Fermented dairy was linked to lower mortality, but the pattern shifted at higher intakes

by · News-Medical

A 19-year analysis of US adults reveals a striking dose-response pattern that could help clarify how fermented dairy fits into long-term health.

Study: Fermented dairy consumption and all-cause and cardiovascular mortality in US adults. Image Credit: Pixel-Shot / Shutterstock

Want to read later? Download your clean, ad-free, print-friendly PDF copy by clicking here.

A recent study published in the journal Scientific Reports suggests an association between reported consumption of fermented dairy foods and lower all-cause and cardiovascular mortality among United States (US) adults.

Diet is an important modifiable factor that may influence long-term health and mortality risk. As people age, the burden of chronic diseases also increases. Cardiovascular disease remains a major cause of death worldwide. This has prompted growing interest in dietary factors that may be associated with lower cardiovascular and all-cause mortality.

Fermented dairy foods are of particular interest because fermentation can alter their nutritional and biological properties, but the association between their consumption and mortality risk among population subgroups remains unclear.

About the study

In the present study, researchers analyzed NHANES data from 1999 to 2018 to investigate whether fermented dairy food consumption was associated with all-cause or cardiovascular mortality.

The study comprised 37,366 individuals from 10 NHANES cycles, each conducted over a two-year period. From the survey population, individuals under 20 years of age, pregnant women, and those with incomplete data on follow-up, food intake, demographic variables, chronic disease status, body mass index (BMI), or biochemical parameters were excluded.

The team assessed consumption of fermented dairy foods using 24-hour dietary recalls. The 1999 to 2002 cycles used a single recall, while the 2003 to 2018 cycles used the mean of two recalls collected 3 to 10 days apart.

High-density lipoprotein (HDL), triglycerides (TG), fasting plasma glucose (FPG), and hemoglobin A1c (HbA1c) were measured using standard methods. Using International Classification of Diseases, 10th Revision (ICD-10) codes, the researchers determined disease-specific mortality, with participants followed through 31 December 2019.

Cox proportional hazards models estimated hazard ratios (HRs) quantifying associations between fermented dairy intake and mortality. Kaplan-Meier analysis compared survival between consumers and non-consumers, while restricted cubic spline (RCS) curves revealed non-linear dose-response associations.

The researchers adjusted the models for sociodemographic variables such as age, gender, race, marital status, education, and family economic status, as well as comorbidities, physical activity, smoking behavior, and alcohol intake.

Separate subgroup analyses examined whether the associations differed across participant groups. In sensitivity analyses, they investigated whether the results remained consistent after adjusting for total calorie intake in fermented dairy intake.

Results and discussion

Among participants who reported consuming fermented dairy, the median daily intake was 28 grams. These participants had a lower median age and were more likely to be women, non-Hispanic White, married or living with a partner, and to have higher educational attainment.

The group had slightly higher BMI and total cholesterol (TC), with higher HDL levels. Consumers were more physically active and more likely to report alcohol consumption. They also had lower prevalences of hypertension, diabetes, coronary heart disease, and stroke.

Cancer was more common in this group. They had slightly lower FPG and triglyceride-glucose index (TyG) values, while HbA1c distributions differed even when medians were identical, compared with non-consumers.

Over a median follow-up of 9.4 years, 5,646 deaths occurred, including 1,791 cardiovascular deaths. Observed mortality was lower among consumers, with 12.7% dying from any cause compared with 18.1% of non-consumers, and 3.9% dying from cardiovascular disease compared with 5.9%.

After multivariable adjustment, fermented dairy consumption was associated with an 18% lower hazard of all-cause mortality (HR, 0.82) and a 20% lower hazard of cardiovascular mortality (HR, 0.80) than no consumption.

RCS modeling revealed a J-shaped association between fermented dairy food consumption and mortality risk. Combined with segmented regression analysis, the findings suggest that consuming fermented dairy foods at less than approximately 150 grams per day may be associated with lower all-cause and cardiovascular mortality. Within this range, higher intake remained associated with lower mortality in the segmented analysis.

At intakes of 150 grams per day or more, no statistically significant association was detected. The researchers found no significant differences in this pattern across the analyzed subgroups, and energy-adjusted sensitivity analyses produced comparable results.

Cheese, yogurt, sour cream, and buttermilk are among the fermented dairy foods produced through processes typically driven by lactic acid bacteria. In addition to the nutrients naturally present in dairy, these foods provide protein, amino acids, phosphorus, calcium, and B-complex vitamins, including B2 and B12.

Fermentation can generate bioactive peptides with antioxidant and antihypertensive activity, while short-chain fatty acids (SCFAs) and polyamines may have anti-inflammatory effects.

Prior research cited by the authors has linked probiotics and other fermented dairy components to lower insulin resistance and blood lipid levels, but these mechanisms were not directly tested in the NHANES analysis. The nutrient profile of fermented products may help explain the findings. The study cannot establish causality.

Conclusion

The findings suggest an association between moderate consumption of fermented dairy and lower all-cause and cardiovascular mortality among US adults. The one- or two-day diet recalls may not reflect habitual intake.

The analysis lacked detailed information on dairy fat content and could not adjust for chronic kidney disease. Residual confounding remains possible. The trend below 150 grams per day may also reflect characteristics of the no-intake and very-low-intake groups.

These observations can guide further nutrition research, but they do not show that changing fermented dairy intake would reduce mortality. In future studies, researchers could examine causal relationships and explore the biological pathways that contribute to them. Repeated 24-hour recalls, food frequency questionnaires (FFQs), detailed dairy fat information, and kidney function measures could strengthen confidence in future findings.

Journal reference: