Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Lectures by Greg Podgorski, Utah State University Diet Advice From DNA? Current.

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings

Lectures by Greg Podgorski, Utah State University

Diet Advice From DNA?Diet Advice From DNA?

Current Issues in Biology, Current Issues in Biology, Volume 6Volume 6

Scientific AmericanScientific American


Diet Advice From DNA?

• Less than a decade after deciphering the human genome sequence, web-based genetic tests abound

• Nutrigenetic tests aim to provide dietary and life-style recommendations based on a person’s genetic profile

• There is good science behind the concept of nutrigenetics, but the current practice of nutrigenetics companies illustrates how commercialization often races ahead of science

Concept Review



• We simply don’t have an adequate enough understanding of how particular genes contribute to health and disease

• Dietary recommendations based on MTHFR gene variants is an example of the overreach of commercial nutrigenetics

•The MTHFR gene encodes an enzyme that breaks down the amino acid homocysteine

Concept Review



• Some studies have found that elevated homocysteine levels are associated with increased risk of heart disease or stroke

• There are two common MTHFR gene variants; one variant produces a low activity enzyme

• Having the low activity form of MTHFR elevates homocysteine levels

Concept Review



• Increasing vitamin B intake can reduce homocysteine levels

• It is logical to expect that decreasing homocysteine levels in people with the low activity MTHFR variant will protect against heart disease and stroke

• However, five studies have failed to find this connection

• This scientific doubt has not stopped nutrigenetics companies from marketing tests for MTHFR and basing dietary recommendations on the results

Concept Review



• The Government Accountability Office (GAO) ran a sting operation on four nutrigenetics companies

• Investigators ordered 14 tests on two different DNA samples

• Each questionnaire submitted with the DNA samples described adult men and woman of different ages, weights, and lifestyles

Concept Review



• The recommendations made using the same sample of DNA were often vastly different and sometimes contradictory

• The personalized reports alternated between predictions that could apply to anyone and advice based entirely on the lifestyle questionnaire

• The GAO concluded that the results provided by these companies could not have been determined from the genetic test results

Concept Review



• In at least one case, personalized profiles were used to market an expensive dietary supplement that contained the same ingredients found in over-the-counter multivitamins available at a fraction of the cost

Concept Review



• A concern with bogus nutrigenetic testing is that it may dampen public faith in the validity of more legitimate genetic tests

• A challenge in nutrigenetics and other types of genetic testing is that for most disorders many genes are involved and these genes interact

• In any complex disorder, it’s unlikely that we know all the genes and even for those we do know, the effect of their interactions is notoriously difficult to predict

Concept Review



• Another concern with today’s web-based nutrigenetics is that obtaining a profile that predicts low risk provides a false sense of security

• Individuals who believe they are at low risk will be less likely to take the preventative care and screenings known to truly reduce disease risk

Concept Review



• There is increasing interest in regulating at-home genetic tests

• Under current law, the FDA (Food and Drug Administration) can only regulate tests sold as medical device kits to clinical laboratories

• Most genetic tests fall outside this domain and cannot be regulated

Concept Review



• If misused, nutrigenetics can undermine the faith of a public primed to expect great things from the Human Genome Project

• If, however, nutrigenetics can provide the impetus for effective regulation of genetic testing, it will promote the use of basic genetics research for human well-being

Concept Review


Diet Advice From DNA?Testing Your Comprehension

The idea of nutrigenetics is to provide dietary guidelines based on:a) family historyb) a person’s particular set of genes c) genetic predispositions to lifestyle choicesd) the interaction between nutrients and gene regulation



The idea of nutrigenetics is to provide dietary guidelines based on:

b) a person’s particular set of genes



The goal of reducing homocysteine in people with low MDHFR activity is to:a) reduce the risk of heart disease and strokeb) reduce the risk of obesityc) correct vitamin B deficiencyd) correct problems in protein digestion



The goal of reducing homocysteine in people with low MDHFR activity is to:a) reduce the risk of heart disease and stroke



Lowering homocysteine through diet has been found to:a) decrease the risk of heart attack and strokeb) have no significant affect on the risk of heart attack and strokec) increase the risk of heart attack and stroked) lead to vitamin B deficiency



Lowering homocysteine through diet has been found to:

b) have no significant affect on the risk of heart attack and stroke



The strength of the link between homocysteine levels and health has:a) caused many nutrigenetics companies to go out of businessb) caused nutrigenetics companies to stop testing for MTHFR gene variants c) caused nutrigenetics companies to provide a disclaimer on interpreting MTHFR test resultsd) not caused any change in the way nutrigenetics companies interpret MTHFR test results



The strength of the link between homocysteine levels and health has:

d) not caused any change in the way nutrigenetics companies interpret MTHFR test results



The GAO concluded that the nutrigenetics companies they investigated provided diet advice:a) that was harmful to clientsb) that rested on a firm scientific foundationc) that was based solely on the family history d) that could have applied to anyone and was based on lifestyle



The GAO concluded that the nutrigenetics companies they investigated provided diet advice:

d) that could have applied to anyone and was based on lifestyle



Current nutrigenetics recommendations do not account for the fact that:a) there are variants of genes b) dietary recommendations may change according to a person’s genetic profilec) different genes often interact in complex waysd) levels of metabolites such as homocysteine can be influenced by diet



Current nutrigenetics recommendations do not account for the fact that:

c) different genes often interact in complex ways



The FDA is able to regulate:a) most forms of genetic testingb) all forms of genetic testingc) human genome-related research d) medical device kits sold to clinical labs



The FDA is able to regulate:

d) medical device kits sold to clinical labs



A concern about existing nutrigenetics testing is that it will:a) make people lose confidence in all forms of genetic testingb) increase the number of unnecessary medical testsc) increase health care costsd) reduce sales by pharmaceutical companies



A concern about existing nutrigenetics testing is that it will:a) make people lose confidence in all forms of genetic testing


Diet Advice From DNA?Thinking About Science

In animal studies, raising the levels of the cholesterol carrier HDL decreases the risk of heart disease. If people are found with a genetic variant that causes low HDL levels and increasing intake of vitamin K increases HDL levels, what is the most critical thing to know before recommending vitamin K supplementation in people genetically predisposed to low HDL?a) how long vitamin K supplementation can increase HDL levelsb) the DNA sequences of the normal and variant genec) whether increasing HDL in people influences heart disease riskd) the way vitamin K influences HDL levels


Diet Advice From DNA?Thinking About Science

In animal studies, raising the levels of the cholesterol carrier HDL decreases the risk of heart disease. If people are found with a genetic variant that causes low HDL levels and increasing intake of vitamin K increases HDL levels, what is the most critical thing to know before recommending vitamin K supplementation in people genetically predisposed to low HDL?

c) whether increasing HDL in people influences heart disease risk


Diet Advice From DNABiology and Society

Nutrigenetics testing should be under strict federal control

StronglyAgree

StronglyDisagreeA. E.C.B. D.


Diet Advice From DNAInterpreting Charts and Graphs

Which of the following statements is supported by the figure?a) the number of gene tests and number of laboratories has increased at about the same rateb) the number of gene tests performed per laboratory has decreased over timec) the number of gene tests performed per laboratory has stayed constant over timed) the number of gene tests performed per laboratory has increased over time


Diet Advice From DNAInterpreting Charts and Graphs

Which of the following statements is supported by the figure?

d) the number of gene tests performed per laboratory has increased over time

Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings Lectures by Greg Podgorski, Utah State University Diet Advice From DNA? Current.

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