Nutrigenetic testing: a dietitian’s assistant or an overhyped fad?
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Genetic testing has been around for a long time offering people the key to understanding their potential health risks, planning pregnancy and diagnosing genetic deficiencies. Many individual therapies rely on genetic screening, including diet intervention methods.
Dietitians know that DNA and diet interact. Molecular analysis of genes responsible for metabolism provides important insight essential for creating a balanced diet. Additionally, they help understand the nature of eating habits and even predict risks. While that seems to be a viable idea, nutrigenetic testing has become a controversy-surrounded topic.
What is the controversy about?
It started with an academic paper published in the Journal of the American Medical Association in 2017. The article questions the genetic-based approach to weight
loss. The research involved 609 participants who followed either a low-carb or low-fat diet based on their genetic data. Possessing one of the three genetic markers such as FABP2 (rs1799883), PPARG (rs1801282), and ADRB2 (rs1042714) served as a basis for a diet choice in each particular case.
Before the research it was believed that these markers could identify which type of diet will help a person lose weight. At the end of the research, the group of people following a low-carb or low-fat diet according to their genetic makeup lost more weight than those without a genetic predisposition to particular diets. However, the weight difference was so small that it had absolutely no statistical significance. The findings of the research prove that these three genes are not accountable for your food choices.
To the big surprise of its many advocates, results of the study have been misinterpreted as “DNA diets don’t work,” which was followed by negative press coverage. Genetics-based diets even became associated with snake oils and quackery. With all the negativity swirling around this type of diet, people seem to forget its true meaning.
What is a diet?
“Are you on a diet?” Probably everyone who ever skipped dessert heard these words at least once. The thing is that diet is typically associated with temporary ration adjustments aimed at weight loss. In reality, diet is a set of personal nutritional habits. If you happen to eat fast food every other day or prefer vegetables over meat — this is a diet.
The point is that diets serve different purposes. There is a wide range of disease prevention, biometrics-based and therapeutic diets that are not used for weight loss. Nutrigenetic diet is one of them.
So what exactly does nutrigenetics do?
Nutrigenetics provides the key to treating DNA deficiencies. All metabolic processes are encoded in the DNA of each living organism. For example, a mutation preventing vitamin D absorption puts at risk the maintenance of a balanced diet due to its insufficient supply. Nutrigenetics offers a way to solve this problem by adopting a vitamin-D-enriched diet, which compensates for the vitamin lack. A person following this diet will receive a sufficient amount of protein, fat, carbohydrates, and vitamins.
Nutrigenetics is a scientific discipline that studies the relations between genetic alterations, nutrition, and diseases. Each person has an individual set of genes that influence metabolism. A nutrigenetic test will let you know about your tolerance to specific products and substances (lactose, gluten, alcohol, vitamins). Its results are used for personalized dietary advice.
It’s because DNA sequences can’t be changed, nutrigenetic diets are valid throughout a lifetime. If a person is genetically lactose intolerant, they will remain such for the rest of their life and will follow the same dietary recommendations.
Just like any diet, nutrigenetics diets comply with the modern nutrition science recommendations. Nutrigenetic services follow the official recommendations of WHO, NIH, American Heart Association and use the most recent standards of caloric and macronutrient distribution. However, knowing your affinity towards deficiency of some nutrients gives you an advantage of maintaining a more balanced diet.
Another valuable asset of DNA analysis is that it helps predict the onset of certain diseases. Making timely dietary corrections is a way to avoid the risks. For example, if according to the genetic testing, a person has a predisposition to the high homocysteine levels (that often leads to the cardiovascular diseases, particularly hypertension), their diet should be based on a DASH (Dietary Approaches to Stop Hypertension). Another example, specific mutations in APOE gene drastically increase the risk of the Alzheimer’s disease. People with such gene mutations are recommended to switch to a MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet that has a potential to halt the neurodegenerative disease.
Taking a nutrigenetic test should be a conscious step. It’s a way to unlock your DNA-encoded properties to maintain a healthy daily menu based on your genetic predispositions.
What does the health science say?
Let’s take a look at some examples when a DNA-based diet can help prevent certain health conditions.
The most notable example of putting nutrigenetics to use is phenylketonuria. It is a genetic condition caused by a mutation in the PHA (phenylalanine hydroxylase) gene. People with phenylketonuria must avoid products that contain phenylalanine, such as soy, hard cheese, certain nuts, red meat, tuna, and eggs. Following a strict diet is the only way to avoid severe cognitive disorders caused by phenylketonuria. Without nutrigenetics, it would be impossible to gain knowledge about a person’s affinity towards this condition, let alone making proper dietary interventions.
People are divided into fast and slow caffeine metabolizers. It is scientifically proven that the CYP1A2 gene is responsible for this property. Fast metabolizers experience a reduced stimulating effect of caffeine and derive significant health benefits from coffee. Meanwhile, slow metabolizers should avoid excessive coffee consumption as it leads to a higher risk of cardiovascular diseases. Knowing your caffeine metabolizing group (according to CYP1A2 gene variation) allows to avoid potential health risks.
If you are among the lucky fast caffeine metabolizers, don’t rush to add milk to your coffee. According to the National Health Institutes, over 65% of the world population is intolerant to milk sugar (lactose), experiencing discomfort in the stomach after drinking milk. The majority of people are born with high levels of lactase, a lactose-breaking enzyme. However, its levels may drop while aging, leading to complete lactose intolerance that causes stomach ache, swelling and diarrhea. People genetically prone to lactose intolerance need to care about their gut microbiome. A diet rich in lactic acid bacteria, as well as sticking to lactose-free dairy, in most cases alleviate the symptoms.
There are many people without a gluten sensitivity who try to avoid gluten to feel healthier. But for 1% of the population suffering from celiac disease it’s a vital necessity. They have a health condition in which immune system overreacts to gluten causing inflammation.
There is no better preventive measure for celiac disease as effective as a gluten-free diet. On the other hand, for people who can tolerate gluten, this diet can be extremely harmful. This is because many gluten-free products lack vitamin B and iron but contain excessive amounts of fat and sugar.
For a long time, scientists were unable to explain what triggers celiac disease. But now it is known as a genetically predetermined condition in which HLA genes are the most important genetic factors causing its development. Celiac disease can be diagnosed with a series of tests, including genetic. The effects of celiac disease can be reduced by switching to a gluten-free diet.
Some gene variations can interrupt the digestion of vitamins, which is the cause of many diseases. For example, the MTHFR gene encodes an essential enzyme involved in folate metabolism — vitamin B9 cycle enzyme. Folate deficiency is caused by a single nucleotide variation in this gene and may trigger schizophrenia, depression, cardiovascular diseases, and pregnancy abnormalities. Folate deficiency results in elevated levels of homocysteine that induces numerous pathological conditions. Smoking and excessive fats consumption can worsen this condition. At the same time, consuming folic acid supplements combined with mild physical activity lowers this risk.
Getting enough vitamin D from food is good, but it is essential that it is properly digested. VDR, a vitamin D receptor protein, is responsible for mediating this process. A mutation of the VDR gene leads to poor digestion of the vitamin because of its abnormal shortage. People with this condition need to get more daily vitamin D by deliberately adding it to their diet.
Fatty acids and vegetarianism
Since the earliest days of human farming, FADS or “vegetarianism genes” were spreading among the farmers. Even with no animal source of fatty acids, their organisms started to rely more on internal synthesis of these compounds. The discovery of FADS genes gave the reason that some people are more accustomed to the vegetarian diet.
In fact, some variations in FADS1 and FADS2 genes can reduce the need for omega-3 and omega-6 unsaturated fatty acids. Switching to a vegetarian diet often comes with a change in such processes as blood formation, immune system, reproductive system, and more. Without a carefully balanced diet, vegetarians risk facing a deficiency of many crucial nutrients, including unsaturated fatty acids. The bottom line is that even if you have inherited “vegetarian” FADS, it doesn’t mean that a vegetarian diet is the best choice for you.
Alzheimer’s disease, the most common form of dementia, still has no cure. Fortunately, some methods lower the risks of dementia. It is crucial to adopt a healthy diet and lifestyle. In this regard, researchers from California have created a complex protocol that reduces dementia symptoms in 90% of patients, including individuals with an APOE4 variation, a gene that increases the likelihood of Alzheimer’s disease up to eleven times. To that end, the protocol suggests consuming low-glycemic food with pre- and probiotics, dietary supplements such as vitamins D, B12, B6, B9, 0,5 g of melatonin, and exclusion of red meat. Additionally, researchers recommend eating with a 12-hour fasting between breakfast and supper, meditation, physical activity, eight-hour sleep, and increased attention to dental health.
Genetic tests are an essential motivator to change your eating habits. Knowing your genetic predisposition to the unbalanced nutrient digestion and the risk of hereditary disease encourages you to adopt a healthy diet.
What is genetic testing?
It won’t help you lose extra pounds. Relying solely on genetic testing in obesity treatment isn’t right. A genetic component is just one of the factors in predisposition to excess weight together with microbiome, age, habits, lifestyle, and others.
In 2017, 23andMe embarked on extensive research with the aim of finding a connection between genes and weight. The company hopes to discover the individual factors that will be of great use for individual weight loss programs.
It doesn’t determine your optimal exercise routine. The ability to tailor an effective individual fitness program around genetic test results сertainly is a hot topic nowadays. The centerpiece of the argument lies in the fact that genes are accountable for predisposition to certain types of exercise, as well as for potential injuries and recovery times. For example, DNAFit analyzes genes that affect muscle work. Slow (red) muscle fibers contract slower but are more durable. Fast (white) muscle fibers contract faster but get tired sooner. Based on an individual genetic predisposition to a specific type of muscles, the company is able to predict how a person can achieve the optimal results in fitness.
Information about their genes and muscle fibers is genuinely useful for athletes. However, fitness advice (as any other) should be based on a variety of biological data, including blood tests and microbiome analysis. Relying solely on genetic testing in this matter is not right, as it can only tell whether an individual needs more physical activity and if they have any health risks.
It doesn’t predict your future. Direct-to-consumer (DTC) genetic tests are meant for informative purposes. Knowing about your health risks doesn’t mean they will necessarily occur. Nevertheless, some factors do increase the likelihood of pathogenesis, such as inflammation, infections, getting insufficient sleep and low physical activity.
Diagnostic tests also analyze other genes responsible for hereditary conditions that occur in 100% of all people with particular variations such as phenylketonuria, mucoviscidosis, and Marfan syndrome. These tests are conducted in healthcare institutions, and their results are used for therapy planning.
How not to fall victim to genetic testing controversies?
Above all, companies must provide science-backed results accompanied by valid explanations. It is important to clearly state what information about DNA the test can give and what information is off limits.
In the modern world, being genetics-savvy isn’t something extraordinary. In most cases, a dietitian or genetic consultant find DNA tests results reasonable for therapy — be it a recommendation as to adding specific nutrients to meals or assessing potential disease risks and ways to eliminate them. In the future, genetic tests are likely to gain popularity due to their affordability and accuracy. It’s the easiest way for people to understand their body and make proper health decisions.
Unfortunately, modern medicine can’t treat DNA mutations in humans or any being for that matter. Still, the negative influence of genetic variations can be decreased by healthy nutrition and staying clear of bad habits.
Nutrigenetic science evolves rapidly, new gene-trait connections discovered each year. Nutrigenetic services update their gene pools constantly, getting ever closer to unlocking true potential behind personalized nutrition. We are only in the begining of our journey to discover this influence, but the recent discoveries ensure us that the key to this secret is somewhere nearby.