Calcium in diets
Calcium is the most abundant mineral in the human body. Over 99 percent of total body calcium is found as calcium hydroxyapatite in bones and teeth.
It is an essential nutrient required for important biological functions including nerve conduction, muscle contraction, cell adhesives, mitosis, blood coagulation, heart beat regulation, stimulation of hormone secretion and building and maintaining healthy bones and teeth and structural support for the skeleton.
In the past, early humans obtained calcium though the consumption of a wide variety of plant species. Cereal grains are the fruit of the plant, which is the part of them that accumulates the least amount of calcium.
Since the agriculture revolution, the maim food source of calcium in the diet of most population is dairy products. It is classically associated with diary products: milk, yoghurt and cheese are rich sources of calcium, providing the major share of calcium from foods in the general diet in the United States and Canada.
Other good sources of calcium include sardines, oysters, clams, tofu, molasses, almonds, calcium-fortified foods, and dark green leafy vegetables such as broccoli kale, collards and mustard and turnip greens. Other vegetables such as spinach, rhubarb, card and beets greens contain respectable amounts of calcium.
Several factors that may decrease the absorption of calcium include the presence of oxalate, phytate, fibers in foods.
A diet that is high in protein, fat and/or sugar affects calcium uptake. The average American diets of meats, refined grains, and soft drinks leads to increase excretion of calcium. Diets high in animals protein necessitate higher intakes of calcium as well, because such diets promote calcium excretion.
Calcium is absorbed by active transport and passive diffusion across the intestinal mucosa. Passive diffusion becomes more important at high calcium intakes.
In general, balanced diets provide from 800 to 1,200 of calcium per day. The minimum daily requirements of calcium is 400 to 500 mg and an intake below this amount may cause a negative calcium balance.
Calcium in diets
