Bone Health and Gut Motility: Calcium Supplementation Strategies and the Remarkable Weight Loss Effects of Dietary Fiber
Calcium plays a vital physiological role. Firstly, it is a major component of bone minerals, accounting for 40% of total bone mineral composition. Bone minerals give bones their strength, providing structural support. The interconnected bones form cavities of specific shapes, protecting the organs within these cavities. Simultaneously, bones serve as a calcium storage depot for the body. Secondly, calcium regulates various physiological activities; for example, the transmission of nerve impulses, muscle contraction, and blood clotting all require the participation of calcium ions.
When calcium intake is insufficient, blood calcium levels drop. Calcium is then released from bones into the bloodstream to maintain a constant blood calcium level and ensure normal physiological functions. Therefore, the main consequence of insufficient calcium intake is impaired bone health. Calcium deficiency in children can cause rickets, while in adolescents, it prevents bone density from reaching its peak, resulting in insufficient bone calcium reserves. In the elderly, insufficient calcium intake accelerates bone calcium loss, leading to osteoporosis and fractures.
Insufficient calcium intake is a global nutritional problem because the calcium content of commonly consumed grains, fish, poultry, eggs, and meat is very low. The deficiency is particularly pronounced in my country. According to the 2002 National Nutrition and Health Survey, calcium is one of the nutrients with the largest gap between intake and requirement among Chinese residents, with the average daily intake per person less than half of the recommended intake. This is related to our dietary structure, as dairy products are the primary source of calcium in the diet, but the average daily intake of milk and dairy products per person in my country is only 26.5 grams, and in rural areas, it is only 11.4 grams per person per day. Although the number of urban residents drinking milk has increased year by year in recent years, the lack of dairy supply in rural areas is difficult to solve in the short term.
How can we increase the calcium intake of Chinese residents? Besides dairy products, dark green leafy vegetables and soy products are also rich sources of calcium, so try to eat more of these foods. Milk, soybeans and their products, as well as dark leafy vegetables, are high in calcium, as are dried shrimp and sesame paste. However, it's important to note that we don't eat a lot of these foods. For example, we might only eat 25 to 50 grams of dried shrimp or sesame paste per day, while we can consume 250 to 500 grams of milk and vegetables daily. Dark green leafy vegetables contain several times more calcium than light-colored vegetables, but spinach and amaranth are high in oxalic acid. Oxalic acid binds with calcium, preventing its absorption by the body. Therefore, it's advisable to blanch spinach to remove the oxalic acid before eating it.
The recommended daily calcium intake for adults in my country is 800 mg, while the recommended intake for adolescents aged 11-18 and adults over 50 is 1000 mg. This is difficult to meet for those who do not consume dairy products. If sufficient calcium cannot be obtained from the diet, calcium supplements can be taken as needed. Generally, commercially available calcium supplements, such as calcium carbonate, calcium citrate, and calcium gluconate, have an absorption rate of about 30% in adults, similar to the absorption rate of calcium from milk.
Recently, there have been many questions in the media regarding the safety of calcium supplements. Generally speaking, calcium supplementation is safe. Even so, it's important to avoid excessive calcium intake. The Chinese Nutrition Society recommends that the tolerable upper limit of calcium is no more than 2000 mg per day. Commercially available calcium tablets typically contain 300 mg or 600 mg of calcium per tablet, and supplementing with 300 mg or 600 mg of calcium daily will not be excessive. However, I have noticed that many calcium-fortified foods on the market, such as calcium-fortified milk bread and calcium-fortified noodles, do not specify the amount of calcium added. Blindly supplementing calcium through various means can lead to excessive intake.
Dietary fiber is a food component that is both familiar and unfamiliar to most people. It is not a nutrient, but due to its important physiological functions, it has received attention from nutritionists and is frequently mentioned in health programs on television and in newspapers; some even call it the seventh nutrient. The exact definition of dietary fiber remains controversial internationally. Dietary fiber is the edible part of plants, a polymer of carbohydrates with a degree of polymerization of at least 3. It is not absorbed in the human small intestine but can be fermented by the microbial community in the large intestine. Dietary fiber includes pectin, gums, mucilage, cellulose, hemicellulose, and lignin, among others.
Its physiological functions include: promoting intestinal peristalsis and absorbing water for expansion, which facilitates defecation. By reducing the time feces remain in the intestines, it may reduce the incidence of colon cancer. Dietary fiber can reduce cholesterol absorption, lowering the concentration of total cholesterol and low-density lipoprotein cholesterol (bad cholesterol) in the blood plasma, thereby reducing the risk of coronary heart disease. Dietary fiber can delay gastric emptying and glucose absorption, thus reducing the rapid rise in postprandial blood glucose and insulin, which is beneficial for blood sugar control in diabetic patients.
Foods rich in dietary fiber are generally bulky and low in energy density, which can increase satiety, reduce energy intake, and play a significant role in weight control. The main food sources of dietary fiber are grains, legumes, vegetables, and fruits. The outer layer of grains has a high dietary fiber content; therefore, whole wheat flour has a much higher dietary fiber content than refined enriched flour. Excessive dietary fiber intake can cause gastrointestinal discomfort and may reduce the bioavailability of certain minerals. Recommended dietary fiber intake for adults varies across countries, but most fall within the range of 20–30 grams per day.
Proper nutrition provides essential material support for human health, and a balanced diet is the foundation of proper nutrition. A balanced diet is one that provides a comprehensive range of nutrients that are neither deficient nor excessive, meeting the body's health needs. Maintaining a healthy weight requires dietary control. The principles of a balanced diet should also be applied when planning a diet for weight control. A balanced diet should provide the body with sufficient quantities of all the necessary nutrients, without excess.