Liking brussel sprouts is in your DNA

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Hi, everyone. I had to post this additional information about brussel sprouts because it’s quite interesting.

Apparently, researchers say there’s a genetic explanation why some people love brussels sprouts — while others would rather eat dust for Christmas dinner. Scientists from the Eden Project have propogated a theory that a love or hate of the cruciferous vegetable comes down to your DNA.

It’s been claimed that a particular mutated gene — which is present in about half of the world’s population — decides whether or not we will like sprouts.

People with the mutation are said not to taste the bitterness of the Brussels sprouts, caused by a bitter chemical similar to PTC (Phenylthiocarbamide) and are therefore more likely to enjoy them.

A spokesperson for the team told the Metro: (http://www.metro.co.uk/news/885718-if-you-hate-brussels-sprouts-it-could-be-in-your-dna-say-scientists) “Christmas dinner isn’t usually associated with science.

“This hands-on project helps to do exactly that, as it explores why some people like and some hate Brussels sprouts.”

‘Tis the season to be … healthy – eat brussel sprouts

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Eat healthily at christmas time

In this festive period, with cold and windy conditions outside, gloomy economic forecasts in the media and little daylight hours, it’s not really a surprise that so many people want to treat themselves.

But don’t worry, some of the food we eat at this time of year is actually very good. Take for example the brussel sprout.

Brussel sprouts along with cabbage, cauliflower and swedes form the cruciferous family. They are all rich in antioxidants and are believed to reduce the risk of lung and colon cancers.

colon and lung cancer cells

Brussel sprouts are also nutritious. Just look at the nutritional content / values of x1 cooked brussel sprout:

nutients in brussel sprouts

More information:

I have also found an amazing resource on brussel sprouts if you’d like to find out more:

  1. world’s healthiest: food brussels sprouts
  2. a website dedicated to brussel sprouts!

Recipe:

And because its a food blog, check out this interesting recipe for brussel sprouts:

  1. tofu and shredded brussel sprouts recipe

Conclusion:

So next time your about to turn your nose up at the humble brussel sprout remember, it’s a wonder food.

A tomato a day keeps depression at bay

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The Daily Mail today reported that there is, “yet another good reason to tuck into that salad: eating tomatoes could ward off depression”.

Tomatoes are rich in lycopene, the chemical that gives them their distinctive colour. Lycopene is an antioxidant, a type of naturally occurring chemical believed to help protect against cell damage.

tomato

Previous research suggests foods high in antioxidants could have a preventative effect against physical diseases such as strokes. In this study, the researchers were interested in seeing if a similar preventative effect could also apply to depression.

The researchers assessed the mental health and dietary habits of 986 Japanese people aged over 70 years. They found that those who reported eating tomatoes two to six times a week were 46% less likely to report mild or severe symptoms of depression than those who said they ate tomatoes less than once a week. No such association was found for other vegetables.

This study has many limitations to consider, including a potential error in the way they measured dietary intake. Crucially, an inherent weakness of this type of research (a cross-sectional study) is that it can’t prove a direct cause and effect between reported tomato consumption and mental health.

It can also be subject to confounders. For example, it could be that in some cases, people who eat a lot of fresh fruit live a healthier lifestyle and take lots of exercise – and the exercise could be having the beneficial effects on mental health.

With those caveats in mind, this study is consistent with the advice that eating a healthy, varied and balanced diet is beneficial for both physical and mental health.

Where did the story come from?

The study was carried out by researchers from Japanese and Chinese universities and was funded by grants from the Japanese Ministry of Education and Ministry of Health and the Japan Arteriosclerosis Prevention Fund. No conflicts of interest were declared.

The study was published in the peer-reviewed Journal of Affective Disorders.

The media coverage of the study was balanced and included a useful testimony from the researchers indicating that they could not be sure if lycopene in tomatoes directly affects the mind.

What kind of research was this?

This was a cross-sectional survey looking at the potential link between intake of vegetables and tomato products and depression.

The researchers state that defective antioxidant defences are related to symptoms of depression. That is, people who are more vulnerable to cell damage caused by ‘rogue’ molecules called free radicals, may also be more prone to experiencing depressive symptoms.

They were interested to investigate whether vegetables, which are known to be good sources of antioxidant chemicals, may have a protective effect. They were particularly interested in lycopene, a powerful antioxidant present in high levels in tomatoes.

Cross-sectional studies can only highlight associations – they cannot prove cause and effect (in this case, they can’t prove that eating tomatoes causes less depression or protects against it).

Depression and its causes are complex. The causes may include genetics, environment, and personal circumstances. Additional factors, outside of antioxidant intake, influence this relationship and this type of study is unable to account for them all.

Check earlier posts on my favourite vegetable: the tomato:

Are organic tomatoes better for your health?

Do tomatoes prevent strokes?

Food Photographed with A Scanning Electron Microscope by Caren Alpert

Tomato hairs defend tomato

 

What did the research involve?

Information on 986 ‘community dwelling’ (not in hospital or residential care) elderly Japanese individuals aged 70 years and older was analysed in this study. Participants were living in one of the major cities in the Tohoku area of Japan.

The participants’ dietary intake was assessed using a validated self-administered diet history questionnaire. This required participants to indicate the average frequency they ate each of a list of 75 food items over the past year, ranging from “almost never” to “two or more times per day”.

The questions on tomatoes included fresh tomatoes as well as tomato products such as tomato ketchup and “tomato stew” – a Japanese dish consisting of beef stewed in tomato juice.

Other vegetables were categorised into:

  • green-leaf vegetables
  • cabbage and Chinese cabbage
  • carrot, onion, burdock, lotus root and pumpkin
  • Japanese white radish (daikon) and turnips

Tomato and tomato product consumption was then categorised into three separate consumption groups:

  • one or fewer servings per week
  • two to six servings per week
  • one or more servings per day

Depressive symptoms were evaluated using a Japanese version of a 30-question Geriatric Depression Scale (GDS). The scale used two cut-offs: 11 (mild and severe depressive symptoms) and 14 (severe depressive symptoms). Participants were also categorised as having mild or severe depression if they used anti-depressive drugs.

Numerous other measures were taken, including:

  • height
  • body weight
  • blood pressure
  • indicators of past health
  • current medication intake
  • sociodemographic variables such as age, gender, and educational level
  • perceived social support – for example, was there a friend or relative readily available if a participant fell ill

Participants with no information on diet, or who had a history of cancer or impaired mental ability, were excluded from the study.

The analysis compared differences in tomato and vegetable intake to see if they were significantly related to reports of depressive symptoms. Depressive symptoms were defined as mild or severe depressive symptoms (GDS of 11 or more) or use of antidepressants.

What were the basic results?

The prevalence of mild and severe depressive symptoms in the group was 34.9% when combined and 20.2% for only those categorised as severe.

There were significant differences in the baseline characteristics of those reporting different tomato consumption levels for a range of variables, including gender, smoking status, education level and marital status, and others.

Tomato consumption seemed high in this population as there were:

  • 139 (14%) people in the one or fewer servings per week group
  • 325 (33%) in the two to six servings per week group
  • 522 (56%) in the one or more serving per day group

After adjustment for potentially confounding factors, the relative risk of having mild and severe depressive symptoms (combined) was 52% less in those eating tomatoes or tomato products once or more each day, compared with those reporting consumption of once a week or less (odds ratio (OR) 0.48 95% confidence interval (CI) 0.31 to 0.75).

The risk reduction was slightly less (46%) for those eating two to six servings of tomatoes or tomato products compared to those reporting consumption of once a week or less (OR 0.54, 95%CI 0.35 to 0.85).

The analysis showed a statistically significant trend (p<0.01) linking higher tomato consumption to lower levels of depressive symptoms.

Similar results were obtained when they considered only severe depressive symptoms (GDS of 14 or more) which showed a 40% reduction in those eating tomatoes or tomato products once or more each day compared with those reporting consumption of once a week or less (OR 0.60, 95% CI 0.37 to 0.99).

The analysis reported here was adjusted for the confounders discussed above, as well as:

  • smoking and drinking habits
  • physical activity
  • cognitive status
  • self-reported body pain
  • total energy intake
  • reported intake of all kinds of fruits, green tea, and vegetables

No significant relationships were observed between intake of other kinds of vegetables and depressive symptoms.

How did the researchers interpret the results?

The researchers concluded that, “this study demonstrated that a tomato-rich diet is independently related to lower prevalence of depressive symptoms. These results suggest that a tomato-rich diet may have a beneficial effect on the prevention of depressive symptoms. Further studies are needed to confirm these findings.”

Conclusion

This cross-sectional study examined the relationship between the intake of various vegetables and tomato products (a major source of lycopene) and depressive symptoms in elderly Japanese people.

They found a statistically significant trend indicating higher levels of tomato or tomato product were associated with less risk of depressive symptoms.

By contrast, no other vegetable groups were found to be significantly linked with depressive symptoms.

This study had some strengths, including its adequate size and that it adjusted for a large number of variables that may have influenced the link between diet and depression in its analysis. However, there are also some important limitations to consider, including the following points.

Notes:

The type of study

An inherent limitation of cross-sectional studies is that they can only highlight associations between diet and disease – they cannot prove cause and effect, for example, whether eating lots of tomatoes (lycopene) causes fewer signs of depression, or whether people displaying more signs of depression eat less tomato products. Depression and the causes of it are likely to be complex and so there will be many additional factors, outside of antioxidant intake through tomatoes, that influence this relationship and which this type of study cannot account for. If all these factors were adequately accounted for, there may be no link between tomatoes and depression found. Further studies would be needed to see if this is the case.

How depression was assessed

The measure used in the study (the Japanese version of the Geriatric Depression Scale), was just that, a measure of the severity of symptoms of depression. There was no attempt to clinically diagnose depression. So, those reporting mild or severe depressive symptoms may have been a mix of people who had been formally diagnosed with depression and those that hadn’t.

Tomato eating habits were self-reported

The measure of diet was self-assessed by asking people to recall their consumption of various foods from the previous year. This may be prone to significant error in recalling this information accurately which could bias the overall results.

Do Japanese people eat more tomatoes than us?

The majority (56%) of the Japanese participants reported eating tomato products once or more per day, which may be considered a high level of consumption by other countries’ standards. This highlights the fact that diets across the world vary greatly and the results of studies linking diet to disease in other countries are not always directly relevant or applicable to the UK.

Links to the headlines

Yet another good reason to tuck into that salad: Eating tomatoes could ward off depression. Daily Mail, December 4 2012

Happy salad days: Eating tomatoes twice a week helps ward off depression. Daily Mirror, December 5 2012

Links to the science

Niu K, Gio H, Kakizaki M, et al. A tomato-rich diet is related to depressive symptoms among an elderly population aged 70 years and over: A population-based, cross-sectional analysis. Journal of Affective Disorders. Published online July 25 2012

High fructose corn sugar causing global diabetes epidemic

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“Syrup found in biscuits, ice cream and energy drinks fuelling diabetes on a ‘global scale’,” according to the Daily Mail, highlighting that countries that use large amounts of fructose corn syrup have diabetes rates “20% higher” than countries where it is less used.

high fructose corn syrup

This report comes from an ecological study looking into whether there is a link between diabetes levels and the availability of high fructose corn syrup (HFCS). Availability is a measurement of how much of a substance is produced or imported into a country – it does not automatically relate to consumption.

HFCS is used as a sweetener in a wide range of processed food and drinks, but its use and consumption varies widely between countries.

The study found that countries that produced and sold the most HFCS also had higher levels of diabetes when compared with countries with the lowest levels of HFCS availability.

Prevalence of diabetes was 8.0% in the countries with high HCFS availability, compared with 6.7% in countries with lower availability – a difference of approximately 20%.

However, this informative study has some limitations and did not set out to prove that high levels of HFCS consumption caused an increased prevalence of diabetes. Importantly, it did not show that the people with diabetes were consuming more HFCS.

Ecological studies such as these are useful but should be interpreted alongside other studies looking into associations between dietary intake (including HFCS), weight and diabetes at an individual level, so that a complete picture of the potential relationships involved can emerge.

Biscuit-loving UK readers of the Mail’s alarming headline will be pleased to hear that consumption of fructose syrup in this country is negligible – a measly 0.38kg per person per year. In the US a whopping 24.78kg per person per year is consumed – more than 65 times that consumed in the UK.

Where did the story come from?

The study was carried out by researchers from the University of Oxford (UK) and the University of Southern California (US). No funding source was reported.

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

Despite a typically arresting headline, the Daily Mail’s reporting of this research is well balanced. Especially useful is the reporting of absolute differences between diabetes rates in the countries: “Rates of diabetes were 8% in high-consuming nations and 6.7% among low consumers – a difference of 20%.”
This is useful for readers to get a feel for the magnitude of the difference being talked about.

syrup

The usual temptation for media outlets is to only report the headline-grabbing “20% higher” figure without any further explanation, which can leave readers thinking the news is more startling than it actually is.
The Mail should also be praised for including a useful graph that shows readers the sharp differences between HFCS availability in different countries, which is a good visual aid.

What kind of research was this?

This was an ecological study looking at the relationship between the availability of high fructose corn syrup (HFCS) and the prevalence of type 2 diabetes across different countries.

An ecological study is an epidemiological study that analyses data at a population level, rather than at an individual level.

HFCS is a corn syrup modified to increase the level of fructose and is used a lot in some processed foods and beverages as a sweetener to replace sugar, as well as prolong shelf life and appearance.

It is found in a host of items, from soft drinks and breakfast cereals to breads, fast food and yoghurt.

Due to historical and economic reasons – namely a series of US trade tariffs – the use of HFCS is particularly widespread in the US, as it serves as a cheaper substitute for more expensive imported sugar.

The researchers report that a growing body of evidence supports the hypothesis that in addition to overall sugar intake, fructose is especially detrimental to health and increases the risk of type 2 diabetes.

It states that the epidemics of obesity and type 2 diabetes we’re currently seeing constitute an “alarming public health concern”, and that global increases in the use of HFCS in food and beverage production may be contributing to this.

What did the research involve?

Using published resources, the researchers estimated country level estimates of:

  • total sugar availability
  • HFCS availability
  • total calorie availability
  • obesity
  • diabetes prevalence

The information sources used by the researchers included:

  • diabetes prevalence – International Diabetes Federation (IDF), Diabetes Atlas (fourth edition) and global estimates reported by the Global Burden of Metabolic Risk Factors of Chronic Diseases Collaborating Group (GBMRF)
  • food availability – the Food and Agriculture Organization of the United Nations (FAOSTAT) database of 200 countries
  • HFCS production – an international sugar and sweetener report and data on HFCS quotas for EU countries by F.O. Licht, a commercial organisation that provides information and analysis on some aspects of the global commodity market

Information from 43 different countries was analysed, some of which did not use HFCS at all. The researchers then looked for correlations between the dietary elements (total sugar, HFCS and total calories availability) and the rates of obesity and diabetes.

Some of the analysis adjusted for the effects of body mass index (BMI), as well as population and gross domestic product (GDP) obtained from International Monetary Fund (IMF) tables.

What were the basic results?

Data on 43 countries was available covering the use of HFCS (kg per year per person) alongside estimates of total sugar intake (kg per year per person), BMI, and the estimates of diabetes prevalence from two separate sources (IDF versus GBMRF).

Use of high fructose corn syrup per person

high_fructose_corn_syrup11

The US was by far the highest consumer of HFCS out of the 43 nations assessed at 24.78kg per year per person, far ahead of second place Hungary at 16.85kg per year per person. The UK was far lower, at 0.38kg per year per person. Fourteen countries registered 0kg per year per person – all except India were European.

Countries with high HFCS availability versus countries with low HFCS availability
The researchers compared measures from those countries with low availability of HFCS (21 countries) versus high availability of HFCS (21 countries). Countries with high availability were defined as having an average value of more than 0.5kg HFCS per person per year.

The average HFCS consumption in the low-availability countries was 0.1kg per person per year, compared with 5.8kg per person per year in the countries classed as having high availability.

The report stated that all indicators of diabetes were higher in countries that had high availability of HFCS compared with those that had low availability. This trend was more significant for the IDF measure of diabetes prevalence.

Countries with high HFCS availability had an average diabetes prevalence of 7.8%, compared with 6.3% in those with low availability (p=0.013). So, the high-availability countries had approximately 20% higher diabetes prevalence than those with low availability (23.8%)

Using estimates of fasting glucose levels to estimate diabetes prevalence showed the difference was 5.33mmol/L in high HFCS availability countries, versus 5.23mmol/L in low availability countries.

Other influencing factors

There were no significant differences between countries of different availability of HFCS (high versus low) for BMI, total calorie intake, cereal intake, total sugar intake and “other sweeteners” intake.

The researchers interpreted this as meaning that the differences in diabetes prevalence may have had more to do with the level of HFCS availability, rather than these additional factors.

How did the researchers interpret the results?

The researchers concluded that, “Our analysis revealed that countries electing to use HFCS in their food supply have a diabetes prevalence that is ~20% higher than that in countries that do not use HFCS […] even after adjusting for country-level estimates of BMI, population and gross domestic product.”

They linked their own finding to previous research that they reported “showed that increasing consumption of HFCS in the twentieth century was the primary nutritional factor associated with increasing prevalence of type 2 diabetes.”

This led them to warn that, “The increasing popularity of HFCS around the world should, therefore, be considered seriously due to its potential contribution to increases in fructose in the global food supply and its association with the global prevalence of type 2 diabetes.”

They also make the point that even modest increases in disease prevalence can have a significant economic impact if a disease is both common and its treatment complex. They state that the health costs of treating diabetes in the US during 2007 was $174bn. A 20% reduction in diabetes prevalence would save $34.8bn, or approximately $95m per day.

Conclusion

This ecological study suggests that countries with a high availability of high fructose corn syrup (HFCS) – defined as more than 0.5kg per person per year – may have higher diabetes levels than those defined as having low HFCS availability.

Countries where availability was defined as high had approximately 20% higher rates of diabetes than those defined as having low availability.

While informative, this study does not prove cause and effect. For example, this study does not show that individuals with diabetes consumed higher levels of HFCS or that this consumption contributed to their diabetes.

Ecological studies such as these need to be interpreted alongside other studies investigating the association between calorie intake (including from HFCS), weight and diabetes at an individual level, so that the full picture of the relationships involved can be established.

Neither HFCS nor diabetes was measured at an individual level, so we cannot assume that the link reported at the country level would be found if the study used individual level data – for example, examining individual diet and diabetes diagnosis.

The low versus high availability of HFCS cut-offs were not justified for clinical or other reasons in the study, and this may have been an arbitrary cut-off.

The choice of where to put this cut-off for low versus high availability and the reasons for such a decision are very important, as selecting a different cut-off point could lead to vastly difference results.

The precise country level estimates of HFCS and diabetes levels are also likely to be subject to significant error that could affect the results.

However, without assessing each information source in detail we cannot say how important this limitation may be, but it is important to be aware of it.

This type of study design is a useful starting point to identify country level trends, but further research is needed at an individual level to explore whether HFCS consumption is linked to diabetes in any way.

Finally, the fact that HFCS availability was relatively low in the UK would suggest that this is less of a public health issue in the UK than in the USA.
However, consumption of HFCS may vary considerably person to person so the Great British biscuit lover should be aware that eating high levels of sugar (HFCS or otherwise) – or indeed fat – is known to have detrimental effects to health.

Green tea reduces bowel cancer risk

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‘Green tea may lower the risk of colon, stomach and throat cancers in women’, says the Daily Mail, perhaps causing readers to rush to put the kettle on.

The Daily Mail reports on a large, long-term observational study of people’s tea drinking habits and their risk of developing cancers of the digestive system.

However, the findings of the study require careful interpretation. The only statistically significant association found was a 14% decreased risk in any type of digestive system cancer (such as bowel cancer or stomach cancer) in people who regularly drank any type of tea compared to people who were not regular tea drinkers.

The media can be excused for its focus on green tea, as 88% of the tea drinkers in this Chinese cohort were drinking green tea. However, when the researchers restricted their analysis to the women who only drank green tea, the association between tea and cancer became only borderline statistically significant – at the upper end of the margin of error, the preventative effect could be zero.

Also, despite the headlines, no significant association was found between any tea consumption – or green tea alone – and risk of any specific digestive system cancer.

Overall, this is an interesting and well conducted study, but it does not provide conclusive evidence that drinking green tea – or any other tea – will influence your risk of cancers of the digestive system.

Where did the story come from?

The study was carried out by researchers from Vanderbilt University School of Medicine, Nashville, the National Cancer Institute, Rockville, US, and the Shanghai Cancer Institute, China. Funding was provided by the National Cancer Institute.

The study was published in the peer-reviewed open-access, American Journal of Clinical Nutrition.

The media reports of this study were fair, and while there is some slightly misleading interpretation about a ‘green tea effect’, this does not really affect the overall reporting of the conclusions.

What kind of research was this?

The researchers highlighted the fact that animal and laboratory studies have suggested that certain antioxidants found in tea may have a protective role against cancers of the digestive system. Antioxidants are molecules that are thought to protect against cell damage. However, previous observational studies in humans have given inconclusive results.

The current prospective cohort study aimed to see whether tea consumption affected the risk of digestive system cancers in middle-aged Chinese women.

The researchers made the choice to study Chinese women, as previous studies have focused on Japanese people, who have different drinking habits.

They decided to investigate women taking part in the Shanghai Women’s Health Study (SWHS) because the women in this cohort reported low levels of smoking and alcohol consumption. These other behavioural factors could have the potential to confound the relationship (for example, the amount of tea consumed could have a relationship to how much a person smokes tobacco and drinks alcohol – and both are known risk factors for cancers of the digestive system).

However, despite the researchers trying to reduce the possibility of confounding from these factors, there is still the possibility of confounding from other lifestyle or environmental factors which may influence tea drinking behaviour and cancer risk.

What did the research involve?

Between December 1996 and May 2000 the SWHS study recruited 74,941 women aged 40-70 years from seven urban areas in Shanghai, China.

At enrolment they were interviewed and completed a self-report questionnaire collecting information including:

  • body measurements
  • physical activity
  • alcohol
  • smoking
  • diet (including tea consumption)
  • menstrual and reproductive history
  • medical history
  • occupational history
  • information from each participant’s spouse (such as medical history and smoking and alcohol habits)

Diet and physical activity were assessed through previously well-established questionnaires for these types of factors.

The researchers excluded participants who had ever smoked or who drank alcohol regularly.

They also excluded those with missing data on the variables of interest, reported drinking implausibly high amounts of tea (more than 700 grams a month – the average tea consumption in the UK is around 150 grams a month), or reported any history of cancer.

Questions on tea included:

  • the age they started drinking tea (or stopped if they no longer drank tea)
  • if they drank tea regularly (defined as three or more times per week, continuously for longer than six months)
  • the type of tea they drank and the amount of dry leaves used

Updated information on tea consumption was collected at follow-up at an average 2.6 years. Further two to three yearly surveys gained information on cancer diagnoses, which were confirmed via home visits and reviews of medical records. The cancer registry was also reviewed to confirm the site of cancer. Participation rates were above 95% at all follow-up points.

When conducting statistical analyses between tea consumption and risk of cancers of the digestive system the researchers took into account:

  • education
  • occupation
  • marital status
  • body mass index (BMI)
  • waist-hip ratio
  • physical activity
  • meat, fruit and vegetable intake
  • spousal smoking habits
  • family history of cancers of the digestive system or diabetes

Tea drinkers were compared to women who never drank tea regularly (meaning they did not meet the above criteria for regular drinking).

Regular tea drinkers were further split into the following catogories:

  • tea drinking for less than 15 years and less than 100 grams a month
  • less than 15 years and 100 grams or more a month
  • 15 years or more and less than 100 grams a month
  • 15 years or more and 100 grams or more a month

What were the basic results?

A total of 69,310 women were followed for an average 11 years, during which 1,255 digestive system cancers occurred, including cancers of the stomach, oesophagus, colorectum (large bowel), liver, pancreas and gallbladder, or bile duct.

Just under a third of the women (28%) reported being regular tea drinkers. Most tea drinkers (88%)  reported drinking green tea only or green tea in combination with black or scented tea (5%). Only a small proportion of women only drank other tea types:

  • 3.54% only drank scented tea – that is, jasmine tea (white or green tea plus jasmine flowers) or green, black, or oolong tea in combination with herbs, other flowers, or fruit
  • 1.1% drank black tea alone or in combination with scented tea
  • 0.7% drank only oolong tea
  • 1.4% drank other types of tea

On average, people drank 100g of tea per month, and the average duration of tea consumption was 15 years.

The researchers’ main finding was that, compared with women who never drank tea regularly, regular intake of any type of tea was associated with a 14% reduced risk of any cancer of the digestive system (hazard ratio 0.86, 95% confidence interval [CI] 0.74 and 0.98). There were also significant trends for the digestive system cancer risk to decrease as the amount of tea consumed and the duration of tea drinking increased.

However, when looking at the individual cancers, tea drinking had no significant effect on the risk of any specific digestive system cancer.

Also, despite the fact that most tea consumed was green, when they restricted their analyses to only those women who reported drinking green tea (either alone or in combination with other teas) the reduced risk of any type of digestive system cancers became only of borderline significance (hazard ratio 0.86, 95% CI 0.75 and 1.00).

Again, no significant association was found between only green tea consumption and any specific type of cancer (though in all analyses there was the same general direction of the effect – that is towards reducing risk).

How did the researchers interpret the results?

The media interpretation of this story appears to come from the researchers’ main conclusion: ‘In this large prospective cohort study, tea consumption was associated with reduced risk of colorectal and stomach/oesophageal cancers in Chinese women’.

However, though there was a general trend towards reduced risk for individual cancers, none of the analyses for these specific cancer types were statistically significant.

Conclusion

This study has strengths:

  • it included a large sample of almost 70,000 Chinese women
  • it followed them up for 11 years
  • it reliably collected data on lifestyle factors and cancer outcomes
  • it had high participation rates at all follow-up points

Importantly, the researchers have also adjusted their analyses for sociodemographic, lifestyle and medical factors which could have a potential confounding influence on cancer risk.

Further to this, the study benefits from studying only a non-smoking, non-drinking population of women: tea drinking may be related to smoking and alcohol intake, which are well established risk factors for digestive system cancers. As such, smoking and alcohol could be confounding any association between tea drinking and cancer, so it was useful that these two factors not been ruled out from the start.

Therefore, this is a well conducted study, but when interpreting the findings it is important to consider the following points:

  • The only significant association found was a 14% decreased risk in any type of digestive system cancer with regular drinking (defined as three or more times per week, continuously for longer than six months) of any type of tea compared to non-regular drinking. The media focus on green tea is understandable as 88% of the tea drinkers in this cohort were drinking green tea. However, when the researchers restricted their analysis to the women who only drank green tea, the association between green tea and cancer became only borderline statistically significant.
  • Also, despite media headlines and a general trend towards reduced risk, no significant association was found between any tea consumption – or green tea alone – and risk of any specific digestive system cancer.
  • This study only included Chinese women, and therefore the results may not be applicable to men or women of different cultures, who may have very different tea drinking habits and other lifestyle habits or environmental exposures that may alter their risk of digestive system cancers.
  • Related to this, it is not known whether the green tea described here would be exactly the same as the green tea sold in the UK, or whether the 88% of women in this cohort could just be describing that their tea leaves were green in colour, as opposed to black.

Overall, this is an interesting and well conducted study, but it does not provide conclusive evidence that drinking green tea – or any other tea – will influence your risk of digestive system cancers.

From the current evidence, in general the most effective methods that may reduce your risk of digestive system cancers, are to eat a healthy diet, quit smoking if you smoke, limit alcohol intake, take regular exercise and try to maintain a healthy weight.

Do tomatoes prevent strokes?

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“Tomatoes are ‘stroke preventers’,” BBC News has claimed.

The news is based on a study looking at the levels of various chemicals called carotenoids in men’s blood and their long-term risk of stroke.

Carotenoids are naturally occurring chemicals which give fruit and vegetables their colour. They can act as antioxidants. Antioxidants are believed to help protect against cell damage from molecules known as “free radicals” and “singlet molecular oxygen”. Antioxidants are thought to work by reacting with an unstable molecule and bringing it under control.

tomato

Some have suggested that antioxidants may have a protective effect against stroke by reducing damage to blood vessels.

In this study, the researchers found that men with the highest levels of a chemical called lycopene (known to be an antioxidant) in their blood had a 55% reduced risk of stroke compared with those who had the lowest levels. Lycopene is the chemical that gives tomatoes their distinctive red colour.

An important limitation of this study is that, although it included 1,000 men, only 67 strokes occurred. This makes for a very small sample size, which decreases the reliability of the risk calculations.

Overall, this research cannot show that the levels of lycopene were directly responsible for the differences in stroke risk, and it is also unclear how lycopene could prevent strokes. However, the findings of this study support the recommendation to eat a balanced diet rich in fruit and vegetables.

Where did the story come from?

The study was carried out by researchers from the University of Eastern Finland, Lapland Central Hospital and University Hospital of Kuopio, Finland. It was funded by Lapland Central Hospital.

This study was covered accurately by the BBC. However, the researchers looked at blood levels of lycopene, which is a marker of tomato intake, but they did not directly look at tomato consumption itself, which the BBC headline seems to suggest.

That said, it is reasonable to assume that most middle-aged Finnish men would be getting their lycopene intake from tomatoes, rather than from more exotic sources such as papaya or pink guava.

The researchers were also looking more generally at all the major types of carotenoids, rather than lycopene only.

What kind of research was this?

This was a prospective cohort study. It aimed to determine the association between blood concentrations of carotenoids at the start of the study and the risk of stroke during follow-up.

Carotenoids studied by the researchers included:

  • lycopene
  • a-carotene, found in vegetables such as carrots and spinach
  • β-carotene, the substance that gives carrots their orange appearance
  • a-tocopherol, more commonly known as vitamin E
  • retinol, more commonly known as vitamin A

A prospective cohort study is the ideal study design to investigate whether carotenoids influence stroke risk.

However, this type of study cannot show direct cause and effect (causation), since there may be other factors that explain any associations seen (called confounding factors).

For example, people who eat a diet high in carotenoids may also have other healthy lifestyle habits such as not smoking. These other factors could be associated with reduced risk, rather than the carotenoids themselves.

A more ideal design, which would balance out other confounding factors, would be a randomised controlled trial which randomised people to diets high or low in carotenoid-containing fruits and vegetables.

However, as a diet low in fruit and vegetables is known to be bad for health, such a trial may not be practical or ethical to perform.

What did the research involve?

The researchers recruited into the study a representative sample of 1,031 men living in and around the city of Kuopio in Finland who were aged between 42 and 61 and had no history of stroke. At the start of the study, fasting levels of carotenoids were measured from blood samples. The researchers also measured participants’:

  • blood levels of low density lipoprotein (“bad” fat)
  • high density lipoprotein (“good” fat)
  • cholesterol and triglycerides (specific fats)
  • blood pressure
  • body mass index (BMI)

They also collected information on known risk factors for stroke, such as:

  • alcohol consumption
  • physical activity
  • diabetes
  • smoking

The researchers then followed up the men until they had a stroke or until the study came to an end. They followed the men for an average of 12.1 years. The number of strokes was determined from the FINMONICA stroke register, the Finnish national hospital discharge registry and death certificate registers.

The researchers then looked to see whether there was an association between blood levels of carotenoids at baseline and the risk of stroke, adjusting for some possible cofounders (age, examination year, BMI, blood pressure, smoking status at baseline, levels of serum low-density lipoprotein and cholesterol, diabetes and history of stroke).

What were the basic results?

During the study, 67 men had a stroke, 50 of whom had the most common type of stroke – an ischaemic stroke – which is caused by a blood clot. The men who had a stroke were older, had higher blood pressure, were more likely to have diabetes and had lower blood concentrations of lycopene.

The researchers divided blood carotenoid levels into quarters, and compared men with the highest levels with men with the lowest levels.

Men with the highest levels:

  • had a decreased risk of stroke by 55% (hazard ratio 0.45, 95% confidence interval [CI] 0.25 to 0.95)
  • had a decreased risk of ischaemic stroke by 59% (hazard ratio 0.41, 95% confidence interval 0.17 to 0.97)

Blood levels of the other carotenoids studied were not associated with stroke risk.

How did the researchers interpret the results?

The researchers concluded that: “High serum [blood] concentrations of lycopene, as a marker of intake of tomatoes and tomato-based products, decrease the risk of any stroke and ischaemic stroke in men.” They also stated that a balanced diet including fruits and vegetables “may prevent stroke”.

Conclusion

In this study, men in Finland with the highest blood levels of lycopene at the start of the study had a 55% reduced risk of stroke and a 59% reduced risk of ischaemic stroke (caused by a blood clot) over the following 12 years. However, levels of other carotenoids studied were not associated with stroke risk.

This study has the limitation that serum levels of lycopene cannot be shown to be responsible for the differences in stroke risk, as it is possible that other factors could explain the reduction in stroke risk. In particular, the researchers did not collect any information on dietary intakes. Therefore their analyses did not account for dietary factors, and also, although they adjusted for several other potential confounders that could influence the association, they did not adjust for physical activity. However, the researchers did collect information on baseline physical activity.

These things are important, as higher carotenoid levels could be associated with a healthy lifestyle, including healthy diet and regular physical activity, and it could be these things that are influencing stroke risk, and not the carotenoid themselves.

Information on serum levels of carotenoids and fats, smoking, physical activity and other factors were only measured at baseline. This is important because it is possible that these could have changed over the course of the study.

Another important limitation is that, although the study included 1,000 men, only 67 strokes occurred. When these men with stroke were further divided into four categories depending on their carotenoid level, this made very small sample sizes, which decreases the reliability of the risk calculations. The results of this study will therefore need to be confirmed in a larger group of people, and other population groups such as women or other ethnic groups.

While this study cannot prove that lycopene reduces stroke risk, it certainly lends support to the recommendation to eat a balanced diet rich in fruit and vegetables. Whether or not such a diet can reduce stroke risk, a large body of evidence shows that it can cut your risk of heart disease as well as some types of cancer.

Links to the headlines

Tomatoes are ‘stroke preventers’. BBC News, October 9 2012

Eating tomatoes may stave off a stroke: research. The Daily Telegraph, October 9 2012

Links to the science

Karppi J, Laukkanen JA, Sivenius J et al. Serum lycopene decreases the risk of stroke in men: a population-based follow-up study. Neurology. Published online October 9 2012

Brock Davis Plays with his Food

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Rice Krispyhenge

Gummy Bear Skin Rug

Broccoli House

Banana Peel Trucker

Cucumber Killer Whale.

Minneapolis designer Brock Davis does the strangest things with his food. From designing a broccoli house to a gummy bear skin rug and the fantastic rice krispyhenge, he never seems to run out of ingenious ideas. (Via thisiscollosal)

Food Photographed with A Scanning Electron Microscope by Caren Alpert

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San Francisco-based fine art and commercial photographer Caren Alpert combines her loves for photography, food, and art in these gorgeous photos taken with an electron microscope. Alpert captures the microscopic, almost other-worldly surfaces of common foods.

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