How does genetics affect the way we taste salt and how our blood pressure responds to it? Implications for personalised dietary recommendations

 
Salt sensitivity of blood pressure is defined as an increase in blood pressure after consuming large amounts of salt. While in salt-sensitive people we observe a salt-induced increase in blood pressure, in salt-resistant individuals such an increase is not observed. Salt-sensitive individuals may be at an increased risk of high blood pressure and cardiovascular disease later in life. Salt sensitivity is determined by genetics. More specifically, genetic variations called single nucleotide polymorphisms (SNPs) in genes coding for proteins that transport salt across our body. If individuals are informed of genetic predisposition to salt sensitivity while they are still young, they might reduce their salt intake and avoid developing high blood pressure or cardiovascular disease. Since research is limited in the UK, we aimed to explore if a genetic variation in the gene called SLC4A5 affects blood pressure response to a high-salt diet in healthy young adults.

After consuming a low-salt diet consisting of three grams of salt per day for a week and then a high-salt diet consisting of 18 grams of salt per day, we observed that approximately 30% of our study population were salt-sensitive. We also observed that individuals who carried the AA version of the SLC4A5 gene had significantly higher blood pressure after consuming a high-salt diet compared to those that carried the AG or GG version of the gene. If individuals with the AA version are at higher risk of developing blood pressure later in life, can they be provided with personalised advice to reduce their salt intake to prevent disease development? If we are to advise them to reduce their salt intake, what could be the factors that would drive them to eat large amounts of salt?

Considering that taste of food and food liking are the main determinant of our food intake, to answer the second question, we aimed to explore if genetics also determine our preference for salty taste and then in turn our salt intake. We explored this in a similar cohort of young adults. After tasting five tomato soups with salt content ranging from low to high, we observed that individuals that had the CC version of the TRPV1 gene, that can be found in taste cells in our tongue, prefer tomato soup with higher salt content compared to individuals that had the TT or CT version of this gene. Furthermore, preference for soup with higher salt content was associated with higher actual salt intake. We concluded that genetics may be a driver of salt intake and should be considered when providing personalised dietary recommendations to reduce salt intake.

Finally, we aimed to answer this question: If individuals are informed of high genetic risk for salt sensitivity and recommended to follow a diet lower in salt, would they reduce their salt intake? For this purpose, we recruited another cohort of young adults, genotyped them for the SLC4A5 genetic variation and measured their habitual dietary salt intake. We informed individuals that had the A version of the gene that they were at higher risk of being salt-sensitive and to keep their salt intake at no more than 4 grams per day. Those that had a different version (C version) were informed they are at lower risk of being salt-sensitive and should keep their salt intake within the recommendations of no more than 6 grams of salt per day. After a month, we measured their dietary salt intake again to compare to the intake before they were aware of genetic risk. No change in salt intake was observed, suggesting that informing young adults of high genetic risk of high blood pressure does not motivate them to change this dietary behaviour.

Taken together, our results suggest that genetics determine blood pressure response to salt and preference for salty taste. In order to provide effective personalised dietary recommendations, we should consider how to best convey this information to target consumers and, in case of reducing salt intake in young adults, consider their preference for the taste of salt.

Dr Leta Pilic:

Dr Leta Pilic is a registered nutritionist, researcher and lecturer in Nutrition and Genetics at St Mary’s University in London. Her main research interests are gene-diet interactions in the context of chronic disease prevention and the effects of genetics on food choice and dietary intake.

Nutrition and Genetics research group:

The Nutrition and Genetics research group at St Mary’s University Twickenham was established by Dr Yiannis Mavrommatis in 2014. With Dr Mavrommatis as the group lead, there are currently three PhD students (Ammi King, Viviane Da Silva Anastacio and Angeliki Kapellou) and two independent researchers (Dr Leta Pilic and Dr Catherine Graham) conducting research in nutrition and genetics. This is primarily in the context of prevention of chronic disease such as obesity, cardiovascular disease and diabetes. In addition, considering the sports science focus of the university, the group is exploring interactions between genetics and diet in the context of sports performance.