What is a DNA-based diet?
Have you ever felt frustrated by the notion that your friend across the table can eat whatever he/she wants without the obvious consequences, whereas you visit the gym daily and count your calories and have tried every fad diet on the market and still cannot reach your weight goal? I am certain you have, and you are not alone!
Well, according to accumulated scientific clues…”one size” type diets may not fit all and we may be looking at a potential different future for the way we nourish ourselves, the way we exercise, and the way we take our medications…based on our genetic makeup.
Identical twins aside, there are no two humans that are exactly alike. Each one of us is a unique creation (for better or for worse), and we express various visible variations in physical and facial features as well as our ethnic, gender, and age differences. We know that not all individuals react similarly to the same medications nor do people react similarly to various dietary patterns…and so it stands to reason that we may also differ in the way our body handles different foods…right?
Indeed, Dietary Reference Intakes, which are the recommended dietary intakes for individuals in the US are to some extent personalized recommendations in that they are based on gender, age, and whether one is pregnant or not. Daily caloric intake recommendations are further personalized in that they are based on additional characteristics such as one’s height, weight, and level of physical activity. Other nutrient needs such as protein are also based on additional characteristics such as life events and health status (See your dietitian…). However, do the genetic variations among us suggest that each one of us requires personalized customized nutrition prescriptions to reach our health and weight goals?
Also see: Can your DNA make you good at sports?
First let’s clarify some terminology
Nutrigenomics is an emerging scientific field that examines the effect of specific foods on gene expression (activation or de-activation of genes), which holds an important promise in disease prevention.
Epigenetics (epi=outside of genetics in Greek) is the study of chemical reactions and factors that influence expression of genes. In other words, even a pair of identical twins that have the same DNA may differ from each other in personality, risk of disease and other markers related to the expression or lack thereof of their genes.
Nutrigenetics is another emerging scientific field that examines the effect of genetic variation on utilization (absorption and digestion) of nutrients or in other words: our metabolism.
Warning: this part may be a bit too scientific…. feel free to skip to the final message…
The following are a few examples of scientific findings that suggest linkage between genetic makeup and body weight/diet:
– The Human Obesity Gene Map 2005 was an extensive scientific review of studies that examined the genetic connection to our body weight. The review identified approximately 20 genes that were associated with obesity.
What are some possible mechanisms for this association?
– Genetic control over inhibitory control of eating (stop when you have had enough to eat): Inefficient inhibitory control of eating is known as a risk factor for unhealthy eating and obesity. The main area in the brain responsible for this control is the prefrontal cortex. Heni et al. (2014) found association between variations of the FTO gene (considered to be the obesity risk gene) and brain activity in the prefrontal cortex, suggesting that individuals that carry a certain variation of the FTO gene tend to overeat and are at a higher risk for obesity. 2
– Genetic effect on food preference/food choices: We know that all diets work…the actual challenge is staying on and making the dietary changes a lifestyle choice. We should be just fine if we were asked to stay on a diet that involved foods we love… right?
– A review of studies conducted by Garcia-Bailo et al. (2009) suggests that genetic variation in taste detection plays a role in determining our individual food preferences that in turn affects our dietary behaviours and subsequently our body weight 3.
– Some suggest the “fat taste” to be the sixth taste (in addition to the five sweet, sour, bitter, salty, and umami tastes). Stewart et al. (2010) 4 found that certain people are able to detect small amounts of fat in food (hypersensitivity to fat) compared to others. The study showed an association between oral fat hypersensitivity and lower caloric and fat consumption as well as a lower BMI (Body Mass Index, an indicator of body weight).
– Genetic effect on metabolic pathways:
– Arkadianos et al. (2007) 5 showed that when people were placed on a diet based on their individual genetic makeup they were more likely to follow the diet and to experience a more sustainable weight loss. The researchers based their dietary recommendations on 24 variants of 19 genes involved in metabolism. For example: individuals that carried a certain variation of the PPARG gene that is thought to be associated with insulin sensitivity and blood glucose control were more successful on a low glycemic diet with extra exercise.
– A recent famous study that was conducted at Stanford University by Dr. Christopher Gardner and Dr. Mindy Dopler Nelson 6 is making headlines with further promising support to the notion that people tend to lose more weight if they follow a genetically appropriate diet. This study screened individuals for three specific genes previously identified as predictors of weight loss: ABP2, ADRB2, and PPAR-gamma. The data analyzed was collected from a previous study (The “A TO Z” study that compared the effect of low fat diets vs. low carbohydrate diets on weight loss). Results indicated that over a period of 12 months participants within each diet group (low fat or low carbohydrate) that were assigned a genetically-appropriate diet lost 5.3% body weight compared to only 2.3% weight loss experienced by individuals on diets that were not on a genetically-appropriate diet.
The study has since been expanded to a broader study that is estimated to be completed in Dec 2016.
What DNA-based diet plans are available on the market?
This is a market in its infancy. Despite the fact that evidence is still preliminary, many companies are now offering various kits for genetic screening and are promising DNA-based personalized dietary advice.
While some may offer reliable genetic screening, validity of many of those companies may be questionable: A 2006 investigation of several Direct-To-Consumer such companies was conducted by the Government Accounting Office in the US using fictitious customers. The investigation revealed that identical DNA samples received contradictory advice. 9 Several of these companies even encouraged the fictitious customers to purchase dietary supplements from them stating (without scientific basis) that those supplements could “repair damaged DNA or cure diseases”.
A “Take Home” message
Identifying diet-gene interactions has a great potential and stands to benefit people that seek personalized dietary guidance. So…should you go and get your DNA screened for your best dietary bet? … Not so fast…. Additional aspects should be investigated, such as examining the role of gene interactions and environmental impact on gene expression. In addition, consulting experts is a must as practice of Nutrigentics requires extensive knowledge and understanding of nutrition, biochemistry, metabolism, and genetics.
Although Nutrigenetics holds great promise, it is still a science in its infancy and much more research is warranted before personalized nutrition can be considered a beneficial approach, and consumers are advised to remain cautious.
Final message: Before attempting any diet consult with your doctor and make sure you understand the implications on your health and possible interactions with your medications and/or supplements. It is important to consult with a dietitian for nutrition information and for expert dietary advice: what foods are high in carbohydrates? Which carbohydrate foods are healthful and better for promoting weight loss? How much fat do we need in our diet? How much protein? Which fats are better for us? Do we need supplementation or can we get all we need from our food? Those are all questions worth addressing before choosing your dietary path.