Evidence of specific age-related declines in our biochemistry that are put off, avoided, reduced or otherwise slowed by the practice of calorie restriction - known as "dietary restriction" in some scientific circles - should no longer be a surprise. Here's another piece of welcome research for those who like to cut out the empty calories:
Diminished stem cell functions with age may be a major cause of anemias and other defects. Unfortunately, treatments that increase stem cell function can also increase the incidence of cancers. Lifelong dietary restriction (DR) is known to decrease spontaneous cancers and lengthen lifespan. This study examines the effect of DR on the ability of bone marrow cells to repopulate irradiated recipients and produce erythrocytes and lymphocytes.
Hematopoietic stem cell (HSC) numbers are highly variable in aged BALB mice, however, the observed loss of marrow function is due to a major loss in repopulating ability per HSC. DR greatly ameliorates this loss of function with age. In contrast, function per HSC in B6 mice is neither affected by age nor by DR.
Thus, DR increases or maintains increased marrow repopulating ability with age in the 3 different genotypes tested, but effects on function per HSC depend on genotype. The fact that DR increases or maintains stem cell function with age, while decreasing cancer, has far-reaching health implications.
Good news all round.
You'll recall that age-related decline in the capacity of stem cells to repair and generate new tissue likely has as much to do with the aging of their cellular support environment as any inherent change in the cell population. Are the stem cells becoming damaged, are they ramping down as a part of an evolutionary program to avoid cancer, or is the cellular environment controlling it all? A great deal of work is presently focused on answering these questions, and then doing something about it.