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Creating a detailed four week food diary for the dietary recollection of fish intake has removed some of the potential for errors associated with FFQs such as the reliance upon self estimation of intake (Liu et al., 2013; Bowman et al., 2012). Using a battery of cognitive tests allowed the investigation of whether non-oily fish consumption had a domain specific effect on cognitive performance. Assessing dietary fish intake over a period of four weeks may not represent general consumption and intake may vary depending on the time of year. Likewise, current intake may not reflect the individuals’ life time intake (Gillette- Guyonnet et al., 2013) and participants may have increased their consumption of fish in midlife because they were aware of the potential health benefits associated with increased fish consumption (Morris et al., 2009). For example, consumption of fish has been recommended for those with heart disease and is associated with a decreased risk of heart attack and coronary disease (NHS, 2013; Morris, 2009; Kalmijn et al., 1997).

Tinned tuna was one of the most commonly consumed fish by this cohort. Participants also consumed larger amounts of salmon and haddock relative to the other varieties but there was no effect of these types of fish on MMSE score. Increased consumption of the other varieties of fish consumed by this cohort may lead to an effect of these fish types on cognitive performance although this cannot be determined by the present data.

The participants in this cohort volunteered to take part in the study. As a result they may not be a true representation of the general population. It is possible that those participants who consumed a greater amount of fish per month were

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more likely to possess a healthier diet over all. Wennberg et al., (2012) commented that fish consumption in general seems to be associated with a healthy lifestyle. Cunnane et al., (2009) noted that fish consumers tend to be consumers of other healthy foodstuffs such as fruits and vegetables which are also rich sources of antioxidants. Fish is a major component of the Mediterranean diet (Cunnane et al., 2009; Martínez-Lapiscina et al., 2013), which has in some previous research been associated with a lower risk of developing AD (Scarmeas et al. 2006; von Arnim et al, 2010; Cunnane et al., 2009). Fish is commonly thought of as a healthier dietary option by the general public (Cunnane et al. 2009) and individuals consuming fish, in the case of this chapter, tinned tuna, may be more likely to be aware of other healthier dietary options. This type of diet is likely to protect against other age associated conditions such as diabetes, hypertension and high cholesterol and promote healthy aging overall (Cunnane et al., 2009).

As a non-oily fish, tinned tuna contains lower amounts of fish oils than fresh tuna and other oily fish varieties as the process of ‘tinning’ reduces the fish oil content to that of other non-oily varieties (NHS, 2011). It is possible that any potential benefits of increased consumption maybe due to other nutrients aside from DHA and EPA within non-oily fish. For example, their high protein content (Cunnane et al., 2009), selenium levels (Cunnane et al., 2009; Mehdi et al., 2013; Gao et al., 2007) vitamin content (Cunnane et al., 2009) or low fat content (Scientific Advisory Committee on Nutrition, 2004).

6.5.6 Implications

The results of this food diary study have shown that a diet which includes a larger amount of non-oily fish, specifically tinned tuna, is associated with improved performance on the MMSE with the significance lying in the MMSE’s assessment of short-term recall. The MMSE is recommended as a test of choice for the diagnosis of cognitive impairment by the recently reviewed NICE dementia guidelines (NICE, 2011) and is still used in the early assessment of cognitive impairment (Alzheimer’s Association, 2012). The participant’s score on the MMSE can be considered when determining diagnosis, treatment and research inclusion. Performance may also be compared with normative data

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sets. It is acknowledged that the MMSE has received some criticisms for being insufficiently sensitive to mild forms of cognitive impairment (Mitchell, 2009, Tombaugh and McIntyre, 1994) and the occurrence of ceiling and floor affects are common which creates clusters of scores at the test’s maximum and minimum range (Crum et al., 1993). Despite this the MMSE is still widely used by clinicians and researchers to determine overall global cognitive function and detect early cognitive symptoms.

The fact that tinned tuna intake was able to predict MMSE score, specifically the word recall portion of the task, in a sample of older HE adults may have implications for cognitive testing. The findings also add to the current literature investigating dietary factors and cognitive performance in the elderly. The Alzheimer’s Association comment that GPs will often ask patients about their dietary intake. Should a strong effect remain with further study this may have implications for the promotion of fish as a modifiable dietary factor which may aid cognitive aging. This is relatively inexpensive and is a method that the individual themselves can implement in the home without the need for consultation with clinicians which is time consuming and expensive. There has been very little literature which has incorporated food diaries as a method of measuring fish intake. The use of the food diary in the present chapter has demonstrated that diaries can be useful tools to collect dietary information from elderly participants when conducting research within the field of cognitive neuropsychology.