Cholesterol-Lowering Foods Most Effective When Combined, University Of Toronto Study
Article Date: 09 Mar 2006 - 0:00 PST
Cholesterol-lowering foods such as soy protein, almonds, plant sterol enriched margarines, oats and barley may reduce cholesterol levels more effectively when eaten in combination, says a new University of Toronto study by Professor David Jenkins. The study, which appears in the current issue of the American Journal of Clinical Nutrition, also found that among the subjects who adhered to the diet (one third of test group), this combination of foods reduces low-density lipoprotein cholesterol ("bad" cholesterol) in similar ways as a first generation statin.
"The benefit of statins to individuals at high risk for cardiovascular disease is not in question here," says Jenkins, a professor in the Department of Nutritional Sciences and a Canada research chair in nutrition and metabolism. "Previous studies have demonstrated that statins can reduce heart disease risk between 25 and 50 per cent. We don't, however, know the long-term effects of these drugs when used on a large section of the broader population who are at low risk in primary prevention. Taking a pill may give people the false impression that they have nothing further to do to protect their health and prevent them from making serious lifestyle changes. Emphasizing diet changes in general can boost the success rate of statins while providing additional health benefits and a possible alternative for those for whom drugs are not a viable option."
Jenkins and his colleagues prescribed a seven-day menu high in viscous fibres, soy protein, almonds and plant sterol margarine to 66 people - 31 men and 35 women with an average age of 59.3 and within 30 percent of their recommended cholesterol targets. For the first time, 55 participants followed the menu under real-world conditions for a year. They maintained diet records and met every two months with the research team to discuss their progress and have their cholesterol levels measured.
"The participants found it easiest to incorporate single items such as the almonds and margarine into their daily lives," says Jenkins, who is also staff physician of endocrinology at St. Michael's Hospital. "The fibres and vegetable protein were more challenging since they require more planning and preparation, and because these types of niche products are less available. It's just easier, for example, to buy a beef burger instead of one made from soy, although the range of options is improving. We considered it ideal if the participants were able to follow the diet three quarters of the time."
After 12 months, more than 30 per cent of the participants had successfully adhered to the diet and lowered their cholesterol levels by more than 20 per cent. This rate is comparable to the results achieved by 29 of the participants who took a statin for one month under metabolically controlled conditions before following the diet under real-world conditions.
"The study's findings suggest that the average person can do a lot to improve their health through diet," Jenkins says. "People interested in lowering their cholesterol should probably acquire a taste for tofu and oatmeal, keeping in mind that portable alternatives fit best with a modern lifestyle. Save the experimenting for the evening, when you have more time to prepare more complicated meals."
Jenkins is a leading researcher in the nutritional sciences who developed the glycemic index. His previous studies explored the connections between high-fibre diets, soy foods and heart disease prevention, and meal frequency, vegetarian diets and almonds in reducing cholesterol levels.
In future studies, he and his colleagues plan to directly compare the benefits of diet against statins over longer periods among individuals at risk for cardiovascular disease across Canada. They will also investigate the effects of incorporating more mono-unsaturated fats into the diet.
The study was funded by the Canada Research Chairs program, the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada, the Almond Board of California and Loblaw Companies Ltd.
http://www.utoronto.ca
Mayo Clinic Study Explores Link Between Nanoparticles And Kidney Stones
Researchers at Mayo Clinic have successfully isolated nanoparticles from human kidney stones in cell cultures and have isolated proteins, RNA and DNA that appear to be associated with nanoparticles. The findings, which appear in the December issue of the "Journal of Investigative Medicine," are significant because it is one step closer in solving the mystery of whether nanoparticles are viable living forms that can lead to disease -- in this case, kidney stones.
Kidney stones are associated with pathologic calcification, the process in which organs and blood vessels become clogged with calcium deposits that can damage major organs like the heart and kidneys. What causes calcium deposits to build up is not entirely known. Medical scientists at Mayo Clinic are studying calcification at the molecular level in an effort to determine how this phenomenon occurs.
There is a growing body of scientific evidence that links calcification to the presence of nanosized particles, particles so small that some scientists question whether a nanoparticle can live and if so, play a viable role in the development of kidney stones.
The presence of proteins, RNA and DNA does not prove that nanoparticles are viable living forms because a genetic signature has not been identified, says the study's author John Lieske, M.D., a nephrologist with Mayo Clinic. A genetic signature would prove that nanoparticles are indeed living forms that replicate and can cause disease.
"We are looking at how kidney stones start as very small calcifications inside the kidney and then eventually grow into stones," says Lieske. "In the laboratory, we have isolated nanoparticles from kidney tissue and kidney stones, and have successfully propagated them in culture. This does not clearly confirm the role of nanoparticles in the formation of kidney stones, but it offers insight not otherwise known."
Approximately 12 percent of men and 5 percent of women will develop kidney stones by the time they reach 70 years old. Some $5 billion is spent in the United States each year to treat patients with kidney stones, but exactly how kidney stones form is not known. Scientists theorize that if nanoparticles become localized in the kidney, they can become the focus of subsequent growth into larger stones over months to years. Other factors, such as physical chemistry and protein inhibitors of crystal growth, also play a role. But what scientists don't quite understand is why, where and how they start growing, Lieske says.
The study cites evidence that indicates the unlikelihood that events linked to the calcification process are driven solely by physical chemistry, but instead are influenced by specific proteins and cellular responses. Understanding these events will provide clues to develop new therapy to treat kidney stones, the authors say.
"There are at least two novel hypotheses here in terms of how stones might actually form. One: an infectious agent. If that was the case, that would point us in the direction of using different kinds of treatments specific to an infectious agent. Two: the idea that cells drive calcification. That would suggest other alternative therapies," according to Virginia Miller, Ph.D., a specialist in vascular research at Mayo Clinic and a study author.
In addition, researchers examined how urine proteins alter the way crystals and cells interact in binding to cells -- the way in which cells respond to the crystals and assume more of a bone-like morphology and drive calcification over time.
In a second study, due to appear in the December issue of the "Journal of Investigative Medicine," Lieske, Miller and Karim Benzerara, Ph.D., of the Institut de Physique du Globe de Paris, attempted to identify a DNA chemical marker in nanoparticles. The preliminary study suggests that nanoparticles from human samples share spectroscopic characteristics with calcified bacteria that exist in freshwater lakes. However, studies could not confirm whether the nanoparticles are calcified bacteria or hydroxyapatite crystals that precipitated upon proteins present in the culture medium used to replicate the nanoparticles. Researchers did, however, identify chemical bonds between proteins and calcium in nanoparticles that were similar to those found in the bacteria that calcified in the environment.
"Right now the results are inconclusive. In some of the segments we saw a characteristic signal that might suggest DNA, but in others we did not," Miller says.
This is a relatively new area of science, so the tools and processes used in this research have yet to be perfected. "Many of these tools haven't been applied to these systems in a consistent, rigorous way. So we are still in the learning process of how to handle the material. For example, what are the ideal conditions in the laboratory in which we should study nanoparticles?
"It was disappointing that we did not find any consistent DNA information. We think the findings were inconclusive, in part, because of the inability to apply these techniques in conditions suitable to nanoparticles," Miller says.
The Lieske study was supported by grants from the National Institutes of Health, the Ralph C. Wilson Sr. and Ralph C. Wilson Jr. Medical Research Foundation, the Oxalosis and Hyperoxaluria Foundation and Mayo Clinic.
The Benzerara study was supported by a National Science Foundation grant, the Stanford Institute for the Environment, the France-Stanford Center for Interdisciplinary Studies, the U.S. Department of Energy at Lawrence Berkeley National Laboratory, the National Institutes of Health, the Ralph C. Wilson Sr. and Ralph C. Wilson Jr. Medical Research Foundation and Mayo Clinic.
To obtain the latest news releases from Mayo Clinic, go to
http://www.mayoclinic.org/news. MayoClinic.com --
http://www.mayoclinic.com/ -- is available as a resource for your health stories.
Mayo Clinic
http://www.mayoclinic.com/
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