Increased oxidative and inflammatory stress levels contribute to the development of age-associated chronic disorders (AACD), such as cancer; diabetes; muscular atrophy; and cardiovascular, pulmonary and neurological diseases. Studies have found that diets that include a variety of vegetables, fruits, legumes, and nuts are rich in antioxidant vitamins, phytochemicals, monounsaturated fatty acids, and dietary fibre, and have anti-inflammatory effects against aging-related disorders.
However, chewing and swallowing dysfunction, sensory changes, and medication use among older adults may result in changing dietary preferences and poor appetite. Studies have found an association between AACD and an altered dietary pattern characterized by low levels of vegetable and fruit consumption and dietary diversity, which leads to elevated oxidative stress and imbalanced gut microbial composition.
According to the authors of the current study, no previous study has investigated the effects of plant-based snacks on oxidative status and gut microbiota in healthy and sub-healthy older adults. They hypothesised that the consumption of diverse, plant-based, texture-modified snacks could reduce oxidative stress and alter gut bacterial composition in older adults.
They initiated an open-label single-arm intervention study to investigate the effects of consuming plant-based, antioxidant-rich smoothies and snacks (PBASS) on blood antioxidant ability and gut microbial composition in healthy and sub-healthy older adults. They also explored the relationship between antioxidant ability and gut microbes in this group.
Healthy and sub-healthy older adults (n = 59, 15 men and 44 women, aged 65 and older) were recruited in two senior living facilities in Taiwan. The participants’ body weight, height, and waist and hip circumferences, were recorded during the first interview (at baseline). All participants were then requested to consume PBASS daily along with meals provided by the institution for four months.
During interviews held at baseline and at two and four months, the participants were asked about their consumption of regular meals. Anthropometric measurements and fasting blood and faecal samples were also collected at this time.
The team designed four different types of plant-based smoothies with different flavours and colours: orange, green, dark green, and purple, to increase the diversity of plant sources used in the smoothies.
Each serving contained two kinds of vegetables, two kinds of fruits, and one serving of nuts, containing 21–29 g of carbohydrate, 4–5 g of protein, 7 g of lipid, 2.7–4.7 g of dietary fiber, and varying amounts of minerals, vitamins, and phytochemicals. Each serving provided 10–15% of the DRIs of vitamins A, C, and B1, potassium, calcium, and magnesium in addition to being rich in phytochemicals.
To increase intakes of calcium, polyunsaturated fatty acids, vitamin E, and phytochemicals, sesame seed snacks were also provided. Each serving of sesame seed powder and spread, respectively, provided 57.6 and 63.3 kcal, 2.1 g and 2.5 g of carbohydrate, 1.6 g and 1.3 g of protein, 5.5 g and 5.7 g of lipids, and varying quantities of vitamins and minerals.
All participants were provided with five servings of plant-based smoothies and three servings of sesame seed snacks per week for a 4-month period. Compliance rates relating to PBASS consumption were recorded and calculated.
Fasting blood samples and faecal samples were collected from the participants.
Of the 59 older adults recruited for this study, 30 women and 12 men participated fully in the PBASS intervention and blood sample collection process; however, 1 woman and 1 man refused to provide faecal samples at the four month mark.
Resulting data revealed there were notable increases in endogenous antioxidant thiol groups, such as glutathione (GSH), total sulfhydryl (TSH) and protein-bound sulfhydryl groups (PBSH), and total antioxidant capacity (TAC), in the plasma of participants after two months, and these levels continued to rise significantly after four months.
After adjustments were made for age, gender, and compliance of PBASS consumption, results suggest that PBASS consumption may increase systemic antioxidant ability in a time-dependent manner. The team observed a significant increase in erythrocytic TSH and PBSH levels after four months of PBASS consumption; however, levels of GSH, oxidized glutathione (GSH/GSSG), and superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities decreased significantly during this period.
The authors note inconsistent changes in the plasma and erythrocytes in terms of antioxidant indices may have been associated with the condition of erythrocytes, as reflected in the decreased levels of RBC and hematocrit. Alternatively, the decrease in antioxidant enzyme activities may be associated with the production of fewer free radicals and reactive oxygen species, leading to decreased demand in the enzymatic antioxidant defence system.
The report states these results suggest that PBASS may enhance the non-enzymatic antioxidant defence system and the total antioxidant ability in the plasma.
Limitations of this study include the small sample used and the lack of control group. The authors say double-blind, randomized control trials that are well-powered and well-designed are needed to confirm the effects of plant-based, antioxidant-rich snacks on preventing and alleviating the development of AACD.
The authors conclude: "The results of the present study demonstrated that highly diverse, plant-based, antioxidant-rich snacks may elevate antioxidant ability and alter the composition of gut microbiota in older adults within a 4-month period. "This study provides new insights into the associations of antioxidant ability with specific changes in the gut microbiota in older adults. Our results suggest that texture-modified, plant-based snacks are useful nutrition support to benefit healthy aging via the elevation of antioxidant ability and alteration of gut microbiota."
Zhang, J.-Y., et al
"Plant-Based, Antioxidant-Rich Snacks Elevate Plasma Antioxidant Ability and Alter Gut Bacterial Composition in Older Adults"
https://doi.org/10.3390/nu13113872 (registering DOI)