Peak bone mass is when the bone that make up the spine for instance obtain the most bone tissue. Bone tissue includes everything that makes up bone not just calcium, phosphorus, and magnesium. It includes the protein that makes up type I collagen, water and enzymes and all the cells that maintain the health of the bone tissue. Together this living structure is called the bone mass. Peak bone mass is the point as which a bone has reached its highest development of all its various components. The timing of PBM is determined by an interaction of genetic and environmental factors and is different for each set of paired bones in the body. The pairs peak together with slight variation due to small quantities of unequal mechanical strain related to handedness or conditions like scoliosis affect the right and left hip differently for instance. Discounting these considerations, PBM occurs simultaneously in the paired bones throughout the body between the mid 20s through age 40. After the bone passes the peak, it begins to decline in mass gradually.

After PBM Bone Remodeling Replaces Bone Modeling
Bone remodeling replaces modeling in all bones that have reached PBM. Bone remodeling resembles modeling and uses the same cells but is otherwise different. During each normal remodeling cycle, a little more bone is removed than is replaced. Modeling was just the opposite in that with each modeling cycle there was more bone formed than removed so bone mass continually increased.

White adult women cannot stop the loss in bone mass due to remodeling but they can accelerate it. Analysis of normative bone density data on white women in their 30s and 40s shows that on average bone mineral density as measured by DXA in normal white women falls 3% or 0.3% annually. This rate of loss is not slowed by those who take calcium supplements, exercise, or use birth control pills. The loss continues unabated. The rate of loss is highly correlated with the reduction in ovarian testosterone production that peaks are age 30 in women. After age 30 ovarian production of testosterone falls progressively by 1.5% each year until menopause at age 50 when it ceases entirely.

The same normative bone density data in white women aged 40 to 50 years of age show a doubling of their bone loss rate to 6% or 0.6% annually. Again, the loss is inexorable with nothing being able to curtail it. No calcium, no vitamin D, no exercise routine, nothing halts the loss. Then come menopause and the rate of loss doubles again over the next decade.

How Not to Make it Worse
While you can do nothing to stop the slowly increasing bone loss, you can make it much worse. While exercise, calcium, magnesium, and vitamin D fail to keep you from loosing bone at this predetermined rate, if you become mineral or vitamin deficient and fail to be active then your bone loss will accelerate. So you are dammed if you do and really dammed if you don’t. The prescription here is not tough. Maintain a high calcium diet, take 2,000 iu of vitamin D3 every day and do regular moderate exercise 45 min 4 days each week. Try and live as active a lifestyle as possible meaning doing fun things outside that burn calories and help keep you fit. This prescription is not onerous. It is doable and will make a real difference not just for your bone health but for your overall health during middle life and will set you up for a good later life.