Tea: A Natural Ally to Strengthen Bones and Prevent Osteoporosis?

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People often hear about consuming dairy products and taking vitamin D supplements for good bone health. But have you heard about tea consumption for this purpose? Are these facts or premature conclusions?

Good bone health: a matter of molecules and cellular communication

Bones support all the structures in our body. They serve as anchoring points for muscles and form the initial framework for our organs. The inside of bones, called bone marrow, contains hematopoietic cells that, when specialized, produce our blood cells (red blood cells, immune cells like B lymphocytes that produce antibodies). Bones are also an essential calcium reservoir for proper cell function.

Bones initially form from a piece of cartilage that grows during development. To support this growth, the cartilage is infiltrated by blood vessels supplying nutrients and oxygen. Future hematopoietic and bone cells will colonize the cartilage’s central space through this vascularization. For example, the femur’s bone part is the long shaft, and its ends are made of base cartilage.

To maintain bone, a balance is needed between synthesizing molecules composing bone tissue (such as type I collagen in the bone extracellular matrix) and destroying worn-out areas. Synthesis is done by osteoblasts and destruction by osteoclasts, two types of bone cells. Bone remodeling is regulated by numerous molecular signals inside cells that bind to the surface of bone cells.

For example, vitamin D can bind to osteoblasts and osteocytes (structural bone cells), triggering calcium absorption or mineralization. Remodeling also depends on interactions between osteoblasts and osteoclasts. Osteoblasts activate osteoclasts to prevent excess synthesis or can induce their death depending on other surrounding molecular signals.

When bones become fragile

As we age, bone remodeling becomes less efficient, and bones lose rigidity. In some elderly people, especially postmenopausal women (estrogens regulate bone remodeling), this aging accelerates: osteoporosis. It can develop spontaneously with age or as a result of diseases like rheumatoid arthritis or poor lifestyle. It can be very disabling, especially depending on fractures in vertebrae or pelvis.

Many treatments are in development due to limited management of the disease. Prevention efforts include physical exercise and vitamin D supplementation to reduce fragility and fractures.

Tea: the new milk?

One of the first prospective studies on regular tea consumption and osteoporosis was published in 2003 by Pettinger et al. They reported results from cohorts between 1994 and 1998 including 91,465 postmenopausal women aged 50–79 in the USA. The authors found no increased fracture risk or worsening osteoporosis with tea consumption (from one cup to over four cups), contrary to earlier smaller American studies suggesting caffeine in tea negatively affects bone density. However, those studies lacked data on regularity and types of tea consumed, considered in later research.

To study tea’s effects on osteoporosis, research has included in vitro studies (bone cells, osteoclasts/osteoblasts), in vivo animal models mimicking bone aging, and clinical follow-ups.

Laboratory results

Polyphenols in tea are frequently shown in research to regulate bone remodeling by promoting bone formation and limiting destruction. Catechins, especially EGCG, promote mature osteoblast formation that produce an important enzyme (alkaline phosphatase) for their metabolism. They also initiate mineralization and protect osteoblasts from cell death. However, high doses of EGCG can impair osteoblast function in femur slices, so dose is important. EGCG also appears to induce osteoclast death without impairing osteoblast function, maintaining essential interactions. Polyphenols may reduce oxidative stress that damages bone cells during osteoporosis. Most results are for green tea polyphenols, but black tea infusions and thearubigins show similar effects, halving osteoclast numbers and reducing their activity markers.

Animal studies mostly focus on green tea extracts, especially isolated polyphenols. Consuming green tea polyphenols helps preserve bone density and remodeling balance at doses equivalent to 1–4 cups daily. Effects were seen in ovariectomized female rats and aged male rats. Liang et al. recently showed that black tea infusion (1g/10cl) and thearubigin extract given for 12 weeks to ovariectomized rats increased alkaline phosphatase (x1.5) and bone protein BGP (x0.5).

Green tea polyphenols also seem to prevent bone alterations in obese rats after 16 weeks.

Results in humans

Between 2003 and today, most studies show no worsening of osteoporosis or increased fractures with tea consumption. The reputation of caffeine reducing bone density is not supported here.

A meta-analysis of 17 studies in elderly men and women (1988–2014) suggests beneficial effects of tea on osteoporosis (e.g., increased bone mineral density, a marker of bone health) despite study heterogeneity (participants, tea types, etc.). As usual, some data might have been excluded by error.

A 2014 study of 435 elderly tea consumers published in 2016 included factors such as:

Gender
Age
BMI
Tea consumption habits (frequency, years of regular consumption, quantity of tea leaves used annually)

They observed fewer hip and femur fractures when analyzing each factor individually. Accounting for risk factors, reductions remained, though effects were more pronounced in men than women, indicating hormones’ role. Tea type (green, black, oolong) did not seem to impact results, but data is limited.

Tea has not proven to be a revolutionary treatment for osteoporosis. However, no contraindications exist for tea consumption with osteoporosis, and it might reduce fracture risk in some people. More research is needed on which tea types, doses, and consumption durations yield benefits.