February 26, 2010

Low dose vitamin D inadequate to improve neuromuscular function

A report published online on February 3, 2010 in the American Journal of Clinical Nutrition revealed that the equivalent of 1200 international units of vitamin D per day for a period of four months is not enough to stabilize posture by reducing body sway in older individuals with insufficient levels of the vitamin.

Postural body sway is the corrective body movement that results from the control of body position. Increased mediolateral sway was found to be associated with recurrent falling in a group of participants in the Longitudinal Aging Study of Amsterdam. Vitamin D insufficiency has been associated with muscle weakness which increases the risk of falling, and reduced levels of vitamin D have been linked to falls as well as fractures.

In a randomized, double-blinded, placebo-controlled trial, Paul Lips at Vrije University in Amsterdam and his colleagues evaluated the effects of a weekly dose of 8400 international units orally administered vitamin D3 on postural body sway in 226 men and women aged 70 and older who had low serum 25-hydroxyvitamin D levels of between 6 and 20 nanograms per milliliter (ng/mL) upon enrollment. For those whose calcium intake was below 1000 milligrams per day, 500 milligrams calcium (from calcium carbonate) per day was prescribed. Postural body sway and physical performance were assessed prior to and following the trial. Serum 25-hydroxyvitamin levels were re-evaluated after 16 weeks of treatment.

While 25-hydroxyvitamin D levels increased to an average of 26.2 nanograms per milliliter in the group that received the vitamin, this was still well below a minimum optimal level of 50 ng/mL. Although mediolateral sway and physical performance at the trial's conclusion did not differ significantly between those who received vitamin D and those who received a placebo, a post-hoc analysis of patients who had elevated sway at baseline found a reduction in sway among those who received the vitamin. Adverse events were similar in both groups.

"The results of neuromuscular function do not confirm the results of a number of studies that showed higher serum 25-hydroxyvitamin D concentrations to be associated with better physical performance," the authors remark in their discussion of the findings. A possible reason, according to the authors, is that those with severe deficiency, which they categorize as a serum vitamin D level of under 6 nanograms per milliliter, were excluded from the study. Another factor that could explain the results is that many subjects had low mediolateral sway values upon enrollment and relatively high physical function, suggesting that improvements in neuromuscular function may not occur above a ceiling or maximum level. "In a post-hoc subgroup analysis, the patients who were not near the ceiling level of neuromuscular function at baseline did experience an average improvement in mediolateral sway with treatment with 8400 IU vitamin D3," they note. However, the researchers failed to observe that the improvement in serum vitamin D3 still fell short of optimal levels, and as such, may not have been sufficient to exert the intended benefits.

Vertigo

Broadly classified, vertigo is usually either physiologic or pathologic. Physiologic vertigo is normal and occurs when there is a conflict between the signals sent to the brain by the vestibular system and by the other balance-sensing systems of the body. It can also occur when the head is subjected to unfamiliar movements, such as the rolling motion associated with seasickness, spinning for an extended period, or when the head is held in an unusual position (such as when you tilt your head and neck back for an extended period). Physiologic vertigo is usually easily corrected, either by moving the head and neck into a more normal position or by focusing on an external reference point to give the vestibular system an opportunity to stabilize. This is why a person with motion sickness is advised to look into the distance and focus on some faraway point, such as the horizon.

Benign paroxysmal positional vertigo (BPPV) occurs after a sudden movement of the head. It is one of the most common types of vertigo (Crespi V 2004). Women are affected twice as often as men, and the average age of onset is the middle 50s (Salvenelli F et al 2004).

The conventional treatment of vertigo depends on its underlying cause. In the case of BPPV, the most common therapy is repositioning exercises that redistribute the calcium carbonate back throughout the inner ear. There are various forms of repositioning exercises, including the Epley maneuver. In the Epley maneuver, the person lies down and the head is moved from side to side, with each position being held about 20 seconds. This has been shown to redistribute the calcium deposits in the inner ear, thus re-establishing normal function (Epley JM 1994).

If you have vertigo, it is important to see a physician, who will try to uncover any underlying conditions that may be causing the vertigo. In some kinds of vertigo (for example, BPPV), patients may be taught the Epley maneuver and other positional exercises that have been shown to help relieve vertigo.

In other forms of vertigo, particularly Ménière’s disease, the following supplements may help improve symptoms:

• Vitamin C—1000 to 6000 mg daily with food with 500 to 1000 mg of N-acetylcysteine daily
• Vitamin B6—150 mg with food, while vertigo persists
• Ginkgo biloba—120 mg daily
• CoQ10—50 to 200 mg daily with food
• Ginger—As directed on label (especially for motion sickness).

Life Extension Update

• Vitamin D supplements reduce falls in older adults
• Review finds current vitamin D recommendations insufficient to achieve healthy blood levels

What's Hot

• Vitamin D supplementation helps prevent nursing home falls
• Higher dose vitamin D needed to help prevent falls
• Vitamin D plus calcium reduces falls in women

Life Extension Magazine®

• Vitamin D cancer prevention and other new uses
• Guarding against the dangers of vitamin D deficiency

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