15 February 2007

Gene tests solve diet riddles

Nutrigenomics is a very new and exciting approach to the treatment of a wide variety of diseases by means of genetic identification and diet therapy.

Recently DietDoc attended an interesting lecture presented by Yael Joffe, a dietician working in Cape Town, on ‘nutrigenomics’. “What”, you may ask, “is nutrigenomics?”

Nutrigenomics is a very new and exciting approach to the treatment of a wide variety of diseases by means of genetic identification and diet therapy.

Diet riddles
Dieticians, doctors and other healthcare professionals have been aware of what can be classed as ‘diet riddles’ for a long time. ‘Diet riddles’ are situations where one patient will react to diet treatment, while the next patient won’t. The public are just as puzzled and frustrated by this seemingly illogical state of affairs.

Many Health24 readers say that they are religiously sticking to their diet (e.g. for weight loss) and not losing a gram. Other individuals cut their fat intake drastically and see no effect on soaring blood cholesterol levels. Until recently health professionals did not have an answer to these riddles.

Thanks to the development of nutrigenomics we now have a better idea of what factors play a role in ‘diet riddles’.

Researchers have discovered that the way in which different people react to diet therapy, medications and other interventions, is closely determined by their genetic makeup. Each human being is unique from a genetic point of view. We all know that the colour of our eyes, shape of our noses and other typical characteristics are determined by our genetic makeup.

Research into so-called genetic markers (bits of genetic material that carry information for how humans are to develop), indicates that the way in which we will react to diets and medications, what kind of diseases we are likely to develop and even how long we will live, is all written in our genes.

This discovery heralds an exciting breakthrough in human knowledge and will make it possible to treat individual patients much more specifically in future. What is particularly exciting is that a lot of this research has taken place in South Africa. South Africa is also one of the first countries in the world where genetic identification and diet therapy are being combined.

The basic principles of nutrigenomics are that patients, who do not react to specific treatments (diets, medications, lifestyle changes), will be able to have a genetic test done to determine the genetic markers that affect the problem in question (e.g. inability to lower blood cholesterol levels with a low-fat diet).

A patient with a recalcitrant problem will be asked if he is prepared to have a genetic test. If the patient agrees, he will have a buccal swab taken (a swab stick will be used to take a sample of the patient’s cells on the inside of the cheek). The patient will also be required to fill in a Nutri-Gene Questionnaire on his dietary intake, lifestyle and medical history.

The sample and a questionnaire will be sent to GeneCare in Cape Town and this laboratory will analyse both the cell sample and the information contained by the questionnaire. The analysis will make it possible to classify the patient in various ways, e.g. ‘dietary non-responder’ or ‘medication non-responder’ or ‘high-risk for cancer’. With this kind of information, the dietician or doctor who is treating the patient will be able to tailor the treatment to suit the individual’s genetic needs.

To illustrate how nutrigenomics can play a vital role in many aspects of diet and medical treatment, we take a ook at some interesting examples of how people differ in their genetic responses to diet, supplements and medications.

Nutrigenomics and folic acid
Folic acid is one of the B vitamins. Most people require 400 micrograms of folic acid a day to stay healthy. Genetic research has, however, identified a population sub-group that requires twice as much folic acid daily to stay healthy. Individuals with an increased genetic need for folic acid have to ingest 800 micrograms per day of this vitamin, something that is difficult to achieve by diet alone.

If you happen to be a woman and have a genetically greater need for folic acid and your diet is not able to provide 800 micrograms of folic acid on a daily basis, your chances of having a baby with neural tube defects are much greater than in women who need less folic acid. Neural tube defects in infants are directly linked to a dietary deficiency of folic acid.

The woman in our example would, therefore, need to take a high folic acid supplement during the period when she is attempting to fall pregnant and throughout the pregnancy. If you have had a baby with a neutral tube defect or other complications of pregnancy in the past and are trying to fall pregnant again, then it is essential to have yourself tested to see if you have a genetic predisposition for high folic acid intakes.

Imagine how much trauma and grief could be prevented if pregnant women had a gene test before they fell pregnant. A simple test and a simple treatment with folic acid and a vitamin B complex supplement can fully prevent neural tube defects and certain other complications. It is better to take the folic acid together with a vitamin B complex supplement that contains all the B vitamins, because B vitamins always work more effectively when they are taken in combination.

Nutrigenomics is an exciting new development that will make dietary treatment much more specific in future. – (Dr Ingrid van Heerden, DietDoc)

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