Dear Doctor: Calcium blood tests aren’t reliable indicator of body’s calcium stores. Here’s why

DEAR DR ROACH: I am a 60-year-old female. I was diagnosed with primary biliary cholangitis (PBC) in 2020. At the time, I had a bone density scan that showed osteopenia of the left femoral neck with a T-score of -1.3. My 10-year risk of any fracture was 6.9%, with 0.5 % for hip fractures.

My hepatologist wants me to take a calcium supplement, even though my calcium level has always been normal. I have always been overweight and led a very sedentary way of life. I had vitamin D tests done yearly, but the deficiency was, negligently, never addressed by my doctors.

So, my first question is, do I really need to take this supplement? I am concerned that too much calcium may do more harm than good, and my osteopenia may not have been caused by PBC.

The other question is, would taking vitamin K2 along with vitamin D and calcium help to absorb the vitamin D better so that it would not accumulate in my kidneys and damage them in the process? — R.Z.

ANSWER: PBC is an autoimmune disease where the body attacks the bile ducts. Without treatment, it can lead to loss of the bile ducts, eventually leading to cirrhosis and liver failure. Since ursodeoxycholic acid has been available, fortunately, the majority of people with this condition have a normal life expectancy. Few develop cirrhosis.

A lesser-known complication of PBC is osteopenia and osteoporosis. There are several theories as to why this occurs, including decreased growth factors and toxicity to bone-producing cells. Low vitamin D and, possibly, vitamin K2 may play a role as well.

It’s important for all people with osteopenia or osteoporosis to have adequate calcium in their diets. Calcium blood tests are not a reliable indicator of calcium stores in the body, since inadequate calcium intake will cause the body to take calcium out of the bones so that the blood levels remain normal. You can be severely deficient in calcium and dangerously osteoporotic with normal calcium blood levels.

Ensuring adequate dietary calcium then becomes of utmost importance. If you aren’t getting 1,000-1,200 mg of calcium in your diet, then changing your diet to add more, or taking a supplement, is recommended. Kidney stones are a complication of calcium supplementation, and there is controversy surrounding whether the calcification of blood vessels is more likely in people who take calcium supplements. For these reasons, dietary calcium is preferred if possible.

Many people with osteoporosis need supplemental vitamin D to keep their blood levels in the recommended range, which is 30-48 ng/mL (75-120 nmol/L) for a person with PBC and osteopenia, in my opinion.

Although studies in Japan have shown benefit when using vitamin K2 supplementation in people with osteoporosis, I don’t generally recommend it based on multiple other studies that failed to show a benefit. However, for the bone disease associated with PBC in particular, I think K2 is reasonable for people who wish to try it. Vitamin K2 works through its mineralization effect on the bone itself. By carefully monitoring vitamin D blood levels, you can avoid the unusual complication of vitamin D excess.

Finally, becoming less sedentary will help, even if it’s walking an extra 10-20 minutes a day.

* * *Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected] or send mail to 628 Virginia Dr., Orlando, FL 32803.

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