A tall glass of cold milk, once the staple of a balanced diet, has all but disappeared from the North American table. Dairy consumption has declined significantly over the past several decades, and recent studies have shown that this may be a contributing factor in higher incidences of obesity and, more surprisingly, an increase in the aggressive symptoms of pre-menstrual syndrome (PMS).

For years, the medical community has touted the benefits of a calcium rich diet. Calcium is essential for healthy bone development, as well as nerve and muscle function and blood clotting. Ninety-nine per cent of the body's calcium is stored in our bones and teeth, but there is a small amount that must be present in blood and soft tissues if the human body is to function efficiently. When we do not get enough calcium from our diet, the body starts using the essential store of calcium in the bones, leading to structural diseases such as osteoporosis.

We now know that calcium deficiency may contribute to other serious health problems. A large, long term study at the University of Michigan has shown that women with a higher intake of calcium were less likely to suffer from PMS. The equivalent of four daily servings of low-fat milk, yogurt or fortified juice were enough to stave off most of the negative effects of the syndrome. Combined with vitamin D (most milk is fortified with 400 IU per quart), this dairy rich, low-fat regime reduced most symptoms of PMS significantly. This supports the contention that high-fat diets contribute to the depression, irritation and fatigue commonly associated with PMS.

The PMS study points to other health benefits recently attributed to calcium. For decades, researchers have attempted to explore whether there is a meaningful connection between weight and calcium intake. Several recent high-profile studies have established that a higher intake of dairy products can lead to lower levels of body fat in children and adolescents. In adults, low levels of calcium in those who are overweight appear to contribute to the conditions that lead to type 2 diabetes and cardiovascular disease.

But does this mean that you can lose weight by increasing your daily calcium intake? The dietary supplement industry would like us to think so, but the reality is more complex. Although a conclusive laboratory study at the University of Colorado Health Centre determined that calcium does aid in metabolizing fat cells and can contribute to lower overall body mass, the jury is still out on whether calcium as a supplement will help shed pounds.

These recent studies reaffirm the long-held belief that low-fat dairy should be an essential part of any diet. Calcium is key in developing and maintaining healthy bones and teeth, and also affects a woman's mental and physical health prior to and during menstruation. In children, especially, substituting low-fat dairy beverages for pop or juice will have a considerable impact on body fat, especially in the abdominal area. Furthermore, calcium does help oxidize, or break down, fat cells and contributes to a leaner body when combined with a healthy lifestyle.

All the evidence suggests that we should start pouring those tall, cold glasses of milk again.