Final answer:
A deficient calcium intake typically results in no immediate change in blood calcium levels due to the body withdrawing calcium from bones to maintain homeostasis. However, prolonged calcium deficiency can lead to weakened bones and conditions like osteoporosis.
Step-by-step explanation:
If a person has a deficient dietary intake of calcium, the result will generally be no change in levels of calcium in the blood because the body will pull calcium from the bones to maintain blood calcium homeostasis. This compensatory mechanism is part of the body's effort to maintain a constant blood calcium level, which is critical for vital functions such as muscle contraction, blood coagulation, and nerve transmission. Over time, however, this can lead to a decrease in bone density, potentially resulting in conditions such as osteoporosis.
Calcium homeostasis involves several processes, including calcium absorption through the intestines, which is aided by activated vitamin D. When dietary calcium is insufficient, and if vitamin D levels are adequate, the body increases the uptake of calcium from the diet and reduces urinary excretion. Conversely, a vitamin D deficiency can lead to a decrease in absorbed calcium and subsequent depletion of calcium stores from the bones. Furthermore, parathyroid hormone (PTH) plays a key role by stimulating osteoclasts to release calcium from the bone matrix, and by enhancing calcium reabsorption in the kidneys.