Wednesday, May 9, 2012

Fast food is depressing

“Eating junk food has a negative effect on mental health, making those who consume it regularly feel depressed,” said The Daily Telegraph.

The news is based on a Spanish study that looked at how 9,000 people’s consumption of fast food and baked goods, such as pies and pastries, related to their risk of depression. In a week when tax on pasties and pies has been the source of great distress for some, researchers found that people who consumed the most fast food and baked good were 37% more likely to become depressed over a six-year period than people with the lowest consumption.

This study had some strengths. For example, it established people’s diets before they were followed to see if they developed depression, which means their diets preceded their depression. However, it cannot conclusively show that fast food directly causes depression. For example, it is just as plausible that diet and depression are both the result of a common factor. Therefore, it's too early to rebrand the burger and fries as an "unhappy meal".

Where did the story come from?

This Spanish study was carried out by researchers from the University of Las Palmas in Gran Canaria and the University of Navarra. It was funded by the Spanish Government’s Carlos III Institute of Health.

The study was published in the peer-reviewed journal Public Health Nutrition.

The study's methods were covered appropriately by the media. However, the 51% increase in risk of depression that was quoted by the Telegraph and Daily Mail did not appear in the research paper. The paper reported an increased risk of 37%.

What kind of research was this?

This prospective cohort study assessed the relationship between eating fast food or processed pastries and developing clinical depression. The research project, called Seguimiento Universidad de Navarra (SUN), is a long-running cohort study that involves university graduates in Spain. The study continuously recruits new participants, and collects data on a variety of factors using mailed questionnaires.

Prospective cohort studies assess participants and then look at the development of various factors over time. They have the advantage of initially measuring the exposure of interest (in this case, consumption of fast foods or processed pastries) in a group of people who do not already have the outcome of interest (in this case, clinical depression). This allows the researchers to be certain that the exposure came before the outcome, which is important for determining a cause-and-effect relationship.

Cohort studies can collect data on a number of other factors that may also account for the relationship between the exposure and outcome. These factors are known as confounders. Adjusting their results to account for the influence of confounders allows researchers to be fairly certain that these confounding factors do not influence the results. However, they cannot take into account factors that weren’t measured during the study. Therefore, it is possible that, during a cohort study, unknown factors may account for the relationship seen, rather than the exposure of interest.

What did the research involve?

The researchers used data from the SUN study to identify participants for their research. They included people who did not have a clinical diagnosis of depression and who were not taking antidepressant medication (to ensure that the participants were free of depression at the beginning of the study). All participants were also free of cardiovascular disease, diabetes and hypertension.

The participants completed the food frequency questionnaire at the beginning of the study. They assessed two exposure variables: fast food consumption (which included hamburgers, sausages and pizza) and consumption of commercial baked goods (which included muffins, doughnuts, croissants and other baked goods). The researchers then divided the cohort into five groups (quintiles), based on the amount of each food group that they usually consumed.

The participants were then followed up for a median of 6.2 years. The researchers used a mailed questionnaire to determine whether the person had been diagnosed with clinical depression or had been prescribed antidepressant medication during this time.

The researchers collected data on other variables they thought might influence the relationship between eating habits and depression. These included age, sex, body mass index, smoking status, physical activity level, total energy intake and healthy food consumption. They then adjusted for the influence of these variables during the statistical analysis.

What were the basic results?

In total, 8,964 participants were included in the study. Participants with the highest consumption (quintile 5) of fast food and baked goods were more likely to be single, younger, less active and have worse dietary habits than participants with the lowest consumption (quintile 1).

After a median follow-up of 6.2 years, 493 cases of clinical depression were reported.

When assessing the relationship between fast food consumption and the development of depression, the researchers found:

  • There were 97 cases of depression in the group with the lowest consumption (quintile 1) compared with 118 cases in the group with the highest consumption (quintile 5). When the sizes of the quintiles were taken into account, this equated to people with the highest levels of consumption having a 37% greater risk of developing depression than those with the lowest levels of consumption (hazard ratio [HR] 1.37, 95% confidence interval [CI] 1.01 to 1.85).
  • Intermediate levels of consumption (quintiles 2, 3 or 4) were not associated with significantly increased risk of developing depression compared to the lowest consumption level.

When assessing the relationship between commercial pastry consumption and the development of depression, the researchers found:

  • People with the highest level of consumption (quintile 5) had a 37% increased risk of developing depression compared to the lowest consumption group (quintile 1) (HR 1.37, 95% CI 1.01 to 1.85).

How did the researchers interpret the results?

The researchers concluded that their results demonstrate “a positive dose-response relationship between the consumption of fast food and the risk of depression”. In other words, as consumption of fast food increases, so does the risk of depression. They also said that “consumption of commercial baked goods was also positively associated to depressive disorders.”


This study has found an association between consuming high levels of fast food and baked goods and the risk of developing depression. Even though this was a prospective study, it cannot conclusively show that eating lots of hamburgers, sausages and pizza causes depression. The tendency to consume fast food and develop depression may both have stemmed from some common factor, rather than fast food directly causing depression. For example, participants with the highest fast food consumption were generally all single, younger and less active, which may have influenced both their diet and their risk of depression.

Several important factors should be noted:

  • This study used a questionnaire to determine whether a person had clinical depression. This method may be less reliable than either a clinical interview or a diagnosis confirmed by medical records. Some people with depression may not have reported that they had been given a diagnosis. Alternatively, other people may have considered themselves to have depression without having a clinical diagnosis from a doctor. Equally, some people who would have met diagnostic criteria for depression had they seen a doctor may not have realised that they had the condition.
  • Though the researchers adjusted their results for lifestyle and socioeconomic factors that may have influenced diet and depression risk (potentially confounding the relationship between the two), depression may be triggered by many factors. It is difficult to ensure that all possible confounders were taken into account.
  • If there is a direct association between these dietary items and risk of depression, the underlying mechanism by which eating these foods could lead to depression is not known.
  • The cohort excluded people with multiple underlying illnesses and conditions, such as cardiovascular disease and high blood pressure. While this allowed the researcher to ensure these conditions did not influence their results, it makes it difficult to generalise the results to the wider population. Also, these types of illnesses may influence both diet and risk of depression, so it is arguable that including people with them could have been a valid option.
  • The cohort was divided into groups based on their relative consumption of fast foods and commercial baked goods, and not on an absolute level of consumption. Therefore, the results of this study would only apply to a population that had a similar pattern of consumption.

Overall, this study suggests that there may be an association between eating a lot of fast food or baked goods and developing depression. It is, however, difficult to apply the findings to other groups of people, and it is unclear if the relationship would remain under different conditions.

Links to the headlines:

Fast food 'gives you the blues', study finds. The Daily Telegraph, April 2 2012

Links to the science:

Sánchez-Villegas A, Toledo E, de Irala J et al. Fast-food and commercial baked goods consumption and the risk of depression. Public Health Nutrition, March 2012, 15: pp 424-432

Monday, April 9, 2012

Pizzas as salty as the sea

Some takeaway pizzas are saltier than the Atlantic Ocean, say health campaigners concerned about the amount of salt we eat. Several newspapers have reported on the high levels of salt in pizzas from both takeaway outlets and supermarkets. Some of the pizzas contained more than 10g of salt, which is more than an entire day’s salt allowance.


An analysis of 199 pizzas by the Consensus Action on Salt & Health (CASH) group found no low-salt options, with over half the takeaway pizzas containing more than 6g of salt – the recommended daily maximum for healthy adults. Shop-bought pizzas generally fared better, but many still contained more than 5g of salt – close to the daily maximum allowance.
Keeping track of how much salt we eat is important as salt can raise blood pressure, in turn raising the risk of problems such as heart attacks and strokes. Many pizzas were also found to be high in fat and saturated fat, again marking them out as an unhealthy option.

Where has the news come from?

The action group CASH is concerned about the amount of salt we eat and its impact on our health. The group comprises academics, physicians and public health experts. CASH recently conducted a survey that examined the amount of salt in pizzas available throughout London. They included 199 margherita and pepperoni pizzas from takeaways, chain restaurants and supermarkets in their study. The CASH report included information on the amount of salt per 100g of food, as well as the amount of saturated fat contained in the pizzas.

How much salt should I eat?

CASH and NHS Choices recommend that adults consume a maximum of 6g of salt a day (approximately one full teaspoon). However, UK adults currently consume an average of 8.6g a day. The recommended maximum daily levels of salt for children are:
  • under 1 year old – less than 1g
  • 1 to 3 years old – 2g
  • 4 to 6 years old – 3g
  • 5 to 10 years old – 5g
  • 11 years and older – 6g
It is important to limit salt intake as it affects blood pressure and, in turn, the risk of serious health problems such as strokes and heart attacks. CASH estimates that if the nation reduced its intake to recommended levels, it could reduce the number of strokes by 22% and heart attacks by 16%.

Which were the saltiest takeaways?

The CASH survey found that the top five saltiest takeaway pizzas were:
  • Adam & Eve pepperoni pizza in Barnet – 2.73g of salt per 100g of food, equivalent to 10.57g of salt in their 388g pizza
  • La Vera Italia pepperoni pizza in Wandsworth 2.43g of salt per 100g of food, or 10.68g of salt per 439.6g pizza
  • Ciao Bella pepperoni pizza in Havering – 2.21g of salt per 100g of food, or 9.22g of salt per 417.4g pizza
  • Ciao Bella margherita pizza in Havering – 2.13g of salt per 100g of food, or 7.69g of salt per 361.8g pizza
  • Il Mascal Zone pepperoni pizza in Barnet – 2.08g of salt per 100g of food, or 9.21g of salt per 442g pizza
The CASH survey found that more than half of all takeaway pizzas surveyed contained over the recommended maximum of 6g of salt a day. CASH points out that makers of takeaway pizzas do not have to provide nutritional information, which can make it difficult to know how much salt you are consuming.

Which were the saltiest shop-bought pizzas?

The CASH survey found that the top five saltiest shop-bought pizzas were:
  • Tesco full-on-flavour simply pepperoni thin stonebaked pizza (fresh) – 1.8g of salt per 100g of food, equivalent to 4.77g of salt in their 265g pizza
  • Iceland stonebaked spicy double pepperoni pizza (frozen) – 1.7g of salt per 100g of food, or 6.29g of salt per 370g pizza
  • Morrisons extra thin triple pepperoni pizza (frozen) – 1.7g of salt per 100g of food, or 5.81g of salt per 342g pizza
  • Dr. Oetker ristorante pizza pepperoni salame (frozen) 1.68g of salt per 100g of food, or 5.36g of salt per 320g pizza
  • Dr. Oetker Casa di Mama pizza quattro formaggi (frozen) 1.6g of salt per 100g of food, or 6.32g per 395g pizza
Overall, the CASH survey found that 85% of shop-bought pizzas provided nutritional information on the front of the packaging, which may make it easier for customers to choose lower-salt options.

Were there any low-salt options?

Among the 199 shop-bought and takeaway pizzas, CASH did not identify any low-salt options (defined as 0.3g of salt or less per 100g of pizza).
There were, however, several medium-salt options (defined as 0.3-1.5g of salt per 100g). The takeaway with the lowest salt content pizza was Trattoria Pizzeria’s margherita pizza, with 0.778g of salt per 100g of food, equivalent to 2.15g of salt in their 275.8g pizza. However, this pizza contained a high amount of saturated fat.
The lowest salt content in a supermarket pizza was found in the ASDA Chosen by You cheese and tomato pizza, which contained 0.6g salt per 100g of food, equivalent to 0.64g of salt in the 106g pizza. This pizza also had medium levels of saturated fat.

How were the tests performed?

The survey looked at both pepperoni and margherita pizzas available in takeaways in 17 London boroughs and 8 supermarkets. They included 81 takeaway pizzas and 118 supermarket pizzas.
At present, companies selling takeaway pizzas are not required to publish nutritional information such as salt and fat content, so researchers took samples of each pizza and sent them away for lab analysis. They were analysed for the amounts of fat, saturated fat, sodium and calories per 100g. Researchers also recorded the total weight of the pizza, as well as diameter and pepperoni weight.
Supermarket pizzas are required to provide nutritional information on the packaging. For the 118 pizzas in this group, CASH photographed the packages, recording the salt, sodium, calories, fat and saturated fat content per 100g of pizza, as well as whether or not the packaging included a nutritional label on the front, the package weight and the portion weight.

How can I make a low-salt pizza?

CASH says that one way to reduce your daily salt intake and avoid the hidden salt found in many ready-made foods is to make your own pizza. CASH provides the following low-salt, low-fat recipe:
Serves: 2 (1 pizza) Preparation time: 15-20 minutes plus 1 hour rising time Cooking time: 30-40 minutes
For the base 300g strong white bread flour, plus extra for rolling out ½ teaspoon (half a 7g sachet) fast-action yeast Pinch of ground black pepper 100ml warm water 1 tablespoon olive oil, plus extra for greasing 1 garlic clove, crushed
For the sauce ½ teaspoon olive oil 1 small onion, chopped 1 garlic clove, finely chopped 1 tablespoon tomato purée 1 x 227g tin chopped tomatoes Pinch of chilli flakes, or to taste Freshly ground black pepper, to taste Handful of fresh basil, roughly chopped
For the topping 1 yellow pepper, sliced 1 tomato, sliced 100g cooked chicken 2 tablespoons sweetcorn 60g mozzarella, thinly sliced A few basil leaves, torn, plus extra to garnish
  1. To make the dough, mix the flour, yeast and black pepper together in a large bowl. In a separate container, mix the water with the oil and garlic and pour into the flour and yeast. Mix together quickly with a spoon until a sticky dough is formed. Leave to stand for 10 minutes.
  2. Dust your hands and a work surface with flour. To knead the dough, hold one side of the dough down with one hand and, with the other hand, push the other side of the dough away from you, stretching it out. Fold the stretched dough back on top of itself and push it down with your palm. Give the dough a quarter turn and repeat the process for just one minute or until the dough is smooth, elastic and bouncy.
  3. Form a ball with the dough and place it into a bowl greased with a little oil. Cover the bowl with cling film and leave to rise in a warm place for about an hour or until the dough has doubled in size.
  4. Meanwhile, make the sauce. Heat the oil in a saucepan over a medium heat and cook the onion and garlic for 5 minutes or until the onion becomes soft and transparent. Stir in the tomato purée followed by the chopped tomatoes, chilli and pepper. Simmer on a low heat for 15-20 minutes until the sauce becomes thick. Stir in the basil for the last few minutes. Use a hand blender to make a smooth sauce.
  5. Once the dough has risen, preheat the oven to 240°C/475°F/gas 9. Dust a baking sheet with a little flour and use your hands to push the dough outwards to form a round base approximately 30cm (12 inches) across.
  6. Spread the tomato sauce over the pizza base using the back of a spoon. Scatter the toppings over the pizza, top with the basil leaves and cook in the oven for 10-15 minutes or until golden brown. Scatter the remaining basil leaves on top and serve.

Monday, March 19, 2012

Can fruit and vegetables improve your skin?

Fruit and vegetables are not only nutritious but could also make you “cuter”, according to the Daily Mail. Apparently, eating more foods such as carrots, broccoli, squash and spinach enhances attractiveness and gives the skin a healthy glow within six weeks.

These rather fruity claims are based on a small experimental study that investigated whether people could improve their complexion by eating the yellow-red carotenoid pigments found in many fruits and vegetables. In the first phase of the study, 35 people completed dietary questionnaires and had their skin colour recorded over a six-week period. The researchers found that a modest increase in self-reported fruit and vegetable consumption over the period was related to an increase in skin colouration (yellowness and redness). In the second part of the study, the researchers enrolled 24 young students and asked for their subjective opinions of the attractiveness of computer-created, colour-manipulated images, which the researchers said reflected different degrees of fruit and vegetable consumption.
No conclusions can be drawn from this small, short study, which has numerous limitations. To assess more reliably whether fruit and vegetable consumption caused skin colour change, the researchers could have performed a trial asking people to eat different diets and looked at the results it had. Also, the researchers did not account for other factors that might affect complexion, such as exposure to daylight and exercise, and can provide no evidence that the diet caused the observed skin colour over the short six-week period. In the second part of the study, the subjective opinions of 24 people cannot be interpreted as a universal measure of attractiveness.
Regardless of whether or not fruit and vegetables enhance our complexion, including them in a healthy, balanced diet has many other known health benefits.
Where did the story come from?
The study was carried out by researchers from the University of St Andrews and was funded by the Economic and Social Research Council and by Unilever Research and Development USA. Unilever is a large food manufacturer. The research was published in the peer-reviewed scientific journal PLoS One.
This apparent “good news” study was widely reported in the papers, for the most part uncritically. The BBC included comments from independent experts, one of whom pointed out that the study did not take account of food preparation technique and another who said the effects of daylight could not be ruled out. The Mail’s report, which said that people who increased their fruit and vegetable intake became more attractive, and even “cuter” in an online version of the story, was misleading because it attempted to combine the results of two separate experiments.
What kind of research was this?
This experimental study set out to examine the effects of fruit and vegetable intake on skin colour, and specifically to find out how much dietary intake needs to change and for how long to have a perceptible change on skin colour. A second part of the study looked at the minimum colour change required to make skin look healthier and more attractive.
The authors say that a recent cross-sectional study has associated higher fruit and vegetable consumption with human skin colour (yellowness), mainly because of the presence of carotenoids, the yellow-red organic pigments abundant in many fruit and vegetables. Carotenoids are described as high in antioxidants, which the authors say may be beneficial for skin health. They say that the accumulation of carotenoids imparts colour to the skin, but that it is not known how much is needed to give the skin a healthy colour. In evolutionary terms, a healthy skin colour, they argue, indicates suitability as a mate and is therefore beneficial in sexual selection.
What did the research involve?
In the first experiment, the researchers monitored the fruit and vegetable intake of 35 individuals (21 women and 14 men) over a period of six weeks. Participants were undergraduate students, mostly of Caucasian origin. None of them wore facial makeup or reported recent sunbathing or use of self-tanning products. Researchers recorded their diet and skin colour at an initial session and in two follow-up sessions at three and six weeks, between March and June 2010.
Students completed a validated food-frequency questionnaire to establish their daily fruit and vegetable intake, from which researchers worked out a daily average. The participants reported consuming an average of 3.41 fruit and vegetable portions daily over the three sessions. Skin colour and “reflectance” (the amount of light reflected off the skin) were recorded using a specialist device called a spectrophotometer. The measurement of skin colour included three separate components: skin lightness and degrees of yellowness and redness.
Skin colour on seven body locations was recorded:
•the left cheek
•right cheek
•part of forearm
•outer bicep

The researchers analysed whether there were any associations between changes in diet and changes in skin colour over this period. They also conducted a further analysis to investigate whether changes in skin colour associated with dietary changes were caused by the absorption of carotenoids or melanin, a skin pigment that gives the skin its colour and which also protects against UV rays.
In a second experiment involving 24 students (19 women and 5 men), the researchers investigated the effects of skin colour changes on perception of health and attractiveness, using what they call “psychophysics”. For this, they took close-up photos of two women and two men (all of whom were white), taking various precautions to reduce the possibility of reflection from external light and ensuring each image was colour calibrated.
They then digitally created two on-screen face-shaped colour masks, which they say represented the average skin colour of 15 high and 15 low fruit and vegetable consumers, as derived from a previous study. The skin areas of the photos were manipulated to create a row of 22 images for each face, with the middle one showing the original face and those either side varying in their colour tone. The full set of 22 images represented a total range of colour equivalent to a change of plus or minus 5.55 fruit and vegetable portions a day.

The 24 students were asked to view the images and, in three separate tasks, to choose the face that appeared healthier, more yellow or more attractive.

What were the basic results?
In the first experiment, the researchers found that changes in fruit and vegetable consumption over a period of six weeks significantly correlated with changes in skin “redness and yellowness” over the same period, across all seven measured regions of the body.
However, when they considered only the three facial areas (left cheek, right cheek, forehead), researchers found no significant association between changes in fruit and vegetable intake and changes of redness or lightness in complexion. There was only a marginal association between dietary changes and an increase in facial yellowness. They also found that the changes in skin “reflectance” were significantly associated with the absorption of carotenoids and not melanin (which means they could be attributed to compounds found in fruit and vegetables rather than to the skin’s natural pigment).
In the second experiment, they found that modest dietary changes are required to enhance apparent health (2.91 more portions of fruit and veg a day) and attractiveness (3.3 more portions a day).
How did the researchers interpret the results?
The researchers concluded that increased fruit and vegetable consumption confers “measurable and perceptibly beneficial effects” on Caucasian skin appearance within six weeks. This effect, they say, could potentially be used as a “motivational tool” in dietary intervention.
This small study attempted to look at how fruit and veg intake affected attractiveness and skin tone in two experiments. The first found that self-reported increases in fruit and vegetables over a period of six weeks were associated with changes in complexion. The second asked people to rate the attractiveness of digital facial images manipulated to reflect different levels of fruit and vegetable consumption.
Despite all the prominent, positive news coverage this research received, no conclusions should be drawn from this experimental study, which has numerous limitations. There is no reason why the first part of this study could not have been conducted using a randomised controlled design that assigned people different diets and then followed them over time to assess skin colour change. This would have been relatively simple and would probably have given much more reliable results. Instead, the study asked just 35 students to report their dietary intake over the course of the six weeks while having their skin colour assessed. The study had a small number of participants, and the results cannot prove that the diet caused the change over this short period. For example, changes in complexion could be related to other factors including exercise, exposure to daylight and even sleep.
In the second experiment, researchers tried to link this association between complexion and diet by asking 24 people to give their subjective perceptions of the health and attractiveness of computerised facial images that had been manipulated to show varying complexions, apparently related to fruit and vegetable intake. Again, no significance should be attached to these results. Judging how attractive someone is involves many other factors, not just their skin tone.
Overall, this widely reported research can't tell us very much about whether fruit and vegetables have a beneficial effect on complexion, although there are plenty of other good reasons to eat fruit and vegetables.

Links to the headlines:
Fruit and veg 'give healthy glow'. BBC News, March 8 2012
Eating fruit and veg 'boosts attractiveness'. The Daily Telegraph, March 8 2012
Best incentive yet for improving your diet: how fruit and veg could make you cuter. Daily Mail, March 8 2012

Eat your five-a-day if you want a glowing complexion, say scientists. Metro, March 8 2012

Links to the science
Whitehead RD, Re D, Xiao D et al. You Are What You Eat: Within-Subject Increases in Fruit and Vegetable Consumption Confer Beneficial Skin-Color Changes. PLoS ONE 7(3): e32988

Sunday, February 26, 2012

Flavonoids in citrus fruits ‘cut stroke risk’

Grapefruit and oranges “appear to protect against having a ‘brain attack’”, the Daily Mail has reported. The Mail says that these and other citrus fruits can protect the brain from stroke due to their antioxidant content.

The research behind this story involved almost 70,000 women taking part in the Nurses’ Health Study. They were asked to complete food frequency questionnaires (which asked them to recall how frequently certain foods were consumed during a specified period of time) every four years and over around 14 years of follow-up the researchers documented the numbers of strokes that occurred, overall and by type.

The researchers found that women who had the highest intake of flavanone (a crystalline compound found in citrus fruit) had a reduced risk of ischaemic stroke. However, they found no association between consuming actual citrus fruits and juices and being at risk of ischaemic stroke, and no association between consumption of flavonoids overall and risk of stroke.

This makes these findings far from conclusive. Whether citrus fruits and the chemicals they contain have any association with stroke risk needs more investigation. But on the basis of this study alone, there is no evidence that women who eat citrus fruits will reduce their risk of stroke. However, a balanced diet high in fruit and vegetables is known to be beneficial to health and can reduce the risk of several diseases, including cardiovascular disease.

Where did the story come from?

The study was carried out by researchers from the University of East Anglia and other institutions in the US and Italy, and was funded by the National Institutes of Health, Department of Health and Human Services. It was published in the peer-reviewed medical journal Stroke.

The Daily Mail does not accurately represent the findings of the study. Its headline, “How eating oranges and grapefruit can cut the risk of a stroke”, contradicts the finding that there was no significant association between intake of citrus fruits and juices and risk of stroke.

What kind of research was this?

This was an analysis of women enrolled in the ongoing Nurses’ Health Study in the US. The researchers aimed to use data from this cohort study to examine associations between subclasses of flavonoids and risk of stroke. Flavonoids are plant chemicals believed to have antioxidant properties, and are found in several food groups, including citrus fruits, berries, onions, certain pulses, tea and wine.

Cohort studies such as this are not great at showing cause and effect. In this study, researchers circulated regular food frequency questionnaires at the same time as looking at clinical outcomes. It is difficult to guarantee that food intake patterns preceded the development of cardiovascular disease. Furthermore, because food frequency questionnaires are self-completed, they are also likely to contain inaccuracies and may not represent the pattern food intake over a lifetime. Finally, it may be difficult to ensure that other things that could be associated with both diet and risk of stroke (confounding factors) have been taken into account.

What did the research involve?

The Nurses’ Health Study started in 1976 and enrolled 121,700 female nurses aged 30 to 55. Participants completed follow-up questionnaires on diseases and lifestyle factors every two years, as well as food frequency questionnaires every four years. In this study, researchers looked at food questionnaires completed from 1990 onwards (the time when the questionnaires covered sufficient fruit and vegetables to assess flavonoid intake). This study included the 69,622 women who had sufficient information on food intake and who did not report a stroke before 1990.

The researchers constructed a database to assess intake of the different flavonoid subclasses. Intake of individual subclasses was calculated as the total consumption frequency of each food, multiplied by the content of the specific flavonoid for the specified portion size. The six flavonoid subclasses were reported to be those commonly consumed in the US diet:
■flavanones (eriodictyol, hesperetin, naringenin)
■anthocyanins (cyanidin, delphinidin, malvidin, pelargonidin, petunidin, peonidin)
■flavan-3-ols (catechins, epicatachins)
■flavonols (quercetin, kaempferol, myricetin, isohamnetin)
■flavones (luteolin, apigenin)
■polymers (including proanthocyanidins, theaflavins, and thearubigins)

The outcome of stroke was self-reported, with reports verified by review of medical records.

What were the basic results?

Over 14 years of follow-up there were 1,803 strokes among the 69,622 participants (52% ischaemic strokes – caused by a blood clot, 14% haemorrhagic – caused by a bleed in the brain, and the rest – of unknown type).

The average intake of total flavonoids was 232mg per day. Tea was reported to be the main contributor to total flavonoid intake, followed by apples and oranges or orange juice. Women who ate more flavonoids tended to:
■exercise more
■have a greater intake of fibre, folate, fruits and vegetables
■have a lower intake of caffeine and alcohol
■be less likely to smoke

The researchers found that women who consumed the highest quantity of the flavanone subclass had reduced risk of ischaemic stroke compared with those who consumed the lowest quantity of flavanone (relative risk 0.81, 95% confidence interval 0.66 to 0.99). The relationship between flavanones and stroke overall was not reported.

As 95% of flavanones are reported to be derived from citrus (in this study, oranges and orange juice were the highest contributors), they looked for a relationship between intake of citrus fruit/juice and risk of ischaemic stroke but found no significant association (relative risk 0.90, 95% confidence interval 0.77 to 1.05).

How did the researchers interpret the results?

The researchers conclude that flavonoid intake was not associated with risk of stroke, but that increased intake of the flavanone subclass reduced the risk of ischaemic stroke. They say that because experimental data suggests that the flavanone content of citrus fruits may protect the heart, there may be an association between citrus fruit consumption and stroke risk.


Despite the news headlines, this study provides no evidence that women who eat citrus will reduce their risk of stroke.

The researchers found a link between higher intake of flavanones and reduced risk of ischaemic stroke, but:
■no association between the actual consumption of citrus fruits and juices and risk of ischaemic stroke
■no association between total flavonoid intake and risk of stroke

The researchers didn’t report on any association between flavanone, flavonoid, or citrus consumption and risk of stroke overall. There was no association with haemorrhagic stroke and presumably there was none found for stroke overall.

Further problems with making the conclusions stated in the headlines include:
■The design of this cohort study and therefore cannot easily imply cause and effect. The researchers excluded women who had experienced a stroke prior to 1990, but assessed both food consumption and stroke outcomes over the following 14 years. This makes it difficult to ensure that food intake patterns preceded the development of cardiovascular disease.
■Food frequency questionnaires are self-completed and often contain inherent inaccuracies, and may not represent a lifelong food intake pattern.
■The researchers used the most recent US Department of Agriculture databases categorise individual foods according to their content of flavonoid chemicals. However, they do not further describe how they did this in their report. As the researchers acknowledge, there is potential for the misclassification of flavonoids using this method as there is wide variation in flavonoid content of foods. Flavonoid content of fruit depends on their geographical origin, growing season, different cultivars, agricultural methods and processing. It is also difficult to say how flavonoids are processed in the body.
■The researchers did adjust their analyses for multiple potential dietary, lifestyle and medical factors, but it is possible that some confounding factors that could be associated with both diet and risk of stroke have not been taken into account.

Whether or not citrus fruits and the chemicals they contains have any association with stroke risk may be a topic for further research. However, on the basis of this study alone, there is no evidence that women who eat grapefruit, oranges, or any other citrus fruit will reduce their risk of stroke.

Wednesday, February 8, 2012

10 ways to stop leaks

For many people with incontinence, the following self-help tips and lifestyle changes are enough to relieve symptoms.

1. Daily pelvic floor exercises

These can be really effective at reducing leakage, but it’s important to do the exercises properly. Find out how to do pelvic floor exercises.

You may have to do these exercises for three months before you see any benefits.

2. Quit smoking

If you smoke, you put yourself at risk of incontinence because coughing puts strain on your pelvic floor muscles. Advice to help you stop smoking is available from your GP or pharmacist. You can also call the NHS smoking helpline on 0800 022 4 322.

Read more about how to stop smoking.

3. The right exercise

High-impact exercise puts pressure on your pelvic floor muscles and can increase leakage. Sit-ups can also make you leak by straining your pelvic floor muscles. If you want to strengthen your pelvic floor to relieve symptoms, replace jogging and aerobics classes with Pilates. This gentle method of stretching and strengthening core muscles is becoming more popular as a treatment for stress incontinence.

4. Avoid lifting

Lifting puts strain on your pelvic floor muscles so avoid it wherever you can. When you do need to lift something, such as when picking up children or shopping bags, tighten your pelvic floor muscles before and during the lift.

5. Lose weight

Being overweight can weaken your pelvic floor muscles and can cause incontinence because of the pressure of fatty tissue on the bladder. Your symptoms may improve, and could clear up completely, if you lose the excess weight.

To check whether you're a healthy weight, use our Healthy weight calculator. Your body mass index (BMI) is a measure of whether you're a healthy weight for your height.

Read more about how to lose weight.

6. Deal with constipation

Straining to empty your bowels weakens your pelvic floor muscles and makes leakage worse. Never delay the urge to empty your bowels. If you have constipation, it may help to change your diet and lifestyle. Eating more fibre and taking more exercise can help. It may also help if you change the way you sit and use your muscles to empty your bowels. A specialist physiotherapist can advise you on this.

Read more about food and diet.

7. Cut down on caffeine

Caffeine irritates the bladder and can make incontinence worse. Coffee has the biggest effect, so stop drinking it or switch to decaffeinated. Fizzy drinks, tea and cocoa also contain caffeine, so cut down on these too and replace them with water and herbal or fruit teas.

8. Cut down on alcohol

Alcohol is a diuretic, a substance that makes you urinate more often. Cutting down may help your incontinence symptoms.

Read more about how to cut down on your drinking.

9. Drink enough water

Drink six to eight glasses of water a day (but not more) unless your doctor advises you otherwise. Many people with urinary incontinence avoid drinking fluids as they feel it causes more problems. However, limiting your fluid intake makes incontinence worse because it reduces your bladder's capacity.

10. Food for thought

Avoid spicy and acidic foods, such as curries and citrus fruits, as they can irritate the bladder and make symptoms worse.