Red meat and food guides.

KEY POINTS

* A re-examination of equivalence between meats and alternatives in food guides is required in view of new recommendations for intakes of long-chain omega-3 fatty acids and the issue of bioavailability in relation to iron and zinc.

* While plant-based alternatives provide protein, with some exceptions, they are generally poorer sources of bioavailable iron and zinc and do not contain vitamin B12 or long-chain omega-3 fatty acids.

* If a single guide to suit all styles of eating is retained, consideration will need to be given to the amounts recommended for this food group.

* An alternative is to provide separate guides for omnivorous and vegetarian cuisines, in which case the plant-based alternatives in the former could be relocated with the vegetable category, or in the case of nuts and seeds, within a category of healthy fats and oils (as sources of essential fatty acids and fat-soluble vitamins).

INTRODUCTION

In 2006, a new set of nutrient intake recommendations, the Nutrient Reference Values (NRVs), were jointly produced by the Australian and New Zealand Governments under the auspices of the National Health and Medical Research Council. (1)

The NRVs contain recommendations about the daily amounts of the various nutrients required for adequate physiological function and/or prevention of deficiency states (estimated average requirements (EAR), and recommended dietary intakes or adequate intakes) and, for some nutrients, there was an additional set of recommendations for chronic disease prevention, an area not addressed in earlier versions of national nutrient recommendations.

Traditionally, the role of diet in chronic disease prevention has been primarily addressed in the essentially qualitative Australian Dietary Guidelines, (2-4) which provide general guidance on optimal patterns of eating for health within the cultural context. The guideline statements take the form of food choice strategies, such as 'eat less fat'. The Dietary Guidelines also address related issues that can affect chronic disease risk, such as the need for physical activity, prevention of weight gain and breastfeeding.

In the NRVs, suggested dietary targets for reduction of chronic disease risk were set at the 90th percentile of current population intake for selected micronutrients, dietary fibre and long-chain omega-3 fatty acids and, for macronutrients, an acceptable macronutrient distribution range (AMDR) was set for protein at 15-25% energy, for fat at 20-35% energy, and for carbohydrate at 45-65%. AMDRs were also set for n-6 fats at about 5-10% of energy, and total omega-3 fats at 0.5-1% of energy. This paper discusses the application of these new values in the development of food guides, and in particular the position of red meat in this context.

TRANSLATING NUTRIENT RECOMMENDATIONS INTO FOOD INTAKE PATTERNS

For education purposes, nutrient recommendations such as the NRVs have been 'translated' into a set of recommendations for amounts of foods or food groups using a computer modelling process (5) and relevant food databases to form a national food guide. The current Australian guide, (6) which is soon to be updated to match the new NRVs, is called the Australian Guide to Healthy Eating (AGHE).

The recommendations for nutrient intakes, the food guide and various sets of dietary guidelines are interrelated and, over time, are becoming more overtly integrated. For example, the AGHE was integrated in the latest reviews of the Dietary Guidelines, and the nutrient recommendations were expanded to encompass considerations for chronic disease.

The information contained in the national food guide is presented as recommendations for consumption of various serves per day of selected food groups. These are groupings of foods with a general commonality of nutrient profile. In Australia, the commonly used food groups (so-called core food groups) are a cereals/grains-based group (breads, cereals, rice, pasta, noodles), a milk-based group (milk, yoghurt, cheese), fruits, vegetables and legumes, and a group sometimes termed meats and alternatives (meat, fish, poultry, eggs, nuts, legumes). In the AGHE, the cereals group is described as providing carbohydrates, protein, fibre and a wide range of vitamins and minerals; the milk group as providing calcium as well as protein, riboflavin and vitamin B12; fruits as providing vitamins, notably vitamin C and folate, natural sugars and fibre; and vegetables and legumes as providing vitamins especially vitamin A and C, folate, minerals, dietary fibre and carbohydrate.

The meat and alternative category is perhaps the most nutritionally diverse food group designed to include the needs of both omnivores and vegetarians. According to the AGHE, this category provides protein, iron, zinc, niacin and vitamin B12 and states that, within this group, red meat is a particularly good source of iron and zinc. Protein is provided by all foods in the current meat and alternatives group. Iron is more of an issue because of the low bioavailability of plant-based iron sources. As with iron, zinc from animal sources is generally better absorbed than zinc from plant foods. Vitamin B12 is found only in animal-based foods, so dietary vitamin B12 deficiency can be a problem in strict vegetarians, who exclude all sources of animal products, such as eggs and dairy products, and/or do not take a B12 supplement or consume sufficient amounts of B12-fortified plant products.

The recent inclusion of recommendations for intakes of long-chain omega-3 fatty acids in the NRVs warrants consideration in relation to equivalence across the meat and alternatives group. At present, the two main dietary sources of long-chain omega-3 fatty acids are included in this group, namely fish and red meat. This inclusion of long-chain omega-3 fatty acids in the NRVs is in recognition of their important role as membrane lipids, particularly in nerve tissue and the retina. In recent years, research has shown both cardiovascular and anti-inflammatory benefits of long-chain omega-3 fatty acids. (1,7)

THE PROBLEM OF EQUIVALENCE

Figure 1 shows the nutrient equivalences for the key nutrients discussed above, across this food group for approximately equicaloric serves of meat and non-meat choices. For a serve providing about 600-850 kJ (the energy range identified by the AGHE), nuts and seeds provide substantially less protein per serve than the animal-based foods or legumes. Legumes in turn provide markedly less than the flesh-based animal foods but a similar amount to eggs.

The lean red meat, eggs and legume serves are the best providers of iron; however, the iron content of legumes is highly variable and is less bioavailable than that from animal sources. Bioavailability was addressed in setting the new NRV for iron, where iron intake requirements for plant-based diets were set some 80% higher than for omnivore diets. Non-red meats (chicken, pork), fish, nuts and seeds are generally much poorer sources of iron than lean red meats.

For zinc, the lean red meat and pork serves are the outstanding contributors, providing two to three times as much per serve compared with the other options.

Vitamin B12 and long-chain omega-3 fatty acids are provided only by the animal-based options. Fish generally provides the highest amount of long-chain omega-3 per serve, but the contribution is highly variable, with fish providing anywhere from 100 to 2500 mg/100 g, depending on the type and fattiness of the fish. In Australia, because of the animal feeding practices, beef and lamb (as well as chicken) also provide significant amounts of long-chain omega-3. A serve of lean beef/lamb will provide about half the long-chain omega-3 of a serve made up of 50% snapper (a lower-fat fish) and 50% tuna (an oily fish). A serve of pork or eggs provide lesser amounts, but none is available from the plant-based options. Vitamin B12 is provided only by the animal-based options, and among these, chicken is a somewhat lesser source. Liver and kidney are particularly good sources.

A recent computer simulation analysis of the potential contribution of the various 'meat and alternatives' options to nutrient intake in men, women and pregnant women (8) showed that diets designed to conform to the current AGHE incorporating serves of vegetable origin from this group did not meet the new NRV for vitamin B12 and long-chain omega-3 fatty acids for any of the groups assessed, nor for zinc in men and pregnant women or iron in women and pregnant women. This paper concluded that the placement of legumes, nuts and seeds in future food guides may need review, and that the recommended number of serves from the meats and alternatives group may also need to be reconsidered. Even within the 'meat-based' options, there were some highly variable contributions seen in this analysis. For example, three serves of eggs and four serves of pork were required to deliver the adequate intake for long-chain omega-3 fatty acids for men, whereas only one serve of fish or red meat was required. With respect to zinc, three serves of chicken, four serves of eggs and five serves of fish were needed to achieve the EAR for men, whereas only one serve of red meat was required. To address this lack of equivalence, the AGHE currently recommends that lean red meat be eaten three to four times each week.

[FIGURE 1 OMITTED]

RED MEAT AND FOOD GUIDES

If a wider variety of choices within this food group are to be encouraged, more than one 'serve' a day from the 'meat and alternatives' group (or a substantially increased serve size than that currently used in the AGHE) would appear to be necessary. It is of interest to note that the most recent US (9) and Canadian Food Guides, (10) based on the new US-Canadian Dietary Reference Intakes, (11) have a substantially higher intake recommendation for the group as a whole than the basic AGHE pattern (about 170 g/day meats for an average man in the USA and 225 g/day in Canada). This is closer to the upper end of the 'alternative' eating pattern of the AGHE of 1.5--two serves for men (100-200 g). While the US and Canadian recommendations differ with respect to the daily 'meat' recommendations, there is a twofold variation in the recommendations for the non-meat alternatives arising from the different approaches used in determining equivalence for these options (energy, protein, iron, zinc or some combination thereof).

As Figure 1 shows, if nutrient density (nutrient/unit energy) is the basis for comparison, then lean red meat is the optimal choice within this food group providing all the key nutrients ascribed to the group, being the outstanding contributor to bioavailable iron and zinc and a good contributor to protein, vitamin B12 and long-chain omega-3 fatty acids. Fish is very good for these latter two nutrients but substantially poorer for iron and zinc; pork is not quite as good as red meat for iron or long-chain omega-3; chicken is substantially poorer for iron, zinc and vitamin B12; and eggs are poorer in zinc and long-chain omega-3 fatty acids.

Of the non-meat alternatives, none provides any vitamin B12 or long-chain omega-3. Legumes are the best option for iron and zinc, but the nuts and seeds are very poor sources of these nutrients. Nuts and seeds, however, are very valuable sources for vitamin E and, together with legumes and other plant-based foods, in epidemiological studies have been associated with a number of health benefits related to chronic disease prevention.

SUMMARY

The issue of nutritional equivalence and nutrient density is of particular importance in energy-restricted diets where there is a need to choose nutrient-dense options. To this end, regular inclusion of lean red meats in energy-restricted diets provides the best option to ensure adequate nutrient intake for the key nutrients provided by this group.

REFERENCES

1 Commonwealth Department of Health, NZ Ministry of Health, National Health & Medical Research Council. Nutrient Reference Values Including Recommended Dietary Intakes. Canberra: NHMRC, 2006.

2 National Health & Medical Research Council. Dietary Guidelines for Australian Adults. Canberra: NHMRC, 2003.

3 National Health & Medical Research Council. Dietary Guidelines for Children and Adolescents in Australia. Canberra: NHMRC, 2003.

4 National Health & Medical Research Council. Dietary Guidelines for Older Australians. Canberra: NHMRC, 1999.

5 Cashel K, Jefferson S. The Core Food Groups: The Scientific Basis for Developing Nutrition Education Tools, Rescinded. Canberra: National Health and Medical Research Council, 1995. Rescinded February 2000.

6 Commonwealth Department of Health & Family Services. The Australian Guide to Healthy Eating: Background Information for Nutrition Educators. Publication No. 2361. Canberra: CDHFS, 1998.

7 World Health Organisation. Diet, Nutrition and Prevention of Chronic Disease. WHO Technical Report Series 916. Geneva: WHO, 2003.

8 Shrapnel W, Baghurst K. Lack of nutritional equivalence in the 'meats and alternatives' group of the Australian Guide to Healthy Eating. Aust J Nutr Diet (in press).

9 United States Department of Agriculture. Mypyramid. Washington: USDA, 2006. (Cited 10 June 2007.) Available from URL: http://www.mypyramid.gov/mypyramid/index.aspx

10 Health Canada. Eating Well with Canada's Food Guide. Ottawa: Ministry of Health, 2007. (Cited 10 June 2007.) Available from URL: http://www.healthcanada.gc.ca/foodguide

11 Food and Nutrition Board: Institute of Medicine. Dietary Reference Intakes. Washington, DC: National Academy Press, 1998-2004. (Several volumes).

Katrine BAGHURST

University of Adelaide, Adelaide, South Australia, Australia