Most people try to eat a healthy diet but many find the advice on offer confusing, especially when scientists appear to contradict themselves! For years we have been told that saturated fat was really bad for us and now we are being told that perhaps it is not that bad. To understand how scientists decide what they think is good or bad and why they sometimes seem to change their minds, we need to understand how they arrive at their conclusions.
In order to study how our diet impacts on our health over the years, scientists make use of data from large cohort studies, were thousands of volunteers are asked to complete detailed questionnaires about their eating habits. These cohorts are then encouraged to continue to supply data at regular intervals, extending over many years. In this way we can track their health trajectory and look for common factors that appear to be important in the development of diseases such as heart disease and diabetes. To some extent these studies depend on doctors asking the "right" questions in the first place. As time has gone on and our knowledge of the dietary causes of illness has grown, so we have been able to refine the studies.
For example, a study costing many millions of US dollars, called the Women's Health Initiative Dietary Modification Trial, which began in 1993 and reported in 2006, found that limiting dietary fat had no effect on heart disease, breast cancer, colorectal cancer, or body weight, as had previously been thought. The researchers recruited almost 50,000 women between the ages of 50 and 79 years. Of these, 19,541 were randomly assigned to follow a low-fat diet. Their goal was to lower their fat intake from almost 38% of calories to 20%. Another 29,294 women were randomly assigned to continue their usual diets. Both groups were given diet-related educational materials.
Studies such as these have helped to overturn earlier advice to limit saturated fat in our normal diet. Of course this does not mean that a high fat diet is good for us, as eating too much fat will make us fat, which is a known risk factor for many poor health outcomes.
The power of the cohort method to discriminate between different components of our diet depends to a large extent on the size of the study. It is for this reason that scientists have developed an approach called "meta analysis" were they are able to combine data from more than one cohort, to greatly increase the reliability of their findings. This has enabled more precise advice on the components of a healthy diet such as eating oily fish or including dark green vegetables like broccoli.
Most recently a group of international researchers analysed 19 studies involving 68,094 elderly people and found that in 92 per cent of cases LDL cholesterol - low-density lipoprotein, or "bad" cholesterol - did not increase the chance of death caused by heart disease. They also found that people with high levels of LDL cholesterol were less likely to die prematurely from other diseases, such as cancer. The results, published in the journal BMJ Open, are the latest from a series of studies that undermine accepted theories involving diet and health.
As far as fat in the diet is concerned the current consensus seems to be that the fats found in fish, nuts, seeds, and vegetable oils such as olive oil are probably good for us. The fat in diary products such as whole milk and yogurt, eggs, cheese, and butter is not as harmful as once thought. Red meat is probably okay in moderation but avoid cooking methods were the fat is burnt, as this can give rise to carcinogenic changes. Fats to avoid include processed meats and the trans fats found in margarine and used in factory produced cakes and biscuits. The positive message is that we can enjoy a wide range of different foods in moderation - that's the key.
Cafe Scientifique are informal and accessible events were important scientific topics are addressed and discussed. The audiences consist of people who are interested in science but generally never have the opportunity to discuss their views with, and ask questions of, someone "in the know". No scientific knowledge is assumed by the speakers, so anyone can participate.
The events start with a short talk from the speaker, who is usually a scientist or a writer on science, who introduces the topic. After this there is usually a short break to allow glasses to be refilled and conversations to start. This is followed by an hour or so of questions and answers and general discussion. Anyone who wants to can ask a question.
Cafes Scientifique are hosted in a range of venues. Most are in bars or cafes, but some use bookshops, theatres or community spaces. Meetings of Cafes Scientifiques are held regularly, every month and take place in the evening.
Cafes Scientific cover a wide range of issues relating to science and technology. Topics covered have included AIDS, the Big Bang, biodiversity, cancer, code-breaking, consciousness, Darwinism, ecology, evolution, extreme life, foetal experience, genetically modified organisms, global warming, infertility, nanotechnology, the Public Understanding of Science movement, sports science, superconductors and more.
If you happen to live near a university and would be interested in getting a Cafe Scientifique off the ground, then I would encourage you to contact them. All universities in the UK are expected to encourage public engagement and will be delighted to suggest a range of interesting and entertaining speakers. To locate your nearest Cafe, click here.
To listen to Ann Grand, an Associate Lecturer with the Science Communication Unit of the University of the West of England, talking about the Cafe Scientific movement, click on the video below.
Michael McSorleyMichael writes about his recent visit to the Algarve. As always, he makes you want to see the places he is talking about for yourself. His description of a triple pancake smothered in cream and chocolate sauce sounds tempting, though perhaps not the healthiest option! Click here to read the article.
Regular readers will know that Jeanette has been going through the long and difficult process of "down sizing". This month Jeanette reflects on the "seasons" of life, with their inevitable changes. Change though can be both challenge and opportunity. Click here to read Jeanette's article.
Food for thought
"The first half of life is about compulsion; the second half is about choice."
Shoshana Zuboff - A New New Adulthood.
Shoshana Zuboff is a Professor at Harvard Business School, where she led a programme called School for the Second Half of Life. To read Professor Zuboff's thought provoking short essay, click here.
Reflections is intended to showcase short pieces of poetry or prose that reflect on our life experience. This month features another poem by my late friend and colleague, Philip Clarke.
To read "Country Station in the Rain", by Philip Clarke, click here.