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United States Department of Agriculture

Agricultural Research Service

Can your diet affect your genes? Stay tuned
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By Philip Reeves

A new field of nutrition has emerged over the past few years. It is called nutrigenomics and deals with how genes and dietary nutrients interact to support health or cause disease. It tries to find out how an individual's diet might affect ones health and whether the diet might be altered to maintain a balance between health and disease and to determine what diet is right for an individual.

Your genes are made up of strands of DNA. DNA is made up of four specific chemical compounds called adenine, cytosine, guanine and thiamine. Most of the time, these compounds are referred to by their initials A, C, G and T. They are strung together in various combinations to form individual genes, which have specific functions.

The function of a gene is to produce strands of messenger ribonucleic acid called mRNA. mRNA is made of the chemical bases A, C, G and uracil (U) instead of T. Individual mRNAs then are used to string various amino acids together to make specific proteins, which run the different body functions.

Sometimes when DNA is produced by the body, mistakes are made. These mistakes can result in whole sections of the DNA being left out or just a single letter at a specific place being changed from one to another, say an A is substituted for a C. This then leads to mistakes in how the amino acids are aligned in a protein. This then might affect the function of the protein, leading to a particular disease, usually referred to as a “genetic” disease. These mistakes can be passed on to future generations.

There are a number of these diseases of which phenylketonuria is an example. This is a disease where a mistake is made in the DNA and if people with PKU get too much phenylalanine in their diets, it will build up in the blood and eventually spill over into the urine. Too much phenylalanine in the blood can lead to toxicity problems, especially in the brain.

There are no cures for this disease, but it can be controlled by monitoring the amount of phenylalanine consumed in the diet. The techniques of gene therapy are now being studied to find a better way to control this disease.

Other changes in the letters of DNA might not cause irreparable harm but might cause a person's body to respond to a dietary nutrient in a different way than that in a normal person's body.

It has been known for some time that some people can eat an unhealthy diet with high fat and still maintain a high concentration of HDL, the good cholesterol, in their blood.

Researchers have found that about 25 percent of the population has a single letter mutation in the gene for one of the HDL proteins. They also found that these people do not have naturally higher HDL, but that the appearance of this condition in these individuals is modified by polyunsaturated fatty acids in their diets.

Women with this condition have 13 percent higher HDL when they eat high amounts of PUFAs than those that do not.

A connection between nutrient intake and cancer is found in individuals with a mutation in a gene that produces a protein that metabolizes the vitamin folic acid. Individuals with this mutation have 68 percent lower risk of colon cancer when they eat adequate amounts of folic acid. However, when they eat low amounts of folic acid, their cancer risk is increased.

High dietary selenium is also known to reduce the incidence of colon cancer; however, the gene responsible, if there is one, is not known.

Of course, no two individual are alike, so the eventual goal of this type of work is to design a test where an individual's DNA can be analyzed for genes and mutations associated with specific diseases. Then dietary intakes could be designed on an individual basis.

Although this field is progressing rapidly and some tests already are available, more work is needed before accurate predictions about nutrient/gene interactions and health and disease can be made.

In the meantime, the new government resource,, provides you the opportunity to individualize your own person food guide pyramid. There, you can gauge how close you are coming to getting the recommended amount of each required nutrient in your diet on a given day.

At the same time, you also can make judgments about how well your exercise program is going.

Last Modified: 12/8/2006
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