Conflicting evidence for daily calcium supplementation

Evidence from a recent meta-analysis (September 2015) published in the British Medical Journal goes against the long-standing recommended daily intake of calcium. In fact, one of the lead authors concluded “Most people don’t need to worry about their calcium at all.” His reasoning behind this is that randomized control trials have shown only a slight reduction in risk for fractures with calcium supplementation. At present, the U.S. daily recommended intake for calcium is approximately 1000-1200mg per day. Other countries have different daily recommendations (mostly lower amounts).

The meta-analysis looked at the results from 26 randomized control trials. Some of the major findings include serious adverse events such as kidney stones, gastrointestinal symptoms, and cardiovascular events. It was noted that only two randomized controlled trials evaluated dietary calcium’s effect on fracture risk. Both trials lacked significant power and therefore statistical significance was unable to be achieved.

It is estimated that women lose 0.5% to 1% of bone mass per year after age 40. Calcium supplementation has been recommended for the prevention of osteoporosis.

Previous researchers have expressed concern for the risk of hypercalciuria (elevated calcium in the urine) and hypercalcemia (elevated calcium in the blood) in post-menopausal women. The end result can be the formation of kidney stones. Other meta-analysis have shown an increased for cardiovascular events such as myocardial infarction in those post-menopausal females who take excess supplemental calcium.

There are several points to consider when looking at the results of these studies. While not universally accepted, calcium obtained through a normal diet is likely superior to taking supplemental calcium. Secondly, most need to monitor how much calcium they actually obtain through their regular diet. Some may not need any additional supplementation.

In regards to the newly published meta-analysis, there are additional co-factors, including Vitamin K2 and Vitamin D deficiency which must be considered before concluding that we should not worry about calcium.

Unfortunately, these published findings make it more difficult for clinicians and patients to reach any definitive conclusion regarding daily calcium intake.

This meta-analysis was funded by pharmaceutical giants, Merck, Amgen, Lilly, and Novartis.

 References:

Tai V., Leung W., Grey A., Reid IR., Bolland MJ. Calcium intake and bone mineral density: systematic review and meta-analysis. BMJ. 2015 Sept 29;351.

Gene mapping of the inner ear: Effects on hearing and balance

Hearing loss associated with aging or other disorders is a significant public health problem.

Within the inner ear are specialized sensory cells that include hair cells. Additional supporting cells also contained in the cochlea, provide structural and functional support to the hair cells. Collectively, these specialized cells help detect sound and enable us to hear. Similar specialized cells located in the utricle (pouch near the cochlea) help us maintain balance. This is part of the vestibular system.

These specialized cells are not able to repair themselves or regenerate. Aging along with certain medications, injuries, disease processes, and infections can lead to a loss of hearing and balance problems.

Research scientists from the University of Maryland School of Medicine and scientists from Tel Aviv University Sackler School of Medicine have collaborated in identifying a technique to help isolate a family of proteins that are essential for inner ear cell development.

Historical methods of analyzing gene activity have usually required thousands of cells. In contrast, the research teams, supported by the National Institute on Deafness and Other Communication Disorders (NIDCD) utilized a new technique for analyzing gene activity within one cell. This has allowed the researchers to better understand developmental patterns associated with the inner ear and vestibular system. This new knowledge may help lead to identifying ways to promote regeneration within the inner ear.

In a second study, the researchers used RNA sequencing technology to search for common regulatory regions within the genes expressed in specialized hair cells. They found a group of gene regulators known as Regulatory Factor Xs (RFX) are particularly active in the hair cells. This is believed to play a large part in hearing. In mice who lacked two RFX proteins, loss of hair cells and hearing occurred within 2 weeks after birth. Deafness occurred at approximately 3 months.

References:

National Institute on Deafness and Other Communication Disorders (NIDCD)

http://www.nidcd.nih.gov/news/releases/15/Pages/10152015.aspx

A compound related to Vitamin B3 may prevent hearing loss

A recent study published in Cell Metabolism by researchers from Weill Cornell Medical College and the Gladstone Institutes have identified a simple compound that may help prevent hearing loss. The compound nicotinamide riboside (NR) is a precursor to vitamin B3.

Noise induced hearing loss is a problem that can affect anyone at any age. The National Institutes on Deafness and Other Communication Disorders (NIDCD) estimates that more than 26 million Americans between the ages of 20 and 69 suffer from noise induced hearing loss. Hearing loss can result from a one-time exposure to an intense sound or from continuous exposure to loud sounds. Continuous or prolonged exposure to sounds over 85 decibels can cause hearing loss.

The process of hearing is based on a series of events that convert sound waves into electrical signals. Vibrations travel to the inner ear causing wave like ripples within the fluid inside the cochlea. There are tiny hair cells sitting along the top of inner membrane. These hair cells move up and down pushing against the sterocilia which transmits a signal to the auditory system within the brain. It is believed that exposure to loud noise can cause to damage to the junction where the nerves and hair cells meet, resulting in hearing loss.

Previous studies had identified that a chemical compound known as nicotinamide adenine dinucleotide (NAD+), which is chemically related to NR in this study, did protect nerve cells from injury however, it is an unstable compound. Using this information, researchers tested NR in lab mice and found that regardless whether the compound was given before or after exposure, NR did prevent hearing loss. It is believed that NR increases the activity of a protein known as SIRT3 (sirtuin 3) which is located within the mitochondria of the cells and is involved in regulating function.

The results of this study appearing to be promising. The researchers believe that the compound NR may also be useful for treating other disorders that are also mediated by the activity of protein sirtuin 3 such as hypertension, diabetes, and other metabolic syndromes.

References:

National Institutes on Deafness and Other Communication Disorders (NIDCD)

Brown KD, Maqsood S, Huang JY, Pan Y, Harkcom W, Li W, Sauve A, Verdin E, Jaffrey SR. Activation of SIRT3 by the NAD+ precursor nicotinamide riboside protects from noise-induced hearing loss. Cell Metabolism. 2014 Dec 2; 20(6): 1059-1068.