Dear Doctor: If vitamin D and calcium don't reduce the risk of bone fractures in older adults, as I recently read, is there any point in taking them?

Dear Reader: For years, the medical community has been touting calcium and vitamin D to prevent fractures; I've been guilty of this practice as well. Although some studies suggested that calcium and vitamin D could help prevent osteoporosis, the degree of improvement was never overwhelming. Still, we held fast to our medical dogma. Now, as you mention, a study has shown the need to look at the data without bias in order to provide more nuanced counsel to our patients.

The research, recently published in the Journal of the American Medical Association (JAMA), reviewed 33 studies -- with a total of 51,145 participants -- assessing the risk of fractures in people taking either calcium alone, vitamin D alone or calcium with vitamin D.

The calcium-only studies included various types of the mineral: calcium citrate, carbonate, malate and gluconate. The seven studies assessing the impact on hip fractures showed no improvement with the use of calcium. In fact, researchers found a 53 percent increase in the risk of hip fractures among people taking calcium. The findings on spinal fractures were more positive. Nine studies assessed that connection, finding a 17 percent decrease in risk with calcium use. Seven studies assessed total fracture rate, finding a 12 percent decrease in risk, but the rate was not considered statistically significant.

The studies that assessed the specific impact of vitamin D similarly failed to produce positive results. In the nine studies of vitamin D use and hip fracture, researchers found a 21 percent increase in the risk of fracture among those taking vitamin D. The studies assessing the impact on spinal fracture and total fractures simply found no benefit.

The studies assessing the impact of calcium combined with vitamin D yielded only marginally better results. Although the seven studies looking at the impact on hip fractures found no reduction in risk, the three studies looking only at spinal fractures did show a 37 percent reduction in risk. The studies that looked at total fracture rate showed a non-significant 10 percent reduction in risk.

The 33 trials varied in length from four months up to seven years. Of note, many studies conducted for longer periods were more likely to show a reduction in the risk of spinal fractures with the use of calcium or vitamin D, which may be because calcium and vitamin D are slow to improve bone density.

The JAMA study did not specifically look at people with osteoporosis. For them, calcium has been shown effective in maintaining bone density. A 1992 study of female nursing home residents (who have a higher likelihood of osteoporosis) found that calcium and vitamin D decreased the rate of hip fracture by 43 percent and the overall fracture rate by 32 percent.

So, if you have osteoporosis, I would recommend calcium and vitamin D. If you're a healthy person without osteoporosis, calcium and vitamin D may produce a slight decrease in the risk of spinal fracture. Overall, however, there seems to be little benefit to this supplementation.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: After the hurricane in Houston, a lot of moms donated their breast milk to help the babies. Is that safe?

Dear Reader: For as long as women have been giving birth, they have been sharing breast milk. In earliest history -- references to the practice date back to 2000 B.C. -- this was in the guise of the wet nurse. That is, a lactating woman who breastfed infants who were not her own. If a mother is unable to either breastfeed or express her own milk, the World Health Organization cites donor milk as the next best feeding option.

That's because breast milk is the optimal food for infants. Not only is it a source of probiotics for gut health and antibodies to fight off viruses and bacteria, but studies show that breastfed babies get fewer ear infections, have a lower incidence of obesity, and have a lower risk of conditions like asthma, diabetes and eczema. They are less likely to develop gastroenteritis and diarrhea than babies raised on formula, and have a lower incidence of SIDS, or sudden infant death syndrome.

In recent years, we've seen the advent of milk banks. These are services that collect breast milk donations for use in hospitals for pre-term infants, and for use by women who can't produce enough of their own milk. The donations come from women who have undergone medical screening, often including blood tests. The donor milk is then processed and, at several points in the process, tested for pathogens.

This is important because babies can be exposed to infections and diseases, including the HIV virus, via breast milk. Human milk can contain chemical and environmental contaminants, illegal drugs, and even certain prescription and over-the-counter drugs. And like any food, breast milk must be collected and stored properly to avoid spoilage and microbial contamination.

To answer your question, yes, breast milk that comes from a reputable milk bank is safe. Steps are taken to screen the donors and then properly process the milk. And while many women take part in the hundreds of online private milk-sharing networks that have sprung up around the country, the Food and Drug Administration recommends against them.

The FDA cites the lack of rigorous donor screening as a primary concern. Peer-to-peer networks rely on self-reporting of the donor's physical health. Also, recipients of donor milk within these networks are dependent on each donor's dedication to following good hygiene practices in both collection and storage.

When it comes to processing donor milk, the milk banks use the Holder method of pasteurization. This involves heating the milk to a relatively low temperature, one that kills pathogens but leaves the beneficial qualities of the milk largely intact.

At this time, there are no universal health and safety guidelines for milk sharing, though a few states have established standards for milk banks to adhere to. If you'd like to learn more about milk banks, or want to find one in your area, the Human Milk Banking Association of North America, or HMBANA, can help. It's a voluntary professional association that suggests safety guidelines for donor screening, milk collection, storage, testing and distribution. You can find it online at hmbana.org.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Every morning upon waking, I feel an even/steady pulsing of about 200 beats per minute, although my pulse is normally about 60 beats per minute. I'm 84, with no symptoms of atrial fibrillation and a body mass index of 24. I take no medications and have no aches and pains. Again, this high pulse rate occurs only when I wake up, and I feel normal at the time. What could be causing this, and should I be concerned?

Dear Reader: Yes, you should be concerned. At the age of 84, even with extreme exertion, your pulse should not be so high.

Before we explore potential causes, let's discuss what creates the pulse, or heart rate. The pulse rate that you feel in your wrist or neck occurs with contraction of the ventricles, the large muscular portions of the heart. Normally, the atria, which sit atop the ventricles, initiate the pulse, which then travels down the ventricles.

The pulse rate can be affected by, among other things, disorders of the atria, including -- as you mentioned -- atrial fibrillation. This haphazard rhythm of the atria can indeed produce pulse rates of 200, but not the even, steady pulse that you describe. Atrial flutter -- a regular rapid beating of the heart that, like fibrillation, can originate from multiple parts of the atria -- is possible but perhaps unlikely because the fast beating of the atria would only be able to cause contraction of the ventricles at certain intervals. Thus, pulse rates of 300, 150, 100, 75 or 60 are possible, but a 200 rate would occur only under certain conditions. Atrial tachycardia -- a regular rapid beating originating from one section of the atrium -- can cause rates of 200, so this is a possibility.

Disorders of the ventricles also can cause a very rapid heart rate. Here, instead of the atria initiating the pulse rate, a portion of the ventricles creates its own rate. This can occur when the muscular part of the heart is damaged, leading to an electrical impulse that causes the whole ventricle to contract. Ventricular fibrillation, like atrial fibrillation, is a disorganized rhythm of the heart and the leading cause of sudden cardiac death. Due to your lack of symptoms and the regularity to your pulse rate, this seems unlikely.

Perhaps most likely is ventricular tachycardia, which has a regular rhythm with rates greater than 100 and can have rates as high as 250. Besides having a fast heart rate, those with short bursts of ventricular tachycardia may not feel any other symptoms.

We also have to consider the fact that this happens only in the morning. That takes us to our bodies' circadian rhythm, which means the core processes of the body fluctuate depending upon the time of day. For that reason, increased blood pressure, heart rate, blood vessel constriction and clotting are greatest in the morning. Similarly, heart attacks are more frequent in the morning, as are ventricular fibrillation and tachycardia.

Note that alcohol withdrawal and intoxication can increase this risk of abnormal heart rhythms.

Conditions like atrial fibrillation and atrial flutter increase your risk for strokes, while ventricular fibrillation and tachycardia may increase the risk of sudden death. Undoubtedly, I recommend seeing your doctor. He or she can order a heart monitor to measure your heart rate and, more important, determine what type of rhythm is causing this.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)