Inadequacies of Dietary Iron Intake in Normal- and Overweight Young University Students from Leicester, England ^†

Abstract

Iron (Fe) deficiency is a public health concern in the United Kingdom (UK). The dietary intake of Fe was determined in 111 (20.45 yrs. old; 78 females; 41 Asian, 41 African, and 27 European) De Montfort University (DMU, UK) students between 2015 and 2016. Overall, 25.7% and 8.3% of this population were overweight and obese; meanwhile, 9.2% were underweight. The dietary intake of Fe was significantly higher in male participants (17.700 vs. 13.634 mg/day), which could be attributed to the significantly higher intake of foods rich in bioavailable iron, specifically meat (271.553 vs. 193.063 g/day) in males. Moreover, the dietary intakes of Fe did not show statistical differences according to BMI or ethnic background, which might be attributed to the low/different number of responses. The dietary intakes of Fe recorded were higher than the reference nutrient intake (RNI) established for male (8.7, range = 6.257–43.809) and female (14.7, range = 4.748–40.693; all in mg/day) populations in the UK for most of the participants. Suboptimal iron status could have a negative impact on academic performance that should be tackled by implementing public health strategies to improve body Fe status in university students.

1. Introduction

There is global concern regarding micronutrient malnutrition as this can affect different organ systems and development in humans, and can influence academic performance in young adults [1]. Iron (Fe) deficiency is a public health concern in Western countries, including the United Kingdom (UK), and is common in young women. This has been attributed to changes in dietary patterns towards an increased consumption of high-energy low-micronutrient foods (i.e., fast-food, sugar-sweetened beverages, salty snacks) [1,2,3]. Thus, although the intake of energy is adequate or higher, it is estimated that around 2 billion people worldwide may have micronutrient malnutrition [3].

Young adults are a relevant group of the population that have specific characteristics and features that make them different from children and adults. However, because of their age, individuals aged 18–22 years are generally treated in human biomonitoring studies as adults or are segmented into several groups. Owing to the importance of monitoring dietary habits and nutrient intake, our study aimed to assess the dietary intake of Fe in young adults at De Montfort University (DMU, Leicester, UK), and the potential effect of ethnic background and body weight on the intake of this mineral.

2. Material and Methods

Comprehensive nutrient intake was collected from 111 (20.45 ± 1.16 yrs. old; 78 females) DMU students between 2015 and 2016 from three major ethnic backgrounds/continental origins (41 Asian, 41 African, and 27 European), using a validated variant of the Nutrition Norfolk Food Frequency Questionnaire (version 6, CAMB/PQ/6/1205) [4] and a previous food frequency questionnaire (FFQ) used by our group [5]. Thus, some food items were modified and/or added to adapt the FFQ to the target population following the indications of McCance and Widdowson’s The Composition of Foods [6] for the most commonly consumed foods in the UK. A comprehensive literature review was carried out to include food items that are commonly consumed by the diverse populations living in Leicester (especially Chinese, Eastern and Central European, and South Asian). FFQs are relevant tools in epidemiological studies for evaluating the relationship between diet and health outcomes [7]. The collected FFQs were processed with Nutritics^® software (v.5.7 Research Edition, Nutritics Ltd., Dublin, Ireland), which has previously been successfully used in human biomonitoring and dietary research [8,9,10]. Underweight/overweight individuals were identified based on their body mass index (BMI; using the formula kg/m²) and level of body fat (body fat %) using a Tanita^® scale, depending on their ethnic background/continental origin [11].

Statistical analyses were performed using the free software R-project, version 4.1.0 [12]. Significance scores were based on the Kruskal–Wallis test for nonparametric multiple comparisons and one-way analysis of variance for normal multiple comparisons. p-values were adjusted by the Benjamini and Hochberg method [13]. For normality, the Shapiro–Wilk test was used (p-values lower than 0.05 did not show Gaussian distribution). Differences were considered statistically significant at p-values lower than 0.05.

3. Results and Discussion

According to their BMI values, 25.7% and 8.3% of this population were overweight (BMI between 25 and 29.9 kg/m²) and obese (BMI ≥ 30 kg/m²); meanwhile, 9.2% were underweight (BMI < 18.5 kg/m²). The proportion of overweight participants is almost 6% higher than the reported national average in 16–24 year-old individuals in 2021 of 20% [14]. Our results suggested that female individuals were slightly more likely to be overweight or obese, although without statistical differences (p-value = 0.2886), which would be contrary to that described in the Health Survey for England 2021 [14]. However, this might be due to differences in the number of participants studied according to biological sex and the sample variability of students from different ethnic backgrounds attending DMU when compared with other British regions.

3.1. Estimated Dietary Intake of Fe According to Sex

Dietary iron is present in different forms and concentrations in different food groups and products. Iron is divided into two types based on absorption mechanisms: haem iron and non-haem iron [15]. The dietary intake of Fe was significantly higher in male participants (17.700 vs. 13.634 mg/day; p-value = 0.0023), which could be attributed to the significantly higher intake of foods rich in bioavailable iron, specifically meat (271.553 vs. 193.063 g/day; p-value = 0.016) in males. This would be logical as meat and meat products are the food group with the highest content of haem iron, which is two to six times more bioavailable than the non-haem form from other dietary sources [15]. Thus, the significantly higher intakes of different meat products in male participants, specifically bacon (4.911 vs. 1.551; p-value = 0.024), chicken (87.143 vs. 57.532; p-value = 0.009), and duck (3.5 vs. 1.80; p-value = 0.049; all in g/day), might explain the higher dietary intake of Fe observed. However, these results should be considered as preliminary, as more male individuals should be included in this study to make both sex groups more homogenous.

3.2. Estimated Daily Intakes of Fe According to Body Mass Index and Ethnic Background

Moreover, the dietary intakes of Fe did not show statistical differences according to BMI [underweight (11.684 ± 3.586) < obese (12.953 ± 4.790) < overweight (13.327; 8.677, 18.534) < normal weight (15.405 ± 7.632), p-value = 0.546] or ethnic background [European (12.069; 8.064, 19.263) < African (12.673; 9.207, 15.250) < Asian (14.252; 10.928, 18.846), p-value = 0.249; data presented as arithmetic mean ± SD and/or median and interquartile range, according to Gaussian distribution, all in mg/day] for all the individuals combined. The lack of statistically significant differences may be due to the low/varying number of individuals per category/group.

A breakdown of the dietary intakes of Fe for the male and female populations according to BMI and ethnic background is provided in

Table 1. Dietary intakes of Fe (mg/day) according to BMI, for male and female participants.

Sex	BMI	n	Shapiro (p-Value)	Mean	Range	Median (IQR)
Male	Underweight	3	0.012	13.993 ± 4.967	8.257–16.893	16.829 (12.543, 16.861)
	Normal	20	0.005	18.145 ± 9.526	6.257–43.809	16.915 (10.865, 20.972)
	Overweight	8	0.217	18.108 ± 4.927	13.282–27.839	16.401 (15.076, 20.564)
	Obese	1	/	16.673	/	16.673
Female	Underweight	7	0.379	10.695 ± 2.694	7.444–14.253	11.229 (8.284, 12.687)
	Normal	42	0.005	14.101 ± 6.260	4.748–30.014	12.901 (9.430, 17.243)
	Overweight	20	0.001	14.144 ± 9.752	4.774–40.693	9.459 (8.074, 16.629)
	Obese	8	0.167	12.488 ± 4.899	7.267–20.199	11.170 (9.511, 14.562)

n = number of counterparts per group; arithmetic mean results are presented as mean values ± S.D.; median (interquartile range per group); / = data not available.

and

Table 2. Dietary intakes of Fe (mg/day) according to ethnic background, for male and female participants.

Sex	Ethnic Background	n	Shapiro (p-Value)	Mean	Range	Median (IQR)
Male	Africa	10	0.393	15.443 ± 4.624	8.257–21.082	15.729 (11.696, 19.717)
	Asia	13	0.005	17.639 ± 9.002	6.257–43.809	16.673 (13.282, 20.166)
	Europe	9	0.535	20.297 ± 9.451	9.678–38.887	18.327 (13.371, 26.039)
Female	Africa	31	0.000	13.386 ± 7.975	4.774–40.693	10.940 (8.612, 12.996)
	Asia	28	0.025	15.001 ± 6.336	6.969–30.014	13.189 (10.836, 18.204)
	Europe	18	0.035	11.938 ± 6.003	4.748–25.930	9.512 (7.564, 15.753)

n = number of counterparts per group; arithmetic mean results are presented as mean values ± S.D.; median (interquartile range per group).

, respectively.

3.3. Nutritional Recommendations

These results in principle would not show major inadequacies in the intake of Fe according to body weight and continental origin, although they suggest a lower intake of this mineral in obese and underweight individuals, in line with the literature [1]. However, the results are logical as they reflect higher dietary intakes of this essential mineral in those groups with healthy food intake and are related to the increased consumption of high-energy foods with low micronutrient content.

The dietary intakes of Fe recorded were higher than the reference nutrient intake (RNI) established for male (8.7, range = 6.257–43.809) and female (14.7, range = 4.748–40.693; all in mg/day) populations in the UK [14,16,17] for most of the participants. Our results disagree with a similar study carried out in young university students from Liverpool (18–25 years-old, England), which observed a deficit of 6.18 mg compared with RNI in female counterparts [1]; meanwhile, we only detected a deficit of 1.2 mg. These differences might be attributed to small differences in the diet according to ethnic background, although further studies including more participants per group/sub-group would be needed to support this hypothesis. However, the ranges of dietary intake of Fe recorded in DMU students showed a high variation that should be carefully studied, as some individuals presented levels of Fe below those required for correct human functioning, especially female participants.

4. Conclusions

Suboptimal iron status is associated with anemia, physical weakness, and reduced work capacity and tolerance, which could have a negative impact on academic performance that should be tackled by implementing public health strategies and interventions to enhance body Fe status in DMU university students, particularly in women. Food manufacturers should also be involved to develop new food products targeting young female adults that could aid the dietary intake of Fe and other micronutrients.