Holding Back on Adding Salt to Food Linked to Reduced Cardiovascular Risk

Lu Qi, MD, PhD

Encouraging patients to be more cognizant of the amount of salt they are adding to their food could have a dramatic effect on risk of cardiovascular disease, according to a new analysis of the UK Biobank cohort.

An analysis of data from more than 175,000 adults with food frequency questionnaire response information and no history of cardiovascular disease prior to enrollment, results suggest those reporting usually, sometimes, and never/rarely adding salt to their food had 19%, 21%, and 23% reductions, respectively, in risk of incident cardiovascular disease events compared to their counterparts who reported always adding salt to their food.

“Overall, we found that people who don’t shake on a little additional salt to their foods very often had a much lower risk of heart disease events, regardless of lifestyle factors and pre-existing disease,” said Lu Qi, MD, PhD, HCA Regents Distinguished Chair and professor at the School of Public Health and Tropical Medicine at Tulane University, in a statement from the American College of Cardiology. “We also found that when patients combine a DASH diet with a low frequency of adding salt, they had the lowest heart disease risk. This is meaningful as reducing additional salt to food, not removing salt entirely, is an incredibly modifiable risk factor that we can hopefully encourage our patients to make without much sacrifice.”

In the wake of the Salt Substitute and Stroke Study outlining the effects of reducing overall sodium intake on cardiovascular event risk, the current study was conducted by Qi, along with a team colleagues from Tulane University, with the intent of assessing whether the frequency of adding salt to foods is associated with cardiovascular disease risk in prospective cohorts, which investigators noted would be the first time this association was examined in this manner. Using the UK Biobank cohort, which is a large population-based, prospective study including more than 500,000 participants aged 37-73 years recruited from 2006-2010, investigators obtained data related to a cohort of 210,999 participants who completed at least 1 web-based 24-hour dietary assessment from 2009-2012.

From this cohort, investigators excluded an additional 34,429 individuals for having incomplete data on frequency of adding salt to foods, having implausible total energy intake, having a history of cardiovascular disease before the last diet assessment, and indicating their diet for that day was not typical. As a result, the final analytical cohort included 176,570 individuals with a median follow-up of 11.8 years. During this time, 9,963 total cardiovascular disease events, 6,993 ischemic heart disease cases, 2,007 stroke cases, and 2,269 heart failure cases were documented among the study cohort.

As part of the UK Biobank study, participants took part in baseline questionnaires assessing the frequency of adding salt to foods, not including adding salt in the process of cooking, with 5 potential answers: never/rarely, sometimes, usually, always, or prefer not to answer. For the purpose of analysis, investigators used a modified DASH diet score to evaluate the dietary assessments completed from 2009-2012, with the scoring system based on quintiles, with the lowest intake quintile receiving 1 point and the top quintile receiving 5 points for healthy components.

When assessing differences in risk factors and characteristics among individuals reporting lower or greater frequency of adding salt to foods, investigators found those with a lower frequency were more likely to be women, white, have a lower body mass index, have moderate alcohol consumption, and report more physical activity. These individuals were also more likely to adhere to a DASH-style diet.

In analyses adjusted for covariates and the modified DASH diet score, lower frequency of adding salt to foods was associated with a significantly lower risk of total cardiovascular disease events. For incident cardiovascular disease events, those reporting the usually, sometimes, and never/rarely adding salt to food experienced relative risk reductions of 19% (aHR, 0.81 [95% CI, 0.73-0.90]), 21% (aHR, 0.79 [95% CI, 0.71-0.87]), and 23% (aHR, 0.77 [95% CI, 0.70-0.84]), respectively, for cardiovascular disease compared to their counterparts reporting always adding salt to food (P <.001).

Further analysis examining different subtypes of cardiovascular disease demonstrated the strongest association was observed with incident heart failure (P <.001), followed by incident ischemic heart disease (P <.001), but no association was observed for risk of stroke. Investigators noted the lowest cardiovascular disease risk was observed among individuals who combined a DASH-style diet with the lowest frequency of adding salt to food.

Investigators cautioned clinicians to consider the limitations of their study before overinterpretation of results and suggested randomized trials were needed to verify results. Specific limitations noted by investigators included reliance on self-reported data and the observational nature of the study creating the possibility of residual or unmeasured confounding.

This study, “Adding Salt to Foods and Risk of Cardiovascular Disease,” was published in the Journal of the American College of Cardiology.