No effect of 16 weeks flavor enhancement on dietary intake and nutritional status of nursing home elderly

Abstract

There is a lack of data to support the long-term effect of flavor enhancement on food intake and nutritional status. Our aim was to determine if daily addition of 700 mg flavor and/or 300 mg monosodium glutamate (MSG) to the animal protein part of the cooked meal for 16 weeks leads to an increase in energy intake and in body weight in nursing home elderly.

We performed a single blind randomized 16 weeks parallel study consisting of a control group ($n=23$), a MSG group ($n=19$), a flavor group ($n=19$) and a flavor plus MSG group ($n=22$). Main outcome measures were intake of the cooked meal, which was measured by weighing back leftovers during 14 days and body weight. Both were measured before and at the end of the intervention period.

After 16 weeks, energy intake and body weight did not increase within the control group, the flavor group, the flavor plus MSG group and the MSG group. Between the groups, no differences were found in changes in energy intake and body weight.

Enhancing the taste of a cooked meal with flavor and/or MSG does not lead to a higher energy intake and body weight among nursing home elderly. More research is needed to determine the efficacy of flavor enhancement on intake and nutritional status.

Introduction

Aging seems to be accompanied by a lower energy intake in nursing home residents (Eastwood, Davies, Gardiner, & Dettmar, 2002; Lowik et al., 1992; Morley (1997), Morley (2001)) Poor energy intake is an important factor related to weight loss in these elderly (Blaum, Fries, & Fiatarone, 1995) and the latter is associated with higher morbidity and mortality (Chapman, MacIntsoh, Morley, & Horowitz, 2002; Newman et al., 2001).

A potential cause of inadequate intake due to a loss of appetite is the impairment of taste and smell performance (Rolls, 1999). This loss of taste and smell tends to begin around age 60 and becomes more severe in persons aged 70 and older (Doty et al., 1984; Schiffman, 1997; Stevens, Bartoshuk, & Cain, 1984).

On average elderly people prefer higher optimal flavor concentrations in certain foods than young people (De Graaf, Polet, & van Staveren, 1994; De Graaf, van Staveren, & Burema, 1996; Griep, Mets, & Massart, 2000, 1997). Griep, Mets, and Massart (1997) showed that elderly people preferred high-flavored soup, Quorn and yoghurt while young people favored the low-flavor levels. De Jong, De Graaf, and van Staveren (1996) found that elderly preferred higher sucrose concentrations in orange lemonade, strawberry jam and strawberry yoghurt but not in chocolate spread and porridge grain. Kozlowska et al. (2003) also found that the elders preferred higher sucrose concentrations in apple juice compared to young adults.

Higher flavor intensities can be obtained by boosting the concentration of odor and of taste compounds in foods with flavors (mixtures of odorous molecules extracted from natural products or synthesized) and/or monosodium glutamate (MSG). This approach may hold potential for elderly individuals with diminished sensory function to improve food palatability, intake acceptance and immunity (Schiffman, 1998; Schiffman & Warwick, 1993).

In theory, higher flavor concentrations are needed to compensate for the lower chemosensory sensitivity in order to obtain a similar optimal perceived intensity (De Graaf et al., 1996). However, there is little direct evidence that links the higher optimal flavor concentrations in food to an impaired taste and smell sensitivity in the elderly. Koskinen, Kalviainen, and Tuorila (2003) showed that the olfactory performance of the elderly was not associated with hedonic responses to flavor enhanced foods.

In a recent 4 months intervention study in a nursing home, Mathey, Siebelink, De Graaf, and van Staveren (2001) showed that enhancing the taste of cooked meals with flavors plus MSG resulted in a higher food intake at the cooked meal and an increased body weight. Whether the effect of the sensory manipulation was due to the flavors or to MSG is unclear. Therefore, we studied the effect of adding flavor and/or MSG to the cooked meal separately.

Our aim was to determine whether daily addition of flavor and/or MSG to the animal protein part of the cooked meal for 16 weeks leads to an increase in energy intake of the cooked meal and an increase in body weight. We also determined whether or not the increase in intake was related to olfactory sensitivity.