There are few, if any, absolutes in medicine.
For example, the medical establishment spent years telling people that low-fat diets would lower their risk of dying, particularly by lowering high cholesterol and decreasing the risk of cardiovascular disease. Accordingly, many physicians told their patients to stop eating eggs as a means of targeting blood cholesterol levels.
In recent years, however, this dogma was challenged as observational studies did not show a clear association between cholesterol intake via the diet and the risk of cardiovascular disease, leading some of us to adjust our recommendations regarding dietary cholesterol accordingly and say that maybe, in some situations and with situation-dependent moderation, eggs are just fine. Instead, we say, you have to monitor your ratio of monounsaturated, polyunsaturated, and saturated fat intake and adjust those as needed.
You can see this reversal in other areas, as well, such as former guidelines declaring that everyone definitively needed eight to nine hours of sleep at night, while it may in fact be that too little sleep, such as five hours, or too much, such as 10 hours, are more problematic in terms of increasing risk for cardiovascular disease and metabolic syndrome. Instead, something like seven hours of rest may be just fine as long as you wake feeling rested and can make it through the day without feeling too sleepy.
This occasional propensity of medical and public health professions apparently to suddenly reverse course worries some of my patients, and they've expressed those concerns to me. These concerns take on a particular emphasis after a year in which the recommendations regarding the Covid-19 pandemic have at times shifted and swayed like a weather vane in a tornado.
Do these reversals imply that physicians and public health scientists are inherently untrustworthy? Do they suggest a certain level of incompetence? It can be hard to trust someone when you're worried about questions like these.
Obviously, one might suspect a certain level of bias in my answer since I'm a physician myself. From my perspective, though, these changing answers don't represent a wishy-washy approach to patient care, but instead the difficult nature of studying these types of topics. Nutrition, sleep, and public health crises are situations driven by a huge number of variables, and pinning down any one intervention (intake of eggs in a patient with high cholesterol, for example) and separating it from everything else around it (do patients who eat eggs often also eat sausage or bacon?) can be very, very difficult. We use population-based observational studies to try and figure out these answers, but they are only as good as the questions we ask. As we learn to ask better questions (say, by learning more about the different types of fats and their ratios in the diet), we get better answers.
And that's really the crux of the issue. It's not that we get some answers wrong, or at least not only that, but that we keep re-examining, keep exploring, keep digging and digging to make sure that the answers we have are correct. The best physicians and scientists take nothing for granted but are always coming back to make sure the hypotheses fit the known facts and, we hope, are not afraid to reverse course when new information comes to light.
If you ever find yourself wondering why your doctor's advice about eggs, or social distancing during a pandemic, or sleep recommendations change now and then, perhaps it's not a sign that you have a flaky doctor, but instead that you have a dedicated one -- someone who keeps working to find the right answer so they can keep you as healthy as possible.
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