Don't eat tofu if you want a functioning brain

Brain Aging and Midlife Tofu Consumption

Objective: To examine associations of midlife tofu consumption with brain function and structural changes in late life.

Methods: The design utilized surviving participants of a longitudinal study established in 1965 for research on heart disease, stroke, and cancer. Information on consumption of selected foods was available from standardized interviews conducted 1965–1967 and 1971–1974. A 4-level composite intake index defined “low-low” consumption as fewer than two servings of tofu per week in 1965 and no tofu in the prior week in 1971. Men who reported two or more servings per week at both interviews were defined as “high-high” consumers. Intermediate or less consistent “low” and “high” consumption levels were also defined. Cognitive functioning was tested at the 1991–1993 examination, when participants were aged 71 to 93 years (n=3734). Brain atrophy was assessed using neuroimage (n=574) and autopsy (n=290) information. Cognitive function data were also analyzed for wives of a sample of study participants (n=502) who had been living with the participants at the time of their dietary interviews.

Results: Poor cognitive test performance, enlargement of ventricles and low brain weight were each significantly and independently associated with higher midlife tofu consumption. A similar association of midlife tofu intake with poor late life cognitive test scores was also observed among wives of cohort members, using the husband’s answers to food frequency questions as proxy for the wife’s consumption. Statistically significant associations were consistently demonstrated in linear and logistic multivariate regression models. Odds ratios comparing endpoints among “high-high” with “low-low” consumers were mostly in the range of 1.6 to 2.0.

Conclusions: In this population, higher midlife tofu consumption was independently associated with indicators of cognitive impairment and brain atrophy in late life.

Geez, those with high tofu consumption were up to twice as likely to have low cognitive performance. That tofu stuff really messes you up!

The elevated prevalence of cognitive impairment we observed in the highest compared with the lowest midlife consumers of tofu was roughly of the magnitude as would be caused by a four year difference in age or a three year difference in education. In this study population, 20% to 25% of the burden of cognitive impairment appears attributable to midlife tofu consumption—an effect size of enormous public health importance, yet not readily discernable in comparisons across populations of diverse education, occupation, age distribution and genetic composition, especially when studied using different methods.

ED associated with soy and veganism

Hypogonadism and erectile dysfunction associated with soy product consumption.

Abstract
Previous research has focused on the beneficial effects of soy and its active ingredients, isoflavones. For instance, soy consumption has been associated with lower cardiovascular and breast cancer risks. However, the number of reports demonstrating adverse effects of isoflavones due to their estrogenlike properties has increased. We present the case of a 19-y-old type 1 diabetic but otherwise healthy man with sudden onset of loss of libido and erectile dysfunction after the ingestion of large quantities of soy-based products in a vegan-style diet. Blood levels of free and total testosterone and dehydroepiandrosterone (DHEA) were taken at the initial presentation for examination and continuously monitored up to 2 y after discontinuation of the vegan diet. Blood concentrations of free and total testosterone were initially decreased, whereas DHEA was increased. These parameters normalized within 1 y after cessation of the vegan diet. Normalization of testosterone and DHEA levels was paralleled by a constant improvement of symptoms; full sexual function was regained 1 y after cessation of the vegan diet. This case indicates that soy product consumption is related to hypogonadism and erectile dysfunction. To the best of our knowledge, this is the first report of a combination of decreased free testosterone and increased DHEA blood concentrations after consuming a soy-rich diet. Hence, this case emphasizes the impact of isoflavones in the regulation of sex hormones and associated physical alterations.

Aggressive dominance and testosterone

The relation between dominance, anger, and hormones in normally aging men: results from the Massachusetts Male Aging Study.

A Gray, D N Jackson and J B McKinlay
+ Author Affiliations

New England Research Institute, Watertown, Massachusetts 02172.
Abstract

This paper examines the relation of two personality characteristics (dominance and anger) to hormones in normally aging men. The relation of the Jackson Personality Research Form E Dominance subscale and the Spielberger Anger Expression scale to serum levels of 17 endocrine variables, including testosterone (T) and dihydrotestosterone (DHT), cortisol, and prolactin, was examined in 1709 men aged 39 to 70 years randomly sampled from the Boston Metropolitan Statistical Area. Canonical correlation analysis resulted in the identification of a personality profile characterized as dominant with some aggressive behavior that tends to correlate with a hormonal pattern labeled the "availability of androgens." These results partially support previous findings in animals, adolescents, and criminal populations that "aggressive dominance" is related to testosterone.

DHEA supplementation in older men and women

Effects of replacement dose of dehydroepiandrosterone in men and women of advancing age.

Aging in humans is accompanied by a progressive decline in the secretion of the adrenal androgens dehydroepiandrosterone (DHEA) and DHEA sulfate (DS), paralleling that of the GH-insulin-like growth factor-I (GH-IGF-I) axis. Although the functional relationship of the decline of the GH-IGF-I system and catabolism is recognized, the biological role of DHEA in human aging remains undefined. To test the hypothesis that the decline in DHEA may contribute to the shift from anabolism to catabolism associated with aging, we studied the effect of a replacement dose of DHEA in 13 men and 17 women, 40-70 yr of age. A randomized placebo-controlled cross-over trial of nightly oral DHEA administration (50 mg) of 6-month duration was conducted. During each treatment period, concentrations of androgens, lipids, apolipoproteins, IGF-I, IGF-binding protein-1 (IGFBP-1), IGFBP-3, insulin sensitivity, percent body fat, libido, and sense of well-being were measured. A subgroup of men (n = 8) and women (n = 5) underwent 24-h sampling at 20-min intervals for GH determinations. DHEA and DS serum levels were restored to those found in young adults within 2 weeks of DHEA replacement and were sustained throughout the 3 months of the study. A 2-fold increase in serum levels of androgens (androstenedione, testosterone, and dihydrotestosterone) was observed in women, with only a small rise in androstenedione in men. There was no change in circulating levels of sex hormone-binding globulin, estrone, or estradiol in either gender. High density lipoprotein levels declined slightly in women, with no other lipid changes noted for either gender. Insulin sensitivity and percent body fat were unaltered. Although mean 24-h GH and IGFBP-3 levels were unchanged, serum IGF-I levels increased significantly, and IGFBP-1 decreased significantly for both genders, suggesting an increased bioavailability of IGF-I to target tissues. This was associated with a remarkable increase in perceived physical and psychological well-being for both men (67%) and women (84%) and no change in libido. In conclusion, restoring DHEA and DS to young adult levels in men and women of advancing age induced an increase in the bioavailability of IGF-I, as reflected by an increase in IGF-I and a decrease in IGFBP-1 levels. These observations together with improvement of physical and psychological well-being in both genders and the absence of side-effects constitute the first demonstration of novel effects of DHEA replacement in age-advanced men and women.

Men’s music ability and attractiveness to women in a real-life courtship context

Men’s music ability and attractiveness to women in a real-life courtship context

Abstract

This experiment tested the assumption that music plays a role in sexual selection. Three hundred young women were solicited in the street for their phone number by a young male confederate who held either a guitar case or a sports bag in his hands or had no bag at all. Results showed that holding a guitar case was associated with greater compliance to the request, thus suggesting that musical practice is associated with sexual selection.

Cancer mortality and elevation

Cancer mortality, state mean elevations, and other selected predictors.

This ecological inquiry compares cancer mortality rates in the U.S. to the predictor of natural background radiation (via land elevation means) along with eight other predictors thought to be associated with cancer mortality. Age-adjusted cancer mortality in 2006 was compared to the predictors of mean land elevation, percent of smokers, educational attainment, percent of population without health insurance, income, obesity, health perception, physical activity, and diet. Among the six predictors considered appropriate for multiple linear regression, three were found to be statistically significant; from strongest to weakest, these three were: smoking, land elevation, and educational attainment. The predictors of smoking and educational attainment have long been considered associated with cancer mortality. The finding that the predictor of land elevation / natural background radiation is inversely related to cancer mortality is another piece of evidence supporting the theory of radiation hormesis. In this study, land elevation / natural background radiation ranked second in predictive strength regarding cancer mortality, behind smoking and ahead of educational attainment. Since this is an ecological inquiry, no causal inferences can be made.

Small γ-Ray Doses Prevent Rather than Increase Lung Tumors in Mice.

Small γ-Ray Doses Prevent Rather than Increase Lung Tumors in Mice.

We show evidence for low doses of γ rays preventing spontaneous hyperplastic foci and adenomas in the lungs of mice, presumably via activating natural anticancer defenses. The evidence partly relates to a new study we conducted whereby a small number of female A/J mice received 6 biweekly dose fractions (100 mGy per fraction) of γ rays to the total body which prevented the occurrence of spontaneous hyperplastic foci in the lung. We also analyzed data from a much earlier Oak Ridge National Laboratory study involving more than 10,000 female RFMf/Un mice whereby single γ-ray doses from 100 to 1,000 mGy prevented spontaneous lung adenomas. We point out the possibility that the decrease in lung cancer mortality observed in The National Lung Screening Trial Research Team study involving lung tumor screening using low-dose computed tomography (CT) may relate at least in part to low-dose X-rays activating the body's natural anticancer defenses (i.e., radiation hormesis). This possibility was apparently not recognized by the indicated research team.

Evidence supporting radiation hormesis in atomic bomb survivor cancer mortality data

Evidence supporting radiation hormesis in atomic bomb survivor cancer mortality data

A recent update on the atomic bomb survivor cancer mortality data has concluded that excess relative risk (ERR) for solid cancers increases linearly with dose and that zero dose is the best estimate for the threshold, apparently validating the present use of the linear no threshold (LNT) model for estimating the cancer risk from low dose radiation. A major flaw in the standard ERR formalism for estimating cancer risk from radiation (and other carcinogens) is that it ignores the potential for a large systematic bias in the measured baseline cancer mortality rate, which can have a major effect on the ERR values. Cancer rates are highly variable from year to year and between adjacent regions and so the likelihood of such a bias is high. Calculations show that a correction for such a bias can lower the ERRs in the atomic bomb survivor data to negative values for intermediate doses. This is consistent with the phenomenon of radiation hormesis, providing a rational explanation for the decreased risk of cancer observed at intermediate doses for which there is no explanation based on the LNT model. The recent atomic bomb survivor data provides additional evidence for radiation hormesis in humans.

Blue light for infectious diseases

Blue light for infectious diseases: Propionibacterium acnes, Helicobacter pylori, and beyond?

Blue light, particularly in the wavelength range of 405-470 nm, has attracted increasing attention due to its intrinsic antimicrobial effect without the addition of exogenous photosensitizers. In addition, it is commonly accepted that blue light is much less detrimental to mammalian cells than ultraviolet irradiation, which is another light-based antimicrobial approach being investigated. In this review, we discussed the blue light sensing systems in microbial cells, antimicrobial efficacy of blue light, the mechanism of antimicrobial effect of blue light, the effects of blue light on mammalian cells, and the effects of blue light on wound healing. It has been reported that blue light can regulate multi-cellular behavior involving cell-to-cell communication via blue light receptors in bacteria, and inhibit biofilm formation and subsequently potentiate light inactivation. At higher radiant exposures, blue light exhibits a broad-spectrum antimicrobial effect against both Gram-positive and Gram-negative bacteria. Blue light therapy is a clinically accepted approach for Propionibacterium acnes infections. Clinical trials have also been conducted to investigate the use of blue light for Helicobacter pylori stomach infections and have shown promising results. Studies on blue light inactivation of important wound pathogenic bacteria, including Staphylococcus aureus and Pseudomonas aeruginosa have also been reported. The mechanism of blue light inactivation of P. acnes, H. pylori, and some oral bacteria is proved to be the photo-excitation of intracellular porphyrins and the subsequent production of cytotoxic reactive oxygen species. Although it may be the case that the mechanism of blue light inactivation of wound pathogens (e.g., S. aureus, P. aeruginosa) is the same as that of P. acnes, this hypothesis has not been rigorously tested. Limited and discordant results have been reported regarding the effects of blue light on mammalian cells and wound healing. Under certain wavelengths and radiant exposures, blue light may cause cell dysfunction by the photo-excitation of blue light sensitizing chromophores, including flavins and cytochromes, within mitochondria or/and peroxisomes. Further studies should be performed to optimize the optical parameters (e.g., wavelength, radiant exposure) to ensure effective and safe blue light therapies for infectious disease. In addition, studies are also needed to verify the lack of development of microbial resistance to blue light.

Today's adults less healthy than predecessors

Today's adult generations are less healthy than their predecessors: generation shifts in metabolic risk factors: the Doetinchem Cohort Study

Background The health of the elderly of the future is partly determined by their exposure to metabolic risk factors during their life course. Our aim is to study generation shifts in metabolic risk factors.
Design Cohort study.
Methods We used data of the Doetinchem Cohort Study, that started in 1987–1991 and had follow-up examinations after 6, 11, and 16 years (n = 6377). The analyses were stratified by sex and generation, i.e. 10-year age groups (20–29, 30–39, 40–49, and 50–59 years) at baseline. Whether a generation had, at a similar age, a different risk profile compared to a generation born 10 years earlier (i.e. generation shift) was tested by means of generalized estimation equations.
Results The prevalence of overweight, obesity, and hypertension increased with age within all generations, but in general more recently born generations had, at a similar age, a higher prevalence of these risk factors than generations born 10 years earlier (p < 0.05). Unfavourable generation shifts were most pronounced for overweight/obesity, present in men between every generation while in women especially present between the most recently born generations. We observed unfavourable generation shifts in diabetes among men but not among women. No generation shifts for hypercholesterolaemia were observed and favourable generation shifts for low high-density lipoprotein cholesterol between the oldest two generations only. In general, the pattern of generation shifts did not differ according to socioeconomic status. Conclusions The lifelong exposure to especially obesity will increase. As a consequence, more elderly of the future will develop overweight-related diseases such as diabetes and cardiovascular disease.

I foresee giant class-action lawsuits against Big Food.

Psychopathy and Victim Selection

Psychopathy and Victim Selection: The Use of Gait as a Cue to Vulnerability

Previous research has shown that victims display characteristic body language, specifically in their walking style (Grayson & Stein, 1981). Individuals scoring higher on the interpersonal/affective aspects of psychopathy (Factor 1) are more accurate at judging victim vulnerability simply from viewing targets walking (Wheeler, Book, & Costello, 2009). The present study examines the relation between psychopathy and accuracy in assessing victim vulnerability in a sample of inmates from a maximum security penitentiary in Ontario, Canada. Forty-seven inmates viewed short video clips of targets walking and judged how vulnerable each target was to victimization. Higher Factor 1 psychopathy scores (as measured by the PCL-R; Hare 2003) were positively related to accuracy in judging victim vulnerability. Contrary to research with noninstitutional participants (Wheeler et al., 2009), inmates higher on Factor 1 of psychopathy were more likely to rationalize their vulnerability judgments by mentioning the victim’s gait. Implications of these findings are discussed.

Obesity and altitude

Obesity and Altitude

Obesity is a complex and multifactorial chronic disease that remains a military and public health priority in the United States. Recently, we’ve identified a strong association between obesity prevalence and altitude within the US. Our findings were surprising because they indicated the magnitude of this association was large and the pattern of association exhibited a curvilinear dose response in 500 meter categories of altitude. There was a 4-5 fold increase in obesity prevalence at low altitude as compared with the highest altitude category after controlling for diet, activity level, smoking, demographics, temperature, and urbanization. We published our findings in the International Journal of Obesity (advance online publication doi:10.1038/ijo.2013.5) and presented at the 2013 American College of Preventive Medicine conference.

The obesogenic environment

Scientific American: Consumption Junction: Childhood Obesity Determined Largely by Environmental Factors, Not Genes or Sloth

Regardless of the mechanism, these findings also support the notion that the entirety of kids' 21st-century environment—not their self-control or reduced physical activity—is the key culprit in the rise in obesity. "People like to make obesity a disease of blame, but the last 40 years has not seen an epidemic of our children losing willpower," Freedhoff says. "There are dozens and dozens of these environmental factors. Unless we reengineer our children's environments, we are not likely to see any changes in children's weights."

What I notice, and what the article confirms, is that people eat everywhere and all the time. Every occasion, and even every non-occasion, is considered an appropriate time to eat. Going shopping? Eat. Break at work? Donuts! Watching television or at a movie? Beer and chips.

Freedhoff himself is developing a program for families that focuses on "redrafting" kids' and families' environments, starting with more home cooking. "Every parent would die for their child, but most won't cook for their children on a consistent basis with whole ingredients," he says.

Yup.

Ketogenic diet and bipolar disorder

The ketogenic diet for type II bipolar disorder

Successful mood stabilizing treatments reduce intracellular sodium in an activity-dependent manner. This can also be achieved with acidification of the blood, as is the case with the ketogenic diet. Two women with type II bipolar disorder were able to maintain ketosis for prolonged periods of time (2 and 3 years, respectively). Both experienced mood stabilization that exceeded that achieved with medication; experienced a significant subjective improvement that was distinctly related to ketosis; and tolerated the diet well. There were no significant adverse effects in either case. These cases demonstrate that the ketogenic diet is a potentially sustainable option for mood stabilization in type II bipolar illness. They also support the hypothesis that acidic plasma may stabilize mood, perhaps by reducing intracellular sodium and calcium.

Attenuating immunosenescence

Psychoneuroendocrine interventions aimed at attenuating immunosenescence: a review.

There is evidence suggesting that immunosenescence can be accelerated by external factors such as chronic stress. Here we review potential psychoneuroendocrine determinants of premature aging of the immune system and discuss available interventions aimed at attenuating immunosenescence. Chronic stress may accelerate various features of immunosenescence by activating key allostatic systems, notably the hypothalamic-pituitary-adrenal axis. The immunological impact of such neuroendocrine dysregulation may be further amplified by a dramatic decline in dehydroepiandrosterone (DHEA) levels, acting in part as an endogenous glucocorticoid antagonist. Stress-buffering strategies show beneficial effects on various biomarkers in elderly populations. Likewise, supplementation of DHEA, melatonin or growth hormone has yielded significant beneficial effects in a number of studies, including: increased well-being, memory performance, bone mineral density and improved immunocompetence as evidenced by results of in vitro (T cell proliferation, cytotoxicity, cytokine production), and in vivo immune challenges. However, the side-effects of hormonal supplementation are also discussed. Finally, moderate exercise via the promotion of cortisol/DHEA balance or epigenetic modifications, is associated with lower serum pro-inflammatory cytokines, greater lymphoproliferative responses and lower counts of senescent T cells. Taken together, these data suggest that immune system is plastic and immunosenescence can be attenuated psychoneuroendocrine interventions.

Desertification of the Sahara

Sahara went from green to desert in a flash

From lakes and grasslands with hippos and giraffes to a vast desert, North Africa's sudden geographical transformation 5,000 years ago was one of the planet's most dramatic climate shifts.

The transformation took place nearly simultaneously across the continent's northern half, a new study finds. The results will appear in an upcoming issue of the journal Earth and Planetary Science Letters.

The findings come from analyses of dust blown west from Africa and dropped into the Atlantic Ocean. Researchers sifted through 30,000 years of dust and ocean bottom muck retrieved with ocean drilling ships. The changing levels of windblown dust in the ocean sediments provide scientists with clues to Africa's climate and how it has changed over time. Simply put, a lot of dust means drier conditions and less dust means a wetter environment.

The wet period, called the African Humid Period, started and ended suddenly, confirming previous studies by other groups, the sediments revealed. However, toward the Humid Period's end about 6,000 years ago, the dust was at about 20 percent of today's level, far less dusty than previous estimates, the study found. [...]

McGee and his colleagues are now testing whether the dust measurements can resolve a long-standing problem: the inability of climate models to reproduce the magnitude of wet conditions in North Africa 6,000 years ago.

Rapid aminoacidemia enhances muscle protein synthesis

Rapid aminoacidemia enhances myofibrillar protein synthesis and anabolic intramuscular signaling responses after resistance exercise

Background: Ingestion of whey or casein yields divergent patterns of aminoacidemia that influence whole-body and skeletal muscle myofibrillar protein synthesis (MPS) after exercise. Direct comparisons of the effects of contrasting absorption rates exhibited by these proteins are confounded by their differing amino acid contents.

Objective: Our objective was to determine the effect of divergent aminoacidemia by manipulating ingestion patterns of whey protein alone on MPS and anabolic signaling after resistance exercise.

Design: In separate trials, 8 healthy men consumed whey protein either as a single bolus (BOLUS; 25-g dose) or as repeated, small, “pulsed” drinks (PULSE; ten 2.5-g drinks every 20 min) to mimic a more slowly digested protein. MPS and phosphorylation of signaling proteins involved in protein synthesis were measured at rest and after resistance exercise.

Results: BOLUS increased blood essential amino acid (EAA) concentrations above those of PULSE (162% compared with 53%, P < 0.001) 60 min after exercise, whereas PULSE resulted in a smaller but sustained increase in aminoacidemia that remained elevated above BOLUS amounts later (180–220 min after exercise, P < 0.05). Despite an identical net area under the EAA curve, MPS was elevated to a greater extent after BOLUS than after PULSE early (1–3 h: 95% compared with 42%) and later (3–5 h: 193% compared with 121%) (both P < 0.05). There were greater changes in the phosphorylation of the Akt–mammalian target of rapamycin pathway after BOLUS than after PULSE.

Conclusions: Rapid aminoacidemia in the postexercise period enhances MPS and anabolic signaling to a greater extent than an identical amount of protein fed in small pulses that mimic a more slowly digested protein. A pronounced peak aminoacidemia after exercise enhances protein synthesis.

Tl;dr: drink a whey-protein shake immediately after your workout for the best increase in muscle-protein synthesis.

Neuroprediction of future rearrest

Neuroprediction of future rearrest

Identification of factors that predict recurrent antisocial behavior is integral to the social sciences, criminal justice procedures, and the effective treatment of high-risk individuals. Here we show that error-related brain activity elicited during performance of an inhibitory task prospectively predicted subsequent rearrest among adult offenders within 4 y of release (N = 96). The odds that an offender with relatively low anterior cingulate activity would be rearrested were approximately double that of an offender with high activity in this region, holding constant other observed risk factors. These results suggest a potential neurocognitive biomarker for persistent antisocial behavior.

This was published in the prestigious Proceedings of the National Academy of Sciences.

Zinc supplementation decreases incidence of infections in the elderly

Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress

Background: Zinc deficiency, cell-mediated immune dysfunction, susceptibility to infections, and increased oxidative stress have been observed in elderly subjects (ie, those >55 y old). Zinc is an effective antiinflammatory and antioxidant agent.

Objectives: The primary objective was to determine the effect of zinc on the incidence of total infections in healthy elderly subjects. The secondary objective was to determine the effect of zinc on cytokines and oxidative stress markers.

Design: A randomized, double-blind, placebo-controlled trial of zinc supplementation was conducted in elderly subjects. Fifty healthy subjects of both sexes aged 55–87 y and inclusive of all ethnic groups were recruited for this study from a senior center. The zinc-supplemented group received zinc gluconate (45 mg elemental Zn/d) orally for 12 mo. Incidence of infections during the supplementation period was documented. The generation of inflammatory cytokines, T helper 1 and T helper 2 cytokines, and oxidative stress markers and the plasma concentrations of zinc were measured at baseline and after supplementation.

Results: Compared with a group of younger adults, at baseline the older subjects had significantly lower plasma zinc, higher ex vivo generation of inflammatory cytokines and interleukin 10, and higher plasma oxidative stress markers and endothelial cell adhesion molecules. The incidence of infections and ex vivo generation of tumor necrosis factor α and plasma oxidative stress markers were significantly lower in the zinc-supplemented than in the placebo group. Plasma zinc and phytohemagglutin-induced interleukin 2 mRNA in isolated mononuclear cells were significantly higher in the zinc-supplemented than in the placebo group.

Conclusions: After zinc supplementation, the incidence of infections was significantly lower, plasma zinc was significantly higher, and generation of tumor necrosis factor α and oxidative stress markers was significantly lower in the zinc-supplemented than in the placebo group.

If you read the full paper, you find this:

In the zinc-supplemented group, the total incidence of infections was 7 (2 from January through March, 0 from April through June, 3 from July through September, and 2 from October through December). In the placebo group, the total incidence of infections was 35 (8 from January through March, 11 from April through June, 7 from July through September, and 9 from October through December).

The zinc-supplemented group had only 20% of the incidence of infections of the placebo group, a huge difference.

Zinc, testosterone, and men's sexual health

Effects of dietary zinc depletion on seminal volume and zinc loss, serum testosterone concentrations, and sperm morphology in young men.

Identification of the andrological variables most sensitive to zinc depletion would expedite the diagnosis of male reproductive pathology induced by zinc deficiency. Eleven volunteers living on a metabolic ward were fed a diet composed of a mixture of a semisynthetic formula and conventional foods supplemented with ZnSO4 to supply a total of 1.4, 2.5, 3.4, 4.4, or 10.4 mg Zn/d. After an equilibration period of 28 d (10.4 mg Zn/d), all treatments were presented for 35 d each, the first four in random order and the fifth last. Compared with when they were consuming 10.4 mg Zn/d, volunteers consuming 1.4 mg Zn/d exhibited decreased semen volumes (3.30 vs 2.24 mL) and serum testosterone concentrations (26.9 vs 21.9 nmol/L), and no change in seminal zinc concentrations. Compared with 10.4 mg Zn/d, treatments of 1.4, 2.5, and 3.4 mg Zn/d decreased the total semen zinc loss per ejaculate (6.29 vs 3.81, 4.68, and 5.03 mumols/ejaculate). Seminal loss accounted for 9% of total body zinc loss when 1.4 mg Zn/d was consumed. Seminal phosphorus concentrations were elevated during all four phases of zinc depletion (28.4 vs 32.9, 31.0, 34.2, and 33.6 mmol/L). The findings suggest that serum testosterone concentrations, seminal volume, and total seminal zinc loss per ejaculate are sensitive to short-term zinc depletion in young men.

Effect of Oral Zinc Therapy on Gonadal Function in Hemodialysis Patients: A Double-Blind Study

Zinc deficiency may account for the persistence of gonadal dysfunction in a majority of uremic men despite adequate dialysis. Twenty stable patients having hemodialysis three times a week completed a double-blind trial using either 50 mg of elemental zinc as zinc acetate (10 patients) or placebo (10 patients), orally. At the end of the 6-month study period, a significant increase in the mean (± SE) plasma zinc (75 ± 2 µg/dL to 100 ± 2 µg/dL, p < 0.001), serum testosterone (2.8 ± 0.3 ng/dL to 5.2 ± 0.5 ng/mL, p < 0.001), and sperm count (30 ± 3 million/mL to 63 ± 5 million/mL, p < 0.001) occurred in the zinc-treated group, but not in those receiving the placebo. The zinc-treated group also had a significant fall in serum luteinizing hormone (92 ± 10 mIU/mL to 49 ± 26 mIU/mL, p < 0.005) and follicle stimulating hormone (45 ± 9 mIU/mL to 25 ± 7 mIU/mL, p < 0.05), not seen in the placebo group. Patients receiving zinc had an improvement in potency, libido, and frequency of intercourse not found in the placebo group. These results suggest that zinc deficiency is a reversible cause of gonadal dysfunction in patients having regular hemodialysis

Zinc status and serum testosterone levels of healthy adults.

Zinc deficiency is prevalent throughout the world, including the USA. Severe and moderate deficiency of zinc is associated with hypogonadism in men. However, the effect of marginal zinc deficiency on serum testosterone concentration is not known. We studied the relationship between cellular zinc concentrations and serum testosterone cross-sectionally in 40 normal men, 20 to 80 y of age. In four normal young men (27.5 +/- 0.5 y), we measured serum testosterone before and during marginal zinc deficiency induced by restricting dietary zinc intake. We also measured serum testosterone in nine elderly men (64 +/- 9 y) who were marginally zinc deficient before and after 3 to 6 mo of supplementation with 459 mumol/ d oral zinc administered as zinc gluconate. Serum testosterone concentrations were significantly correlated with cellular zinc concentrations in the cross-sectional study (lymphocyte zinc versus serum testosterone, r = 0.43, p = 0.006; granulocyte zinc versus serum testosterone, r = 0.30, p = 0.03). Dietary zinc restriction in normal young men was associated with a significant decrease in serum testosterone concentrations after 20 weeks of zinc restriction (baseline versus post-zinc restriction mean +/- SD, 39.9 +/- 7.1 versus 10.6 +/- 3.6 nmol/L, respectively; p = 0.005). Zinc supplementation of marginally zinc-deficient normal elderly men for six months resulted in an increase in serum testosterone from 8.3 +/- 6.3 to 16.0 +/- 4.4 nmol/L (p = 0.02). We conclude that zinc may play an important role in modulating serum testosterone levels in normal men.

The testosterone level in healthy elderly men doubled over the course of 6 months with zinc supplementation. This may be the explanation for lower T levels in elderly men.

Got zinc?