According to researchers, caffeine interferes with the body’s absorption of calcium. Some experts suggest that excess caffeine might affect bone health. However, it remains unclear whether caffeine contributes to osteoporosis.

People with osteoporosis have low bone mineral density and bone mass, placing them at increased risk of bone fractures.

Some studies have explored the effects of caffeine on osteoporosis, but they have produced conflicting conclusions. Although some research suggests that caffeine interferes with calcium absorption, it is unclear whether and how it affects bone health.

At present, there is not enough evidence to conclude that consuming caffeine — in any quantity — contributes to osteoporosis.

Read more to learn about how caffeine affects bone health, what the research says, and how to promote strong bones.

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Researchers have several theories explaining how caffeine affects calcium in the body.

Some research in animals suggests that caffeine can affect bone growth. In one study, giving caffeine to pregnant rats led to slower bone growth in the fetuses. Experts suggest that caffeine interferes with endochondral ossification, a process that remodels cartilage into the new bone with the help of calcium.

According to researchers, caffeine also interferes with how the body absorbs calcium from food and can increase how much calcium the kidneys eliminate. These two mechanisms can lower how much calcium a person has in their body.

Caffeine can also interfere with how vitamin D binds to receptors. As vitamin D helps the gut absorb calcium, this effect can directly influence the amount of calcium in the body.

Consuming caffeine can also decrease the levels of inositol — a protein that plays a role in calcium metabolism — in the blood. With less inositol in the blood, the kidneys eliminate more calcium, and the body absorbs less of it through the intestine.

However, it is unclear whether caffeine’s effects on calcium affect bone health.

The amount of caffeine that is excessive depends on several factors, with recommendations varying for different people.

For example, the American College of Obstetricians and Gynecologists recommends that pregnant people limit their caffeine intake to 200 milligrams (mg) per day. In otherwise healthy adults, 400 mg of caffeine is usually safe. There are no guidelines defining a maximum daily limit.

The American Academy of Pediatrics does not recommend caffeinated drinks for children and adolescents.

However, its stance on caffeine is due to the substance’s negative effects on young people, which may include difficulty sleeping, increased blood pressure, and emotional problems. The organization does not mention any effects that caffeine may have on bone growth or bone health during puberty.

Researchers are unsure how much caffeine is necessary to lead to negative effects on calcium and osteoporosis.

Although studies have explored how caffeine affects calcium metabolism, researchers are unsure whether these effects contribute to osteoporosis.

A 2015 study on rats showed that high caffeine consumption decreased bone mass and reduced bone formation. However, animal studies do not always represent what will happen in humans.

An older 1992 study examined the effects of coffee drinking in postmenopausal women with fracture osteoporosis. The researchers concluded that coffee consumption was not related to bone tissue turnover, a normal process that involves breaking down and rebuilding new bone tissue.

However, the findings suggest that high caffeine consumption may be associated with increased calcium loss. Due to the link between low calcium and vitamin D intake, this may mean that caffeine is indirectly associated with osteoporosis.

To prevent osteoporosis, doctors suggest getting the recommended daily amount of calcium and vitamin D in the diet. A low calcium diet is a key risk factor for osteoporosis, and substances such as caffeine can mask it. Vitamin D is also important because the body cannot absorb calcium from the intestines without it.

Additional studies using a broad population may help determine the effects of caffeine on osteoporosis.

People who get the recommended daily allowance (RDA) of calcium and vitamin D may counteract the potential negative effects of caffeine.

The RDAs of calcium and vitamin D depend on a person’s age and sex. This table lists the RDA of calcium in milligrams per day (mg/day) and that of vitamin D in international units per day (IU/day) for various age groups:

Age (years) and genderCalcium (mg/day)Vitamin D (IU/day)
51–70 and male1,000600
51–70 and female1,200600
more than 701,200800
14–18 and pregnant or lactating1,300600
19–50 and pregnant or lactating1,000600

However, some experts advise that even small quantities of milk can offset the possible risks of caffeine. Adding 1–2 tablespoons of milk to the diet may be enough.

Some people have an increased risk of osteoporosis regardless of caffeine consumption. As a result, the potential negative effects of caffeine may further increase their risk of bone health issues. For example, children and older adults can experience higher rates of bone diseases and may need to limit their caffeine intake.

During puberty, adolescents experience quick growth because of maximal calcium deposition in the bone. If caffeine influences endochondral ossification and calcium buildup in bone, it may affect a child’s growth.

However, researchers are still unsure whether caffeine affects bone growth and strength in children and adolescents. It is unclear whether it causes osteoporosis in children because the rates of the condition are very low.

In older adults, both males and females are at risk of osteoporosis. Some risk factors include:

  • taking certain medications, such as cancer drugs or steroids
  • having a family history of osteoporosis
  • having low levels of certain hormones
  • experiencing low calcium and vitamin D diet throughout life
  • having certain medical conditions, such as arthritis, anorexia nervosa, or intestinal diseases

Although many types of tea contain caffeine, some research indicates that tea may actually be good for bone health.

According to a 2017 study, green tea polyphenols (GTP) may prevent osteoporosis. The researchers found that GTPs might improve bone mineral density and slow bone loss.

Certain age groups may experience even greater benefits from tea.

The same 2017 study showed increased bone mineral density in older women who drank tea compared with those who did not. However, other research contradicts these findings, reporting that tea had no effect on bone health.

The evidence supporting the effects of drinking tea for preventing osteoporosis is inadequate to confirm its benefits.

Caffeine may interfere with how the body absorbs, metabolizes, and eliminates calcium. Disruption of calcium in the body can contribute to certain bone diseases, such as osteoporosis, but it is unclear whether the effects of caffeine on calcium are significant enough to cause osteoporosis.

Experts suggest limiting caffeine to avoid side effects such as trouble sleeping, increased blood pressure, and emotional issues. Researchers are still working to understand the effects of caffeine on osteoporosis and bone health in different age groups.