Vitamin C Fortified Foods
FOOD FORTIFICATION TECHNOLOGY
Iodine
Iron
Vitamin A
Vitamin D
Vitamin E
Vitamin C
B-Complex Vitamins
Practical Problems Encountered in Establishing Fortification Programmes
The discussion on food fortification technology was based on two working papers, 'Micronutrient Fortification of Food: Technology and quality Control' (CONFORT 2) and 'History of Technology Development for Vitamin A Fortification of Foods in Developing Countries' (CONFORT 5). These two working papers have been attached (see Annexes 4 and 5) as much of the detailed information contained therein is not repeated in this report. The Consultation stressed the need to take an holistic approach to food fortification, and hence emphasised many supporting activities which would facilitate efficacious fortification.
Considerations beyond the methodologies employed in the addition of micronutrients to foods influence to a large extent the potential of food fortification to meet its nutritional objectives. These include: current technologies for determining micronutrient status of target population groups; bioavailability of certain micronutrients in fortified foods, and; impact of traditional practices on the stability of nutrients in fortified foods. Existing problems in these areas as they relate to specific micronutrients are dealt with below.
The focus of the international community has so far been on the three most prevalent deficiencies (Vitamin A, iodine and iron). However, the Consultation considered that other micronutrients, such as vitamin D, E, C and the B-complex, were also important. The Consultation further recognised the mounting evidence suggesting that zinc deficiency may be prevalent in many population groups, but decided not to include this mineral in its deliberations because zinc fortification is not yet widely practised except in special cases such as emergency refugee programmes. The Consultation did not consider the addition of nutrients to foods for special dietary uses, such as weaning foods and infant formulae.
For the purposes of this Consultation, food fortification was defined as in the Codex Alimentarius, namely, "...the addition of one or more essential nutrients to a food, whether or not it is normally contained in the food, for the purpose of preventing or correcting a demonstrated deficiency of one or more nutrients in the population or specific population groups...". However, the Consultation recognised that micronutrient addition also included other considerations such as new scientific findings on the role of micronutrients in better health and changes in dietary patterns. The Consultation recognized the need to better define "demonstrated deficiency" as mentioned in the Codex definition of fortification. The Consultation accepted the definition of "deficiency" as that demonstrated by dietary, biochemical, functional and/or clinical data.
Iodine
The Consultation agreed that salt is one of the most suitable vehicles for iodine fortification for the general population. It has been successfully and, in general, safely used for over 70 years in programmes around the world to prevent iodine deficiency problems.
Two chemical forms of iodine are currently used for iodization; these are iodates and iodides. The Codex Alimentarius standard for food grade salt permits the use of the sodium and potassium salts of iodides and iodates in the iodisation of salt. The level of fortification that has been used ranges from 30-200 ppm. These two forms of iodine, however, need to be harmonized in terms of equivalence in order to avoid trade barriers.
A major consideration in the choice of the two compounds is the purity of the salt. The iodides are more readily degraded in the presence of impurities, whereas the iodates remains stable in salt of lower quality.
Suitable technologies for iodization of salt exist for both large and small scale production plants. There have been four major technologies used in the addition of iodine to salt. These are dry mixing, drip feed addition, spray mixing and submersion. These technologies have been extensively reviewed elsewhere.
Alternative vehicles which may be considered for iodization are milk, bread, flour, sugar and condiments. In addition, fortification of animal feeds can be useful in increasing the iodine content of animal products. Recent data indicate that dietary intake of iodine can be increased by the use of slow release resins added to water. The overall effectiveness of this practice remains to be established.
With the use of iodized salt in food processing, a variety of foods will act as an iodine source. In some countries where iodized salt is provided for home use, it is not only added to food during preparation but also used in the home processing of traditional foods such as cured fish and pickled products. The iodized salt in the home processing of traditional foods provides much of the iodine consumed by certain population groups.
Clearer understanding of the interaction of iodine with other dietary factors needs to be achieved if one is to optimise iodine fortification programmes. It would be desirable to further investigate the interaction of iodine with various goitrogens which may be present in the diets of target populations, so that a more accurate assessment of optimal iodine fortification levels could be determined.
In cases where there is more than one demonstrated micronutrient deficiency in a target population, the addition of more than one micronutrient to a single vehicle (multiple fortification) could be advantageous. The evaluation of new methods of iodine fortification which facilitate multiple fortification should be encouraged.
Sporadic reports of thyrotoxicosis have been reported especially in iodine fortification programs which were poorly monitored. The prevalence of this side effect can be reduced by close monitoring of iodine levels in foods which can be adjusted based on monitoring of human urinary iodine excretion.
The Consultation was of the opinion that monitoring of any iodine fortification program by quality assurance of the fortification process and periodic evaluation of urinal iodine status are of critical importance in ensuring the success and long term sustainability of any such program.
Iron
Cereals are the most widely used vehicles for iron fortification although many others, such as milk products, sugar, curry powder, soya sauce and cookies have been successfully used.
Elemental iron (particularly micronized), iron sulphate and iron fumarate are examples of preferred iron fortificants. Selection of the iron fortificant is dependent on the food vehicle. The colour of iron compounds is often a critical factor when fortifying lightly coloured foods. The use of more soluble iron compounds (eg. iron sulphate) often leads to the development of off-colours and off-flavours due to reactions with other components of the food material, but they have the advantage of being highly bioavailable. Vitamin C is known to increase the bioavailability of non-heme iron forms. In some countries bovine haemoglobin concentrate, which has an exceptionally high bioavailability, is being used as a heme-iron fortificant in local feeding programmes.
The presence of phytates, polyphenols and calcium are known to adversely affect the bioavailability of non-heme iron fortificants. Increasing evidence indicates that in such cases sodium iron-EDTA may prove to be a better choice of fortificant in the future as iron from the EDTA-complex remains bioavailable even in the presence of iron absorption inhibitors. A three year study in humans has shown no adverse effects. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has given sodium iron-EDTA tentative approval for use as a fortificant. However, at present, there is little available information on food grade specifications for the compound.
Given the wide variability of iron bioavailability, influenced by physical and chemical properties of the fortificant as well as the presence of substances which either inhibit or improve iron absorption, there is a need to develop convenient models for the evaluation of iron bioavailability. Improved information on the bioavailability of iron in fortified foods should be used to assess the necessity of revising levels of iron fortification in some products. This is particularly important as an increasing range of iron fortificants with different physico-chemical properties, is being developed and marketed.
Iron fortification practices should be based on feedback from comprehensive surveillance programmes monitoring their impact on iron status. It should be noted that iron overload is not a concern in growing children and menstruating women, but since the iron requirement of these groups is much higher than for adult male populations, there is a need to evaluate the long-term risks of excessive iron intake in the latter group, as consumption of the fortified foods is generally not restricted to the group at greatest risk of deficiency. A combination of nutrition intervention strategies should be used to meet the high iron requirements of these population groups. It is important to assess the contribution of iron fortification in combination with other strategies for the control of iron deficiency in specific age/sex groups, so as to establish optimal goals for iron fortification of foods.
Surveillance data of iron status should be interpreted with caution because of the known alteration of serum ferritin levels and other indicators of iron status in the presence of recent infection. Serum transferrin receptor determination appears promising in the evaluation of iron status in the presence of infection. Furthermore, it should be stressed that not all anaemia is due to iron deficiency, although the latter is most common.
Several aspects of the interaction between iron and other nutrients, such as vitamin A, iodine, zinc and calcium, need to be investigated in relation to the possibility of multiple fortification. The stability and the cost of fortificant compounds as well as the bioavailability of the nutrients need to be considered.
The Consultation also noted that meal composition and dietary variety are important factors in optimizing iron status.
Vitamin A
Foods which have been successfully fortified with vitamin A include margarine, fats and oils, milk, sugar, cereals, and instant noodles with spice mix. Moisture contents in excess of about 7-8% in a food are known to adversely affect the stability of vitamin A. Beyond the critical moisture content there is a rapid increase in water activity which permits various deteriorative reactions to occur. Repeated heating, as may be experienced with vegetable oils used for frying, is known to significantly degrade vitamin A. The hygroscopic nature of salt has prevented its use as a vehicle for vitamin A fortification in countries of high humidity. In trying overcome this problem, a new vitamin A fortificant, encapsulated to provide an additional moisture barrier, was evaluated with limited success. The cost of using highly protected fortificants can be prohibitive in many cases.
In developed countries vitamin A fortification is limited to milk and dairy products, margarine and fat spreads and breakfast cereals. Current levels of fortification of Vitamin A are generally considered as safe.
Carotenoids can be used as a source of vitamin A. However the conversion and bioavailability of the carotenoids is known to be affected by the vitamin A status of the individual and by dietary composition. A conversion factor of 6:1 (six milligrams of beta carotene equivalent to one milligram of retinol) is currently being applied in calculating intake. The cost factor in using carotenoids as the source of vitamin A activity in fortification is generally considered prohibitive.
Vitamin D
There are a limited number of food vehicles suitable for vitamin D fortification. These include margarine, vegetable oils and dairy products.
Vitamin D metabolism is linked to calcium absorption and parathyroid hormone. Susceptible populations for marginal vitamin D status include children under three years of age, the elderly and any population where cultural practices or climatic conditions prevent exposure to sunlight. Some research is currently being conducted to evaluate the effect of sun screens on vitamin D status. It is important to note, however, that there is a need to develop reliable, accurate, simple and rapid methodology for the assessment of vitamin D status. Without this it is difficult to make required adjustments to fortification practices based on feedback from comprehensive monitoring of the impact of fortification on vitamin D status.
Vitamin E
Vitamin E, as tocopherol acetate, is added to fats and oils including margarine and fat spreads and breakfast cereals.
Vitamin E intake is known to be related to the total dietary intake of fat and it has been shown to enhance absorption and bio-conversion of dietary carotenoids to vitamin A. Emerging evidence indicates that daily intake of vitamin E greater than 30 IU may afford protection against the development of degenerative diseases. Optimal levels of fortification of vitamin E should be reassessed based on such scientific evidence.
Vitamin C
There are technologies available for vitamin C fortification of fruit juices, fruit juice drinks, other related beverages, dairy products and some breakfast cereals. Vitamin C, as used in foods, is known to improve iron bioavailability. High moisture content (greater than 7%) in the presence of oxygen is known to adversely affect the stability of vitamin C in cereals. There is a need to develop more stable vitamin C compounds and evaluate their use in the fortification of a range of vehicles.
There is much ongoing investigation on the role of vitamin C in the prevention of chronic diseases such as cardiovascular disease, cancer and cataracts. Based on the outcome of such research it may be desirable to revise fortification practices for this vitamin.
B-Complex Vitamins
There are no problems related to the technology of the addition of B vitamins to cereals and grains. The development of off-flavours due to the thermal instability of thiamine is easily circumvented by adding this vitamin following all heat treatments.
Riboflavin is thought to be associated with anaemia prevention and its role in this association needs to be clarified. The status of B complex vitamins is known to be marginal in populations with low consumption of animal foods (milk, meat, liver) and/or those which use low extraction (highly refined) products of cereals and grains such as flour as well as in populations in transition from rural to urban settlements. Food fortification with B complex vitamins may be appropriate for such populations. The development of improved methodologies for the evaluation of B-vitamin status would be a valuable tool in establishing the need for fortification in target populations and in the monitoring of these programmes.
A confirmed association between dietary folic acid intake and neural tube defects has been reported. Populations with marginal or low folic acid intake may therefore benefit from fortification of staples with folic acid. Furthermore, folic acid together with vitamin B6 and vitamin B12 have been reported to decrease plasma homocysteine levels; the latter is reported to be inversely associated with the development of ischaemic heart disease. Further investigation of these relationships is relevant to the evaluation of the adequacy of current fortification practices.
Practical Problems Encountered in Establishing Fortification Programmes
With the expanding range of fortificant compounds available and the need to use various vehicles according to the designated target groups, there is need to consider the technologies best suited to achieve a fortified product with the desired properties. The Consultation agreed that, ideally, a fortified food should:
- Be commonly consumed by the target population;
- Have a constant consumption pattern with a low risk of excess consumption;
- Have good stability during storage;
- Be relatively low in cost;
- Be centrally processed with minimal stratification of the fortificant;
- Have no interaction between the fortificant and the carrier food;
- Be contained in most meals with availability unrelated to socio-economic status;
- Be linked to energy intake.
Selection of an appropriate vehicle is a critical step in successful fortification. In many cases identification of suitable vehicles is made difficult by the absence of reliable information on dietary habits of the target population.
The desirability of providing detailed methodologies for the fortification of foods to countries with limited resources interested in carrying out such activity, was recognised. It was decided, however, that the primary task of the Consultation should be to use its experience to guide policy-makers towards an understanding of the complexity of the issues involved in food fortification, rather than to provide a 'procedural manual' for the production of selected fortified foods. In recognition of the fact that the need for information on technical procedures in the fortification of foods still exists, the Consultation recommended that a database, documenting fortification practices and new developments, be established and maintained. This would facilitate ready access to such information internationally, thus reducing wastage of resources and improving efficiency in the establishment of food fortification.
- There have been a number of important lessons learned in the technical research and development work carried out for food fortification processes. These include:- The long time and high cost required for the development of new combinations of fortificants and vehicles must be considered in planning fortification activity.
- Fortificants must meet quality criteria specifications explicitly established for each application, including; chemical stability, appearance, bioavailability and homogeneity.
- Field testing of fortified food must be done at several locations in the country of intended fortification use, due to differing environmental conditions, and consideration should be given to problems potentiated by scaling up production activities from pilot to industrial scale.
- In certain situations promotion of production and consumption of fortified foods proved to be a critical factor influencing the acceptability of the food.
- Active participation must be maintained by all partners involved in fortification programmes. These should include; relevant governmental organizations, food industry, trade organizations, consumer organizations, academic and research facilities, marketing specialists and interested international organizations and agencies.
Source: https://www.fao.org/3/w2840e/w2840e03.htm
