Tuesday, 24 April 2012

Even the coolest ones can loose it

Have you ever had one of those moments when your brain just blanks out? Was it a stressful situation? Was it maybe during an exam? Or when you were supposed to remember someone’s birthday and all you could think of was ... nothing ... Just embarrassment... 

Well, don’t worry, science has proven that stress is the reason why you blank out.

This month’s Scientific American has published a review article that explains how stressful situations can trigger signals in our brain, leading to a loss of control over its ‘executive functions’.

According to the authors “when things are going well, the prefrontal cortex acts as control centre that keeps our baser emotions and impulses in check. (...) Acute, uncontrollable stress sets off a series of chemical events that weaken the influence of the prefrontal cortex while strengthening the dominance of the older parts of the brain”.

Essentially, stress is giving control over thought and emotion to the so-called ancient structures of the brain - hypothalamus and other earlier evolved structures - the areas responsible for more basic functions as eating or having fear.

“The growing understanding that acute stress can severely compromise the function of higher “executive” areas in the human brain has drawn the interest of investigators. They are now not just trying to understand what happens in your head when you freeze but also developing behavioural and pharmacological interventions to help you keep your composure”, said the authors.

And now some interesting science bit and bobs. Why does this happen?

1.     The prefrontal cortex is so sensitive to stress because it makes up a full third of the human cortex; it matures more slowly than other brain areas (only reaches full maturity after the teen years have passed); it houses the neural circuits for abstract thoughts and allow us to concentrate and stay focused on task, while storing information and making memories.

2.     Under normal circumstances the prefrontal cortex controls our emotions, desires and habits. However, under stress, the brain is flooded with chemicals such as adrenaline or dopamine, which are released by neurons, and the prefrontal cortex is shut down, passing the control over to deeper, ancient areas of the brain, such as the hypothalamus or the amygdala.

3.     Recent studies have shown that some people may be more vulnerable than others to stress because of their genetic makeup or because of a previous exposure to stress.  Under normal situations, after hormones like adrenaline or dopamine switch off circuits in the prefrontal area, enzymes chew up these neurotransmitters so that the shutdown does not persist. In this way, we can return to our baseline when stress abates. Certain forms of a gene can weaken these enzymes, making people more vulnerable to stress and, in some cases, mental illness.

4.     John Morrison of the Mount Sinai School of Medicine and his colleagues have shown that chronic stress appears to expand the intricate web of connections in our lower emotional centers, whereas the areas in our prefrontal cortex actually shrink. They have shown that prefrontal dendrites can regrow if the stress disappears, but this ability to rebound may vanish if the stress is especially severe.  This chain of molecular events makes us more vulnerable to subsequent stress and most likely contributes to depression, addiction and anxiety disorders, including post-traumatic stress.

5.     Gender appears to be a factor in determining how we react to stress. In women, the hormone estrogen may amplify sensitivity. It has actually been proven that life stress poses a greater risk for depression in women than men and is more likely to reduce abstinence from certain addictive behaviors, such as smoking, for women as compared with men.

Why the brain has built-in mechanisms to weaken its highest cognitive functions, making it “dumber” at key life-decision moments, is still a very intriguing question. Researchers are investing greatly to bring insight in to this matter. In the meantime, the next time you are taking a test or speaking in public and your mind goes blank, say to yourself:  “This is just my brain loosing its grip, hold on, just calm down!”. It maybe not give you the correct answer, but it might bring you a comforting smile. 

Let's give this a thought, shall we?

Saturday, 7 April 2012

A sweet treat for Easter!

Does eating chocolate regularly make you thinner? Not really but don’t loose all your hope because…

Scientists from the University of California believe that there is a link between regular chocolate consumption and a lower body mass index (BMI*).

In a recent study published in the journal Archives of Internal Medicine (March 26th), Dr. Beatrice Golomb and colleagues analysed the diet, exercise and mood levels of about 1000 healthy US individuals and found that those who ate chocolate a few times a week were, on average, slimmer than those who ate it occasionally.

This link remained even when other factors were taken into account, such as the calorie intake (frequent chocolate consumption was actually linked to more overall calories), the frequency of exercise or the mood levels.

According to the authors, it is the how often you eat chocolate that is important rather than how much you eat (they found no link between the quantity of chocolate consumed and the BMI).

Previous studies have shown that chocolate consumption has other metabolic benefits, such as insulin sensitivity, blood pressure and cholesterol levels. To Dr. Golomb and her team, this study “now extends the favourable associations of chocolate to metabolic factors”.

“Chocolate products are often rich in sugar and fat, contributing to assumptions that chocolate boots BMI”, says the team in this report. Nonetheless, one possible explanation for these findings is that the antioxidants present in chocolate (called catechins) contribute to lean muscle mass and reduce weight, as shown previously in studies in rodents. The team suggests that a clinical trial in humans is now needed to see if this is indeed the case.

Study details:

1) The study analysed data from 1018 healthy men and women aged 20 to 85 years old (average 57). 972 patients had their BMI calculated (average 28) and 975 answered the food frequency questionnaire.

2) Data was collected regarding chocolate consumption, calorie intake, saturated fat intake, fruit and vegetables consumption (used as controls), exercise and mood levels.

3) Results have shown that on average the individuals ate chocolate 2 times/week and exercised 3.6 times/week. Chocolate consumption frequency was linked to greater calorie and saturated fat intake and higher mood scales. It was not linked to greater activity but to lower BMI.

In conclusion, before you reach for a chocolate bar next time, think that it is, to a great extent, your diet composition that will influence your BMI, rather than solely the quantity of what you eat.
But, hey, it is Easter, so give yourself a treat (preferably dark chocolate that has antioxidants that fight free radicals ;0) )!!!

Let's give this a thought, shall we?

* BMI is a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems. It is calculated by dividing one’s weight by the square value of one’s height. Normal values range from 18.5 to 24.9. Bellow that those values a person is considered underweight. Between 25 and 29.9 a person is overweight and above 30 a person is obese. 

Sunday, 1 April 2012

Muddy Kids

To all overprotective parents: it is official, early exposure to germs is beneficial for your kids. So let them go outside and play in the mud!!!!

In a study published last week in the Science journal (on the 22nd of March), researchers have shown in mice that exposure to microbes during childhood protect children from developing asthma and other diseases such as inflammatory bowel disease.

Immunologists think that children’s susceptibility to allergies and other autoimmune disorders may be due to the lack of exposure to germs. They consider an early exposure to bacteria and microbes as an important feature for the healthy development of youngsters’ immune system, which in turn shields them against asthma and other allergies in later life. This theory is called the ‘Hygiene Hypothesis’ and it has now gotten stronger with last week’s findings.

Dr. Richard Blumberg, co-author of the study says, "We have co-evolved with microbes for millions of years. There is a very beneficial role for microbes in health. What our study now shows is the critical importance of those microbes in the earliest periods of life."

Details about the study:

1)     For this study the scientists developed two groups of mice – one germ-free raised under sterile conditions and another one raised under normal laboratory conditions. They found that the animals exposed to germs had a stronger disease fighting immune system. The animals raised in sterile conditions were sicker and had inflammation in their lungs and colon (similar to asthma and bowel problems in humans). The researchers found that this was due to an increase of activity of a special immune cell type called invariant natural killer T cell (iNKT).

2)     Animals exposed to germs in the first weeks of their lives were less vulnerable to infections. Adults didn’t show these beneficial effects. Lack of exposure in early life could not be compensated later on.

3)     The researchers have found that the levels of a protein called CXCL16 were higher in the colon and lung tissues of the sterile mice than in the normal mice and that by blocking that protein they could reduce the number of iNKT and the amount of inflammation in those tissues.

Even thought this study has been made in mice and no humans can ever be that germ-free, it is still extremely important as it opens up a lot of questions about how long this early-exposure window lasts and which microbes are involved. Also, it brings light into a possible mechanism involving the protein CXCL16 and the activity of iNKT, helping immunologist to understand and treat asthma and other autoimmune diseases. 

However, before I finish, I would like to make a quick remark:
When letting your kids going out there and ‘eating of dirt and playing in the mud’, you will always have to be a little bit cautious. If you live in the city, your playgrounds may contain high levels of lead and even if you live in a rural area, you might live near fields that have been treated with soil amendments containing toxic pollutants and antibiotic resistant pathogens. So be cautions, ok? I’m not telling you to just let them loose.

Let’s give this a thought, shall we?

(and by the way, this is NOT an April Fools' prank :0) )