|November 2002 |
Vitamin D needed by girls to attain peak bone mass
Iron overload related to increased cardiovascular risks in premenopausal women
A study that will appear in the December 2002 American Journal of Clinical Nutrition reiterates the danger of elevated iron stores and cardiovascular disease risk in women of reproductive age. Although iron deficiency is frequently a problem in this group, the proportion of women who are iron replete has risen in industrialized countries. Iron is a mineral essential to human life, but high levels have been shown to promote peroxidation and tumorigenesis.
The Emory University researchers evaluated information obtained from the third National Health and Nutrition Examination Survey (NHANES III). Healthy, nonpregnant women, ages 20 to 49, were divided according to whether their serum ferritin concentrations were low, medium or high. Data was included from 1,178 non-Hispanic Caucasians, 1,093 African-Americans and 1,075 Mexican-American women. The researchers examined data on body mass index, triglycerides, total and HDL cholesterol, glucose and blood pressure.
Among all racial groups, indicators of cardiovascular disease, were significantly associated with higher serum ferritin values. The strongest association was observed for Mexican-American women, who had higher glucose and triglycerides and lower HDL values than the other racial groups examined, despite having lower iron stores, suggesting a specific racial response.
AHA report affirms aspirin reduces initial heart attack risk by one third
Zinc supplements lower mortality in children with diarrhea
Diarrhea is strongly associated with childhood mortality in developing countries. In research published in the November 9 2002 issue of British Journal of Medicine, an international team of scientists evaluated 8,070 Bangladeshi children with diarrhea, and found significantly lower rates of hospitalization and death and those given zinc supplements than in those who did not receive them.
The randomized, controlled trial was conducted in the Matlab area of Bangladesh, in which diarrhea accounts for approximately one third of all deaths in children age one to four. Children 3 to 59 months old were enrolled from November 1998 to October 2000. During the first four months of the trial, 40% of diarrheal episodes were treated with zinc supplements. This rate rose to over 80% in the seventh month and remained at that level. The treated children received 20 milligrams elemental zinc per day for two weeks during each episode of diarrhea.
In the children who lived in areas randomized to receive the zinc supplements, duration of diarrheal episodes and hospital admission rates were 24% lower than the comparison group. Deaths not due to injuries were 51% lower in those who received zinc than in those who did not. This difference was almost entirely due to a decrease in diarrhea and lower respiratory infections deaths.
Study coauthor and associate professor, International Health, Johns Hopkins Bloomberg School of Public Health, Abdullah H Baqui, stated, "The lower rates of child morbidity and mortality with zinc therapy represent substantial benefits from a simple and inexpensive intervention that can be incorporated within existing diarrheal disease control efforts which should significantly improve child health and survival."
American Heart Association recommends omega-3s
In the November 19 2002 issue of the journal Circulation, the American Heart Association issued a statement recommending that healthy people consume omega-3 fatty acids from fish and plants to protect their hearts. Fish contains omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), while plant foods such as soybeans and flaxseeds contain alpha-linoleic acid (ALA).
Total antioxidant potential lowers stomach cancer risk
An article that appeared in the October 2002 issue of the journal Gastroenterology, showed that the total antioxidant potential from fruits and vegetables in the diet is inversely related to the risk of gastric cancer. The study is the first to examine the total antioxidant potential of the diet rather than the effects of single dietary antioxidants.
Giving and living
A five-year study scheduled to be appear in the journal Psychological Science, has found a 60% reduction in the risk of dying within that period for people who are helpful to others compared to individuals in the same age group who provide less assistance to others. The study, funded in part by the National Institutes of Health, analyzed information on 423 couples who were part of the University of Michigan Institute for Social Research Changing Lives of Older Couples Study.
Four hundred twenty-three couples were interviewed to obtain information in regard to their level of assistance to relatives, friends and neighbors as well as the amount of emotional support that gave and received to their spouse. Over the course of the five years, 134 participants died. After controlling for age, gender, emotional and physical health, it was found that people who reported that they provided no help to others had twice the risk of dying during the five year period than those who reported being helpful.
Lead author and University of Michigan Institute for Social Research psychologist Stephanie Brown noted that these findings may be explained by the evolutionary advantages of assisting others. She stated, "Older adults may still be able to increase their fitness (defined as the reproductive success of individuals who share their genes) by becoming motivated to stay alive and prolonging the amount of time they can contribute to family members. Of course, this possibility relies on the assumption that a motivation for self-preservation can influence mortality. And in fact, there is evidence to suggest that individuals with a 'fighting spirit' survive longer with cancer than individuals who feel helpless or less optimistic about their chances for survival. Now it seems that the same may be true of a 'giving spirit."
Zeaxanthin protects the eye in animal study
Two studies published this month, in the November 2002 issues of Investigative Ophthalmology and Visual Science and Experimental Eye Research, have found a protective benefit in the eye for the carotenoid zeaxanthin. Zeaxanthin and lutein are carotenoids found in the diet that are are powerful antioxidants and are taken up by the retina of the eye. Their concentration is particularly high in the macula area, and some studies have suggested that they may help protect against macular degeneration.
The researchers, from Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, used quail as an animal model because the birds' retinas resemble that of humans. In the first study, carotenoid-deficient quail were divided into groups that received a diet supplemented with or without zeaxanthin for one week. The birds were then exposed to damaging light. It was found that retinas containing the highest concentration of zeaxanthin showed minimal damage, while low zeaxanthin levels correlated with severe damage.
The second study utilized quail that received carotenoid-deficient, normal or zeaxanthin-supplemented diets for six months before the birds were exposed to damaging light. Again, extensive damage to the retina was found in birds that were carotenoid deficient, demonstrated by dead and dying photoreceptors. Quail who received zeaxanthin experienced the least amount of retinal damage.
Principal investigator C. Kathleen Dorey, commented, "Our studies showed that light damage was strongly influenced by the amount of zeaxanthin in the retina, and that significantly greater retinal protection was provided at dietary levels higher than those normally occurring in the diet. Zeaxanthin has been extensively studied for safety and has been reviewed as a dietary ingredient by the FDA. We hope this work further stimulates interest in clinical trials, and believe that zeaxanthin has a potential to eventually complement other strategies to improve the treatment of this vision-robbing disease."
Evidence that increased reactive oxygen species are link between magnesium deficiency and hypertension
The relationship between high blood pressure and magnesium deficiency has been explored in several studies, producing conflicting evidence. A study published in the November 2002 issue of the Journal of Hypertension submits the hypothesis that insufficient levels of magnesium may lead to hypertension by increasing the formation of reactive oxygen species, harmful molecules that cause oxidative damage.
The University of Montreal researchers divided stroke-prone spontaneously hypertensive rats into three groups that received a control diet containing normal levels of magnesium, a magnesium-free diet and a high magnesium diet, and systolic blood pressure was measured each week for sixteen weeks. In a second experiment, stroke-prone spontaneously hypertensive rats received a control diet, a magnesium-free diet and a magnesium-free diet combined with Tempol, a superoxide dismutase mimetic for seven weeks. Superoxide dismutase is one of the antioxidants naturally produced in the body.
Rats in the low magnesium group experienced an exacerbation in the development of hypertension after five weeks, accompanied by a reduction in oxidative stress markers which increased rapidly after two weeks. The ability of blood vessels to dilate in response to acetylcholine was decreased in the low magnesium group compared to controls. Vessel wall hypertrophy was greater and vascular superoxide higher in the rats who received the magnesium deficient diet compared to those on the high magnesium diet. However, rats on magnesium-free diets receiving Tempol did not experience a progression of hypertension or the vascular changes seen in magnesium deficient rats who did not receive the antioxidant.
In an accompanying editorial, Richard D Bukoski writes that the research provides, "the first link between an essential dietary nutrient and the key molecular pathways involved in regulating vascular smooth muscle growth and structure." (Journal of Hypertension 2002, 20:2141-2143)
Hibernation compound protects against stroke damage
Research conducted by Medical College of Georgia neuroscientist Dr Cesario V Brolongan, reported at the annual meeting of the International College of Geriatrics this month has found that a compound that squirrels use to hibernate helps protect the striatum of the brain from up to 75% of the damage that occurs during a stroke. The compound, known as delta opioid peptide, puts cells in a reversible state of suspended animation. Delta opiod peptide, which also exists in humans, may also help to protect brain cells from damage induced by Parkinson's disease. The findings were also reported partially in the journals Cell Transplantation and NeuroReport.
Iron deficiency may result in neuron loss seen with aging
Researchers at Children's Hospital Oakland Research Institute in Oakland, California have hypothesized that the brain cell loss observed in aging and in Alzheimer's disease and other neurologic disorders may simply be the result of iron deficiency. Acting on the knowledge that the synthesis of the major form of iron in cells known as heme declines with age, Hani Atamna, Bruce N Ames MD, and colleagues blocked heme synthesis in cultured human and rat neurons and found metabolic changes that were similar to the changes induced by Alzheimer's disease.
The scientists used two human brain cell lines and one line of rat neurons. After blocking heme synthesis and observing a decrease in mitochondrial complex IV, activation of nitric oxide synthase, changes in amyloid precursor protein, and alterations in iron and zinc status, the researchers attempted to induce the cells to multiply which led to the heme deficient cells dying, demonstrating that heme synthesis has a role in brain cell survival.
The report lists a number of similarities between the consequences of heme deficiency and "normal" aging, including loss of mitochondrial complex IV and increased oxidative stress.
The synthesis of heme depends on several nutrients, including vitamin B6, lipoic acid copper and zinc, as well as iron. The increased levels of iron that occur with aging may be a result of inefficient synthesis of heme, leading to a functional deficiency of iron. While deficiencies in iron and vitamin B6 are widespread, insufficient intake of any of these nutrients can result in diminished heme levels. Heme synthesis is also impaired by the presence of lead, aluminum and other toxic metals. These new findings suggest that some neurodegenerative disorders could be caused by dysregulated heme synthesis, which may be prevented or treated by correcting nutritional deficiencies.
Selenium protects against bladder tumors
A study of former smokers published in the the November 2002 issue of the journal Cancer Epidemiology Biomarkers & Prevention showed that with high quantities of tissue selenium offered protection against bladder tumors. Previous research has shown the trace element may help protect against certain cancers. However, this protective benefit was not seen in nonsmokers or current smokers. The study's authors suggest that the reason for this finding may be due to selenium's antioxidant effect.
Lead study author and assistant professor of epidemiology at Maastricht University in the Netherlands, Maurice P.A. Zeegers offered an explanation: "The lack of effect of selenium status among nonsmokers is consistent with this hypothesis, since those who never smoked have not been exposed to smoking induced oxidative stress."
The study involved 120,852 Dutch men and women, 431 of whom had cancer of the bladder, who were part of a large population-based study on cancer and diet. Subjects completed questionnaires on cancer risk factors such as diet and smoking history. Toenail clippings from the participants were used by the researchers to measure selenium levels. While the group with the highest selenium levels, which measured 30% higher than the group with the lowest levels, experienced fewer bladder cancer diagnoses, former smokers experienced the greatest protective benefit from selenium, with 50% fewer bladder tumors than those whose selenium levels were lower. No other factor was found to have an equal impact on bladder cancer.
Dr Zeegers added, "A selenium marker should preferably reflect long-term selenium intake. Available evidence suggests that selenium levels in toenails reflect intake integrated for the previous 12 months or longer . . . Further research is needed to evaluate the influence of selenium on one of bladder cancers, the invasive form, when compared to the non-invasive form."