Nutrigenomics and Beyond Informing the Future: Workshop Summary (2007) / Chapter Skim
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1 Scientific Session I: Human Genetic Variation and Nutrition
1 Scientific Session I: Human Genetic Variation and Nutrition
Pages 7-16
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From page 7... ...
Collins, M.D., Ph.D., Director, National Human Genome Research Institute, National Institutes of Health Over the past decade the field of genomics has seen spectacular and exciting progress. The human genome has been sequenced; and a host of new fields, including genomics, proteomics, and metabolomics, have been developed to use the information made available from the identification of genes and related products.
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From page 8... ...
The second way is to provide an understanding of nutrition at the level of the individual, exploring how nutrients affect people differently, depending on genetic variation. The first step toward realizing that vision is finding the genetic variants involved in human disease, or what Collins termed "those ticking time bombs that are lurking within our genomes." The problem is that until recently researchers have not had at their disposal efficient and cost-effective tools for finding the genetic variants that increase the risk of common diseases or identifying the environmental triggers, such as diet, that may set them off.
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From page 9... ...
The Genomics Reolution There is comparatively little variation in genetic makeup between individuals. When the genetic sequences of two individuals are aligned and compared, only about 1 of every 1,000 base pairs of the nucleotide sequence of human DNA exhibits variance.
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From page 10... ...
But, some of those differences, probably a couple hundred thousand or so, do have important phenotypic effects. It is those that we are most interested in learning about, even though their effects are likely to be subtle." To understand a complex disease, particularly one for which nutrition is important, researchers must identify which of the approximately 10 million common SNPs in the human genome are associated with an increased risk of that disease.
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From page 11... ...
"So, instead of genotyping all 10 million SNPs in each study participant's genome, researchers can pick a carefully chosen set of about 300,000 marker SNPs for European ancestry or Asian populations, and these serve as very effective proxies for the rest," said Collins, adding that African populations require slightly more SNPs because their longer population histories have led to somewhat less linkage between the SNPs. Thanks to the data generated by the HapMap Project, a whole-genome study of 2,000 subjects today requires a total of only 600 million genotypes instead of 20 billion.
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From page 12... ...
"There is also $14 million a year for the next 4 years to develop innovative technologies to measure those environmental exposures, including dietary intake and physical activity, in a more rigorous fashion than what has often been the case in these kinds of studies." Even as scientists are beginning to appreciate the potential of nutrigenomics, the public is already fascinated. For instance, a number of Internet sites offer products based on the idea that one's diet should be dictated by one's DNA.
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From page 13... ...
To avoid that fate, Collins said, "We need to give it some good science to grow on." IMPLEMENTATION OF THE HUMAN HAPMAP INITIATIVE AND LARGE-SCALE POLYMORPHISM STUDIES Presented by Daid Cox, Chief Scientific Officer, Perlegen Sciences, Inc. Over the past 20 years researchers have learned that most complex traits involve probably 20 or more individual genetic changes, according to David Cox.
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From page 14... ...
The gene would then explain a relatively small part, for example, 2 percent, of the total variation in the population, that is, which people get heart disease versus which people do not; but the risk would still be significant enough to pay attention to the gene, particularly in combination with other genes with similar contributions. For a gene with this level of effect, one would need several hundreds of subjects of each variant type, that is, those with two copies of Variant A and those with two copies of Variant B, to achieve sufficient statistical power to identify the gene's contribution with a reasonable level of certainty and accuracy.
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2006. Low-fat dietary pattern and risk of invasive breast cancer: the Women's Health Initiative Randomized Controlled Dietary Modification Trial.
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NUTRIGENOMCS AND BEYOND Ordovas summarized by indicating that "it is particularly important for people of GG type to minimize their consumption of polyunsaturated fat in order to keep their levels of the good cholesterol as high as possible." Conversely, people with the GA or the AA form of the gene can achieve increases in good cholesterol levels by increasing their dietary intake of polyunsaturated fat. It is thus important for both doctors and researchers to take into account the genetic makeups of their patients when they try to understand and predict the effects of diet on health.
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