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Vitamin D3 is usually well-absorbed by the body

BY KEITH ROACH, M.D.

DEAR DR. ROACH: I am 60 years old and generally healthy, but my vitamin D is low (below 20). I took 50,000 IU of vitamin D2 for six weeks, then 2,000 IU of vitamin D3 daily for the past two years. Recently, I started magnesium glycinate, because I read in a journal that it helps D3 get absorbed better in our body and that otherwise, 90% of D3 is passed in stool or urine.

Is that correct? If yes, then is magnesium glycinate the right option for it to absorb easily in our body? — R.I.C.

ANSWER: Vitamin D3 is normally well-absorbed by healthy people without needing any other supplements. Bile is needed for absorption of all D vitamins, as they are fat-soluble, so people with severe obstructive liver disease, as well as people with other malabsorption syndromes, may have difficulty.

For vitamin D to be passed in the urine, it would need to be absorbed. However, vitamin D is normally excreted mostly through stool, even after absorption.

Magnesium is necessary for proper bone health, so magnesium supplementation is appropriate for people with low magnesium level. This is uncommon, but it is a concern in people taking some diuretic medications. It’s possible that the journal you read may have meant absorbed into bone, not into the body.

A simple blood test of your vitamin D level will confirm adequate absorption, and it should be checked if there is a reason to suspect malabsorption.

DEAR DR. ROACH: Should senior citizens think long and hard about whether they are endangering their mental health when riding roller coasters? I didn’t know there is a cushion between my skull and my brain, and it’s drying out just like other parts are at my age. I caved under pressure from my grandchildren, and rode one that jerks riders’ heads from side to side. I started experiencing symptoms of brain damage, and my doctor said I could have had a concussion on that ride.

The only sign there said that people with neck or back problems might want to stay off the coaster, but no warning was given about age. What do you think? — C.S.

ANSWER: The meninges and cerebrospinal fluid act as shock absorbers for the brain, but they aren’t perfect. In older adults, the brain normally shrinks a little, so there is more room for it to move and be damaged under acceleration.

I found several studies looking at the accelerations on a person’s head in a roller coaster compared with sports, such as a “header” in soccer, and car crashes. The authors concluded that the risk of brain damage (i.e., concussion or traumatic brain injury) was low. However, I found many case reports of neurological damage due to roller coasters. A study from Stanford suggested that two people on the very same ride could have very different head pressures from each other.

Although I couldn’t find evidence to support it, I agree with you that some older adults will have more susceptibility to injury due not only to loss of shock-absorbing capability in the skull, but also with changes to muscles, joints, reflexes and bones with age. This could lead to a greater potential for harm.

I still think that older people who enjoy roller coasters can do so with minimal risk, but the risk isn’t zero.

Certainly, people who have noticed symptoms after such a ride should avoid the most aggressive of these rides, which can exert a great deal of pressure.

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