Calcium absorption occurs throughout the entire human intestine and refers to the transport of the calcium we receive from food, across the gut lining, and into the blood.
Various different hormones produced by specific glands in the neck, work together to control the amount of calcium absorbed from the gut, increasing absorption when levels in the blood are low and reducing absorption when levels in the blood are high.
One of these hormones is known as Vitamin D. Vitamin D is not readily available from many foods in the diet and is usually produced within the skin after exposure to sunlight. People who do not receive adequate exposure to sunlight throughout the year may require supplements.
To ensure adequate absorption of calcium from the gut into the blood, it is important to consume good amounts of calcium.
Many foods contain calcium however; the amount of calcium that is actually released and absorbed (bioavailability) is variable depending on the food.
Consumption of certain foods together with calcium providing foods can inhibit the absorption of calcium. For example foods such as cereals and vegetables contain compounds known as phytates, oxalates and urates which bind to calcium in the gut and prevent it from being absorbed into the blood.
Therefore consumption of calcium providing foods such as milk and dairy with cereals or vegetables can actually lead to less calcium absorption, than consumption of milk/dairy alone.
The calcium in milk is much more readily available as milk contains no inhibitory substances but rather contains lactose and protein which promote absorption.