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RESEARCH SUPPORTIVE OF ZMA SUPPLEMENTATION
1. The effect of zinc depletion on muscle function
was tested in 8 male subjects. After receiving 12 mg Zn/day for 17 days,
the subjects received 0.3 mg Zn/day for either 33 or 41 days. The
subjects were then divided into two groups for zinc repletion. Group A
subjects received overnight infusion of 66 mg of Zn on Day 1 and 10 and
then were fed 12 mg Zn/day for another 16 days. Group B subjects were
fed 12 mg Zn/day for 21 days. Peak force and total work capacity of the
knee and shoulder extensor and flexor muscle groups were assessed using
an isokinetic dynamometer at baseline, at two points during depletion,
and at repletion. Plasma zinc levels decreased by an average of 67%
during depletion and remained 9% below baseline after repletion. The
peak force of the muscle groups was not found to be significantly
affected by acute zinc depletion, however, shoulder peak force
(strength) was found to be reduced by 9.2% in the extensor muscles.
Total work capacity (muscle endurance) for the knee extensor muscles and
shoulder extensor and flexor muscles declined significantly by 28.1%,
24.1% and 26.4%, respectively. This study demonstrates that muscle
endurance, or total work capacity, declines rapidly with acute zinc
depletion and the degree of the decline was correlated with the
reduction in plasma zinc concentration.
Van Loan, MD, et al. The Effects of Zinc Depletion on Peak Force and
Total Work of Knee and Shoulder Extensor and Flexor Muscles. Int J of
Sport Nutr, June 1999, Vol. 9, No. 2, 125-135.
2. A study was conducted to determine the effects of magnesium
supplementation on strength development during a double-blind, 7-week
strength training program in 26 untrained subjects (14=placebo, 12= Mg),
18-30 years old. Pre and post peak quadriceps torque (leg press)
measurements were made using an isokinetic dynamometer. The leg muscle
strength of the magnesium supplemented group significantly increased by
26%, compared to only 10% for the placebo group.
Brilla, LR, et al. Effect of Magnesium Supplementation on Strength
Training in Humans. J Am Coll Nutr, July 1992, Vol 11, No. 3, 326-329
3. Serum zinc levels were determined in 160 training athletes (103 males
and 57 females). In 23.3% of male and 43% of female athletes, serum zinc
was significantly below the "normal range".
Haralambie, G. Serum zinc in athletes in training. Int J Sports Med 2
(1981) 135-138.
4. Magnesium, zinc and copper status of 270 US Navy Sea, Air and Land
(SEAL) trainees was determined from dietary intakes and biochemical
profiles. The dietary intakes of 34% and 44% of the trainees were below
the RDA for Mg and Zn, respectively. The blood plasma concentrations of
Mg and Zn were significantly below the "normal range" for 23% and 24% of
the trainees, respectively.
Sing A, et al. Magnesium, Zinc and Copper status of US Navy SEAL
trainees. Am J Clin Nutr 1989;49:695-700.
5. Serum zinc levels were measured in 20 adolescent gymnasts (9 boys, 11
girls, age 12-15). They had 26% lower serum zinc levels (0.599 +/- 0.026
mg/l) when compared to 118 matched controls (0.810 +/- 0.014, p <
0.001). The gymnasts serum zinc levels were positively correlated with
adductor strength (r=0.468, p < 0.05). The 11 of 20 gymnasts with serum
zinc < 0.6 mg/L had lower insulin-like growth factor binding protein 3
levels than the others (2.326 +/- 0.064 vs 2.699 +/- 0.12, p < 0.01).
This protein is supposed to reflect growth hormone activity. Thus, zinc
is lowered in trained adolescent gymnasts and this reduction could play
a role in abnormalities of growth or muscular performance.
Brun J, et al. Serum zinc in highly trained adolescent gymnasts. Bio
Trac Elem Res, 1995, Vol. 47, 273-278.
6. Twenty-one professional football (soccer) players underwent a maximal
exercise test on a cycloergometer, with progressively increasing
workloads until VO2max. On the whole these subjects had low serum zinc
because nine (43%) of them had a hypozincemia (0.54 +/- 0.01 mg/L) which
suggested a zinc deficiency. The subjects with low serum zinc had a 26%
lower power output (123 +/- 8.71 vs. 166.27 +/- 14.84 watts, p = 0.029)
and exhibited a 35% higher increase in blood lactate (lactic acid)
during exercise (7.51 +/- 0.81 vs. 5.57 +/- 0.33 mmol/L, p <0.04)
resulting in a 24% lower 2 mmol lactate threshold (44.7 +/- 3.9% vs.
58.9 +/- 4.8% of maximal power output p < 0.04). In conclusion, this
study suggests that zinc status may influence blood rheology (flow)
during exercise by an effect related to lactate accumulation.
Khaled S, et al. Serum zinc and blood rheology in sportsmen (football
players. Clin Hemo and Micro 17 (1997) 47-48.
7. Ten collegiate basketball players serum mineral levels were measured
before official practice began and immediately following the competitive
season. Diets were monitored and remained the same throughout the four
month period. Mean serum values for Mg and Zn decreased pre-season to
post- season by 16% and 41%, respectively.
Lefavi RG, et al. Reduced serum mineral levels in basketball players
after season. Med and Sci in Sports and Exer. Vol. 27, No. 5, May 1995
8. Twelve professional volleyball players and 12 control subjects were
studied to determine the effects of daily physical training on serum,
sweat and urine zinc concentrations. The professional athletes trained
every day in two sessions, one in the morning (work in the gym for 2
hours) and another in the afternoon (specific work on the sports field
for 3 hours). Simultaneously, 12 male volunteer university students, who
were moderately trained, participated as the control group. The study
was conducted over a period of 10 weeks. Pre-post tests were made using
a progressive bicycle ergometer (increasing 30 W every 3 minutes to
reach a maximum tolerated power). Pre-post blood samples were obtained
at rest and immediately following exercise. After ten weeks of training,
the professional athletes showed a significant increase in 24 hour
urinary zinc excretion (22% greater losses), in contrast to a slight
decrease (2% less) in the controls. The athletes also showed a very
significant increase in the zinc loses in sweat compared to the
controls. The athletes sweat zinc concentrations increased by an
astounding 300%, compared to only 30% increases in the control group.
The athletes serum zinc levels decreased by 4%, compared to a 2%
decrease in the control group. Finally, the post exercise cortisol
levels of the athletes significantly increased by 93%, compared to only
an 18% increase in the controls. The authors stated that the athletes
"cortisol levels increased in response to the exercise work load stress,
and this behavior seems to be related to muscular damage". The authors
went on to say that "It seems that the changes in zinc metabolism found
in the study may be damage, increased protein turnover and increased
zinc excretion (via sweat and urine). Because strenuous exercise during
a period of competition can induce a "catabolic state" and has been
shown to increase skeletal muscle protein turnover, it is likely that
urine zinc is derived from muscle tissue". The authors concluded by
saying that "Zinc supplementation and/or stress control appear to be
indicated in athletes. In our practical opinion, we think that
alterations in zinc metabolism with increases in zinc excretion and
stress levels lead to a situation of latent fatigue with a decrease of
endurance".
Cordova A, et al. Effect of training on zinc metabolism: changes in
serum and sweat concentrations in sportsmen. Ann Nutr Metab, 1998 42:5,
274-82.
9. Plasma zinc, iron, copper and selenium levels were measured in 66
Navy SEAL trainees before and after a 5 day period of sustained physical
and psychological stress called "Hell Week". The trainees pre-post
plasma zinc levels decreased by 33%.
Singh A, et al. Biochemical indices of selected trace minerals in men:
effect of stress. Am J Clin Nutrition 1991; 53:126-31.
10. Nine healthy, male subjects (18-40 years) were supplemented daily
with 365 mg of magnesium as aspartate for 14 days. Before and after the
supplementation period each subject performed a rigorously identical one
hour ergometer exercise. The magnesium supplementation significantly
reduced the subjects plasma levels of the catabolic "stress" hormone
cortisol by an average of 25% (P < 0.025), which remained decreased
during the exercise. The magnesium also significantly lowered the
subjects' heart rates throughout the exercise period by an average of 8%
(P < 0.03). Golf SW, et al. Plasma aldosterone, cortisol and electrolyte
concentrations in physical exercise after magnesium supplementation.
Clin Chem Clen Biochem, 1984, Vol. 22, pp. 717-721.
11. Medical students were tested to determine the acute effect of zinc
supplementation on cortisol levels. The test was started at 7:00 AM
after a 12 hour fast. Serial blood samples were collected from an
experimental zinc group and controls at 30 minute intervals for 240
minutes. A subgroup of 7 subjects (3 men, 4 women) ingested 25 mg of
zinc immediately after the baseline collection and their cortisol levels
were compared to 8 matched controls who received a placebo. The control
group started out with an average cortisol level of 11 mcg/dL and fell
to 9 mcg/dL at 240 minutes, which is an 18% reduction. The zinc
supplemented group started out with an average cortisol level of 16 mcg/dL
and significantly dropped to 6.5 mcg/dL, which is a 59% reduction. In
summary, the zinc supplemented group had a 41% greater reduction in
cortisol levels compared to controls. The fact that zinc inhibits basal
cortisol secretion in humans may be related to a direct blockade of
cortisol synthesis and secretion in the adrenal cortex.
Brandao-Neto J, et al. Zinc acutely and temporarily inhibits adrenal
cortisol secretion in humans. Bio Trace Elem Res, 1990, Vol. 24, 83-89.
12. Nine runners urine zinc and chromium levels were measured on a run
day and compared to the levels on a non run day. The runners daily
losses of zinc in urine were 50% greater on a run day compared to a non
run day.
Anderson, R. Strenuous running. Bio Trac Elem Res, Vol. 6 (1984) 327-
336.
13. A percentage of testosterone is converted to dihydrotestosterone
(DHT) by the enzyme 5a-reductase. An invitro study was conducted to
determine the inhibition of 5a-reductase activity by zinc sulphate and
azelaic acid. When added at concentrations of 3 or 9 mmol/l, zinc was a
potent inhibitor of 5a-reductase activity. At a high concentration of 15
mmol/l, zinc completely inhibited 5a-reductase. The addition of vitamin
B-6 potentiated the effect of zinc and resulted in a two-fold increase
in the inhibition of 5a-reductase. A moderate concentration of 1.5 mmol/l
of zinc in combination with 0.025% of vitamin B-6 inhibited the
5a-reductase activity by 90%. The zinc and vitamin B-6 combination may
be effective at limiting DHT production and could represent a potential
therapeutic agent in the treatment of androgen related pathology.
Stamatiadis D, et al. Inhibition of 5a-reductase activity in human skin
by zinc and azelaic acid. Brit J of Derm, 1988, Vol. 119, pp. 627-632.
14. Androgen metabolism and aromatization, androgen and estrogen
receptor binding and circulating levels of reproductive hormones were
studied in zinc deficient rats. The zinc deficient group had
significantly lower serum concentrations of testosterone (2.8 +/- .07
nmol/L) compared to the controls (8.7 +/- .07 nmol/L). This represents a
remarkable 68% reduction in circulating testosterone levels. Scatchard
analysis of the receptor binding data showed a significantly higher
number of estrogen receptors in the zinc deficient group (36.6 +/- 3.4
fmol/mg protein) than in controls (23.3 +/- 2.4 fmol/mg protein) and a
significantly lower number of androgen binding sites in rats fed the
zinc deficient diet (6.7 +/- o.7 fmol/mg protein) than in controls (11.3
+/- 1.2 fmol/mg protein). To summarize, zinc deficiency caused a 41%
reduction in the number of androgen binding sites and a 57% increase in
the number of estrogen receptors. These findings indicate that zinc
deficiency significantly reduces circulating testosterone concentrations
and modifies sex hormone receptor levels.
Om AS, et al. Dietary zinc deficiency alters 5 alpha-reduction and
aromatization of testosterone and androgen and estrogen receptors. J
Nutr, 1996, Apr, 126:4,842-8.
15. Androgen binding was studied in zinc deficient rats. The
experimental group of animals were maintained on a zinc deficient diet
for 3 months. Scatchard analysis of the data revealed that the number of
androgen binding sites in the zinc deficient rats was 31 +/- 5.2 fmol/mg
cytosol protein. This was significantly lower than that (84 +/- 11.5
fmol/mg protein) of the controls. This 63% decrease in the number of
androgen receptor cites in the zinc deficient state indicates that this
metal is extremely important in the androgen binding process in the
target cells.
Chung KW, et al, Androgen receptors in ventral prostate glands of zinc
deficient rats. Life Sci,1986, Jan 27, 38:4, 351-356.
16. Nine men participated in an 85 day zinc depletion/repletion study
divided into 3 metabolic periods: 18 day baseline, a 44 day depletion,
and a 23 day repletion. 12 mg of zinc per day was fed to the men during
baseline and were held constant after adjustments during the baseline
period. Plasma zinc declined from 77.1 +/- 0.03 mcg/dl at baseline to
28.1 +/- 0.07 mcg/dl at depletion; concentrations returned to 77.9 +/-
0.03 mcg/dl at repletion. Total body weight, fat, fat-free mass (FFM),
and bone mineral did not change during depletion, but total body water
increased 5.3% +/- 1.9%, or about 2 kg or 4.4 lbs (P <0.05) by the end
of the depletion and returned to baseline values at the end of
repletion. The percent water in FFM increased from 71% +/- 1 to 75% +/-
(P <0.05) at the end of depletion and was associated with a small
decrease in body protein. The data suggest that zinc depletion impairs
water balance.
Sutherland B, et al, Effect of experimental zinc depletion on body
composition and basal metabolism in men. The FASEB Journal, Mar. 10,
1995, Volume 9, Number 4.
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