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Diet Advice From DNA?
Current Issues in Biology, Volume 6
Scientific American
Lectures by Greg Podgorski, Utah State University
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Concept Review
• 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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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-thecounter multivitamins available at a fraction of the cost
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The idea of nutrigenetics is to provide dietary guidelines
based on:
a) family history
b) a person’s particular set of genes
c) genetic predispositions to lifestyle choices
d) the interaction between nutrients and gene regulation
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The idea of nutrigenetics is to provide dietary guidelines
based on:
b) a person’s particular set of genes
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The goal of reducing homocysteine in people with low
MDHFR activity is to:
a) reduce the risk of heart disease and stroke
b) reduce the risk of obesity
c) correct vitamin B deficiency
d) correct problems in protein digestion
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The goal of reducing homocysteine in people with low
MDHFR activity is to:
a) reduce the risk of heart disease and stroke
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
Lowering homocysteine through diet has been found to:
a) decrease the risk of heart attack and stroke
b) have no significant affect on the risk of heart attack
and stroke
c) increase the risk of heart attack and stroke
d) lead to vitamin B deficiency
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
Lowering homocysteine through diet has been found to:
b) have no significant affect on the risk of heart attack
and stroke
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The strength of the link between homocysteine levels
and health has:
a) caused many nutrigenetics companies to go out of
business
b) caused nutrigenetics companies to stop testing for
MTHFR gene variants
c) caused nutrigenetics companies to provide a
disclaimer on interpreting MTHFR test results
d) not caused any change in the way nutrigenetics
companies interpret MTHFR test results
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The GAO concluded that the nutrigenetics companies
they investigated provided diet advice:
a) that was harmful to clients
b) that rested on a firm scientific foundation
c) that was based solely on the family history
d) that could have applied to anyone and was based on
lifestyle
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The GAO concluded that the nutrigenetics companies
they investigated provided diet advice:
d) that could have applied to anyone and was based on
lifestyle
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
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 profile
c) different genes often interact in complex ways
d) levels of metabolites such as homocysteine can be
influenced by diet
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
Current nutrigenetics recommendations do not account
for the fact that:
c) different genes often interact in complex ways
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The FDA is able to regulate:
a) most forms of genetic testing
b) all forms of genetic testing
c) human genome-related research
d) medical device kits sold to clinical labs
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
The FDA is able to regulate:
d) medical device kits sold to clinical labs
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
A concern about existing nutrigenetics testing is that it
will:
a) make people lose confidence in all forms of genetic
testing
b) increase the number of unnecessary medical tests
c) increase health care costs
d) reduce sales by pharmaceutical companies
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA?
Testing Your Comprehension
A concern about existing nutrigenetics testing is that it
will:
a) make people lose confidence in all forms of genetic
testing
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
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 levels
b) the DNA sequences of the normal and variant gene
c) whether increasing HDL in people influences heart
disease risk
d) the way vitamin K influences HDL levels
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA
Biology and Society
Nutrigenetics testing should be under strict federal
control
Strongly
Agree
A.
B.
C.
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
D.
E.
Strongly
Disagree
Diet Advice From DNA
Interpreting 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 rate
b) the number of gene
tests performed per laboratory has decreased over time
c) the number of gene tests performed per laboratory has stayed
constant over time
d) the number of gene tests performed per laboratory has increased
over time
Copyright © 2010 Pearson Education, Inc. publishing as Benjamin Cummings
Diet Advice From DNA
Interpreting 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