Fr. Pat,
Vitamin B12 deficiency causes a type of megaloblastic anemia called pernicious anemia (and also specific damages to the neurological system). Kidneys are not involved in any way in the absorption and utilization of Vitamin B12. Almost all people with end-stage renal disease (ESRD) have an entirely different and unrelated type of anemia, due to low production of the hormone erythropoietin that is needed to make red blood cells by the bone marrow. People with ESRD do not have a higher rate of pernicious anemia compared with people without ESRD. Since people with ESRD do not need more Vitamin B12 than “normal” people, I do not see that otherwise healthy people with one kidney -- i.e., us LKDs -- would need to take Vitamin B12.
HOWEVER, Fr. Pat, it may be a good idea for *you* -- and I and other oldsters, whether or not LKDs -- to take supplemental Vitamin B12. Absorbing Vitamin B12 in food requires stomach acid. Some of us oldsters, and other people on certain medicines, produce little or no stomach acid and do not know it. If they do not absorb any Vitamin B12 from their diet, the body first uses up all the Vitamin B12 stored in the body, and then, with no more stored Vitamin B12 to use, Vitamin B12 deficiency starts -- with no symptoms until pernicious anemia and/or the other damage is felt or discovered. Medical tests can be done to determine if one is absorbing Vitamin B12 from one’s diet -- but it is cheaper and less hassle to simply take Vitamin B12 daily [for instance, by taking a daily vitamin pill like Centrum for people age 50+ or equivalent]. (This is not an advertisement for Centrum -- in fact, I take a generic equivalent for less than half the price of Centrum. I, like you, became an oldster long ago -- and, to boot, I am taking a medicine that often causes the stomach to produce little or no stomach acid.) The doses of all vitamins in daily vitamin pills, equivalent to Centrum for age 50+, are not so high that they cause more cancer or heart disease. (Yes, too much of certain vitamins can cause disease.) BTW, lack of stomach acid interferes with absorption of Vitamin B12 *only* from food, but does not interfere with absorption of Vitamin B12 from vitamin pills. Centrum for age 50+ and equivalent have 17 times the Recommended Daily Allowance (RDA) for Vitamin B12, and thus it can be absorbed in sufficient amounts by people with no or little stomach acid. High intake of Vitamin B12 does not cause disease.
Vitamin D: Many people with ESRD have problems with proper bone development. Those problems are not due to inadequate intake of Vitamin D or to low levels of Vitamin D among people with ESRD. Exposing skin to sunlight and dietary intake, including milk that usually is fortified with Vitamin D, is more than adequate. Thus, I do not understand why all LKDs should take Vitamin D.
HOWEVER, due to fear of sunlight-induced skin cancer plus changes in occupational work and yards-work, more people are less exposed to direct sunlight for periods of time, thus causing some to have “insufficient” Vitamin D levels, or even (progressively lower) “mild, moderate, or severe” deficiency. (People with dark skin and/or living in northern climates tend to have lower levels of Vitamin D than others.) In the case of this vitamin, the test for Vitamin D level is easy and relatively inexpensive. I think it is worth it to be tested for Vitamin D level, before us oldters or others start taking Vitamin D pills.
I hope this helps, Fr. Pat. As always, you are an inspiration for all us LKDs of any or no faith! Bill