What is osteoporosis? Show Osteoporosis is the thinning of your bones. It affects about 25 percent of women over age 65 and 5 percent of men over age 65, according to the Centers for Disease Control and Prevention (CDC). A variety of risk factors can determine your risk for the disease. Some are preventable, and some are unavoidable. What causes bone thinning? Bone is living tissue with holes inside. The inside has a honeycomb-like appearance. Bones affected by osteoporosis have larger holes and are more fragile. Understanding osteoporosis begins with understanding how bones are made. You repeatedly place demands on your bones. Because of these demands, your bones are constantly remodeling themselves. Bone remodeling occurs in two phases. First, special bone cells called osteoclasts break down bone. Then, other bone cells called osteoblasts create new bone. Osteoclasts and osteoblasts can coordinate well for most of your life. Eventually, this coordination can break down, and the osteoclasts begin to remove more bone than the osteoblasts can create. When you’re young, your body creates a lot of bone. In your mid-20s, your bone mass is at the maximum level. After that, you start to lose bone mass slowly as your body dissolves more bone than it rebuilds. Parathyroid hormone (PTH) is an important contributor to the bone remodeling process. High levels of PTH can activate osteoclasts and cause excessive bone breakdown. Calcium in your blood triggers the release of PTH. Low calcium levels in the blood, or hypocalcemia, can cause high levels of PTH. It can also cause your own bone to release calcium to make sure you have enough calcium in your blood. You need calcium for:
Your body will mine your bones for calcium if you don’t have enough in your blood. Getting enough calcium throughout your life is important to prevent bone thinning. In your teens and early adult years, you’re building bones. Sufficient calcium intake at that time ensures healthy bones later on. As you get older, eating enough calcium-rich foods helps reduce the amount of bone breakdown. Vitamin D is essential for maintaining the calcium in your bones. Vitamin D helps you absorb calcium through your intestines. Many older adults don’t get enough vitamin D. Up to 50 percent of older adults with hip fractures have very low levels of vitamin D, according to the National Institutes of Health. Without enough vitamin D, your bloodstream will not properly take up the calcium in milk, calcium supplements, or other sources. Low levels of vitamin D will also trigger a series of events that lead to activation of osteoclasts. It also leads to increased production of PTH, which creates even more osteoclasts. Osteoporosis is more likely to affect older women, especially white and Asian women, than men. One reason for this is the impact of falling estrogen levels after menopause. A consistent estrogen level is important for maintaining the rhythm of bone remodeling. If estrogen levels decrease, this changes the levels of certain messaging chemicals that help maintain a healthy balance of bone production and breakdown. Osteoclasts then become more active without estrogen, and your body breaks down more bone. Certain medical conditions and some medications can speed up the process of osteoporosis. This is called secondary osteoporosis. It occurs most often as a result of taking glucocorticoid steroids. Steroids like cortisol and prednisone directly slow down osteoblasts and speed up osteoclasts. They make it harder for your body to absorb calcium, and they also increase how much calcium you lose in urine. Taking thyroid hormones can also increase your risk of bone thinning. Thyroid hormones speed up the bone remodeling process. This increase in speed results in an increased chance of imbalance between osteoblasts and osteoclasts. Abusing alcohol, smoking, and having an eating disorder are additional risk factors for osteoporosis. These interfere with your ability to absorb necessary nutrients, such as calcium and vitamin D. The complex interactions between PTH, calcium, and vitamin D keeps the balance of bone-making and bone-destroying cells. Some health conditions and medications can affect the bone remodeling process and lead to bone thinning. Maintaining the necessary levels of calcium and vitamin D is key to reducing the risk of developing osteoporosis. Read this article in Spanish. Calcium is a mineral most often associated with healthy bones and teeth, although it also plays an important role in blood clotting, helping muscles to contract, and regulating normal heart rhythms and nerve functions. About 99% of the body’s calcium is stored in bones, and the remaining 1% is found in blood, muscle, and other tissues. In order to perform these vital daily functions, the body works to keep a steady amount of calcium in the blood and tissues. If calcium levels drop too low in the blood, parathyroid hormone (PTH) will signal the bones to release calcium into the bloodstream. This hormone may also activate vitamin D to improve the absorption of calcium in the intestines. At the same time, PTH signals the kidneys to release less calcium in the urine. When the body has enough calcium, a different hormone called calcitonin works to do the opposite: it lowers calcium levels in the blood by stopping the release of calcium from bones and signaling the kidneys to rid more of it in the urine. The body gets the calcium it needs in two ways. One is by eating foods or supplements that contain calcium, and the other is by drawing from calcium in the body. If one does not eat enough calcium-containing foods, the body will remove calcium from bones. Ideally, the calcium that is “borrowed” from the bones will be replaced at a later point. But this doesn’t always happen, and can’t always be accomplished just by eating more calcium. Recommended AmountsThe Recommended Dietary Allowance (RDA) for calcium for women 19-50 years of age is 1,000 mg daily; for women 51+, 1,200 mg. For pregnant and lactating women, the RDA is 1,000 mg. For men 19-70 years of age, the RDA is 1,000 mg; for men 71+ years, 1,200 mg. [1] Calcium and HealthThe reviews below specifically looked at the effect of calcium on various health conditions. Scroll down for links to more information on the health effect of specific foods rich in calcium. Blood pressure Several literature reviews on the topic of total calcium intake, from food and supplements, and blood pressure have suggested a possible link to lowering high blood pressure. However, problems with study designs in these analyses (small numbers of participants, differences among the people studied, and various biases in the types of studies included) prevent a new recommendation for the treatment of high blood pressure that would increase calcium intake above the Recommended Dietary Allowance. [2] Larger trials with longer duration are needed to clarify whether increased calcium intakes or the use of calcium supplements can lower high blood pressure. Cardiovascular disease Some research has raised concerns about calcium supplements and heart health. These studies found that taking calcium supplements increased the risk of cardiovascular events in men and women. It has been suggested that high-dose supplements can cause hypercalcemia (toxic level of calcium in the blood) that can cause blood to clot or the arteries to harden, leading to cardiovascular disease. The connection is not yet clear, but a clinical guideline published after review of the available research from the National Osteoporosis Foundation and the American Society for Preventive Cardiology stated that calcium from food or supplements has no relationship (beneficial or harmful) to cardiovascular disease in generally healthy adults. The guideline advises people not to exceed the Upper Limit for calcium, that is, 2,000-2,500 mg daily from food and supplements. [3] Bone health Calcium is one of the most important nutrients required for bone health. Bone is living tissue that is always in flux. Throughout the lifespan, bones are constantly being broken down and built up in a process known as remodeling. Bone cells called osteoblasts build bone, while other bone cells called osteoclasts break down bone if calcium is needed. In healthy individuals who get enough calcium and physical activity, bone production exceeds bone destruction up to about age 30. After that, destruction typically exceeds production. This is sometimes called “negative calcium balance,” which can lead to bone loss. Women tend to experience greater bone loss than men later in life due to menopause, a condition that lowers the amount of hormones that help to build and preserve bone. Getting enough dietary calcium at all ages may help to slow the degree of bone loss, but calcium intakes at any level are not known to completely prevent bone loss. [4] Calcium is less easily absorbed at later ages, and therefore eating a very high amount of calcium will not always resolve the problem. Studies on calcium intake and bone density in postmenopausal women have mixed results. Possible reasons:
Because the results of some large trials found that higher calcium intakes (usually achieved with a supplement) was associated with improved bone density and slightly lower risk of hip fractures, the RDA for calcium for postmenopausal women is higher than at younger ages. [5] Some studies suggest that frail elderly (80 years and older living in institutions) may benefit from supplementation more than “younger” elderly who live independently in the community. [6] A 2018 review of randomized controlled trials by the U.S. Preventive Services Task Force did not find that supplements with calcium and vitamin D taken for up to 7 years reduced the incidence of fractures in postmenopausal women. These women did not have osteoporosis or a vitamin D deficiency at the start of the study and lived independently in the community. The amount of calcium of the supplements ranged from 600-1,600 mg daily. [7] Colorectal cancer Epidemiological studies following people over time suggest a protective role of high calcium intakes (whether from food and/or supplements) from colorectal cancer. [8] However, randomized controlled trials using calcium supplements, with our without vitamin D, have shown mixed results. One reason may be a fairly short duration. Due to higher cost and difficulty with continued compliance from participants, clinical trials tend to be shorter in duration than epidemiological studies. But colorectal cancer can take 7-10 years or longer to develop, during which these trials might not reflect any changes in the colon.
After a review of both cohort and clinical studies by the World Cancer Research Fund and the American Institute for Cancer Research, they reported strong evidence that calcium supplements of more than 200 mg daily and intake of high-calcium dairy foods will likely decrease the risk of colorectal cancer. [11] They noted possible causes including the ability of calcium to bind to certain toxic substances in the colon and prevent the growth of tumor cells. Certain bacteria in dairy foods may also be protective against the development of cancerous cells in the colon. [12] Kidney stones At one time, experts recommended that people with kidney stones limit their calcium intake because the mineral makes up one of the most common types of stones, called calcium-oxalate stones. What we know now is the reverse—that not eating enough calcium-rich foods can increase the risk of stone formation. Research from large trials including the Women’s Health Initiative and the Nurses’ Health Study found that a high intake of calcium foods decreased the risk for kidney stones in women. However the same effect is not true with supplements, as calcium in pill form was found to increase risk. [13,14] A benefit of calcium-rich foods (mainly from dairy) on the prevention of kidney stones was found in a cohort of 45,619 men. Intakes of skim or low-fat milk and cottage cheese or ricotta cheese showed the greatest protective effect. Men who drank two or more 8-ounce glasses of skim milk a day had 42% less risk of developing kidney stones as compared with men who drank less than one glass a month. Eating two or more half-cup servings of cottage cheese or ricotta cheese a week was associated with 30% less risk of kidney stones as compared with men who ate less than one serving a month. It is believed that calcium-rich foods reduce the formation of stones by lowering the absorption of oxalates, which make up calcium-oxalate stones. However, other undetermined components of dairy foods may also be responsible for the decreased risk. [15] Food SourcesCalcium is widely available* in many foods, not just milk and other dairy foods. Fruits, leafy greens, beans, nuts, and some starchy vegetables are good sources.
*Bioavailability of calciumCalcium is a large mineral and not so easy to break down in the gut. The amount of calcium listed on the Nutrition Facts label of a food product is the measure of calcium in the food, but not necessarily the amount the body will absorb. The amount that is actually absorbed and used by the body is called “calcium bioavailablity.” Some foods have higher calcium bioavailability than others. For example, dairy foods have a bioavailablity of about 30% absorption so if a food label on milk lists 300 mg of calcium per cup, about 100 mg will be absorbed and used by the body. Plant foods like leafy greens contain less calcium overall but have a higher bioavailability than dairy. For example, bok choy contains about 160 mg of calcium per 1 cup cooked but has a higher bioavailability of 50%, so about 80 mg is absorbed. Therefore, eating 1 cup of cooked bok choy has almost as much bioavailable calcium as 1 cup of milk. Calcium-fortified orange juice and calcium-set tofu have a similar total amount of calcium and bioavailability as milk, while almonds have slightly lower total calcium and bioavailability of about 20%. This may be useful information for those who cannot eat dairy foods or who follow a vegan diet. A downside to some plant foods is that they contain naturally occurring plant substances, sometimes referred to as “anti-nutrients.” Examples of anti-nutrients are oxalates and phytates that bind to calcium and decrease its bioavailablity. Spinach contains the most calcium of all the leafy greens at 260 mg of calcium per 1 cup cooked, but it is also high in oxalates, lowering the bioavailability so that only 5% or about 13 mg of calcium can be used by the body. The takeaway message is not to avoid spinach, which contains other valuable nutrients, but not to rely on spinach as a significant source of calcium since most of it will not be absorbed by the body. You can also schedule your meals so that you do not eat “calcium-binding” foods like spinach at the same meal as calcium-rich foods or with calcium supplements. If you are scanning food labels to reach a specific amount of daily calcium, continue to aim for the RDAs set for your age group and gender. The RDAs are established with an understanding of calcium bioavailability in food. Also keep in mind that the exact amount of calcium absorbed in the body will vary among individuals based on their metabolism and what other foods are eaten at the same meal. In general, eating a variety of calcium-rich foods can help to offset any small losses. Signs of Deficiency and ToxicityDeficiencyBlood levels of calcium are tightly regulated. Bones will release calcium into the blood if the diet does not provide enough, and no symptoms usually occur. A more serious deficiency of calcium, called hypocalcemia, results from diseases such as kidney failure, surgeries of the digestive tract like gastric bypass, or medications like diuretics that interfere with absorption. Symptoms of hypocalcemia:
A gradual, progressive calcium deficiency can occur in people who do not get enough dietary calcium in the long-term or who lose the ability to absorb calcium. The first early stage of bone loss is called osteopenia and, if untreated, osteoporosis follows. Examples of people at risk include:
Guidelines if you are taking calcium supplements for osteoporosis After a diagnosis of osteoporosis, your physician may prescribe over-the-counter calcium supplements. However, there are several points to consider when using calcium supplements.
ToxicityToo much calcium in the blood is called hypercalcemia. The Upper Limit (UL) for calcium is 2,500 mg daily from food and supplements. People over the age of 50 should not take more than 2,000 mg daily, especially from supplements, as this can increase risk of some conditions like kidney stones, prostate cancer, and constipation. Some research has shown that in certain people, calcium can accumulate in blood vessels with long-term high doses and cause heart problems. Calcium is also a large mineral that can block the absorption of other minerals like iron and zinc. Symptoms of hypercalcemia:
Did You Know?Certain nutrients and medications may increase your need for calcium because they either lower the absorption of calcium in the gut or cause more calcium to be excreted in the urine. These include: corticosteroids (example: prednisone), excess sodium in the diet, phosphoric acid such as found in dark cola sodas, excess alcohol, and oxalates (see Are anti-nutrients harmful?). References
Terms of UseThe contents of this website are for educational purposes and are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The Nutrition Source does not recommend or endorse any products. Which hormone is involved in building and maintaining healthy bone tissue?Testosterone is important for skeletal growth both because of its direct effects on bone and its ability to stimulate muscle growth, which puts greater stress on the bone and thus increases bone formation. Testosterone is also a source of estrogen in the body; it is converted into estrogen in fat cells.
What hormones help bones grow?The pituitary gland secretes growth hormone (GH), which, as its name implies, controls bone growth in several ways. It triggers chondrocyte proliferation in epiphyseal plates, resulting in the increasing length of long bones.
What hormones are involved in bone growth quizlet?Terms in this set (7). Insulin-like growth factors (IGFs) ... . Human Growth hormone (hGh) ... . thyroid horomone. ... . Insulin. ... . sex hormones. ... . Estrogen. ... . parathyroid hormone.. |
Which hormone is involved in building and maintaining healthy bone tissue Select all that apply one some or all responses may be correct?
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