What Is Osteoporosis? Causes, Symptoms, Bone Density, Testing, Diet & Exercise Explained

When people hear the word “osteoporosis,” they may think of it as a condition that only becomes important later in life.

However, bone health is not something that is determined only in older age. How much bone mass we build when we are young, the eating and exercise habits we maintain over the years, and—particularly for women—the hormonal changes associated with menopause can all influence our bones over time.

Osteoporosis can also develop without obvious symptoms in its early stages, and some people first become aware of it after experiencing a fracture.

Even when there is no pain, changes in bone strength may be occurring without being noticed. This is why it is helpful to think about bone health in relation to age, lifestyle and individual risk factors.

In this article, we explain the basics of osteoporosis, including why it is more common in women, the roles of bone mineral density and bone quality, possible signs, common fracture sites, risk factors and testing. We will also look at everyday eating habits, physical activity and fall prevention as part of a broader approach to supporting long-term bone health.

What Is Osteoporosis? Understanding How Bones Become Weaker

Osteoporosis is a condition in which bone strength decreases, making fractures more likely.

It is sometimes described as a condition in which bones become “porous,” but bone strength is influenced by more than simply the amount of bone present. The structure and quality of bone also play important roles.

Although bones may appear hard and unchanging, they are constantly being renewed inside the body. Old bone is broken down through a process known as bone resorption, while new bone is created through bone formation.

This continuous process of replacing old bone with new bone is known as bone remodeling.

When bone resorption and bone formation remain balanced, bone tissue can be maintained. However, ageing, hormonal changes and other factors can shift this balance, and bone mass may gradually decrease when bone resorption continues to exceed bone formation.

As a result, bone strength can decline, making fractures more likely even after relatively minor falls or impacts.

According to materials related to the Japan Osteoporosis Society’s 2025 guidelines, an estimated 15.9 million people in Japan have osteoporosis.

Osteoporosis is therefore not a rare condition. It is an important health issue that becomes increasingly relevant as people age.

Why Is Osteoporosis More Common in Women? Menopause and Estrogen

Osteoporosis can affect men as well as women, but it is particularly common among women after menopause.

One of the main reasons is the female hormone estrogen.

Estrogen is involved in bone metabolism. When estrogen levels fall significantly after menopause, the balance between bone resorption and bone formation can change, making bone mass more likely to decline.

For this reason, the 40s and 50s can be an important time for women to pay closer attention to their bone health.

The Japan Osteoporosis Foundation explains that peak bone mass is generally reached at around ages 15–18 in women and 18–20 in men. Bone mass is then maintained for a period before tending to decline, particularly around and after menopause in women.

This means that thinking about bone health is not something that needs to begin only in older age.

Maintaining balanced eating habits and regular physical activity from a younger age is also important when considering long-term bone health.

Bone Density Is Not the Whole Story: Bone Quality Also Matters

One of the terms most commonly associated with bone health is “bone mineral density.”

Bone mineral density is an important measure of how much mineral, including calcium, is present within the bone.

However, bone strength is not determined by bone density alone.

Bone quality, which includes factors such as the microscopic structure and material properties of bone, also contributes to overall bone strength.

For this reason, osteoporosis is not viewed simply as “low bone density.” Bone density, bone quality and overall fracture risk all need to be considered.

Age, previous fractures, family history, body build and lifestyle factors can also contribute to an individual’s overall fracture risk.

Osteoporosis Can Be Difficult to Notice: Changes to Look Out For

One characteristic of osteoporosis is that a reduction in bone mass may occur without noticeable symptoms.

Because some people only discover they have osteoporosis after a fracture, it is sometimes described as a “silent disease.”

Changes associated with vertebral fractures and other bone problems may include the following:

If you notice changes such as these—particularly if you are postmenopausal, older, or have experienced a previous fracture—it is worth discussing them with a healthcare professional rather than assuming they are simply part of ageing.

Which Bones Are More Commonly Fractured in Osteoporosis?

Fractures related to osteoporosis can occur in different parts of the body, but several sites are particularly common.

Hip fractures, in particular, can have a significant effect on mobility and everyday function in older adults.

According to the Japan Osteoporosis Foundation, more than 80% of proximal femur fractures are triggered by falls.

For this reason, paying attention to bone health and reducing opportunities for falls are both important when considering fracture prevention.

Who Is More Likely to Develop Osteoporosis?

Osteoporosis is associated with both factors that cannot be changed, such as age and family history, and lifestyle factors that may be possible to review.

Osteoporosis is not determined by one factor alone, such as being female or getting older.

A combination of factors can increase an individual’s fracture risk.

Osteoporosis also becomes more common in men with age. In younger people, certain health conditions, medicines or extreme dietary restriction may also affect bone health.

Osteoporosis Testing: How Is Bone Density Measured?

Because osteoporosis cannot usually be identified from symptoms alone, measuring bone mineral density can provide useful information about bone health.

One of the main testing methods is DXA (dual-energy X-ray absorptiometry).

DXA uses two different X-ray energy levels to measure bone mineral density. Measurements of the lumbar spine and proximal femur are commonly used when assessing osteoporosis.

Other methods may also be used in screening programs, including MD measurements of the hand and quantitative ultrasound (QUS), often performed at the heel.

QUS can be useful as a screening method, but assessment with DXA or other appropriate methods is required for the diagnosis of osteoporosis and for evaluating response to treatment.

What Does “YAM” Mean?

In Japan, bone density results may refer to YAM (Young Adult Mean).

This compares an individual’s bone mineral density with the average bone density of young adults, which is expressed as 100%.

However, osteoporosis should not be self-diagnosed on the basis of a bone density number alone.

A doctor will consider factors such as fracture history, age and other risk factors when making an overall assessment.

Bone Health Screening in Japan

As part of Japan’s health promotion programs, osteoporosis screening is positioned for women aged 40, 45, 50, 55, 60, 65 and 70.

Eligibility, testing methods and costs vary between municipalities, so check the information provided by your local city or ward office.

Women around menopause, people who have experienced a fracture after relatively minor force, those with low body weight, or those with a family history of hip fracture may wish to discuss whether bone density testing is appropriate for them.

Eating for Bone Health: It Is Not Just About Calcium

When we think about nutrition for bone health, calcium is often the first nutrient that comes to mind.

Calcium is certainly important, but bones are not made from calcium alone. A balanced diet containing a variety of nutrients, including calcium, vitamin D, vitamin K and protein, is an important foundation.

Calcium: An Important Mineral in Bones

Calcium is the most abundant mineral in the human body, with most of it stored in the bones and teeth.

Under the Dietary Reference Intakes for Japanese (2025), the recommended calcium intake for adult women is 650 mg per day for many adult age groups, and 600 mg per day for women aged 75 and over.

Rather than relying on a single food, it can be easier to include a variety of calcium-containing foods as part of everyday meals.

People who consume little or no dairy can still broaden their sources of calcium by combining foods such as small fish, soy products and vegetables.

Vitamin D: Another Nutrient to Consider Alongside Calcium

Vitamin D is involved in the absorption of calcium from the intestine and in bone formation.

Under the Dietary Reference Intakes for Japanese (2025), the adequate intake of vitamin D for adults aged 18 and over is 9.0 μg per day.

Foods containing vitamin D include fish such as salmon and Pacific saury, mushrooms and eggs.

Vitamin D can also be produced in the skin in response to sunlight.

Sun exposure varies according to season, location and lifestyle, so spending some time outdoors as part of everyday life can be considered while also taking appropriate care regarding UV exposure.

Vitamin K and Protein Are Also Important

Vitamin K and protein are also nutrients to consider as part of a balanced diet for bone health.

Vitamin K is found in foods such as natto and green leafy vegetables. Under the 2025 Dietary Reference Intakes for Japanese, the adequate intake for adults is 150 μg per day.

Bones also contain proteins such as collagen in addition to minerals.

Including foods such as meat, fish, eggs, soy products and dairy products can help create a more balanced overall diet.

Think of Supplements as a Way to Complement Your Diet

Supplements can be one option for complementing nutrients that may be difficult to obtain consistently through everyday meals.

If you choose to use supplements, it is important to review your usual diet and check the nutrients included, the amount provided and the recommended daily intake of each product.

If you have already been diagnosed with osteoporosis or are taking prescription medicines, supplements should not be used as a substitute for treatment. Speak with a doctor or pharmacist if you are considering adding a supplement.

Everyday Exercise Habits for Bone Health

Alongside nutrition, regular physical activity is another important part of looking after bone health.

Everyday movements such as walking and standing place a certain amount of load on the bones. Regular movement can also help maintain muscle strength and balance, which are important when considering fall prevention.

You do not necessarily need to take up a demanding sport. A good starting point is simply to increase the amount of movement you can comfortably maintain in everyday life.

The Japan Osteoporosis Foundation also introduces exercises aimed at maintaining lower-body strength and balance.

However, if you have been diagnosed with osteoporosis, have previously fractured your spine or hip, or experience back or lower-back pain, some types of exercise may place additional strain on the body.

Choose exercise that is appropriate for your individual condition and consult a doctor or physiotherapist when necessary.

Fall Prevention: An Important Part of Reducing Fracture Risk

When thinking about osteoporosis, it is important to consider not only the bones themselves but also how to create an environment in which falls are less likely.

As people age, changes in muscle strength and balance, eyesight, medicines and the home environment can all contribute to falls.

According to the Japan Osteoporosis Foundation, more than 80% of proximal femur fractures are triggered by falls.

When outdoors, pay attention to slippery surfaces, uneven ground, steps and poorly lit areas.

Maintaining muscle strength and balance while also creating a safer living environment can help reduce situations that may lead to a fall and fracture.

Smoking and Excessive Alcohol Consumption

Smoking and excessive alcohol intake are also associated with bone health.

The Japanese Orthopaedic Association includes avoiding smoking and keeping alcohol consumption moderate among lifestyle considerations related to osteoporosis prevention.

If you smoke, consider stopping, and if you drink alcohol, try to avoid excessive consumption.

Bone Health Through Different Stages of Life

Healthy lifestyle habits are worth considering for bone health at every stage of life.

However, bone health and everyday circumstances change with age, so the areas worth paying attention to also change over time.

Teens to 20s: Building Bone Mass for the Future

Childhood, adolescence and early adulthood are important periods for building bone mass.

During these years, a balanced diet containing a wide range of nutrients, including calcium, together with regular physical activity is important.

One area to be particularly careful about is extreme dieting or excessive food restriction focused only on body weight.

The body is still developing during the growing years, so adequate nutrition and healthy daily habits are important.

30s: Maintaining Healthy Everyday Habits

Work, family responsibilities and busy schedules can make it easy for physical activity to decrease or eating habits to become irregular.

Maintaining a balanced diet, regular physical activity and an appropriate body weight can help support bone health in the years ahead.

40s to 50s: Menopause Is a Good Time to Review Bone Health

In women, bone mass tends to decrease more rapidly around and after menopause as hormone levels change.

Alongside balanced eating and regular activity, this can be a useful time to take advantage of osteoporosis screening programs and learn more about your own bone mineral density.

If you have a family history of hip fracture, have previously experienced a fracture after relatively minor force, or have low body weight, consider discussing these factors with a healthcare professional.

60s and Beyond: Think About Both Bones and Falls

As we age, changes in muscle strength and balance can affect fracture risk as well as changes in bone mass.

Alongside maintaining a balanced diet, regular appropriate physical activity and a suitable body weight, creating a living environment that reduces the risk of falls becomes increasingly important.

If you have become noticeably shorter, developed a more rounded back, experience continuing back or lower-back pain, or have experienced a fracture after relatively minor force, speak with a healthcare professional.

Summary: Bone Health Is Built Over Time

Osteoporosis is a condition in which bone strength decreases and fractures become more likely.

Bone mass tends to decline more rapidly in women after menopause, but bone health is not something that is determined only in later life.

Eating habits, physical activity, body weight, hormonal changes around menopause and fall prevention later in life can all contribute to long-term bone health.

Because osteoporosis can progress without obvious symptoms, it is worth paying attention to your bones and everyday habits while you are still feeling well.

Reviewing your daily meals, walking a little more, removing potential trip hazards at home or taking advantage of an opportunity to have your bone density measured are all practical places to start.

Bone health is built through many small habits over time.