Hello, my dearest friends!
Ivan is here today I would like to arise the topic of calcium and it`s influence on weight loss.
Calcium, the most abundant mineral in the body, is found in some foods, added to others, available as a dietary supplement, and present in some medicines (such as antacids). Calcium is required for vascular contraction and vasodilation, muscle function, nerve transmission, intracellular signaling and hormonal secretion, though less than 1% of total body calcium is needed to support these critical metabolic functions. Serum calcium is very tightly regulated and does not fluctuate with changes in dietary intakes; the body uses bone tissue as a reservoir for, and source of calcium, to maintain constant concentrations of calcium in blood, muscle, and intercellular fluids.
The remaining 99% of the body’s calcium supply is stored in the bones and teeth where it supports their structure and function. Bone itself undergoes continuous remodeling, with constant resorption and deposition of calcium into new bone. The balance between bone resorption and deposition changes with age. Bone formation exceeds resorption in periods of growth in children and adolescents, whereas in early and middle adulthood both processes are relatively equal. In aging adults, particularly among postmenopausal women, bone breakdown exceeds formation, resulting in bone loss that increases the risk of osteoporosis over time.
Intake recommendations for calcium and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine of the National Academies (formerly National Academy of Sciences). DRI is the general term for a set of reference values used for planning and assessing the nutrient intakes of healthy people. These values, which vary by age and gender, include:
- Recommended Dietary Allowance (RDA): average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals.
- Adequate Intake (AI): established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy.
- Estimated Average Requirement (EAR): average daily level of intake estimated to meet the requirements of 50% of healthy individuals. It is usually used to assess the adequacy of nutrient intakes in populations but not individuals.
- Tolerable Upper Intake Level (UL): maximum daily intake unlikely to cause adverse health effects.
The FNB established RDAs for the amounts of calcium required for bone health and to maintain adequate rates of calcium retention in healthy people. They are listed in Table 1 in milligrams (mg) per day.
|0–6 months*||200 mg||200 mg|
|7–12 months*||260 mg||260 mg|
|1–3 years||700 mg||700 mg|
|4–8 years||1,000 mg||1,000 mg|
|9–13 years||1,300 mg||1,300 mg|
|14–18 years||1,300 mg||1,300 mg||1,300 mg||1,300 mg|
|19–50 years||1,000 mg||1,000 mg||1,000 mg||1,000 mg|
|51–70 years||1,000 mg||1,200 mg|
|71+ years||1,200 mg||1,200 mg|
* Adequate Intake (AI)
Sources of Calcium
Milk, yogurt, and cheese are rich natural sources of calcium and are the major food contributors of this nutrient to people in the United States. Nondairy sources include vegetables, such as Chinese cabbage, kale, and broccoli. Spinach provides calcium, but its bioavailability is poor. Most grains do not have high amounts of calcium unless they are fortified; however, they contribute calcium to the diet because they contain small amounts of calcium and people consume them frequently. Foods fortified with calcium include many fruit juices and drinks, tofu, and cereals. Selected food sources of calcium are listed in Table 2.
|Yogurt, plain, low fat, 8 ounces||415||42|
|Mozzarella, part skim, 1.5 ounces||333||33|
|Sardines, canned in oil, with bones, 3 ounces||325||33|
|Yogurt, fruit, low fat, 8 ounces||313–384||31–38|
|Cheddar cheese, 1.5 ounces||307||31|
|Milk, nonfat, 8 ounces**||299||30|
|Soymilk, calcium-fortified, 8 ounces||299||30|
|Milk, reduced-fat (2% milk fat), 8 ounces||293||29|
|Milk, buttermilk, lowfat, 8 ounces||284||28|
|Milk, whole (3.25% milk fat), 8 ounces||276||28|
|Orange juice, calcium-fortified, 6 ounces||261||26|
|Tofu, firm, made with calcium sulfate, ½ cup***||253||25|
|Salmon, pink, canned, solids with bone, 3 ounces||181||18|
|Cottage cheese, 1% milk fat, 1 cup||138||14|
|Tofu, soft, made with calcium sulfate, ½ cup***||138||14|
|Ready-to-eat cereal, calcium-fortified, 1 cup||100–1,000||10–100|
|Frozen yogurt, vanilla, soft serve, ½ cup||103||10|
|Turnip greens, fresh, boiled, ½ cup||99||10|
|Kale, fresh, cooked, 1 cup||94||9|
|Ice cream, vanilla, ½ cup||84||8|
|Chinese cabbage, bok choi, raw, shredded, 1 cup||74||7|
|Bread, white, 1 slice||73||7|
|Pudding, chocolate, ready to eat, refrigerated, 4 ounces||55||6|
|Tortilla, corn, ready-to-bake/fry, one 6” diameter||46||5|
|Tortilla, flour, ready-to-bake/fry, one 6” diameter||32||3|
|Sour cream, reduced fat, cultured, 2 tablespoons||31||3|
|Bread, whole-wheat, 1 slice||30||3|
|Kale, raw, chopped, 1 cup||24||2|
|Broccoli, raw, ½ cup||21||2|
|Cheese, cream, regular, 1 tablespoon||14||1|
* DV = Daily Value. DVs were developed by the U.S. Food and Drug Administration to help consumers compare the nutrient contents among products within the context of a total daily diet. The DV for calcium is 1,000 mg for adults and children aged 4 years and older. Foods providing 20% of more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet. The U.S. Department of Agriculture’s (USDA’s) Nutrient Database Web site lists the nutrient content of many foods and provides comprehensive list of foods containing calcium arranged by nutrient content and by food name.
** Calcium content varies slightly by fat content; the more fat, the less calcium the food contains.
*** Calcium content is for tofu processed with a calcium salt. Tofu processed with other salts does not provide significant amounts of calcium.
The two main forms of calcium in supplements are carbonate and citrate. Calcium carbonate is more commonly available and is both inexpensive and convenient. Due to its dependence on stomach acid for absorption, calcium carbonate is absorbed most efficiently when taken with food, whereas calcium citrate is absorbed equally well when taken with or without food. Calcium citrate is also useful for people with achlorhydria, inflammatory bowel disease, or absorption disorders. Other calcium forms in supplements or fortified foods include gluconate, lactate, and phosphate. Calcium citrate malate is a well-absorbed form of calcium found in some fortified juices.
Calcium supplements contain varying amounts of elemental calcium. For example, calcium carbonate is 40% calcium by weight, whereas calcium citrate is 21% calcium. Fortunately, elemental calcium is listed in the Supplement Facts panel, so consumers do not need to calculate the amount of calcium supplied by various forms of calcium supplements.
The percentage of calcium absorbed depends on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorption decreases. Absorption is highest in doses ≤500 mg. So, for example, one who takes 1,000 mg/day of calcium from supplements might split the dose and take 500 mg at two separate times during the day.
Some individuals who take calcium supplements might experience gastrointestinal side effects including gas, bloating, constipation, or a combination of these symptoms. Calcium carbonate appears to cause more of these side effects than calcium citrate, so consideration of the form of calcium supplement is warranted if these side effects are reported. Other strategies to alleviate symptoms include spreading out the calcium dose throughout the day and/or taking the supplement with meals.
Because of its ability to neutralize stomach acid, calcium carbonate is found in some over-the-counter antacid products, such as Tums® and Rolaids®. Depending on its strength, each chewable pill or softchew provides 200 to 400 mg of elemental calcium. As noted above, calcium carbonate is an acceptable form of supplemental calcium, especially for individuals who have normal levels of stomach acid.
Inadequate intakes of dietary calcium from food and supplements produce no obvious symptoms in the short term. Circulating blood levels of calcium are tightly regulated. Hypocalcemia results primarily from medical problems or treatments, including renal failure, surgical removal of the stomach, and use of certain medications (such as diuretics). Symptoms of hypocalcemia include numbness and tingling in the fingers, muscle cramps, convulsions, lethargy, poor appetite, and abnormal heart rhythms. If left untreated, calcium deficiency leads to death.
Over the long term, inadequate calcium intake causes osteopenia which if untreated can lead to osteoporosis. The risk of bone fractures also increases, especially in older individuals. Calcium deficiency can also cause rickets, though it is more commonly associated with vitamin D deficiency.
Groups at Risk of Calcium Inadequacy
Although frank calcium deficiency is uncommon, dietary intakes of the nutrient below recommended levels might have negative health consequences over the long term. The following groups are among those most likely to need extra calcium.
Menopause leads to bone loss because decreases in estrogen production both increase bone resorption and decrease calcium absorption. Annual decreases in bone mass of 3%–5% per year frequently occur in the first years of menopause, but the decreases are typically less than 1% per year after age 65. Increased calcium intakes during menopause do not completely offset this bone loss. Hormone replacement therapy (HRT) with estrogen and progesterone helps increase calcium levels and prevent osteoporosis and fractures. Estrogen therapy restores postmenopausal bone remodeling to the same levels as at premenopause, leading to lower rates of bone loss, perhaps in part by increasing calcium absorption in the gut. Several medical groups and professional societies support the use of HRT as an option for women who are at increased risk of osteoporosis or fractures. Such women should discuss this matter with their health care providers. In addition, consuming adequate amounts of calcium in the diet might help slow the rate of bone loss in all women.
Amenorrheic women and the female athlete triad
Amenorrhea, the condition in which menstrual periods stop or fail to initiate in women of childbearing age, results from reduced circulating estrogen levels that, in turn, have a negative effect on calcium balance. Amenorrheic women with anorexia nervosa have decreased calcium absorption and higher urinary calcium excretion rates, as well as a lower rate of bone formation than healthy women. The “female athlete triad” refers to the combination of disordered eating, amenorrhea, and osteoporosis. Exercise-induced amenorrhea generally results in decreased bone mass. In female athletes and active women in the military, low bone-mineral density, menstrual irregularities, certain dietary patterns, and a history of prior stress fractures are associated with an increased risk of future stress fractures. Such women should be advised to consume adequate amounts of calcium and vitamin D. Supplements of these nutrients have been shown to reduce the risk of stress fractures in female Navy recruits during basic training.
Individuals with lactose intolerance or cow’s milk allergy
Lactose intolerance refers to symptoms (such as bloating, flatulence, and diarrhea) that occur when one consumes more lactose, the naturally occurring sugar in milk, than the enzyme lactase produced by the small intestine can hydrolyze into its component monosaccharides, glucose and galactose. The symptoms vary, depending on the amount of lactose consumed, history of consumption of lactose-containing foods, and type of meal. Although the prevalence of lactose intolerance is difficult to discern, some reports suggest that approximately 25% of U.S. adults have a limited ability to digest lactose, including 85% of Asians, 50% of African Americans, and 10% of Caucasians.
Lactose-intolerant individuals are at risk of calcium inadequacy if they avoid dairy products. Research suggests that most people with lactose intolerance can consume up to 12 grams of lactose, such as that present in 8 ounces of milk, with minimal or no symptoms, especially if consumed with other foods; larger amounts can frequently be consumed if spread over the day and eaten with other foods. Other options to reduce symptoms include eating low-lactose dairy products including aged cheeses (such as Cheddar and Swiss), yogurt, or lactose-reduced or lactose-free milk. Some studies have examined whether it is possible to induce adaptation by consuming incremental lactose loads over a period of time, but the evidence in support of this strategy is inconsistent.
Cow’s milk allergy is less common than lactose intolerance, affecting 0.6% to 0.9% of the population. People with this condition are unable to consume any products containing cow’s milk proteins and are therefore at higher risk of obtaining insufficient calcium.
To ensure adequate calcium intakes, lactose-intolerant individuals and those with cow’s milk allergy can choose nondairy food sources of the nutrient (such as kale, bok choy, Chinese cabbage, broccoli, collards and fortified foods) or take a calcium supplement.
Vegetarians might absorb less calcium than omnivores because they consume more plant products containing oxalic and phytic acids. Lacto-ovo vegetarians (who consume eggs and dairy) and nonvegetarians have similar calcium intakes. However, vegans, who eat no animal products and ovo-vegetarians (who eat eggs but no dairy products), might not obtain sufficient calcium because of their avoidance of dairy foods. In the Oxford cohort of the European Prospective Investigation into Cancer and Nutrition, bone fracture risk was similar in meat eaters, fish eaters and vegetarians, but higher in vegans, likely due to their lower mean calcium intake. It is difficult to assess the impact of vegetarian diets on calcium status because of the wide variety of eating practices and thus should be considered on a case by case basis.
Weight management and calcium
Several studies have linked higher calcium intakes to lower body weight or less weight gain over time. Two explanations have been proposed. First, high calcium intakes might reduce calcium concentrations in fat cells by decreasing the production of parathyroid hormone and the active form of vitamin D. Decreased intracellular calcium concentrations in turn increase fat breakdown and discourage fat accumulation in these cells. Secondly, calcium from food or supplements might bind to small amounts of dietary fat in the digestive tract and prevent its absorption. Dairy products, in particular, might contain additional components that have even greater effects on body weight than their calcium content alone would suggest.
Despite these findings, the results from clinical trials have been largely negative. For example, dietary supplementation with 1,500 mg/day of calcium (from calcium carbonate) for 2 years was found to have no clinically significant effects on weight in 340 overweight and obese adults as compared with placebo. Three reviews of published studies on calcium from supplements or dairy products on weight management came to similar conclusions. A meta-analysis of 13 randomized controlled trials published in 2006 concluded that neither calcium supplementation nor increased dairy product consumption had a statistically significant effect on weight reduction. More recently, a report from the Agency for Healthcare Research and Quality concluded that, overall, clinical trial results do not support an effect of calcium supplementation on weight loss. Also, a meta-analysis of 29 randomized controlled trials found no benefit of an increased consumption of dairy products on body weight and fat loss in long-term studies Overall, the results from clinical trials do not support a link between higher calcium intakes and lower body weight or weight loss.
For additional information on calcium and weight management, see health professional fact sheet on Weight Loss.
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It was developed in cooperation with U.S. Department of Health&Human Services
Ivan, founder of HOWTOEATTOLOSEWEIGHT.COM