The short answer. Adults protect their bones by getting enough calcium and vitamin D, doing weight-bearing, strength and balance exercise, and avoiding smoking and heavy drinking1,2,3,4. Most adults need 1,000 to 1,200 mg of calcium and 600 to 800 IU of vitamin D a day, from food first and supplements if needed1,2.
Bone is living tissue that is constantly being rebuilt. Cells called osteoclasts remove old bone, and osteoblasts lay down new bone in its place5. In children and teens, the body adds more bone than it removes. In healthy young adults, the two roughly balance. With age, and with some diseases, more bone can be removed than is replaced, and bones can weaken5.
After about age 30, bones slowly lose calcium, and in middle age that loss speeds up1. Exercise matters because of how the system works: the cells that direct remodeling respond to whether bone is being loaded by activity or unloaded by inactivity5.
If you want to know how the habits you build in childhood set the stage, our companion post on preventing osteoporosis across the lifespan covers peak bone mass and screening.
A bone mineral density (BMD) test measures calcium and other minerals in bone. Bone with more mineral is denser and tends to be stronger and less likely to break6. The most common test is a DXA scan of the hip and spine6. Postmenopausal women and men 50 or older receive a T-score, which compares your bone density with that of a healthy young adult6:
| T-score | What it means |
|---|---|
| -1 or higher | Healthy bone [6] |
| Between -1 and -2.5 | Osteopenia, low bone density that is less severe than osteoporosis [6] |
| -2.5 or lower | You might have osteoporosis [6] |
The risk of a broken bone rises 1.5 to 2 times with each 1-point drop in the T-score6.
Almost all the calcium in the body is stored in bones and teeth1. If you do not get enough from your diet, your body takes what it needs from your bones, and over time that weakens them7. The NIH Office of Dietary Supplements lists these daily amounts for adults1:
| Age | Recommended calcium per day |
|---|---|
| Adults 19 to 50 | 1,000 mg [1] |
| Men 51 to 70 | 1,000 mg [1] |
| Women 51 to 70 | 1,200 mg [1] |
| Adults 71 and older | 1,200 mg [1] |
More is not better. The upper limit from all sources, including food and supplements, is 2,500 mg a day for adults 19 to 50 and 2,000 mg for adults 51 and older1.
Milk, yogurt and cheese are the main sources of calcium for most people in the United States1. Other sources include canned sardines and salmon with the bones, kale, broccoli and bok choy, and fortified juices, soy and almond drinks, tofu and cereals (check the label)1.
Not every green vegetable is a good source. Compounds in spinach bind calcium, so the body absorbs only about 5% of the calcium in spinach, compared with about 27% from milk8. Caffeine reduces calcium absorption slightly, a smaller effect than low vitamin D status8.
If you take a supplement, calcium carbonate is absorbed best with food, while calcium citrate is absorbed well with or without food1. The body absorbs calcium best in doses of 500 mg or less at a time, so a larger daily amount is better split in two1.
Vitamin D helps your body absorb calcium2. The recommended amounts are 600 IU (15 mcg) a day for adults 19 to 70 and 800 IU (20 mcg) for adults 71 and older2.
Very few foods contain it naturally. Fortified milk, which makes up almost all of the US milk supply, has about 120 IU per cup; many plant milks, cereals and some brands of orange juice are also fortified2. Fatty fish such as salmon, trout, tuna and mackerel are among the richest natural sources, and egg yolks have small amounts2.
Your skin also makes vitamin D in sunlight, though clouds, smog, older age and darker skin all reduce the amount, and sunlight through a window does not count2. How much sun is enough is hard to pin down. Some experts suggest about 5 to 30 minutes of sun between 10 a.m. and 4 p.m. on the face, arms, hands and legs, daily or at least twice a week, while noting that the variables make firm guidelines difficult9. Because sunlight also causes skin cancer, health experts recommend sunscreen of SPF 15 or more when you are outside for more than a few minutes2.
A blood level of 20 ng/mL (50 nmol/L) or higher is adequate for bone health in most people2. Too much vitamin D is harmful, and high levels almost always come from supplements, not sunshine2. The upper limit for adults is 4,000 IU a day2.
The NIH says that getting the recommended amounts of calcium and vitamin D from food, and from supplements if needed, will help maintain healthy bones and prevent osteoporosis2. It also notes that vitamin D and calcium supplements slightly increase bone strength in older adults2. The practical reading is food first, and a supplement when your doctor finds a gap.
Two safety points apply if you do take them:
The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) recommends a combination of three types3:
For adults, federal guidelines call for at least 150 minutes a week of moderate exercise, plus muscle-strengthening work at least twice a week3. If you already have low bone density or osteoporosis, NIAMS advises talking with a health care provider before starting a program3.
The research supports exercise. In a Cochrane review of 43 trials in postmenopausal women, strength training for the legs helped most at the hip, and combined programs helped most at the spine11. In the LIFTMOR trial, 101 postmenopausal women with low bone mass did 30 minutes of closely supervised, high-intensity lifting and impact training twice a week for 8 months. Their spine bone density rose 2.9%, while a home-based, low-intensity group lost 1.2%, with one minor back spasm the only reported adverse event12. That program was supervised; heavy lifting is something to plan with a professional.
Cycling is good for heart fitness13. For bone, pair it with weight-bearing and strength exercise3.
Falls and fractures are closely linked. Nearly all hip fractures are related to a fall, and 10% to 15% of falls cause a fracture10. A Cochrane review of 108 trials found that exercise reduces the rate of falls in older adults by 23%, with the clearest benefit from balance and functional exercises14. It may also reduce fall-related fractures14. The US Preventive Services Task Force (USPSTF) recommends exercise to prevent falls in adults 65 and older who are at increased risk15.
NIAMS lists these risk factors for osteoporosis4:
Some of these, such as family history, cannot be changed, while others may be within your control4.
A broken bone from a minor fall, back pain with lost height, or a family history of osteoporosis are reasons to ask about your bone health4. The USPSTF recommends bone density testing for older women and for younger postmenopausal women at increased risk6. Our osteoporosis post covers screening in more detail.
If you are in the Santa Barbara area and have a painful joint or a bone injury, Dr. Scheinberg can examine you, review any imaging and talk through the options. See our treatments or call (805) 682-1394.
Short answers to the questions patients ask most.
Have a question about your own situation?
Call (805) 682-1394NIAMS says a combination is best: weight-bearing exercise such as brisk walking or dancing, resistance training with weights or bands, and balance training such as tai chi3. In a Cochrane review, strength training for the legs helped most at the hip, and combined programs helped most at the spine11.
Reviewed by Dr. Richard Scheinberg, MD, a board-certified orthopedic surgeon in Santa Barbara with 40 years of surgical experience.
