DIETARY FAT AND SPORTS NUTRITION

DIETARY FAT AND SPORTS NUTRITION

ABSTRACT

The general public's view of macronutrients has undergone sweeping changes in recent years. Dietary fats are a key example. Since the anti-fat health education initiatives of the 1980s and early 1990s, certain dietary fats have been increasingly recognized as actually beneficial to health. Athletes, like the mainstream populace, are now getting the message that wise dietary fat (triacylglycerol) choices offer essential fatty acids, blood lipid management, maintained endocrine and immune function, inflammation control, metabolic effects and even potential body composition and performance benefits. Toward this end, many companies now sell specialty dietary fat supplements and recognized health authorities have begun recommending them to certain populations. This review will cover data regarding the physiology, dietary needs, food sources, and potential benefits and risks most relevant to athletes. Practical suggestions for incorporating healthy fats will be made. Both food-source and supplemental intakes will be addressed with interrelationships to health throughout.

INTRODUCTION

Dietary fat has both suffered and enjoyed large swings in public and scientific consensus over recent decades. The fat-reduction public education initiatives of the 1980s and 1990s (Weinberg, 2004), although credited with lower cardiovascular mortality, (Astrup, 2001) have also been linked to over-consumption of dietary carbohydrate and the obesity epidemic facing Western culture (Weinberg,

2004).

The escalating incidence of Syndrome X (central obesity, dislipidemia and glucose intolerance) has helped bring a more "moderate" approach to the Dietary Guidelines for Americans regarding fat's percentage of total kcal (Gifford, 2002). Additionally, an increased recognition of the types  of dietary  fat has  broadened  scientific understanding beyond simply saturated and unsaturated fatty acids. Further, researchers have referred to the potency of various dietary lipids as pharmaceutical in nature (DeCaterina et al., 1996; Fauconnot and Buist, 2001; Watkins et al., 2001). For example, monounsaturated fatty acids, as common to the Mediterranean diet, may reduce cardiovascular risks beyond any effects on plasma lipids, such as via blood pressure normalized glucose tolerance (Perez-Jimenez et al., 2002; Rasmussen et al 1995; Thomsen et al 1995). Highly unsaturated omega-3 fatty acids found in cold water fish reduce inflammation (Browning, 2003n Calder, 1997, 2001 Endres et al., 1989; Endres, 1996; Kremer et al., 1987), mediate psychiatric function (Logan, 2003 Su et al., 2003), alter neuro-endocrine activity (Delarue et al., 2003), and decrease cardiac mortality (Richter, 2003). A less common fatty acid found in dairy and beef, conjugated linoleic acid (CLA), has the ability to dramatically alter body composition in animal models (Belury and Koster, 2004). This type of understanding is leading to changes in both dietary recommendations (American Heart Association, 2002) and a wide variety of dietary lipid supplements.

Athletes have special interests and needs regarding dietary fat. Ironically, many are at risk of being hypocaloric (Burke, 2001; Economos et al., 1993; Venkatraman, 2000), yet they also seek glycogen sparing and fatigue prevention (Hargreaves et al., 2004). These situations are aided by available, energy dense fat (9 kcal-g^-1). Athletes also commonly deal with joint, soft tissue, systemic and even airway inflammation, which may also be affected by fat choices (Browning, 2003; Calder, 1997; 2001; Curtis et al., 2000; Endres et al., 1989; Endres, 1996, Mickleborough et al., 2003). Additionally, overtraining and staleness occur in roughly one-third to one-half of athletes (Kentta et al., 2001). These disorders have established endocrine and psychiatric components such as depressed testosterone or testosterone:cortisol ratio (Roberts et al., 1993; Urhausen et al., 1995), increased epinephrine during intensity-type overtraining (Fry et al., 1994), and even major depression (Armstrong and VanHeest, 2002; Uutisalo et al., 2004). All of these maladies have been positively affected by various amounts and types of dietary fat in various settings (Delarue et al., 2003; Dorgan et al., 1996; Hamlainen et al., 1983; Logan, 2003; Reed et al., 1987; Su et al., 2003). It is also interesting to speculate that the effect of maintained total fat intake on sex hormones (Dorgan et al., 1996; Hamlainen et al., 1983, Reed et al., 1987) and the reported protective effects of omega-3 fats against bone catabolism (Albertazzi and Coupland, 2002; Fernandes et al., 2003; Watkins et al., 2001), may have future application to the "female athlete triad", in which energy balance, sex hormones and bone mass are compromised. As with all of the potential benefits resented in this review, either directly applied or indirectly associated to athletes, further research is needed.

This review will briefly address the general biochemistry and physiology of dietary fat, dietary needs and food sources of various fats, and potential benefits and risks of various dietary fat manipulations to athletes.