Several factors influence how calcium is absorbed from the digestive tract into the body’s circulation. The higher the amount of calcium consumed in a single meal, the less efficient calcium absorption is likely to be. For this reason, calcium intake is better spread throughout the course of the day rather than ingested in a single sitting.

A person’s age can also have an impact on calcium absorption. Net calcium absorption may be as high as 60 percent in infants and young children, and as low as 15 percent to 20 percent or less in adulthood. For this reason, recommendations for dietary intake of calcium are higher for adults ages 51 and older.

Vitamins and other substances also can affect calcium absorption. Vitamin D is important for calcium absorption. Substances such as phytic acid (found in whole grain bread, beans, seeds, nuts, grains and soy) and oxalic acid (found in spinach, collard greens, sweet potatoes, rhubarb and beans) may bind to calcium and prevent full absorption. For example, milk contains more readily absorbable calcium than spinach, and it would take 8 cups of cooked spinach to equal the calcium in one 8-ounce cup of milk.

Calcium is also excreted from the body through shed skin, nails and hair, urine, feces and sweat. In some people, an increased presence of dietary sodium, protein and potassium increases calcium excretion. Caffeine can also cause a minor increase in calcium excretion.

Certain steps can be taken to boost a person’s calcium intake. These steps include:

• Add low-fat or fat-free milk to coffee. Or, drink low-fat latte or cappuccino.
  
  
• Choose calcium-fortified cereals, juices and soy beverages.
  
  
• Drink low-fat or fat-free milk instead of soda.
  
  
• Make fruit smoothies with low-fat or fat-free yogurt.
  
  
• Snack on calcium-rich treats such as low-fat or fat-free frozen yogurt, ice milk, cheese and pudding.
  
  
• Eat canned fish with edible bones (e.g., salmon, sardines).
  
  
• Sprinkle grated low-fat or fat-free cheese into salads and soups and on pasta.
  
  
• Substitute low-fat or fat-free milk instead of water when making pancakes, mashed potatoes, pudding and instant, hot breakfast cereals.
  
  
• Try goat’s milk. Goat's milk and cow's milk contain about the same amount of calcium.
  
  
• Use diced calcium-set tofu in stir-fried vegetables.
  
  
• Add low fat powdered milk to soups and drinks.