4. Discussion
In this scoping review, we collated the existing literature to understand what is known about the Malaysian population’s diet quality. We reviewed findings that indicate the quality of Malaysian diets, factors that influence them, and the impact of diet quality on health outcomes across the lifespan of Malaysians. The findings of this review, we believe, will provide an actionable reference for policymakers and researchers to tackle the double burden of under- and over-nutrition in Malaysia, a rapidly growing middle-income country.
The choice of diet quality indicators used in Malaysian studies reflects the co-existence of over- and undernutrition. Food variety-based scores are more useful in determining diet quality in maternal and child nutrition, while the HEI and DQI are more useful in studying the relationships between diet and non-communicable disease (NCD) risk
[10]. Accordingly, Malaysian diet quality studies focusing on nutrient adequacy in maternal and child nutrition used the FVS or DDS, while studies focusing on NCD risks used the HEI or its modified versions. Defined by the nature of scoring, food variety-based scores were associated with higher energy intake in the study of mother and child dyads whereas higher scores on the HEI or its modified versions were associated with lower fat (higher carbohydrate) intake in the studies included in this review. The high prevalence of obesity and related chronic diseases relative to undernutrition could explain the predominant use of the HEI or DQI and their derivatives in Malaysian diet quality studies. It is therefore interesting to see that studies conducted among indigenous communities
[32][37], rural settings
[40][42][43][44][41][45], and in lower-income neighborhoods
[39] used the DDS or FVS. These studies also tended to focus more on sociodemographic factors affecting food insecurity and the association of diet quality indices with nutritional status. Studies using the HEI or DQI or their modified versions tended to be more in the urban
[55][34][36][38][47][48][49][35] and clinical settings
[46][52][53][54][50][51]. The latter were also more likely to focus on the association of diet quality with cardiometabolic or chronic disease risks. However, there were exceptions to this assumption. Chua et al.
[30] and Chong et al.
[21][22] used the HEI versions to evaluate diet quality in the indigenous and fishing communities, respectively, while their objectives did not significantly vary from the other studies conducted in such settings. The literature search also showed that the HDI and MDS had not been used widely in the Malaysian setting. In summary, the preferred tools for diet quality measurement in Malaysia have been the DDS or FVS in undernutrition or maternal and child health settings and the HEI and its adaptations in settings that focused on chronic diseases.
Overall, Malaysian diet quality showed scope for dietary improvement across all the populations studied. The HEI and its modified scores in Malaysian studies ranged from 17% to 72%, with a median in the mid 50%. Similarly, DDS scores ranged from 6.38 to 12.69, out of a maximum possible score of 15. This may seem counterintuitive given that Malaysia is well-known as an affordable food haven, a melting pot of rich multi-ethnic culinary traditions. However, Malaysia has been ranked 43rd of 133 countries in the Global Food Security Index (GFSI)
[56] and has experienced increased Westernization of its urban diets
[3][57]. Eating healthy also has been found to add to daily dietary costs
[34]. Therefore, while Malaysia is known for its tasty cuisine, eating healthy every day may be beyond the affordability of the rural and urban poor. This once again is consistently demonstrated in the positive relationship between diet quality and proxy indicators of income (education, household income, personal income, food security, household food expenditure, daily dietary costs) across many studies included in this review. Existing Malaysian studies have predominantly included low-income households, indigenous communities, or households in rural settings, and therefore this sampling could have accentuated the relationship between income and dietary quality. Thus, nutrition intervention programs for the under-privileged could be tailored to the target populations based on their age and ability. Such interventions could include a mixed supply of healthy foods, subsidies for healthier food purchases, nutrition education, kitchen garden establishment, and poverty eradication activities, as required.
Lower diet quality scores in Malaysian studies are seen among school and university students from urban settings and adults from indigenous communities or rural settings. Pregnant women and women of childbearing age also show poor diet quality. This is of concern given that early influences during critical periods of prenatal and postnatal development result in epigenetic changes that impact health and behavioral outcomes of the new-born and that are carried on into adulthood and future generations
[58][59][60].
Associations between age and diet quality were inconsistent among the studies reviewed. While two of the reviewed studies
[34][32] showed that diet quality improved with age, Leiu et al.
[47] and Nohan et al.
[48] showed a negative association between age and diet quality. It is important to note that participant age showed a marked spread in only one
[34][47][48][32] of the four studies that reported an association between age and diet quality. The food groups found to be deficient in these studies were fruits, vegetables, dairy, and legumes, while excessive intakes of meat, salt, sugar, and fat were also documented. While it is difficult to compare these smaller individual studies to the more extensive national data, it should be noted that two distinct dietary patterns were associated with younger age in the national surveys
[3]. Younger adults in Malaysian national surveys were more likely to be associated with two major dietary patterns (i) “Western” (fast-food, carbonated drinks, confectionery, condiments, and sauces) and (ii) “Mixed” (breakfast cereals, fruits, vegetables, dairy, and legumes). These dietary patterns were also associated with urban residence and higher incomes. The majority of the participants in the four studies of interest in this review (approximately 60–100% of respondents) could be classified as coming from low-income households with a monthly household income of less than RM 3500
[61] and were from urban/semi-urban settings (except Chua et al.
[32]). Thus, it is unclear whether a dichotomous preference for either a more high-fat-salt-sugar laden “western” pattern or a more prudent “mixed” pattern among the younger respondents in the studies could explain the inconsistency in the association between age and diet quality.
Two studies included in this review showed women to have better diet quality than men. This phenomenon has been noted globally
[62] and within Malaysia
[3] and is driven by women’s preferences for a healthier lifestyle. More frequently, in Malaysian national data, men adhered to fast food and meat-based dietary patterns compared to women
[3]. Ethnicity did not show a consistent relationship with diet quality in the studies we reviewed. This could be of interest to future investigations that appropriately focus their study on that subject.
The associations demonstrated in these studies support the utility of the diet quality indicators used in Malaysia for maternal and child health and NCD risk evaluation. Diet quality assessed using the DDS was shown to be associated with appropriate body weight for age in children, and higher FVS scores were associated with higher energy intake in the study of mother and child dyads. Poorer diet quality indicated by lower HEI/modified HEI scores was associated with being overweight, visceral obesity, higher postprandial glycemia, hypertension, and breast cancer risk in adults. This provides validation for using the HEI or its modified versions to assess unhealthy diets related to chronic diseases in Malaysian adults. In -line with these findings, good dietary quality with better DQI scores also indicated better skeletal mass in the elderly. However, HEI scores were not associated with cardiovascular risks in Malaysian adolescents, despite 35% of the respondents showing at least one metabolic risk. Thus, the FVS and DDS may be useful for the rapid screening of diet quality in studies relating to maternal and child health, while the HEI and its modified versions are useful for studying diet-chronic disease relationships among Malaysian adults. However, the utility of these indices among Malaysian adolescents requires further investigation. It must be noted that the M-HEI used in a few of the included studies evaluates conformance in seven food groups (grains and cereals; vegetables; fruits; meat, poultry and eggs; fish and seafoods; legumes; and milk and dairy products) and two nutrients (fat and sodium) with Malaysian Dietary Guidelines
[63]. This iteration of the HEI does not include the evaluation of saturated fat intake, as palm oil is a common cooking oil in Malaysia, and saturated fat intake will not sufficiently differentiate the participants.
This review showed that most diet quality studies in Malaysia included lower-income households from urban, semi-urban, and rural settings predominantly in the Klang Valley, including Selangor and Kuala Lumpur. There were also some data from Terengganu, Negeri Sembilan, and Kelantan. Given that food choice is a combination of affordability, availability, convenience, and conditioned personal preference, concerted efforts should be made toward nationwide representation to better evaluate the influence of sociodemographic factors on diet quality in this multi-ethnic country. Various versions of the HEI have been used in Malaysia. It is crucial to evaluate the agreement between these versions and flag distinctions, if any. Associations between dietary quality for the population and the food environment, including proximity to grocery stores, restaurants, and eateries, would provide the information required for policy formulation. This would be especially important, given the high frequency of eating out in Malaysia
[64]. Finally, prospective studies should be undertaken to validate the ability of these indicators to predict chronic disease risk in this population, as the existing evidence is predominantly cross-sectional.