Recently after bootcamp some of us were discussing the speed with which conflicting data is presented to us and to our patients — lo carb diet is better than lo fat – or vice versa. Vitamin A is an anti-oxidant so it must reduce health risks – no, it increases cancer. Estrogen is good for everyone at menopause, nope now it’s reserved for women with significant night sweats and sleep deprivation or other similarly disruptive symptoms. The same for calcium – everyone should take it, no it causes kidney stones an heart disease.
Why do we keep changing our minds?! One of the goals in starting this website was to provide sound scientific information to counter the never-ending slew of miracle cures and latest fad foods. Even within the medical journals now, there is confusion because of the reporting of conflicting results. And in the past, only the most well-known journals had results reported in the popular press. Now you can hear from many self-declared nutrition experts (ilke myself), touting their personal favorites.
As a medical community, it’s not for lack of knowledge or because we’re trying to drive you crazy. The changing recommendations are based on studies. However, studies about food and supplements are notoriously difficult for many reasons:
— Each person’s starting point may be different. A person who has a low level of a vitamin, for instance, might derive more benefit from taking it in pill form daily than one whose level was normal at the start. Someone who can’t stop eating carbs once they start may lose more weight if they can stay on a low carb diet; other’s may feel better and lose more weight with more carbs and less fat.
— Many studies have too few people enrolled to have the data apply to everyone. A study involving 50 people has less reproducibility in the general population than one involving 10,000, as the cardiology studies do. A small study can be done and have one conclusion, then a larger study may find a different situation.
— Food or vitamin intake is self-reported and is likely to be erroneous – our memories are not so good and we always aim to impress ourselves and others when answering questionnaires.
— A study usually looks at a particular part of the diet. There are too many variables in what other foods and supplements people might consume. So it’s difficult to ‘control’ all outside factors as you would like to do in a truly scientific experiment.
— Sometimes an association between a food and a disease is found, but this is NOT the same as proving the food is the cause of the disease. To exaggerate a point, let’s say a study shows that people who eat more mushrooms have a lower risk of heart disease; this doesn’t prove that the mushrooms saved them – it was that they were active in the fields all day picking vegetables, ate less meat and more stir-fried vegetables, slept better, etc. You get the picture. Again, too many variables.
— Vitamins aren’t necessarily absorbed or useful in the same way when taken in pill form instead of in foods where they are found naturally. Just because we’re told that foods with certain nutrients are good for us doesn’t mean that the study in which the pill form is used will show any benefit. This has been the case with fish oil, vitamin A and others.
— The studies are often short in duration and may under- or over- estimate actual benefit that would be derived over years. Longer term studies may then disprove the findings of the shorter studies.
— Sometimes a study shows that certain lab values improve in the short term, like cholesterol. But that doesn’t mean that the longer term studies will show that the lower cholesterol level actually leads to a decreased rate of heart attacks or strokes. So there might be one recommendation in favor of, and a later recommendation against the same medication.
— Sometimes a food or pharmaceutical industry group has a vested interest in a study’s outcome, so you need to look at who funded the study and where it’s published.
SO when you hear about a new study, whether related to medical treatments, nutrition, supplements, or other issues, don’t be the first to jump on the bandwagon. Think about how many people they studied, for how long, how they tried to assure that only one variable changed between the two groups they’re comparing, were they able to prove cause or just association, and ask who funded the study. These are some of the factors we as physicians try to ask about articles to avoid being tossed here and there with the changing tide. Questions?? Write to us at LadyDocs!
Next week we’ll talk more about how to stay sane in a world of too much medical information (TMMI).