Everyone knows that dairy products are high in calcium. Dairy products provide about 75 percent of the calcium in American diets. In spite of this, children in their highest growth years receive only 10 to 25 percent of their needed calcium. Some of the excellent sources of calcium also are excellent sources of
many other nutrients. Many vegetables provide abundant calcium along with high levels of vitamins A, C, K and folate; please refer to Graph 9-1. Whole sesame seeds are one of the richest sources of calcium and also provide muchneeded vitamin E and selenium. Nuts, seeds, and legumes are healthy sources of calcium. Tofu is often set with calcium and can be a very high source of dietary calcium.
Graph 9-1 Calcium content of some common foods.
Calcium Absorption
Calcium enters the intestines from two sources. One of the sources is from the diet, which may include supplements. Calcium is also recycled back to the digestion in digestive juices. Calcium is absorbed in the upper part of the intestines in an active transport process. With higher levels of calcium intake, diffusion also plays a role in absorption from the intestines into the blood. The absorption of calcium from the intestines is controlled by the active form of vitamin D, calcitriol. Calcium absorption is highest at 400 mg daily with about 30 percent absorption.
Higher intakes of calcium result in lower absorption. Calcium absorption diminishes in old age, partly because of lower calcitriol levels. Not only is calcium absorption low, but losses are rather high. The first 400 mg of dietary calcium is needed just to cover normal losses. About 200 mg of unabsorbed calcium from both the diet and from digestive juices is lost in the feces each day. The skin, hair, and nails lose an average of 60 mg daily, necessitating an additional intake of 200 mg (calculated at 30 percent absorption). Oxalates can bind to
calcium and cause excretion, but this effect is not significant in most diets.
Table 9-1 Adequate intake levels for calcium for all ages.
many other nutrients. Many vegetables provide abundant calcium along with high levels of vitamins A, C, K and folate; please refer to Graph 9-1. Whole sesame seeds are one of the richest sources of calcium and also provide muchneeded vitamin E and selenium. Nuts, seeds, and legumes are healthy sources of calcium. Tofu is often set with calcium and can be a very high source of dietary calcium.
Graph 9-1 Calcium content of some common foods.
Calcium Absorption
Calcium enters the intestines from two sources. One of the sources is from the diet, which may include supplements. Calcium is also recycled back to the digestion in digestive juices. Calcium is absorbed in the upper part of the intestines in an active transport process. With higher levels of calcium intake, diffusion also plays a role in absorption from the intestines into the blood. The absorption of calcium from the intestines is controlled by the active form of vitamin D, calcitriol. Calcium absorption is highest at 400 mg daily with about 30 percent absorption.
Higher intakes of calcium result in lower absorption. Calcium absorption diminishes in old age, partly because of lower calcitriol levels. Not only is calcium absorption low, but losses are rather high. The first 400 mg of dietary calcium is needed just to cover normal losses. About 200 mg of unabsorbed calcium from both the diet and from digestive juices is lost in the feces each day. The skin, hair, and nails lose an average of 60 mg daily, necessitating an additional intake of 200 mg (calculated at 30 percent absorption). Oxalates can bind to
calcium and cause excretion, but this effect is not significant in most diets.
More about Calcium:
0 comments