Baseline characteristic distribution
Data from 5394 participants were analyzed whom 1267 were newly diagnosise hypertensives. The mean follow-up period was 6.2±0.02 years. The baseline characteristics were summarized according to the dichotomous consumption of ABFs (Table 1). The main consumption of ABFs was RPM, with an average of 1.68 servings per day. Participants with higher consumption of all five ABFs were more likely to have a higher educational level, to spend more time sitting and less time doing physical activity, and to consume more fruit. Males, drinkers, and individuals who consumed more sugar-sweetened beverages, also tended to consume more meat and dairy products. Higher consumption of RPM meant more vegetable intake and less whole grains intake. Participants with higher consumption of poultry consumed fewer vegetables, nuts and legumes, as opposed to those who consumed more dairy products. Contrary to individuals with a higher intake of eggs, participants with a higher seafood intake ate less whole grain. Participants, who consumed more RPM, seafood, dairy products, and eggs, consumed more sodium.
TSA
The TSA model was used to predict the associations between changes (serving/day) in specific ABFs components and risk of hypertension (see Table 2). A meaningful substitution effect was found between RPM and eggs. Model A suggested that replacing 1 serving/day of RPM with eggs were associated with a 14.8% lower risk of hypertension (HR = 0.852, 95%CI: 0.781–0.934). As expected, the opposite association was seen when eggs was dropped out of the model (Model E). The line where risk of hypertension varies with the amount of substitution is shown in Fig. 2(A). The slopes of lines are different between different ABFs substitute patterns. With the maximum slope of 0.3%, substituting RPM with eggs was associated with the greatest benefit in reducing the risk of hypertension.
However, there was a strong correlation between individual ABFs and total ABFs, especially between RPM and total ABFs consumption (r = 0.64), which implies the multi-collinearity (Table 3).
CoTSA
The regression results with ilr coordinates are presented by modeling a multivariable Cox proportional hazards regression (Table 4). Coordinates with RPM in the numerator were a significant predictor of hypertension. The first ilr-coordinate that contained all the information, regarding RPM relative to the remaining ABFs, was a significant predictor of hypertension (HR = 1.015, 95%CI: 1.003–1.027).
The means of the compositional values were 50%, 23%, 17%, 7%, and 3% for RPM, eggs, seafood, poultry, and dairy products, respectively. This implied that the average consumption proportion of different ABFs varied, and the ranges of substitution between different ABFs were dissimilar (Fig. 2(B)). Since the mean consumption proportion of RPM was 50%, the substitution curve between RPM and other ABFs was plotted in a symmetrical range, while the substitution curve between RPM and another ABF was drawn in an asymmetrical range. Based on the proportional means, increasing the intake of RPM by 50%, while decreasing other ABFs, equivalently was associated with the largest expected hypertension risk (HR: 1.063, 95%CI: 1.050–1.076); whereas the inverse replacement was negatively associated with a meaningfully expected hypertension risk (HR: 0.909, 95%CI: 0.898–0.920). The estimated risk of hypertension by replacing 50% of RPM intake, equivalently, with poultry, seafood, dairy products, and eggs were 0.942 (95%CI: 0.912–0.972), 0.942 (95%CI: 0.900-0.988), 0.919 (95%CI: 0.879–0.962) and 0.944 (95%CI: 0.924–0.964), respectively, yet significant substitution effects were not found when replacing all proportions of poultry (HR:1.006, 95%CI: 0.975–1.039), seafood (HR:1.010,95%CI:0.965–1.056), dairy products (HR:1.045,95%CI: 0.999–1.093), and eggs (HR:1.012,95%CI:0.991, 1.034) with RPM. Furthermore, in the case of a fixed amount of substitutes, the maximum risk changes took place, in the substitution between RPM and dairy products.
To investigate the effects of baseline difference in ABFs consumption proportions among individuals on predicting risk of hypertension, we took two participants (Participant A and Participant B) with different consumption proportions of ABFs for example and their substitution effects were further analyzed. The proportions of RPM, poultry, dairy products, eggs, and seafood for Participant A and Participant B were 10%, 13%, 45%, 22%, 10%, and 70%, 9%, 7%, 2%, 12%, respectively. The substitution effects that occurred between RPM and dairy products in participant A and participant B were estimated by CoTSA and TSA, respectively, in Fig. 3. Participant A and participant B needed to make various changes to achieve meaningful substitution effects which implied that when RPM is replaced by dairy products, participant A and participant B need to respectively decrease to 10% and 60% to significantly reduce the risk of hypertension and need to conversely increase to 40% and 6% to significantly increase the risk of hypertension.
In addition, to achieve equally beneficial substitution effects, participant A and participant B needed to replace RPM with different consumption proportions of dairy products. For example, when the risk of hypertension decreased by 5% (HR decreased to 0.95), participant A had to replace all RPM (10%) with dairy products, while the amount of substitution was 64% for participant B. However, the risks estimated by TSA were consistent regardless of the differences in baseline ABFs consumption.
We further estimated the substitution effects between RPM and poultry, seafood, eggs, and all other ABFs in participant A and participant B respectively (Fig. 4). Whether based on the average or individual (Participant A and participant B) consumption of ABFs, substituting dairy products for RPM was associated with a greatest benefit in reducing the risk of hypertension. This implies that, to achieve the same HR, the lowest amount of substitution was required between RPM and dairy products. For instance, the risk of hypertension for participant B could be reduced by 5% (HR = 0.95) most effectively by replacing approximately 62% of RPM with dairy products, compared to the replacement of about 65% RPM by all other ABFs, and 68% by eggs, poultry, and seafood (Fig. 4), while for the average consumption of ABFs the amounts of replacement were 43%, 47%,and 48% respectively (Fig. 2(B)).