Zinc
Zinc helps children thinkApril 10, 2005 Eleven-year-olds that took zinc supplements for five days each week had better mental performance after three months than their classmates, said researchers yesterday.
The children taking an extra 20mg of zinc responded more quickly and accurately on memory tasks and with more sustained attention than classmates who did not take the mineral.
Beneficial effects were seen regardless of the youngsters’ previous zinc status, said the researchers led by Dr James Penland from the US Agricultural Research Service’s Grand Forks Human Nutrition Research Center in North Dakota.
The findings, presented at the Experimental Biology meeting this week, suggest that there could be new demand for fortified foods and supplements for this age group.
Although zinc nutrition has been related to motor, cognitive and psychosocial function in very young children and adults, this is the first study of its effect in adolescents.
Zinc deficiency is not uncommon, even in nations such as the United States, and the risk is particularly high in adolescents, said Dr Penland, because they are undergoing rapid growth and often have poor eating habits. They may not consume enough zinc-rich foods like red meat, fish and grains.
Moreover the current recommended daily allowance is only 15mg for adults in the US, and up to 9.5 mg a day for men and 4-7 mg a day for women in the UK.
In the study, 111 girls and 98 boys consumed four ounces of fruit juice containing either 0, 10 or 20 mg of zinc gluconate each school day for 10 to 12 weeks. Students, their parents and teachers did not know who was receiving which, if any, zinc supplementation.
At the beginning and end of the study, students performed a battery of tasks designed to measure mental and motor skills, like attention, memory, problem-solving and hand-eye coordination.
Students, their parents, and teachers filled out questionnaires about the students’ mental, physical and social abilities and skills, school performance, and problems in any of these areas to provide a measure of psychosocial function.
Blood samples measured zinc status before and after the treatment.
Compared to the students who received no additional zinc, students who consumed an additional 20 mg zinc each day decreased reaction time on a visual memory task by 12 per cent versus 6 per cent; increased correct answers on a word recognition task by 9 per cent versus 3 per cent; and increased scores on a task requiring sustained attention and vigilance by 6 per cent versus 1 per cent.
Those who received only 10 mg a day, the US Recommended Dietary Allowances (RDA) for this age group, did not significantly improve performance, however.
Supplementation at either the 10 mg or 20 mg did not appear to improve motor and social skills, although girls receiving the placebo experienced a 10 per cent increase in conduct problems during the study while the behaviour of girls receiving any level of zinc supplementation remained unchanged, reported the researchers.
Previous studies have shown that zinc is needed for growth and immune function and may be important for eye-hand coordination and reasoning in very young children. It also appears to influence memory, muscle strength and endurance in adults.
Brain Cell Growth Boosted By DHEA Supplements
‘Anti-aging’ hormone DHEA Found to Boost Brain Cell Growth August 24, 2004
Human neural stem cells, exposed in a lab dish to the steroid DHEA, exhibit a remarkable uptick in growth rates, suggesting that the hormone may play a role in helping the brain produce new cells, according to a new study published this week in the online edition of the Proceedings of the National Academy of Sciences (PNAS).
The new work, conducted by a team of scientists at the University of Wisconsin-Madison, provides some of the first direct evidence of the biological effects of DHEA on the human nervous system, according to Clive Svendsen, the study’s senior author and an authority on brain stem cells at UW-Madison’s Waisman Center.
“What we saw was that DHEA significantly increased the division of the cells,” said Svendsen, a UW-Madison professor of anatomy and neurology. “It also increased the number of neurons produced by the stem cells, prompting increased neurogenesis of cells in culture.”
DHEA or dehydroepiandrosterone is among the most abundant naturally occurring steroids in the blood of young humans, but levels decline with age and its physiological effects are poorly understood.
A synthetic form of the hormone is sold over-the-counter as a dietary supplement in the US, thought to have anti-aging properties and to offer prevention against cancer and heart disease, Alzheimer’s and other diseases. But scientists know relatively little about the drug and its basic biological effects on humans.
“We don’t know much about DHEA, but this new work adds a piece to the puzzle,” said Svendsen, who conducted the study with colleagues Masatoshi Suzuki, Lynda S. Wright, Padma Marwah and Henry A. Lardy, all of UW-Madison. “This is the first real evidence of DHEA’s effects on human neural cells.”
Svendsen and Suzuki carried out the experiments by growing human fetal neural stem cells in culture. The cells form aggregates known as ‘neurospheres,’ which were exposed to a cocktail of DHEA and growth and inhibitory factors, and observed a 29 per cent increase in new brain cells compared to cells grown in a medium with the same factors, but without DHEA.
“We saw such a pure effect of DHEA,” Svendsen said.
“It’s the only steroid we tested that had such a direct effect on stem cell growth and new neuron formation,” according to Suzuki.
The new work is important because it provides a direct window to the controversial hormone’s effects on critical human cells. Similar studies have been conducted in mice and rats, but those models have shortcomings that are difficult to address, Svendsen notes.
“There are previous studies in rats that suggest DHEA is neuroprotective, but the problem with DHEA in rats is that it is not a major metabolite in that animal so its effects may not be the same as those seen in humans,” he said. According to Lardy, metabolic products of DHEA hormone have also been shown to aid memory retention in old mice.
Despite hints from the studies in rodents that DHEA may play a role in enhancing the brain and memory, the new findings reported in the PNAS article were a surprise, he said.
“We assumed the compounds we were testing would be more active than DHEA in brain stem cells,” Lardy explains. In previous studies, Lardy, with Wisconsin biochemistry colleagues James Ntambi and Brian Fox, showed that DHEA blocked a step in fat synthesis.
“The effects of DHEA on brain stem cells is a completely new finding,” said Lardy. “The problem of whether DHEA itself is having this effect, or if there’s another metabolite of the hormone involved, still exists.”
One of the intriguing aspects of the new work, according to Svendsen, is the possibility that DHEA could have some positive effects on the adult human brain.
It is known that DHEA amounts fall progressively during aging, and reduced levels of DHEA have been reported in both adolescents and adults with major depressive disorders. And given the fact that adult humans have neural stem cells that continue to make new neurons in some parts of the brain, there is a possibility that DHEA could play a role in moderating the genesis of new brain cells.