New study reveals that beta cells-responsible for making insulin in the human body do not replicate after the age of 30. Researchers found that the number of beta cells remains static post age 30, by using radioactive carbon 14 produced by ground nuclear testing in the 1950s and '60s.

    To assess the adult human beta cell turnover and longevity , Bruce Buchholz, scientist at the Lawrence Livermore National Laboratory, and collaborators from the National Institutes of Health used two methods. By using LLNL's Center for Accelerator Mass Spectrometry, Buchholz measured the amount of carbon 14 in DNA in beta cells and discovered that after age 30, the body does not create any new beta cells, thus decreasing the capacity to produce insulin as a person ages. Because DNA is stable after a cell has gone through its last cell division, the concentration of carbon 14 in DNA serves as a date mark for when a cell was born and can be used to date cells in humans.

    "We found that beta cells turn over up to about age 30, and there they remain throughout life. The findings have implications for both Type 1 and Type 2 diabetes," said Buchholz. Older people whose inability to secrete sufficient insulin to regulate blood or increased insulin demand in obese people are the common causes of T2 diabetes. "It could be due to loss of beta cells with age. The body doesn't make new ones in adulthood and there might not be enough cells to control blood sugar," he said.