Have you ever wondered why we are constantly bombarded by a constant stream of such fundamentally contrasting dietary advice via a plethora of media channels? We are inundated on a daily basis on the ultimate weight loss tactic or optimal nutrition breakthroughs; however, there essentially seems to be no clear-cut, comprehensive scientific consensus concerning the optimal diet, as the information drags you in polar opposite directions. In fact, the science increasingly points towards the fact that there is — no one diet that fits all approach—. We are all inherently different, which may explain why we respond physiologically differently to nutrition strategies and why no universally accepted diet can be identified.
Now, can you imagine a world where your DNA is encoded from birth? Where you will have access to intelligence of the diseases you are strongly predisposed to developing based on your DNA. Where dietary advice will be personalised to your individual genotype. This nutrition revolution is gradually becoming reality. The completion of the Human Genome Project in 2003 has enabled the development of various techniques to characterise common genetic traits, leading to significant progress in the field of gene-nutrient interactions.
This realisation has scientists and entrepreneurs racing to deliver more effective nutritional advice based on individual factors such as genetic makeup, gut bacteria, body type and chemical exposures. This may also shed light on the apparent injustice of why some people struggle with weight loss strategies whilst strictly adhering to what is deemed to be a healthy diet, whilst others can seemingly eat whatever they like without this reflecting on the scales.
Genotype-based nutrition has the potential to provide individuals at high risk of chronic diseases, such as diabetes, cardiovascular disease and cancer with customised nutritional advice to reduce disease risk and onset. There is convincing evidence that a broad range of variations in population gene expression exist, which may explain the unique differences in biological response to how we absorb and metabolise nutrients and, as such, predisposition to developing chronic diseases. Interactions between genotype and diet will become increasingly important when assessing disease risk and preventative management.
Cardiovascular disease and gene-nutrient interactions
Research shows that people’s cholesterol levels can respond very differently to dietary intervention methods depending on their genetic makeup.
Apoliprotein E (ApoE) is a protein involved in lipid metabolism. Individuals possess one of three different forms of ApoE, depending on their genotype: ApoE2, ApoE3, or ApoE4. Those with ApoE4, representing approximately 15% of the population, are more likely to have higher concentrations of cholesterol. In fact, those individuals possessing an ApoE4 genotype who consume a diet low in saturated fat are more likely to respond favourably to this dietary intervention; they will exhibit observable reductions in cholesterol levels, despite their genetic predisposition. This signifies that consuming a heart-friendly diet may be more pertinent for those with an ApoE4 genotype compared to other ApoE types, where effects may be negligible. However, until these people can be identified, recommending a heart-healthy diet to everyone is imperative.
Furthermore, individuals expressing the Apoliprotein (ApoA1) genotype will exhibit a higher HDL (“good cholesterol”) level in response to increased intakes of polyunsaturated fatty acids (PUFAs), which are considered healthy fats. Contrastingly, the science shows that individuals with a differing genotype display positive impacts on HDL cholesterol levels by decreasing PUFA intake. As such, it can be inferred that it would make sense for some people to consume higher amounts of PUFAs than others, depending on genotype, to reduce cardiovascular disease risk.
Researchers have discovered several gene polymorphisms strongly associated with type 2 diabetes risk, which can be modified with diet. The research suggests that individuals, who have been profiled with a higher predisposition to diabetes, may modulate their risk by consuming a low glycaemic index diet (GI).
The “Personalised Nutrition Project” led by a team of Israeli researchers, suggests that individuals have very different blood sugar responses to the same food —with some showing large spikes even after consuming supposedly healthy choices—. During digestion, carbohydrates are broken down into glucose, which are then released into the bloodstream. After consuming a meal, it is normal to experience an increase in blood sugar levels, termed “post-prandial glucose response”. However, consistently high blood sugar blood levels in the long run can increase the risk of weight gain, and disorders such as type-2 diabetes, high blood pressure and heart disease.
The study followed a cohort of 800 healthy and pre-diabetic individuals, whereby data was collected round-the-clock, to measure the effect of food on blood sugar levels. Many exhibited stark differences in their response to foods with the same GI. Some of the volunteers, dubbed 'carb-sensitive', had a higher blood sugar reaction in response to the more carbs they ate. This was in direct contrast to the 'carb-insensitives' whose blood sugar could increase even on a low-carb meal. Many responded very differently to fat consumption, and interestingly, tomatoes pushed up blood glucose response in some individuals, despite containing relatively low carbohydrates. The researchers suggest that carefully tailoring diets to meet individuals' blood sugar tendencies could be the wave of the future.
More research is required as the interactions among genes, microbiome, diet, environment and lifestyle are infinitely complex. Moreover, the effects of gene variants on risk of a complex disease are often inconsistent. Thus, a more robust evidence-based approach is required to improve the predictive accuracy of personalised nutrition. The future does seem to hold the promise of personalised nutritional recommendations based on genetic data, which will help fine-tune the prevention of nutrition-associated diseases. However, we have yet to progress in this field due to the complex nature of genes in the relationship between diet and health outcome.
Sophie Bruno is a Registered Dietitian living and working in Brussels (Belgium). Read Sophie's foodie blog which will enable you to learn, increase your knowledge & cultivate yourself in the field of nutrition & health directly from Brussels