There is no doubt that vegetarianism offers many health benefits. The excessive fat and animal protein that characterize our diets today is at the root of many of the diseases afflicting us, while high dosis of vitamins, minerals and fiber signal a meatless diet and give a clear example of the nutritional virtues of this way of eating.�

But vegetarian diets also have their pitfalls. Possible problems include incomplete proteins, amino acids that do not meet the body's needs and a shortage of some kinds of oligoelements. The only way to avoid them is with a perfect knowledge of the food you eat and by following a diet that, even though it is vegetarian, is as varied and rich as possible. This goal is easier to meet for vegetarians who eat fruit, vegetables, legumes, eggs and dairy products. The former provide top-quality protein, while the latter assure, among other things, major doses of a critical element for the body: calcium.

Calcium is one of the most abundant minerals in the human body. Its highest concentrations are found in the bones and teeth (up to 98%), although it is also found in the blood, muscles and hair. To form structures like bones, calcium must be joined with phosphorus and it is absorbed in the intestine. But in order for calcium to get where it is supposed to be, it needs sufficient vitamin D, the right pH level in the digestive tract and minimal exercise. Also needed to assimilate calcium are a certain level of fat and protein.

A strict vegetarian diet that excludes all dairy products is not a diet without calcium. This mineral is present in green-leaf vegetables such as cabbage, whole wheat grains, nuts and some kinds of algae, soy and other legumes. The concentrations can be higher than that of milk, yogurt or cheese, and these foods would be perfect substitutes for all of these foods were it not for the fact that the calcium in the vegetables is less readily available. This means that the body utilizes the calcium in milk better than the calcium in, say, cabbage. The reason is that dairy products, besides calcium, contain vitamin D and lactose and both improve the absorption of calcium. Furthermore, there are other appealing sources of calcium such as spinach or broccoli, which contain oxalates -substances that impede assimilation of calcium. So in order to get a minimum intake of calcium, you have to ingest a lot more spinach than milk. For each glass of milk you would need to eat 15 plates of spinach. In the same way, keep in mind that eating a lot of tomatoes or leeks, which are rich in oxalates, would hinder absorption of calcium obtained through other foods.�

Another factor to keep in mind is that excessive intake of fiber from whole grains, vegetables and fruit also impedes absorption of calcium. Therefore a strict vegetarian needs to know the accessibility of the calcium they eats, match their consumption level to the body's requirements and combine the components of their diet correctly.

Also, remember that calcium requirements vary with age. During infancy, pregnancy and after menopause, the requirement is around 1,200 mg a day. This goes down to around 800 mg a day in other stages of life.

Although dairy products are the main source of calcium, it is best to opt for foods like yogurt, which are easier to digest than milk and full of micro-organisms that are good for the intestines. It is also better to choose foods low in fat, since calcium is not found in this component of milk or its derivatives. Also, oxalates and fiber are not the only compounds that impede absorption of the mineral: an excess of salt, caffeine and alcohol block calcium's benefits.

One way to meet your daily calcium requirement is with dietary supplements. These are often consumed by women in menopause who are battling diseases like osteoporosis. It is essential to know that calcium only accumulates calcium until age 30 and that from then on, the body lives off whatever was stored up in infancy and youth.