Milk

The composition and nutritional qualities of milk make it an almost complete food. While no food can meet all our needs and keep the body running efficiently on its own, milk is the food that comes closest to this ideal.

A rich variety of nutrients

Milk generally contains 3.8% fats, 3.3% protein, 5% lactose, 1% minerals and nearly 87% water. Depending on whether it is used to make cheese, ice cream or yogurt, for example, certain nutrients are favoured, such as protein for cheese, or are reduced, such as fats in milk.

Milk can meet all of a child's needs during the first months of life. Adults require the same nutrients as children or adolescents, but not in the same proportions.

Once growth and development are completed, the nutrient intake serves to maintain the body. Milk's rich variety of nutrients make it a basic food of a balanced diet.

Calcium

The calcium content of milk and dairy products is incomparable. Daily adult consumption of two to four servings of milk and dairy products provides the body with all the calcium it needs to main good bone capital. It is difficult to meet the body's calcium requirements without the contribution of milk and dairy products. Nearly 99% of the calcium contained in the body is found in the skeleton, providing it with its strength and rigidity. The remaining calcium (1%) contributes to muscle contraction, blood coagulation and nerve sensitivity.

Calcium in milk is so valuable because of two factors: the quantity contained in a serving (250 mL or 8 ounces of milk contain 307 mg of calcium) and the great ease with which it is absorbed, or in other words, its high bioavailability. Bioavailability means the capacity of a nutrient (in this case calcium) to be absorbed and used by the body.

Did you know that calcium in milk contributes to a steady heart rate and normal blood coagulation?

The following table illustrates the bioavailability of calcium in certain foods.

Food	Quantity	Calories	Calcium content (mg)	% of quantity absorbed	Quantity absorbed per serving (mg)	Servings to replace 1 serving of milk
Milk	8 oz (250 ml)	121	315	32,1	101,1	1
White beans	1 tasse (250 ml)	276	143	17	24,3	4
Broccoli	1/2 tasse (125 ml)	23	38	52,6	20	5
Cabbage	1/2 tasse (125 ml)	21	103	58,8	60,6	1 2/3
Almonds	1/2 tasse (125 ml)	441	200	21,2	42,4	2 1/3
Spinach	1/2 tasse (125 ml)	22	129	5,1	6,6	15 1/3

Adaptation from Weaver and Pilawcki, 1994. Source: Dairy Bureau of Canada

Certain factors influence the quantity of calcium absorbed by the body. They are:

The body's needs. Calcium absorption is higher when the body's needs are greater (growth, pregnancy, breastfeeding).
Vitamin D increases the quantity of calcium absorbed. Exposure to ultraviolet rays in everyday activities and milk consumption is the best ways to obtain the vitamin D the body needs. In the absence of vitamin D, the quantity of calcium absorbed is insufficient to meet the body's physiological needs.
Lactose, or milk sugar, favours calcium absorption.
Physical exercise that requires a person to support his or her own body weight, such as walking or dancing, reduces calcium loss.
Consumption of caffeine and alcohol favours calcium loss in urine.

Nutrients other than calcium

The proteins contained in milk are high quality, meaning that they contain all the essential amino acids, nutrients that our body is incapable of synthesizing. It is important to remember that proteins are the basic building blocks of all living tissue. Part of our protein requirements can be met by milk and dairy products.

Milk and dairy products are an important source of vitamins. They provide us with B complex vitamins, particularly riboflavin, and vitamin A.

Riboflavin helps the body use the energy supplied by food and facilitates efficient operation of the nervous system. One serving of milk provides 26% of our daily riboflavin requirements.

Vitamin A is essential to night vision. It helps keep the skin healthy and soft. It is added to skim and partly skim milk to compensate for the Vitamin A lost in skimming. One glass of milk provides 8% of our daily Vitamin A requirements.

Vitamin D is added to milk to facilitate calcium absorption and strengthen our bones. One glass of milk provides 44% of our daily Vitamin D requirements.