First thing is an acid called Oxalic acid. This is a naturally-occurring substance found in some foods that binds with important nutrients, making them inaccessible to the body. Oxalic acid may combine with calcium, iron, sodium, magnesium, or potassium to form less soluble salts known as oxalates. Oxalates also occur naturally in plants.

Foods generally found include: apples asparagus, chocolate, cocoa, coffee, most berries (especially strawberries and cranberries), most nuts (especially peanuts), beans, beets, beet greens, bell peppers, black pepper, parsley, rhubarb, spinach, swiss chard, summer squash, sweet potatoes, and tea.

Plant foods with high concentrations of oxalic acid (over 200 ppm) include (but are not limited to): lamb's-quarter, buckwheat, star fruit, black pepper, purslane, poppy seeds, rhubarb, tea, spinach, plantains, cocoa and chocolate, ginger, almonds, cashews, garden sorrel, mustard greens, bell peppers, sweet potatoes, soybeans, tomatillos, beets and beet greens, oats, pumpkin, cabbage, green beans, mango, eggplant, tomatoes, lentils, and parsnips.

The good news is that cooking destroys the oxalic acid therefore asparagus, beets, beet greens, chard, cranberries, green peppers, rhubarb, and spinach are all best eaten cooked.

Although spinach has a lot of calcium, it also contains a substance -- oxalic acid -- that binds up its calcium and prevents absorption of all but about 5 percent of it. However, the oxalic acid in spinach and other foods does not interfere with absorption of calcium from other foods eaten at the same time.

The second is a substance called Phytate. Phytic acid, found in the bran of whole grains, nuts, and the skins of legumes, can bind to calcium to form and insoluble complex, thereby decreasing the absorption of calcium. Phytic Acid binds with calcium (and iron, magnesium, phosphorus, and zinc) in the intestinal tract preventing absorbtion. Phytates/phytic acid are the storage form of phosphorus bound to inositol in the fiber of raw whole grains, legumes, seeds, and nuts. Although these foods have a high phosphorus content, the phosphates in phytates are not released through the digestive process. Phytates, particularly in such raw foods as bran, are a concern because they can bind a portion of the iron, zinc, and calcium in foods, making the minerals unavailable for absorption.

If one looks back at traditional cultures you will see that for thousands of years whole grains have been prepared by soaking or fermenting them prior to cooking. Phytic acid which occurs in unsprouted grains, seeds, and legumes, is particularly rich in the bran. When bread is leavened by yeast, enzymes degrade phytic acid and phytates pose no problem. Phytic acid is also destroyed during baking and food processing.

Enzymes, called phytases, destroy phytates during certain food processes such as: the yeast-raising of dough, the sprouting of seeds, grains, legumes, the roasting of nuts, presoaking beans, cooking, fermentation as in tempeh, miso, and natto, combining acidic foods with zinc-rich foods, etc.

Soybeans contain high levels of phytates; some researchers say more than other beans. Additionally, soy's phytates are so stable that many survive phytate-reducing techniques such as cooking. (The phytates in whole grains can be deactivated simply by soaking or fermenting. It is possible that only long periods of soaking and fermenting - as are used in making miso, natto, shoyu, tamari, and tempeh (but not tofu, soymilk, texturized soy protein, or soy protein isolate) - significantly reduce the phytate content of soybeans.

The third reason is the effects of a high protein diet. People are increasingly concerned about adopting healthier diets. However, many are prevented from necessary changes because of myths about certain nutrients. For example, people feel that they should eat increased amounts of meat in order to get adequate protein and large amounts of dairy products in order to get adequate calcium to avoid osteoporosis.

But, please consider the following: Countries with the highest consumption of dairy products, such as the United States, Sweden, and Finland, also have the greatest incidence of female osteoporosis. Eskimos, who consume the highest amounts of calcium of any of the world's people, have the highest number of cases of osteoporosis. Osteoporosis occurs relatively infrequently in China, even though they consume very little milk or other dairy products.

The reason is that people on meat- and dairy- based diets are getting far too much protein, generally 2 to 3 times the amount required, and when the excess protein is excreted, calcium and other minerals are drained from the body also.

The main problem is the consumption of animal protein; studies have shown that protein from non-animal sources has health benefits. So the answer to preventing osteoporosis is not to consume a lot of dairy products, but to reduce animal protein consumption through a balanced, nutritious diet centered on the "New Four Food Groups": fruits, vegetables (especially broccoli, a very calcium-rich food, without the negatives of animal products), grains, and legumes.

Many plant foods are good sources of calcium. Especially good sources are dark leafy greens (such as kale and mustard, collard, and turnip greens), broccoli, beans, dried figs, sunflower seeds, and calcium-fortified cereals and juices.

Consuming excessive amounts of protein can seriously damage human health. It can result in a negative calcium balance and osteoporosis, because calcium and other minerals are lost in the urine, along with the excess protein.

When protein is broken down in the body, acid is produced. The body compensates by buffering the acid through a complex process that involves the release of calcium from the bone. The calcium is then excreted in the urine. The higher the protein intake, the more calcium is lost. Protein-containing foods vary in the amount of acid they generate. Although animal proteins are commonly assumed to produce more acid, this is not always true. Fish, meat, poultry, cheese, and many grain products have a high potential renal acid load (PRAL), a measure of acid production. Milk and yogurt have a low PRAL. Fruits and vegetables have a negative PRAL, meaning they supply alkali that can help buffer acid.

Therefore if a person has a high protein intake they should incrase the amount of calcium in their diet. To offset the loss of calcium in the urine caused by processing protein, a high calcium intake can protect bone health. However, too much calcium can also be detrimental and intake should not exceed 2500 mg per day.

To protect your bones, consume a diet adequate in protein (0.36-0.45 grams of protein per pound of body weight), high in fruits and vegetables, moderate in sodium, and high in calcium. Adding a calcium supplement like HealthSmart Nutrition's Coral Cal-Min (http://www.air-water-nutrition-healthsmart.com/open/coral-cal-min/coral_cal.htm) or a whey powder such as HealthSmart Nutrition's undenatured CFM Whey (http://www.air-water-nutrition-healthsmart.com/open/Nutrition/whey_protein.htm)which contains a high calcium is helpful along with other good sources of calcium which include yogurt, fortified rice milk, tofu processed with calcium sulfate, collard greens, kale, mustard greens and blackstrap molasses. In addition to eating well, physical activity in your daily routine can help to strengthen bones.