Quality of plant-based diets and risk of fragilty

Numerous studies have shown that high-quality diets rich in fruit and vegetables, such as the Mediterranean diet, the Dietary Approach to Stop Hypertension (DASH) or a diet represented by the alternate healthy eating index, prevents the risk of frailty in older adults (Leon-Munoz, 2015 ; Satija, 2015).

Plant-based diets have recently gained attention due to their health effects in preventing non communicable diseases, particularly cardiovascular diseases (Satija, 2015). This beneficial effect is mainly due to specific food groups found in this type of diets such as whole grains, fruits, vegetables and plant‐based proteins from legumes, nuts and tofu (Satija, 2015 ; Hemler, 2019).

However, not all plant‐based diets are necessarily healthy, as they may contain plant-based foods with low nutritional quality and negatively associated with chronic diseases, namely refined carbohydrates, added sugars or ultra‐processed foods (Satija, 2015 ; Dehghan, 2017).

In addition, emerging studies and position papers alert on the potential nutrient deficiencies that could be caused by adopting a vegetarian diet such as vitamin B12 and other vitamins and micronutrients. This concern is especially important in older adults, because nutrition deficiencies have been associated with higher risk of frailty (Cruz-Jentoft AJ, 2020 ; Rodríguez-Mañas, 2021). This finding was also supported by the EPIC-Oxford cohort where vegan and vegetarians had higher risk of fractures than meat eaters (Tong, 2020).

Yet, no recent studies have examined the association between the quality of plant-based diets and risk of frailty in women aged ≥60 years. The aim of this study is therefore to evaluate the association between the quality of plant-based diet and the risk of frailty.

Participants consuming healthy plant-based foods have an overall a healthy lifestyle

In order to reflect the quality of plant‐based diets, two separate plant-based diet indices have been developed:

• a healthful plant-based diet (hPDI) indice, characterized by healthy plant foods;
• an unhealthful plant-based diet (uPDI) indice, characterized by less healthy plant foods (see table 1)

Table 1: Characterisation of healthful and unhealthful plant-based diet indices

Compared with participants with the lowest score in the hPDI, those with a higher score were leaner, more active, less likely to smoke, had higher intake of healthy plant foods and lower intake of less healthy plant foods, and had a smaller number of frailty criteria at baseline.

Conversely, those with higher uPDI were also leaner but less active, more likely to smoke, and had higher intake of less healthy plant foods and lower of healthy plant foods and had a greater number of frailty criteria at baseline.

A higher adherence to a healthy plant-based diet was associated with lower risk of frailty

Following a healthful plant-based diet was inversely associated with the risk of frailty, with relative 19% lower risk of frailty for each 10-unit increment in the hPDI score. On the contrary, a positive association was found between adopting an unhealthy plant-based diet and the risk of frailty. Further adjustment for physical activity at baseline attenuated the association, but it was still significant. In sensitivity analyses, the associations remained similar among women without frailty criteria at baseline, and after excluding those with cancer, CVD and diabetes at baseline. Likewise, the association remained unchanged with several modifications of the plant-based diet (excluding fruit juices and scoring fish and dairy positively in the healthful plant-based diet).

These findings are in line with those already reported in the Nurses’ Health Study (NHS) where the adherence to a Mediterranean diet, DASH diet, and the alternate Healthy Eating Index-2010 (AHEI-2010) was associated with 13%, 7% and 10% lower risk of frailty, respectively (Struijk, 2020a), whereas higher consumption of sugar-sweetened beverages was associated with higher frailty risk (Struijk, 2020b).

Not all diets rich in plant-based foods are necessarily healthful

The study supports the statement that plant-based diets are not all healthful as findings conclude that a plant-based diet rich in fruits, vegetables, whole grains, nuts and legumes was associated with lower risk of frailty, while the one characterized by higher amounts of juices, refined grains or sugar-sweetened beverages was linked to higher risk. The beneficial effect of hPDI on fraility could be explained by the presence of specific micronutrients such as antioxidants, unsaturated fatty acids, fibre, vitamins and minerals (Satija, 2015 ; Dehghan, 2017). In contrast, products found in uPDI (refined carbohydrates, sugar-sweetened beverages and processed meats) have pro-inflammatory effects (Struijk, 2020b).

Based on: Sotos-Prieto M, et al. Association between the quality of plant-based diets and risk of frailty. J Cachexia Sarcopenia Muscle. 2022;13(6):2854-2862.