04 Sep avocado GMI Study
AVOCADO
The Avocado (scientifically known as Persea Americana) is a fruit belonging to the berry family, with more than 400 varieties. It is thought to have originated from and around Central America and Mexico and has long been considered to have special medical properties. Over time its leaves have been used to treat neuralgia, diarrhoea, and sore throat, while the extracted oil has been used topically as an anti-microbial and analgesic to relieve toothache, skin sores and arthralgia[110-112]. In modern medicine, avocados have been implicated to have cardiovascular benefits, protective effects against UV damage in skin and eyes, anti-inflammatory, analgesic, anti-microbial and also anti-carcinogenic properties[113-116].
Avocados are a low to medium energy dense fruit with a high content of water (about 75%) and fibre (6%), but a low content of sugar and sodium. They contain essential vitamins (B, C, E), minerals, lipids and phytochemicals such as carotene and lutein. Avocados are a rich source of oil, producing 15-30 g/100 g of fruit[117], mostly composed of MUFAs with a relatively low composition of saturated fatty acids[114,118,119].
A study analysing the 2001-2008 NHANES data incorporating the dietary habits of 17567 adults, suggested that avocado consumption was associated with improved weight, waist circumference and BMI, higher HDL and decreased risk of metabolic syndrome[118]. The energy density and fibre content of avocado may play a role in enhancing early satiety and maintaining weight control[114,120,121]. Avocado has the highest fibre content amongst fruit, with approximately 70% being insoluble and 30% soluble[114]. Dietary fibre may aid in maintaining insulin sensitivity as well as reducing fat absorption, factors which are important in preventing the metabolic syndrome and development of NAFLD. In a small animal study, rats fed a cholesterol containing diet supplemented with varying quantities of avocado pulp or cellulose gained less weight when fed avocado pulp and consumed less food overall. Furthermore, a strong negative correlation was seen between hepatic fat deposition and increasing intake of avocado pulp[121]. In another study, rats fed a hypercholesterolemic/fructose diet were compared to rats supplemented with defatted avocado pulp. This resulted in a significant (P ≤ 0.05) decrease in plasma total cholesterol (43.1%), LDL (45.4%) and triglycerides (32.8%), and a significant decrease in LFTs. Subsequent histological analysis also demonstrated reduced liver damage and steatosis in the rats fed avocado[112,120]. Data from other animal studies suggest avocados may possess systemic anti-inflammatory properties[117], can protect against chemically induced liver damage and have antioxidant effects[122].
To date, there have been only a few small preliminary studies in humans looking at the metabolic benefits of avocados, concentrating mainly on the effects on lipid profiles. These showed that avocado enriched diets were associated with a reduction in serum total cholesterol, LDLs and triglycerides, with varying results on HDLs[114]. The exact mechanism of lipid lowering effects of avocados are unknown, but may relate to alterations in PPAR-γ expression, upregulation of adiponectin activity and regulation of glucose and lipid transporting genes[123,124]. These changes are driven by MUFAs, phytochemicals such as carotenoids, chlorophylls and polyphenols, vitamin E and beta-carotene[125,126].
Clinical trials directly evaluating the effect of avocado consumption on NAFLD are lacking, however, given their high MUFA content, lipid lowering, anti-oxidant, anti-inflammatory and weight maintenance properties, they are a reasonable addition to a low fat diet. Further studies are required to determine if supplementation has specific benefits for patients with NAFLD.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4588084/#__sec8title
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