At the large scale better kidney function is related to a lower creatinine level. Creatinine is one of the ‘toxins’ the kidney filters from the blood; it is a breakdown product of creatine, a muscle derived chemical indicating turnover of the muscle. It is generally taught that the greater the muscle mass the higher, within normal ranges, this number will be.
Creatinine is passively filtered from the blood, somewhat actively pumped out and to a smaller degree pumped back into the blood in the kidneys. There is some controversy about the ratios of these functions but little controversy about the value of the kidney clearing this substance from the blood.
Using the protocols outlined in other postings this number improves in the majority of my patients even as their lean body mass increases. Diabetes makes this number worse, that is higher, as does high blood pressure and other causes of small vessel disease.
Here is another important issue: small vessel disease versus large vessel disease. In diabetes and high blood pressure for example we tend to see small vessel disease: i.e. the blood vessels of the eyes, brain, kidneys, finger and toe tips gets worse. These end vessels are small as they are the turn around point of the arteries to the veins and thus return to the heart and lungs. From the trunk to the leaves of a tree the sap flows in smaller and smaller gauge tubules; same with humans. This is why diabetics tend to have damage to the eyes, kidneys, finger and toe tips; these are the areas that fail.
Overall large vessel disease shows up in the carotids and the coronary arteries; leg arteries too.
For our purposes here, following kidney function can be a useful surrogate for small vessel disease. If the kidneys get better, creatinine gets better, and this is an indication of improving small vessel health: brain, eyes, finger tips and toes. After all the kidneys, whatever else they are, are an elaborate enfolding of very, very small blood vessels.
Here is the graph of a man from age 52 to 60, he does not have diabetes and has had no change in his blood pressure medications- stable for years before the numbers in the graph; he has gained many pounds of lean muscle mass over the course of the graphed timeline and as you can see his creatinine level has improved steadily though he eats a diet much higher in protein than in the past and trains at a high level of exertion with resulting exercise induced increase in his blood pressure. For the record, for those who care about such things the same lab technique was employed across all of these results; this can be an issue.
Keep in mind that biology does not deal in straight lines; biology ‘draws straight with crooked lines.’ By this I mean you have to watch trends over long time periods to filter out normal variance of function and behavior. It took 8 years but this man now has normal kidney function; the usual course of time should have had his kidney function getting worse.
Now, you might say, my kidneys are fine thank you very much so why should I care? Go back over your old blood tests and you will find this little number lurking there; unremarked because it was ‘normal.’ But is it getting higher? What is the trend from your creatinine at 20 vs 30 vs 40? Going up? Then get to work and make this neat little surrogate for health better. Get your baseline, change your behavior and track the changes. For this and dozens of other early warning markers there is no other way to defend your well-being. By the time your doc is talking to you about this marker much has been lost, sometimes never to be regained. Act now while the system is still plastic enough to respond.
Have Fun, Smile and God Speed,