Navigating the wealth of nutrition information can be extremely frustrating and time consuming. Even more challenging is then identifying the right fit for you. Should you eat Paleo? AIP? Vegan? Mediterranean? High fat? Low fat? Atkins? South Beach? And let's not get into portion size and frequency. The quest for the perfect diet can inadvertently yield even more stress (and its subsequent implications) thereby defeating the initial purpose of better health. Adding an extra layer of confusion is the fact that a certain way of eating can lead to the remission of a disease in one person while triggering symptoms in another. There is not a one size fits all when it comes to nutrition.
The importance of individually appropriate nutrition was highlighted by a couple of studies. One study (1) found a high individual variability in glucose levels in response to the same meal, while another study (2) concluded that genetically-based dietary advice resulted in improved metabolic outcomes such as reduced blood sugar levels, BMI and better compliance with treatment. Similarly, a French study (3) found that obesity and diabetes, defined as diet-related chronic diseases, are "starting point" diseases potentially leading to other diseases such as CVD, skeletal disease and cancer. The study also concluded that mental illness, liver, kidney and digestive diseases are causes as well as consequences of other diet-related chronic diseases. And while several factors play a role in the development of these diseases, they share some common ground: impaired physiological mechanisms.
For instance, DNA damage is directly linked to the development of degenerative disease (4), such as cancer and premature aging. Several nutrients, such as vitamin E, retinol, calcium, folate and B3 are associated with reduced DNA damage. On the other hand, vitamins B2, B5, and biotin, are associated with more DNA damage while moderate intake of beta-carotene was protective, but too much was damaging. The problem is that what may be too much for me can be just right for you.
Broad dietary recommendations, such as "eat more fruits and vegetables," fail to address specific nutrient needs of an individual, considering the diversity of micronutrient availability in different foods. Identifying precise micronutrient combinations and concentrations that prevent DNA damage via dietary manipulations (i.e., increased folate and specific antioxidants compounds found in certain foods) can play a key role in the prevention and control of specific cancers .
For instance, it is known that the color and phytonutrient profile of foods and vegetable is associated with unique health properties. One study (5) looked at the protective effects of colorful fruits and vegetables on the 10-year incidence of stroke and found that the consumption of white fruits and vegetables (such as apples and pears) was associated with 9% lower risk of stroke. Another study (6) found that purple and red fruits and vegetables were associated with lower weight and abdominal fat, and there was also an improvement in blood sugar and total cholesterol for women. A better understanding of the interplay of phytonutrient composition and health outcomes is key to providing targeted recommendations. Phytoprofiling (7) seeks to identify specific bioactive compounds in fruits and vegetables that are beneficial to health, providing better insight into their healing properties and facilitating the development of phytotherapeutic agents.
This is all relevant to concept of personalized nutrition, which has been gaining more spotlight in the past few years. It is known that genetic differences distinctly influence metabolic responses. These intricate interactions can be explored not only to ameliorate or cure diseases, but also to prevent them and improve overall health.
Nutrigenetics aims to identify how genetic variations alter the requirements and responses to nutrients, paving the way for individualized dietary advice. The premise is that genetic variants alter nutrient metabolism potentially leading to the development of disease. Similarly, the emerging field of metabolomics (8) studies human as well as gut flora metabolites (derivatives of metabolism) and its interactions with other biochemical processes in the body, therefore seeking to identify biomarkers of impaired physiological mechanisms.
Both nutrigenetics and metabolomics facilitate personalized nutrition by acknowledging the complex interactions between genes, nutrients and human metabolic responses. As a result, the acquired information can be used to devise a nutrition plan specific to the individual.
However, the promise of personalizing dietary recommendations based on genetic information has some limitations. Several of the tests available look at different SNPs (genetic variations), but there is currently a lack of evidence on some of the SNPs analyzed. Additionally, test accuracy and the relevance of these tests for different ethnicities, genders, and ages isn't clear, and the precise role of environmental factors on gene expression must be further explored (9). These issues coupled with the fact that the majority of consumers lack the knowledge to interpret results correctly can render the whole process worthless.
One study (10) found that consumers are more trusting towards genetic-based nutrition advice if it comes from a healthcare professional rather than from companies that sell directly to consumers. This highlights the importance of working with a qualified professional that is capable of translating the genetic information into practical advice, therefore avoiding unnecessary stress and anxiety over the results. Remember that simply having X genetic variant does not necessarily mean you will have X disease.
While personalized nutrition seems to be the future in disease prevention and management, relying solely on genetic testing to dictate a set way of eating may narrow your options because genes only tell half the story. We must remember that the body is a complex machine with a myriad of intricate biochemical reactions that we still can't fully comprehend. Addressing nutritional needs from a holistic perspective that takes into account not only genes, but also past health history, symptoms, lifestyle and preferences in combination with other screening tools is probably a better approach to help you compile your grocery shopping list.
References
1. Zeevi, P. et al. (2015). Personalized Nutrition by Prediction of Glycemic Responses. Cell. 163(5): 1079-1094.
2. Arkadianos, I. et al. (2007). Improved weight management using genetic information to personalize a calorie controlled diet. Nutrition Journal. 6:29.
3. Fardet, A. & Boirie, Y. (2013). Associations between diet-related diseases and impaired physiological mechanisms: a holistic approach based on meta-analyses to identify targets for preventive nutrition. Nutrition Reviews. 71(10): 643-56
4. Fenech, MF. (2014). Nutriomes and personalised nutrition for DNA damage prevention, telomere integrity maintenance and cancer growth control. Cancer Treatment Research. 159: 427-4
5. Oude Griep, L.M. et al. (2011). Colors of fruit and vegetables and 10-year incidence of stroke. Stroke. 42(11): 3190-5.
6. Mirmiran P. et al. (2015). Colors of fruits and vegetables and 3-year changes of cardiometabolic risk factors in adults: Tehran lipid and glucose study. European Journal of Clinical Nutrition. 49.
7. Xie, G. (2013). Toward Personalized Nutrition: Comprehensive Phytoprofiling and Metabotyping. Journal of Proteome Research. 12(4): 1547-1559.
8. San-Cristobal, R. et al. (2013). Future Challenges and Present Ethical Considerations in the Use of Personalized Nutrition Based on Genetic Advice. Journal of the Academy of Nutrition and Dietetics. 113(11): 1447-1454.
9. Nielsen, D.E. et al. (2014). Perceptions of genetic testing for personalized nutrition: a randomized trial of DNA-based dietary advice. Journal of Nutrigenetics and Nutrigenomics. 7(2): 94-104.