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Medical Myths

The do's and don'ts we've all grown up with. Fact or fiction?   2011-06-12

Wait thirty minutes after eating before swimming

Who can forget the childhood frustration of going to the beach, having a lovely picnic and then being told that you had to wait thirty minutes before dashing into the inviting sea? Time had to be wasted by going for a walk along the beach or playing with a ball until the magical time came. Such was the fear installed in some of us that we believed that if we so much as immersed a big toe into water before then, we would surely drown. So what is the basis of this lore – is it a complete old wives’ tale or is there some truth behind it?

The thinking behind it is that digesting food requires increased circulation to the digestive system, thereby reducing the blood supply and consequently oxygen and nutrients to the muscles needed for swimming. This results in cramps, which if sufficiently severe, causes the poor unfortunate person to drown. Physiologically the reasoning is sound as digestion does take energy, but there is little evidence of this resulting in such severe cramps that renders the victim from being able to get to safety. There are no recorded deaths caused in this manner although there are anecdotal stories. Interestingly this myth is common in many cultures although the times for waiting vary (three hours is the recommended time in parts of Italy).

Perhaps the anecdotal drowning after eating involves another factor – alcohol. An Australian study in 2006 found that alcohol was detected in the blood of 30 – 70% of people who had drowned whilst engaged in aquatic recreations.

In short, eating followed by swimming is relatively safe, but a meal accompanied by an alcoholic drink does carry a greater risk.

Chocolate and fried foods give you acne

This ‘truth’ is instilled in us in our adolescence at a time when acne affects many of us. Some say that it is a plot conjured up by parents to try and get their teenage offspring to eat healthier diets, while others claim that they only need to look at chocolate to suffer an outbreak of spots. What are the scientific causes of acne and is there a link with diet at all?

Medical opinion determines the main cause of acne to be the skin’s reaction to hormones. At puberty testosterone levels increase in both girls and boys and this makes the sebaceous glands produce too much sebum which, combined with dead cells, block the hair follicles and cause spots. These often become infected leading to inflammation and pain. As adults, more women than men suffer from acne and it is often tied to times of hormonal fluctuations such as pregnancy and the menstrual cycle. Many people notice outbreaks during times of stress which again may be due to a hormone – cortisol. Genetics also play a part – severe acne tends to run in families. Finally, acne can develop as a reaction to medication.

So does diet have any effect on acne? Generally the thinking is that while no one item of food causes acne, there is a clear link between a healthy diet and a reduction in the symptoms. In Australia there was a study where they compared a group of students who ate a diet high in processed foods with a similar group who ate a diet containing fresh food and vegetables and whole grain. The first group suffered worse episodes of acne.

In short, neither chocolate nor fried food cause acne but too much of either could exacerbate symptoms.

Eggs raise cholesterol and are bad for you

The typical British person over the age of fifty has had a lifetime of conflicting advice over their consumption of eggs. In the fifties eggs were seen as a very healthy food, reinforced by such campaigns as ‘Go to work on an egg’ by the Egg Marketing Board. However, in the sixties and seventies there was a growing awareness of the role of cholesterol in the development of cardio-vascular disease. Eggs were found to have high levels of cholesterol so the advice was to restrict the number of eggs eaten over a week. Then in 1988 Edwina Currie, health minister at that time, issued her famous statement that most of British eggs were infected by Salmonella bacteria. This led to a plummet in egg sales and consumption and her forced resignation. At this point these small spherical foods were perceived as positively toxic by many people. This bad press has remained in the British psyche despite recent claims that eggs are safe to eat.

So where are we today? There is cholesterol in the yolk of an egg but the amount has been reduced over the last decades as the diet of hens has altered. Bone meal was banned after the risk of BSE was identified in the nineties and hens are now fed on healthy grains. Also, the latest research suggests that ingesting the cholesterol in eggs does not greatly affect a person’s blood cholesterol. A study at Surrey University, in which volunteers ate two eggs a day for twelve weeks, showed they had no rise in cholesterol levels and it helped them to lose weight. As a result of such evidence in 2007 the British Heart Foundation withdrew its advice that everyone should limit themselves to three eggs a week. However, the British Egg Information Service found that just under half the people they asked felt they should still not eat them freely.

In conclusion, eggs should now be viewed as a good source of protein and other nutrients and are safe to eat.