Human Limits

Exploring performance and health with Michael J. Joyner, M.D.

Photo of Michael J. Joyner, M.D.

Medical Ignorance vs. Dietary Salt and Breast Cancer

Recent news reports have highlighted uncertainty about dietary sodium guidelines and also the diagnosis and treatment of breast cancer.  When the breast cancer story came out a friend of mine e-mailed and asked for help in making sense of it all.  I want to share parts of my response to her with you and also how it applies to things like the shifting dietary salt guidelines.    Here are some things about medical “knowledge” that are not widely appreciated:


  • We have the ability to detect “abnormalities” that are at the edge of our knowledge.


  • When we detect these things, what do we do…….everything, nothing, something in between?


  • There is frequently a bias in medicine to do more.  However, every intervention has risks and potential unintended consequences.  Where is the balance?  How much risk are you comfortable with?  How can Drs. explain these nuances to patients?


  • Clinical trials are great, but they are average results and the best scientific advice for thousands of people may not be the best for you.  For all trials there are responders, non-responders and sometimes even adverse responders.  This is especially true for salt and blood pressure.  At some level it is a roulette wheel, and all we can do is play the odds.


  • Progress against cancer, especially solid tumors, has been really slow.  There are lots of reasons for this including the idea that there are metastases by the time things are detected.   There are also issues related to basic tumor biology and how fast tumors grow vs. the toxicity of drugs for other tissues.  Finally, tumors have a tremendous ability to adapt and work around drugs.


  • We are trapped in cycles of relative ignorance, over simplified dogmatic responses, followed by more insight.   For example the current idea is that when we can genetically finger print individual cancers “cures” will flow from this knowledge.   A more sober interpretation might be that we will be able to pick and develop better drugs for each individual and improve the odds of a better outcome (note I did not say cure).


  • Disease advocacy groups are wonderful, but sometimes the culture of disease advocacy leads to sound bited messages for really complex things.


  • Things in a number of areas of medicine that had pretty hard core guidelines when I started medical school in the early 80s (for example how we treat heart attack and heart failure, and how we set the ventilators in the intensive care unit) have evolved or even changed 180 degrees since that time.   Outcomes are better but these sorts of sea changes are challenging for everyone.  This happens all the time.


As a result of all of these things (and more) there are lots of educated guesses in medicine.  There is also tension related to research and the need to make “constructive mistakes” to further knowledge and offering people “error free” state of the art care, with the ambiguous caveat that the state of the art changes.  At some level, the more we know the less we know.



Leave a Reply