quality and amount of sperm in humans.

Conclusion

Whether pesticide exposure in the diet is linked to male fertility problems is an important issue, but, as the authors point out, there are several reasons to view the results of this trial with caution:

  • the men were all attending a fertility clinic with their partner, so some of them will have had fertility issues unrelated to their diet or lifestyle
  • they used national surveillance data, rather than looking at individual diets, to assess how much pesticide residue the men had consumed
  • they did not have information on whether the men were eating organic or non-organic food
  • the men had to remember and report on their diet over the previous year, which could affect the reliability
  • their diets were only assessed once, which might have led to misclassification, and diets could change over time

Male fertility can be affected by several factors. Although the researchers tried to adjust their findings for these, it is always possible that both measured and unmeasured confounders affected the results. Further studies looking at this important topic are needed.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

Pesticide residues on some fruit and vegetables harming men's fertility, study claims. The Independent, March 31 2015

Pesticide in fruit and veg could harm man's fertility: Men who eat high levels have half the sperm count of those who ate the least. Mail Online, March 31 2015

Could switching to organic fruit and veg double sperm count? The Daily Telegraph, March 31 2015

Links To Science

Chiu YH, Afeiche MC, Gaskins AJ, et al. Fruit and vegetable intake and their pesticide residues in relation to semen quality among men from a fertility clinic. Human Reproduction. Published online March 30 2015

 Mon, 30 Mar 2015 11:45:00 GMT Meningitis B jab to be added to NHS child vaccine schedule

"All babies in the UK will soon have a potentially life-saving vaccine against meningitis B," The Guardian reports. The vaccine, Bexsero, will soon be offered to babies once they reach the age of two months, followed by two more booster shots.

 

What is meningitis B?

Meningitis B is a highly aggressive strain of bacterial meningitis that infects the protective membranes surrounding the brain and spinal cord. It is very serious and should be treated as a medical emergency. If the infection is left untreated, it can cause severe brain damage and infect the blood (septicaemia). In some cases, bacterial meningitis can be fatal.

 

How common is meningitis B?

The charity Meningitis Now estimates that there are 1,870 cases of meningitis B each year in the UK. Meningitis B is most common in children under five years old, particularly in babies under the age of one.

Initial signs and symptoms of meningitis B in babies include:

  • a high temperature with cold hands and feet
  • they may feel agitated, but not want to be touched
  • they may cry continuously
  • some children are very sleepy and it may be difficult to wake them up
  • they may appear confused and unresponsive
  • they may develop a blotchy red rash that does not fade when you roll a glass over it

For more information, read about the signs and symptoms of serious illness in babies.

 

Why is this meningitis B vaccine in the news?

The development of a safe and effective meningitis B vaccine is the culmination of more than 20 years of research and represents a significant breakthrough in disease prevention.

 

What do we know about the vaccine?

The vaccine, Bexsero, is thought to provide 73% protection against meningitis B, which should significantly reduce the number of cases. The vaccine can be administered to infants aged two months or older either by itself, or in combination with other childhood vaccines.

The vaccine has been tested in clinical trials involving more than 8,000 people.

In infants, it was found to have similar levels of safety and tolerability as other routine childhood vaccines. The most commonly reported side effects were:

  • redness and swelling at the site of the injection
  • irritability
  • fever

It is thought that the vaccine will become available on the NHS in the autumn.

 

Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

Meningitis B vaccine added to UK child immunisation scheme. The Guardian, March 29 2015

Now babies WILL get £20 meningitis jab. After year-long row over cost, NHS gives it the nod. Mail Online, March 30 2015

Meningitis B vaccine deal agreed. BBC News, March 30 2015

Every baby to be vaccinated against meningitis B in world first protection programme. Daily Express, March 30 2015

Links To Science

 


 

 
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