Human fat, antioxidant activity

The appeal of chocolate is universal, but the pleasures of eating chocolate products may perhaps be tempered by their fat and sugar content. However, in a series of human feeding studies it has been shown that the high proportion of stearic acid in the cocoa butter of chocolate does not adversely affect plasma lipids. Two recent reports of antioxidant activity have increased interest in the health aspects of chocolate an in vitro low-density liposprotein (LDL) oxidation study and a short-term in vivo study. Epicatechin, the major monomeric polyphenol antioxidant in chocolate, and an extract of chocolate liquor were both found to stimulate cellular immune response in vitro. 

Numerous researchers have drawn attention to the beneficial properties that avocado could provide to human health. Some of these healthy benehts have been summarized in Figure 8.1. Wilson Grant, in 1960, published the hrst clinical study where avocado intake was associated with the maintenance of normal serum cholesterol levels, or even with their reduction [7]. Later on, in the 90s and beginning of 2000 there was an increase in the number of works that studied the relationship between avocado fat and its effect on cardiovascular diseases, cholesterol, lipid profile, weight control, and diabetes [8-16]. While the principal healthy benehts attributed to avocado fruit are the aforementioned, some others have also been evaluated, such as prevention and treatment of osteoarthritis [17,18], anticancer properties [19-24], protective activity against liver injury [25], skin protection [26-28], reduction of risk of macular degeneration [29], inhuence on short-term memory [30], antioxidant activity [31-37], reduction of metabolic syndrome risk [38,39], and anti-inhammatory effects [31,32,40]. 

Vitamin E is the most potent fat-soluble antioxidant in human plasma. Although vitamin E was first discovered in 1922, its metabolic function remains an enigma. There are eight different molecular forms with vitamin E antioxidant activity, yet the body preferentially retains a-tocopherol. This preference for a-tocopherol has led the Eood and Nutrition Board in its 2000 Dietary Reference Intakes (DRIs) for vitamin E to recommend that only a-tocopherol, not the other forms, meets human requirements for vitamin E. Moreover, only a-tocopherol is recognized by the hepatic a-tocopherol transfer protein (a-lT P). This protein regulates plasma a-tocopherol concentrations and genetic abnormalities in the protein (or its absence) leads to vitamin E deficiency in humans. 

There is only scarce evidence confirming the toxic influence of hydroperoxides from the diet. The toxicity of thermo-oxidized frying fats on humans is better verified. The toxicity of oxidized cholesterol, especially at temperatures higher than lOO C and in the presence of unsaturated lipids, has attracted particular attention, as has the role of oxy fltosterols. Antioxidants continue to be the subject of intensive researches and discussions (Pokomy et al., 2001). Their activity in food is different than in vivo. Although no clear understanding of the prooxidant activity of antioxidants exists, supplementation of antioxidants to food products and to animal organisms does take place. 

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