The study tested both calcium and caffeine. Caffeine had a significant effect at a dose of about 300mg for a human. Calcium had a biphasic effect - lower dose of calcium increased PTH, while a higher dose lowered it. The high dose calcium was equivalent to a human dose of about 1,500mg - 2,000mg calcium, which is within the ranges Peat recommends.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4207951/
"...Possible effects of caffeine on PTH secretion were determined by batch incubation studies of human parathyroid adenoma cells. Three physiologically relevant concentrations of caffeine were evaluated: 1, 10, and 50 μm. Caffeine treatment was applied for periods of 30 minutes in each plate. The results are summarized in Figure 1. Treatment with 50 μm caffeine led to a significant inhibition by 10.4% (25th, 75th percentiles: 7.6, 21) of PTH secretion compared with control (P < .05). For comparison, 0.5 mm Ca2+ caused a 12.4% (0.2, 47.8) increase, whereas 1.8 mm Ca2+ led to a 30.5% (9.8, 41.5) decrease of PTH secretion."
Finally, since caffeine is an often used supplement in Peat-world, and many studies on it are in vitro, here is a human study showing that 250mg caffeien achieved 40micoMol concentration in adult humans. This means that to get an identical effect of caffeine as the uncoupler DNP, a person would need about 6 * 250mg caffeine.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372487/
"...For instance, a mean blood caffeine concentration of ∼ 22 µM was reported in pregnant women at 36 weeks of gestation [44], while a plasma concentration of 40 µM caffeine and 20 µM paraxanthine was observed in humans after ingestion of 250 mg of caffeine [45]. Recently, one study showed that plasma levels of caffeine were between 1–50 µM in umbilical cords of preterm newborns [46]."
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4207951/
"...Possible effects of caffeine on PTH secretion were determined by batch incubation studies of human parathyroid adenoma cells. Three physiologically relevant concentrations of caffeine were evaluated: 1, 10, and 50 μm. Caffeine treatment was applied for periods of 30 minutes in each plate. The results are summarized in Figure 1. Treatment with 50 μm caffeine led to a significant inhibition by 10.4% (25th, 75th percentiles: 7.6, 21) of PTH secretion compared with control (P < .05). For comparison, 0.5 mm Ca2+ caused a 12.4% (0.2, 47.8) increase, whereas 1.8 mm Ca2+ led to a 30.5% (9.8, 41.5) decrease of PTH secretion."
Finally, since caffeine is an often used supplement in Peat-world, and many studies on it are in vitro, here is a human study showing that 250mg caffeien achieved 40micoMol concentration in adult humans. This means that to get an identical effect of caffeine as the uncoupler DNP, a person would need about 6 * 250mg caffeine.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3372487/
"...For instance, a mean blood caffeine concentration of ∼ 22 µM was reported in pregnant women at 36 weeks of gestation [44], while a plasma concentration of 40 µM caffeine and 20 µM paraxanthine was observed in humans after ingestion of 250 mg of caffeine [45]. Recently, one study showed that plasma levels of caffeine were between 1–50 µM in umbilical cords of preterm newborns [46]."