In this 1:1 case-control study with 419 pairs hospital-based CVD cases and T2D controls conducted in South China, we found a higher score between the CHEI or HEI-2015 after diabetes diagnosis, reflecting greater alignment with the latest and authoritative dietary guidelines for the Chinese or the Americans, and had strong favorable associations with lower risk of cardiovascular outcomes among Chinese adults with diabetes.
Several studies and meta-analyses [14–16, 34, 35] have consistently shown that high diet quality, as assessed by HEI, AHEI, DASH, and Med score is inversely associated with the risk of CVD incidence in the general population. In the US Women’s Health study which included 25,994 women (followed-up for 12 years), the consumption of a diet with a high baseline Med score may reduce the risk of cardiovascular events by one-fourth when comparing the upper (Med score 6–9) and lower (Med score ≤ 3) after adjustment for cardiovascular disease risk factors . Similar findings were seen in 1867 middle-aged men from the Caerphilly Prospective Study, in which diets of the highest quality, as assessed by DASH and AHEI-2010 scores, resulted in a significant reduction in the incidence risk of CVD and stroke, but not coronary heart disease, with multivariable adjusted hazard ratios ranging from 0.61 to 0.81 in the highest (vs. lowest) tertiles . Data from the prospective Singapore Chinese Health study showed that the AHEI-2010, which are strongly correlated with the HEI-2010, had an inverse association with the risk of fatal and nonfatal acute myocardial infarction among women and men (p trend, 0.009 and 0.002, respectively) . However, significant protective associations have only been shown between nut consumption  or overall healthy lifestyle  and the risk of CVD among diabetes patients in previous studies. Few studies have examined the risk of CVD regarding national dietary guidelines, particularly among persons with diabetes mellitus. It is unknown how to eat properly to prevent cardiovascular events in diabetic patients who are at high-risk of CVD. The finding of this study is in accordance with observational studies [38, 39] conducted in individuals with diabetes, showing a significant protective effect of intermediate cardiovascular risk factors profile, as indicated by e.g., fasting blood glucose, triglycerides, and systolic blood pressure, in patients who adhered mostly to the HEI-2010 (Daneshzad et al., 2019) or Mediterranean diet , yet an absence of data on CVD incident outcomes in these studies does not allow comparisons with our results. In general, our detections and existing evidence imply that aligning with a healthy dietary pattern after a diabetes diagnosis can momentously contribute to the prevention of cardiovascular complications among patients with T2D.
We also explored the relationship between each food group component scores for participants of CHEI and HEI-2015 and the achievement of treatment targets for participants’ risks. The beneficial effects of high-quality dietary scores may reflect the synergistic effects of diverse foods characterized by a higher intake of vegetables, fruit, whole grains, soybeans and dairy, and a moderate intake of cooking oils, sodium and red meat. Research has shown that whole grains and vegetables are primary sources of dietary fiber conducive to furthering hyperglycemia and improving dyslipidemia owing to the low glycemic index and anticholesterolemic actions . Furthermore, micronutrients including minerals, vitamins, and phytochemicals are rich sources of these foods, all of which include insulin-sensitizing properties, are anti-inflammatory, reduce hypercoagulability, and regulate metabolic and antioxidant pathways to improve macro- and micro-vascular status . The healthy dietary pattern mainly lies in its combined effect among all types of foods and nutrients instead of on any single component. Nonetheless, because our study was an observational study, this association should be interpreted with caution, as future biological mechanical research and possible interventional studies are needed to further illustrate potential mechanisms in the prevention of cardiovascular events among patients with T2D.
In alcohol consumption-stratified analyses, the favorable association between CHEI and cardiovascular events remained significant in non-drinkers but not in drinkers. Taking into consideration the number of participants who drank alcohol, this may be just due to a low statistical power in this subgroup. In addition, the interaction with alcohol consumption was not statistically significant, which does not speak for a different association among drinkers and non-drinkers. Additionally, we further assessed the CHEI score after removing alcohol consumption from the categories, with the results being similar.
To our knowledge, our study assesses T2D patients’ CVD risk associated with adherence to DGC-2016 and/or 2015–2020 DGA for the first time in a case-control design. Moreover, we only included newly diagnosed CVD patients with comparable age and sex to minimize recall bias. Furthermore, we excluded the participants with substantial changes in diet during the prior one year to ensure the representativeness of the habitual diet before diagnosis or interview. Additionally, multiple potential covariates, including explicit risk factors of CVD (i.e. hypertension status, dyslipidemia status, antidiabetic medication use) were included in the analyses for reducing residual confounding. Information bias was also further minimized because the participants were blinded to the hypothesis.
Nevertheless, several limitations of the study should be acknowledged. First, reverse causality could not be fully ruled out in the case-control design because the dietary intake information was assessed after the diagnosis of CVD. To minimize this possibility, we recruited only new cases (diagnosed within 2 weeks) into our study and collected the cases’ diet information using the FFQ from the past twelve months prior to diagnosis. Second, although the FFQs used in our study were validated and implemented during face-to-face interviews by well-trained dietitians, dietary measurement errors are inevitable . Third, the outcomes for the sodium component should be interpreted with caution because discretionary salt being used in cooking was not accurately captured in our FFQs. As with previous epidemiological studies, it is crude and likely to underestimate the ingestion of dietary sodium consumption assessment by using an FFQ. Finally, prior dietary indexes were derived based on current learning, and the CHEI and HEI-2015, originally directed toward general populations, rather than T2D, to prevent chronic disease.