Elsevier

Food Chemistry

Volume 210, 1 November 2016, Pages 56-62
Food Chemistry

Vitamins A and E content of commercial infant foods in the UK: A cause for concern?

https://doi.org/10.1016/j.foodchem.2016.04.014Get rights and content

Highlights

  • A primary experimental evaluation of vitamin A and E in commercial infant foods in the UK.

  • Evidence of excessive intakes of vitamin A and E from a standardised menu.

  • Total daily intakes of vitamins referenced to recommended intakes.

  • Potential cause for concern over deficiency when milk intake is reduced.

Abstract

According to the European Food Safety Authority, currently, there are no reliable data or robust guidelines available in relation to the micronutrient composition of infant foods. This study evaluated the intake of vitamins A and E of infants from ‘ready-to-feed’ foods and formulas. Normal phase high performance liquid chromatography was employed for simultaneous quantification of retinyl acetate, retinyl palmitate, α-tocopherol and γ-tocopherol, reverse phase high performance liquid chromatography for the quantification of β-carotene, and UV spectrophotometry for the quantification of carotenoids from selected infant food samples. Based on the results of this study, the estimated total daily intake of vitamin A (retinol equivalents) and vitamin E (α-tocopherol equivalents) from both infant food and formula milk exceed recommendations set by the UK Department of Health. This requires further analysis of risk of exposure, whilst a cause for concern over deficiency might arise when the intake of milk is compromised.

Introduction

Vitamin A consists of a group of lipid-soluble vitamins that have an important role in growth and development, vision and immune function. Dietary vitamin A is obtained from two sources: pre-formed vitamin A and pro-vitamin A. Pre-formed vitamin A includes retinol, retinal, retinoic acid and retinyl esters, which are available from animal sources mainly in the form of retinyl esters. Conversely, pro-vitamin A precursors in the form of carotenoids are available from plant-derived foods (Department of Health, 1991). Plants synthesise hundreds of carotenoids, but only some act as vitamin A precursors. β-Carotene is the most important carotenoid due to its vitamin A activity compared with other carotenoids, and its widespread availability in the diet. β-Carotene can be converted into two retinal molecules. Absorption rates of pre-formed vitamin A range between 70 and 90%, whereas pro-vitamin A compounds are absorbed less efficiently at rates ranging between 20 and 50% (Preedy, 2012).

Vitamin E is another group of lipid-soluble vitamins consisting of eight isomers: four tocopherols (α, β, γ and δ) and four tocotrienols (α, β, γ and δ). The most biologically active form of vitamin E is α-tocopherol, which is also the most abundant form in the European diet due to consumption of olive and sunflower oils (Wagner, Kamal-Eldin, & Elmadfa, 2004).

Vitamin E functions primarily as a chain breaking antioxidant. It protects membrane phospholipids from peroxidation and prevents free radical generation in cell membranes (Greene, Hambidge, Schanler, & Tsang, 1988). α-Tocopherol can intercept free radicals and prevent the oxidation of the lipids in cell membranes. (Baydas et al., 2002). Immune system cells contain the most vitamin E, arguably because of their exposure to high levels of oxidative stress (Suskind & Tontisirin, 2001). A maternal feeding study observed an association between increased intakes of vitamin E and decreased childhood wheeze and asthma (Devereux et al., 2006). Therefore, vitamin E might have a role in the prevention of asthma and allergic disease inflammation, the incidence of which are increasing in the UK. Oxidative stress and inflammation also have a role in cardiovascular disease and cancer. However, current understanding of the role of vitamin E in these diseases remains unclear (Lee et al., 2005).

Dietary polyunsaturated fatty acid (PUFA) intake influences tissue fatty acid content, and the amount of vitamin E required to prevent lipid peroxidation is directly related to PUFA intake (Greene et al., 1988). The bioavailability and metabolism of vitamin E is largely unclear, ranging between 10 and 79%; nevertheless factors have been identified that affect vitamin E uptake and utilisation within the body, such as the food matrix and the amount and type of fat (Borel, Preveraud, & Desmarchelier, 2013).

During food processing, retinoids and carotenoids can undergo isomerization due to exposure to acids, heat and light. Thermal treatments can cause either isomerization, from trans to cis, or oxidation. However, heating can also promote carotenoid absorption, possibly due to the release of carotenoids from the food matrix. Homogenization of foods can also improve the availability of carotenoids. Processing methods, such as dehydration, blanching and canning, can cause either oxidation or isomerization of carotenoids (Klein & Kurilich, 2000). However, retinol and carotenoids have been found to be relatively stable during most cooking procedures with industrial food processes, such as pasteurization and sterilization, generally, only resulting in small losses (Committee on Toxicity, 2012). Processing of foods, such as drying in the presence of air and sunlight, addition of organic acids, milling and refining, irradiation and canning, have been shown to reduce the vitamin E content, along with high temperatures, prolonged storage and high moisture content. Seasonal changes in vitamin E levels have also been shown in food products (Eitenmiller & Lee, 2004). Therefore, the actual content of vitamin E in commercial infant foods might vary due to processing and seasonality of products used in production.

The diet and nutrition survey of infants and young children (DNSIYC) identified that 58% of children who are fed foods other than milk have eaten a commercial baby or toddler meal (Lennox, Sommerville, Ong, Henderson, & Allen, 2013). These results indicate that commercial baby and toddler meals are major dietary contributors to an infant’s nutritional intake; therefore, these products need to be assessed for their nutritional adequacy. Furthermore, there is currently no clear and complete analytical nutritional data available for commercial ‘ready-to-feed’ complementary infant foods in the UK. McCance and Widdowson (7th Edition), UK food composition tables, contains limited data on the composition of commercial infant foods and, in addition, analytical techniques and nutrient data contained might now be out-dated. It is essential that food composition tables be updated regularly with the foods currently available on the market (Food Standard Agency, 2014).

DNSIYC has shown that mean intakes of vitamins A and E are close to or in excess of Recommended Nutrient Intake (RNI) (Lennox et al., 2013). Furthermore, in the US, 35% of toddlers exceed the Tolerable Upper Intake Level (UL) of 600 μg/day for vitamin A, and vitamin E intakes were found to exceed the recommended adequate intakes in infants below 12 months (Butte et al., 2010).

Vitamin A deficiency is common in developing countries with symptoms including visual impairment (Department of Health, 1991). However, in developed countries, such as the UK, excess vitamin A intakes may be more of an issue. Excess retinol can cause liver and bone damage, hair loss, double vision, vomiting and headaches. It can also decrease vitamin C storage, antagonise the action of vitamin K blood clotting function, and have anti-thyroid effects (Committee on Toxicity, 2014). Toxicity usually arises from chronic ingestion, exceeding the ability of the liver to store or metabolise excess vitamin A.

Potentially, high vitamin E intakes could impact absorption of the other fat-soluble vitamins, such as vitamin A, D and K. Infants have low vitamin K levels and studies have indicated that individuals with low vitamin K levels should not consume excess vitamin E, which can lead to blood clotting problems (Diplock et al., 1998). High intakes of vitamin E could also have a pro-oxidant effect, due to the production of α-tocopherol radicals. However, if antioxidant systems are balanced, for example by the sparing effect of vitamin C, these detrimental effects will not be exhibited (Rietjens et al., 2002). Vitamin E is one of the least toxic vitamins and no evidence of negative effects of vitamin E that occurs naturally in foods have been observed (Eitenmiller & Lee, 2004).

This study assessed the intake of vitamin A (pre-formed vitamin A, retinyl palmitate and retinyl acetate and pro-vitamin A, β-carotene and total carotenoid content as retinol equivalents, RE) and vitamin E (α-tocopherol and γ-tocopherol as α-tocopherol equivalents, α-TE) based on a diet consisting of commercial ‘ready-to-feed’ infant foods and infant formulas in the form of a standardized menu, as suggested by Zand, Chowdhry, Pullen, Snowden, and Tetteh (2012), and the results compared with current recommendations to assess likely infant intakes.

Section snippets

Chemicals

Retinyl acetate, retinyl palmitate, β-carotene, methyl tert-butyl ether (MTBE), α-tocopherol and γ-tocopherol were obtained from Sigma Aldrich (Poole, UK). The reference material (ERM-BD600) was purchased from the Institute for Reference Materials and Measurements for Certified Reference materials (Geel, Belgium). HPLC-grade iso-hexane, ethyl acetate, absolute ethanol, methanol, tetrahydrofuran (THF), and laboratory reagent grade sodium chloride (NaCl), petroleum ether (PE) (bp 40–60 °C) and

Results and discussion

The concentration of vitamin A from pre-formed sources, in the form of retinyl acetate and retinyl palmitate, provitamin A sources, in the form of β-carotene and total carotenoids, and vitamin E, in the form of α-tocopherol and γ-tocopherol, from eight commercial ‘ready-to-feed’ infant foods are presented in Table 3.

There was no significant difference between the two varieties of meat- and vegetable-based infant food products at the 95% significance level for α-tocopherol (p = 0.460),

Conclusions

The concentrations of vitamin A (retinyl acetate, retinyl palmitate and β-carotene) and E (α and γ-tocopherol) were determined quantitatively by HPLC. The estimated total daily intake of vitamin A, converted to RE, from a combination of commercial complementary infant foods and infant formula, based on the standardised menu, was found to exceed upper intake levels for infants (900 μg RE/day). It is worth mentioning that the contribution of vitamin A from infant formula alone was found to be 396 

Acknowledgements

The authors would like to thank Mrs Devyani Amin and Mrs Atiya Raza for their support and assistance in this work. In addition the authors would like to thank Dr Aurélie Bechoff and Dudley Farman from the Natural Resources Institute at the University of Greenwich for their support and use of facilities.

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