A new study led by researchers from the University of Illinois, Urbana-USA along with scientists from the University of Florida-USA and the University of Roehampton-UK have found that daily consumption of avocados by females helps them redistribute abdominal body fat and also helps them maintain insulin sensitivity and proper insulin health.
Though the consumption of avocados have been cross-sectionally linked to lower abdominal obesity, detailed mechanisms and understanding of the effects of avocado consumption on abdominal adiposity and glycemic outcomes remains limited.
The study team planned to analyze the effects of avocado consumption on abdominal adiposity, insulin resistance, oral-glucose-tolerance test (OGTT), and estimated β-cell function were evaluated.
For the study, a total of 105 adults aged 25–45 y (61% female) with BMI ≥25 kg/m2 were randomly assigned to an intervention (N = 53) that received a daily meal with 1 fresh Hass avocado or a control (N = 52) that received an isocaloric meal with similar ingredients without avocado for 12 wk. DXA was used to assess the primary outcomes of abdominal adiposity [visceral adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAAT), and the ratio of VAT to SAAT (VS Ratio)].
Fasted glucose and insulin were used to assess the primary outcomes of insulin resistance (HOMA-IR), and insulin sensitivity (Matsuda index) and β-cell function (Insulinogenic index) were estimated using an OGTT. Changes between groups were compared using an ANCOVA. Secondary analyses were conducted based on sex.
The study findings showed that the control group exhibited a greater reduction in SAAT [–54.5 ± 155.8 g (control) compared with 17.4 ± 155.1 g (treatment), P = 0.017] and increase in VS Ratio [0.007 ± 0.047 (control) compared with –0.011 ± 0.044 (treatment), P = 0.024].
However among females, the treatment group exhibited a greater reduction in VAT [1.6 ± 89.8 g (control) compared with –32.9 ± 81.6 g (treatment), P = 0.021] and VS Ratio [0.01 ± 0.05 (control) compared with –0.01 ± 0.03 (treatment), P = 0.001].
However among males, there was no significant difference between groups in changes in abdominal adiposity or glycemic outcomes.
The study findings showed that daily consumption of 1 fresh Hass avocado changed abdominal adiposity distribution among females but did not facilitate improvements in peripheral insulin sensitivity or β-cell function among adults with overweight and obesity.
The study findings were published in the peer reviewed Journal of Nutrition.
The study findings shows that an avocado a day could help redistribute belly fat in women toward a healthier profile.
A total of one hundred and five adults with overweight and obesity participated in a randomized controlled trial that provided one meal a day for 12 weeks.
The study found that women who consumed avocado as part of their daily meal had a reduction in deeper visceral abdominal fat.
The Diets And Nutrition study was led by Dr Naiman Khan, a Professor of Kinesiology and Community Health at the University of Illinois, Urbana.
Dr Khan told Thailand Medical News, “The goal wasn’t weight loss; we were interested in understanding what eating an avocado does to the way individuals store their body fat. The location of fat in the body plays an important role in health.”
He further added, “In the abdomen, there are two kinds of fat: fat that accumulates right underneath the skin, called subcutaneous fat, and fat that accumulates deeper in the abdomen, known as visceral fat, that surrounds the internal organs. Individuals with a higher proportion of that deeper visceral fat tend to be at a higher risk of developing diabetes. So we were interested in determining whether the ratio of subcutaneous to visceral fat changed with avocado consumption.”
The study participants were divided into two groups.
The first group received meals that incorporated a fresh avocado, while the second group received a meal that had nearly identical ingredients and similar calories but did not contain avocado.
The study team measured participants’ abdominal fat and their glucose tolerance, a measure of metabolism and a marker of diabetes at the beginning and end of the 12 weeks.
Interestingly, it was found that female participants who consumed an avocado a day as part of their meal had a reduction in visceral abdominal fat ie the hard-to-target fat associated with higher risk, and experienced a reduction in the ratio of visceral fat to subcutaneous fat, indicating a redistribution of fat away from the organs.
The study however showed that fat distribution in males did not change, and neither males nor females had improvements in glucose tolerance.
Dr Khan added, “While daily consumption of avocados did not change glucose tolerance, what we learned is that a dietary pattern that includes an avocado every day impacted the way individuals store body fat in a beneficial manner for their health, but the benefits were primarily in females.
It’s important to demonstrate that dietary interventions can modulate fat distribution. Learning that the benefits were only evident in females tells us a little bit about the potential for sex playing a role in dietary intervention responses.”
The study team said they hope to conduct a follow-up study that would provide participants with all their daily meals and look at additional markers of gut health and physical health to get a more complete picture of the metabolic effects of avocado consumption and determine whether the difference remains between the two sexes.
Study coauthor Dr Richard Mackenzie, a professor of human metabolism at the University of Roehampton in London commented, “Our research not only sheds a valuable light on benefits of daily avocado consumption on the different types of fat distribution across genders, it provides us with a foundation to conduct further work to understand the full impact avocados have on body fat and health.
By taking our research further, we will be able to gain a clearer picture into which types of individuals would benefit most from incorporating avocados into their diets and deliver valuable data for health care advisers to provide patients with guidance on how to reduce fat storage and the potential dangers of diabetes.”
A group of oxygenated plant pigments known as xanthophylls have been demonstrated to be pertinent to cognitive health across the lifespan (Erdman et al., 2015; Mohn and Johnson, 2017). Specifically, previous work has focused on lutein, a non-polar, lipophilic carotenoid, that is most commonly found in green leafy vegetables, fruits, such as avocados, and eggs (Abdel-Aal et al., 2013).
Zeaxanthin, lutein’s structural isomer, is derived from similar food items in significantly smaller quantities, and thus lutein and zeaxanthin quantification from foods is generally aggregated. Lutein and zeaxanthin cross the blood-brain barrier to preferentially accumulate within the brain and the macula of the eye.
Lutein is the predominant carotenoid in the human brain, having been shown to comprise 66–77% of total brain carotenoid concentrations (Vishwanathan et al., 2013). Lutein’s specific mechanism of action within the brain is still undetermined, yet theories point towards lutein’s role as an anti-oxidant and anti-inflammatory agent, as well as a contributor to preservation of brain plasticity and efficient gap-juncture connectivity (Khachik et al., 1997).
While the exact mechanisms by which these xanthophylls impart cognitive benefits is yet to be understood, it is known that retinal accumulation of these xanthophylls plays a role in blue light filtration, as well as acting as antioxidant and anti-inflammatory agents involved in protecting retinal tissue (Stringham et al., 2019).
Accumulation of lutein, zeaxanthin, and the intermediate meso-zeaxanthin within the macula is referred to as macular pigmentation, and macular pigmentation has been reported to be highly correlated with xanthophyll concentrations found in deceased human brain samples (Vishwanathan et al., 2016).
Heterochromatic flicker photometry can be used to non-invasively estimate retinal xanthophyll accumulation, referred to as Macular Pigment Optical Density (MPOD), thereby serving as a biomarker for neural xanthophylls (Vishwanathan et al., 2013).
Improvements in MPOD, following avocado consumption, have been associated with improvements in cognitive function (Scott et al., 2017). Approximately 90% of avocado carotenoids are the xanthophylls lutein, zeaxanthin (quantitatively combined), and cryptoxanthin.
One half of a medium avocado (60 g of edible portion) has been reported by the United States Department of Agriculture to contain from 185 μg of the combined lutein and zeaxanthin up to 800–1110 μg, depending on the time of harvest (Dreher and Davenport, 2013). According to the Institute of Medicine, average daily lutein and zeaxanthin consumption for adults ages 19 to 30 was 2032 μg/day (Micronutrients., I. of M. (US) P. on, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc, 2001).
Thus, the addition of one avocado daily could greatly enhance current lutein and zeaxanthin intake among the general population. The avocado provides an ideal food matrix for lutein and zeaxanthin bioavailability, as carotenoids and xanthophylls are more bioavailable when consumed in the presence of fat, and when consumed in food sources rather than obtained through supplementation (Moran et al., 2018).
It has been hypothesized that carotenoids remain within the enterocyte of the small intestine until long-chain fatty acids are available to package and transport the carotenoids through the lymphatic system. Avocados are thus a prime food ingredient for facilitating chylomicron formation and lutein transportation throughout the body.
Due to the high presence of mono- and poly- unsaturated fatty acids (MUFAs, PUFAs; 6.6 g and 1.24 g per 60 g edible fruit, respectively) research has shown that carotenoid absorption from green leafy vegetables and salsa is enhanced with the addition of avocado (Unlu et al., 2004). Therefore, if increased consumption of lutein and zeaxanthin may benefit cognitive health, the avocado is an effective method of dietary delivery.
While cognitive health is of global concern, individuals with overweight and obesity are at a greater risk for cognitive impairment (Yang et al., 2018). Defined as a Body Mass Index (BMI) ≥ 25.0 kg/m2, approximately 70% of Americans suffer from overweight or obesity. Numerous studies have linked mid-life obesity to later cognitive decline in the areas of intellectual functioning, psychomotor performance and speed, visual construction, concept formation, set shifting, and decision making, independent of obesity related physical comorbidities (Prickett et al., 2015).
Previous work has also indicated that adults with overweight and/or obesity exhibit poorer performance during attentional and inhibitory control tasks (Yang et al., 2018). Exact mechanisms of the influence of overweight and obesity on cognitive health have yet to be fully elucidated, but several theories have been proposed, including but not limited to, increased systemic and neural inflammation, alterations in communication between reward and control centers of the brain, and alterations in metabolic activity within brain cortices (Volkow et al., 2009; Lowe et al., 2019; Spyridaki et al., 2016).
Previously, lutein and zeaxanthin intake has been cross-sectionally associated with beneficial cognitive patterns among individuals with overweight and obesity (Edwards et al., 2019a). However, to our knowledge, intervention trials have not been undertaken to determine causality of these relationships among individuals with elevated weight status.
As elevated weight status has been associated with decrements in cognitive performance among populations with and without obesity-related comorbidities (Smith et al., 2011; Saedi et al., 2016), this population may benefit from increased lutein intake, facilitated by avocado consumption.
In addition to examination of the impact of obesity on behavioral and self-report measures of cognitive health, it is important to examine the underlying neural mechanisms associated with cognition. Assessment of executive function, or cognitive control, in individuals with overweight and obesity is important, as this population is at increased risk for cognitive deficits (Yang et al., 2018).
Cognitive control processes allow for the formation of intentional and goal-directed behavior. Cognitive control can be indexed through behavioral measures (i.e. accuracy and reaction time [RT]) or neuroelectric measurement of event-related potentials (ERPs). ERPs refer to a subset of electroencephalographic activity that occurs in response to, or in preparation for, a stimulus or action (Luck, 2012).
Evaluating ERPs in conjunction with behavioral measures allows for assessment of both the behavior induced in the cognitive task, as well as the potential neurocognitive underpinnings of said behavior. While ERPs have been related to obesity, there has also been research showing a potential role for amelioration of obesity-related cognitive deficits with beneficial dietary changes (Smith et al., 2011; Kanoski and Davidson, 2011). Thus, individuals with overweight and obesity may disproportionately benefit from the addition of food items rich in lutein to their diet.
The primary aim of the present study was to determine the impact of 12-week daily consumption of fresh Hass avocado on behavioral and neurolectric indices of cognitive control among persons with overweight and obesity. Additionally, we conducted secondary analyses to explore whether the cognitive benefits derived from daily avocado consumption were dependent on changes in circulating (i.e., serum) and retinal (i.e. MPOD) lutein concentrations.
Our central hypothesis was that, relative to the control group, participants in the avocado treatment group would exhibit greater gains in behavioral performance and neurolectric function during cognitive control tasks. Further, our secondary hypothesis was that changes in lutein status would correlate with benefits in cognitive control.
reference link : https://www.sciencedirect.com/science/article/pii/S0167876019305598?via%3Dihub