You have certainly at least once wondered why some people never gain weight in spite of the fact they eat foods high in fat and carbohydrates. Well, the answer may be in our genes and their interaction with the environment. Depending on our genes, the foods we consume have complex metabolic signals and are processed in our bodies. Then, it’s so important that our diet be in the same line with our needs if we want to have a good health and well-being.

The human genome sequence and also study of the relationship between genes, diet and disease has led to development of a new discipline named “nutritional genomics.” This new science studies the interaction of our genes with food. Nutritional genomics has been divided into two distinct dimensions: nutrigenomics and nutrigenetics.

Nutrigenetics studies the effect of genetic diversity on the interaction between diet and disease; this concept will be associated with the idea of “personalized nutrition” or “individualized nutrition.”

Nutrigenomics is regarded as a study to understand the effect of nutrients on gene expression; so, it is defined based on the possible changes in metabolic pathways.

Similarly, nutritional genomics is on the basis of 5 fundamental principles:

•             1) Diet can be an important risk factor for various diseases in some individuals under certain circumstances.

•             2) Common chemicals in the diet alter gene expression or genetic structure (whether directly or indirectly).

•             3) The effect of diet on health depends on the individual’s genetic makeup.

•             4) Some genes or their variants, which may play a role in chronic diseases, are regulated through the use of an appropriate diet.

•             5) Dietary interventions based on the knowledge of nutritional status, genotye and the nutritional status itself can be applied to prepare individualized diet plan with the focus on the health optimization and also prevention or reduction in the cases of chronic diseases.  

 

These new nutritional researches are helping in creating more personalized diets; therefore, population health and also health of the individuals who may be exposed to certain diseases related to their genetic conditions, will improve.

Consumption trends indicate a possible experience of great prosperity in this new nutrition concept, because consumers want products which help them in taking care of their own health.

There is a lot of interest in the food sector from different companies that they should not lose the genetic path in nutrition science just because of diversifying their product portfolio. And it’s been predicted that this method will have an exponential growth in the upcoming years. Thus, large companies make various investments in research, so that research aid in providing a good insight into the development of these kinds of personalized foods for each of the genetic characteristics.

Researches are currently focused on further identification of bioactive compounds of the diet; because through increasing the available information, we can provide foods with beneficial genetic effects, which are specifically preventing the occurence(incidence) or the intervention of various diseases.

In short, everything reveals that these new concepts transform our diet as our outlook on nutrition is changing.
 

The role of genes in health

A gene is a part of DNA; this means it’s a molecule that contains instruction for building and maintaining organisms.

Not only do DNA instructions define our personality traits and physical appearance, but also they show how body will react in regard to the presence of pathogens, certain foods, contaminants, and other elements of the environment.

Each gene contains information for the construction of a specific protein; this is actually so important for health, because proteins(such as enzymes) are essential for structural roles and also for many of the biological processes in our bodies. Moreover, it can cause problems in an individual if he doesn’t have a specific gene or  if the instruction(code) for building that certain protein is incorrect.

When we talk about the “inherited health issues,” we are actually referring to DNA’s ability in replication and transmission of genetic information from one generation to the next.

The importance of genetic diversity:

Only 0.1% of our genetic material is different relative to another person; this is the reason why each individual is unique. Just this small percentage of genetic variation has brought about multiplicity of our physical traits(eye and hair color, face color, height, etc.) and character traits; it also affects other aspects including our nutritional needs.

Genetic changes play an important role in our health. There are different variations known as polymorphism that express our different traits . On the other hand, some of  genetic changes cause rare diseases called “mutation.”

Polymorphism and mutations can interact with other genes, our environment and habits(physical activity, smoking, diet, etc.); and all of these contribute to type 2 diabetes, asthma, cancer and heart diseases.

Relationship between genetics and personalized nutrition

Because personalized nutrition is a new realm in relation to the genetics, we realize that there is still much more to learn in the scientific world. Thus, you don’t have to worry about the details, but we can apply some simple tips based on what has already been specified.

Here we will discuss about the properties and food sources of nutritional foods and their importance for genetic health:

Nutrients that prevent DNA damage(mutations); the following are important foods for prevention of the mutations that can lead to major(/common) diseases such as cancer or heart diseases:

-              Carotenoids; e.g. carrot, squash, yellow and red pepper, tomato, and leafy green vegetables.

-              Vitamin E; e.g. avocado, seeds, and nuts.

 

Nutritional foods that facilitate DNA synthesis; they are the foods important for cell growth(hair, skin, nails, etc.) and fetal development(/growth) during pregnancy:

-              Folic acid; e.g. whole grains, leafy green vegetables, legumes, and citrus fruits

-              Vitamin B12; e.g. diary products, egg, seafoods, fish and meat

-              Zinc(Zn); e.g. wheat germ, pumpkin seeds, nuts

-              Magnesium; e.g. cocoa(dark chocolate), banana, avocado

 

Nutritional foods  that repair DNA; they are the nutrients so important to repair DNA mutations in our bodies:

-              Vitamin B3(niacin); e.g. peanuts, sunflower seeds, mushrooms and chicken

-              Folic acid; e.g. leaf vegetables, fortified cereals and fruits

It has been noticed that different types of foods bring beneficial properties for genetic health. Also it has to be mentioned that nutritional foods group consists of not only nutrients but also antioxidants, polyphenols, biologically active molecules, etc. Their consumption also causes kind of a synergistic interaction and creates a complicated context; so taking dietary supplements won’t  bring the same benefits all the time.

Nutrition and genetics in relation to blood pressure:

Blood pressure is under strict genetic control. There is ample evidence for sodium role in the development and maintenance of blood pressure.

Often frequency of high blood pressure is concerned with moderate sodium intake in a population. However, sodium intake will not increase blood pressure in all the individuals. Also, sometimes sodium restriction can not lower blood pressure in some of the ones who are suffering from high blood pressure.

According to studies, blacks have higher blood pressure and higher frequency of blood pressure compared with Europeans.

There has been some findings in regard to the recent observation of differences between black and white population. And these indicate the absence of sodium-lithium transporters in red cells of the blacks. This trait seems to be controlled by a specific gene. This case along with other evidence suggest that hypertension is a heterogeneous issue with different genetic mechanisms.

Limitation of salt intake is supported to reduce the frequency of high blood pressure, but still it may not be equally beneficial for all. Moreover, there has still been inadequate clinical or laboratory criteria to describe the degree of salt sensitivity among  individuals.

Nutrition and genetics in diabetes:

Diabetes usually falls into one of these two categories: non-insulin dependent diabetes mellitus(NIDDM) and insulin dependent diabetes mellitus(IDDM). Studies show the presence of genetic factors in both types, but the exact mechanisms have remained unknown.

There are extreme similarities between  identical twins in regard to NIDDM and this suggests that genes play a prominent  role in this disease.

Nutrition and genetics in obesity:

The growth in obesity not only is a function of calorie intake but also includes genetic factors, which has been presented in human and animal studies.

Obesity has been recognized as a familial feature for several decades. Most of the obese patients have at least one obese parent. Nevertheless, family members or relatives also have a lot in common terms of nutrition and environment; for example, other factors such as economic class, age, and gender were significantly involved based on analyses. Recent studies have also shown that most children of  obese parents are overweight; on the other hand, children of relatively fit(/thin) parents are less likely to be overweight.

In respect of other studies, we have also seen high matching in body fat among identical twins.

There is some evidence from studies of identical twins and also from several other studies of ethnic groups indicating that body fat distribution patterns are inherited through parents. This is especially evident among children; for example, Mexican-American children have a high body fat distribution; and independent of fat intake, this is sometimes because of their daily diet. However, it seems like children of European origin have a more lateral distribution of body fat.

Nutrition and genetics in cancer:

It appears that some certain types of cancer are possible to be inherited. However, we are increasingly discovering that most cancers are attributed to the interaction between genetic(hereditary, or endogenous) and environmental(exogenous) factors.

Causes of cancer are classified into three broad groups named genetic, genetic-environmental, environmental causes.

Genetic group: includes cancers which appear to be mostly caused by genetic factors, with little or no effect from the environment. For instance, people with familial adenomatous polyposis(FAP) are in high risk of colorectal cancer.(FAP is a relatively rare but well-known disease in which hundreds and sometimes thousands of adenomatous polyps are found in the rectosigmoid region or throughout the colon and  even appendix. The disease is transmitted by a gene placed on chromosome 5. Its inheritance pattern is autosomal dominant, and an affected  parent passes on the disease to half of the children and then they will show the disorder.

Genetic-environmental group: A good example of this group is the development of malignant growth in people with xeroderma pigmentosum and that requires exposure to an environmental substance(ultraviolet light).(Xeroderma pigmentosum is a really  rare disease in which the individual becomes sensitive to sunlight, has premature skin aging, and is prone to skin cancers.)

Environmental group: In this group, cancer is mainly caused because of environmental factors, which are generally independent of genetic diversity. This group includes most of malignant neoplasms.(neoplasm means abnormal growth of cells and is also known as tumor.)

There are reasons related to the supposition that dietary changes can at least have an effect in cancers related to a genetic mechanism and also similarly for the cancers independent of genetic factors.

Unlike normal somatic cells, cancer cells can divide sequentially and produce unlimited cell lines. To have this property, these cells must be able to maintain their telomere length; and they can acquire this ability through production of telomerase(/terminal transferase). In fact, one cause of cancer in these cells is their ability for the production of telomerase, which can be because of viruses or other mutagenic agents in somatic cells. On the other hand, researchers consider this issue as an Achilles heel for cancer cells. We can design therapies to target the mechanisms of telomere retention  in these cells so that these immortal cells can be transformed into cells with limited division(and actually mortal)and then destroy them.

High consumption of fruits, vegetables, omega-3 fatty acids, and fiber is associated with longer telomeres. Oppositely, high consumption of saturated fatty acids and processed meat is associated with telomere shortening. High level of antioxidants in diet is also related to longer telomeres. Consumption of nutritional foods containing folate, vitamin B12, nicotinamide, vitamin A, C, D, E, magnesium, zinc, iron, polyphenols and turmeric has again been concerned with telomere size(/length) control.

Nutrition and genetics in lactose absorption:

At birth, all humans produce intestinal lactase(lactase-phlorizin hydrolase) to metabolize lactose(the major sugar in milk) into glucose and galactose. Most people lose their ability to digest lactose after weaning due to a gradual decrease in intestinal lactase activity. Such people often face problems such as malabsorption and lactose intolerance. Indigestible lactose is broken down in the gastrointestinal tract of such people by some specific bacteria and causes bloating, diarrhea, bloated stomach(flatulence), even nausea and vomiting in severe cases. However, some people(especially individuals from European descent) won’t lose this ability and they are considered as lactose persistence. A gene controls this persistence in lactose uptake for the  persistence of lactase activity. Individuals who are missing this gene, cannot digest lactose after weaning. Drinking doesn’t stimulate lactase activity in people who no longer have this capacity(/ability).

Only populations of central and northwestern Europe and parts of Africa with a long history of dairy production, have high levels of persistent lactase activity. Probably this gene had a survival advantage for lactase persistence in dairy cultures and then increased in populations over  subsequent generations; because adults who had the ability to absorb lactose and tolerate milk, were more likely to be fertile or maybe because premature death was much less probable among children of these populations. Also in communities where lactose intolerance is a common issue, milk is not widely consumed.

However, most of lactose intolerant individuals can drink at least 250 ml of milk without much difficulty.

The future of personalized nutrition:

Health professionals currently consider factors such as body mass index(BMI), habits, family health history, and patient’s medical history. But, advices along with genetic knowledge can be even more appropriate and effective. Advances in biotechnology are increasingly providing a tool to help health professionals. One instance of these experiments is the nutrients that we can purchase online; their goal is to reveal information about the genes which can have an effect on your nutritional needs and also your risk of getting diseases.

As we focus on the discovery and comprehension of reactions to food based on a person’s genetics and also on how various external factors can influence genetics, these all are indeed revolutions in the world of nutrition.

This means the end of a misguided advice which states everything is good for everyone. And the emphasis here is on providing a good advice according to a person‘s characteristics.   

Evaluation in human nutrition is incomplete without considering fundamental genetic variation. This variation may be reflected as differences in nutritional processes such as absorption, metabolism, function of receptors, and protein excretion. Differences in the activity of enzymes and other functional proteins contribute to the changes in dietary needs and the interaction of certain nutrients with genetically determined biochemical and metabolic factors. This internal change will be completely different from epigenetic changes in certain circumstances such as growth, pregnancy, and old age.

Genetic change can also shape our likes or dislikes for foods and, consequently, nutrition. For example, the inability to taste the synthetic chemical Phenylthiocarbamide is a genetically influenced trait. This prevents a large portion of the population from tasting this chemical while others detect it as an absolutely bitter taste.

Throughout your life, you must have encountered people who sense everything bitter, e.g. they say that eggplant or broccoli taste bitter and they cannot drink sugar-free or even low-sugar coffee. Or those who drink sugar-free coffee, claim that this coffee is bitter but still has a pleasant taste, while its bitterness is unbearable for you!

It all comes down to a gene that is controlled by the dominant allele (T) or the recessive allele (t). To better understand:

Those whose bitterness gene is in the form of TT can sense bitter taste to a great extent; meaning that they sense bitterness while others do not notice at all. For example dark chocolate 70% is too heavy for them and has an unpleasant taste.

Most people have these genes in the form of Tt; these people easily eat chocolates up to 75% bitterness, but 85% bitterness will bother them.

But those who are in the form of tt do not feel the bitter taste and can even eat dark chocolate 98% or drink sugar-free espresso with no problem!