Has agricultural intensification reduced the nutritional quality of food? Dr Anne-Marie Mayer Consultant on Nutrition and Agriculture Self-funded independent research
Questions Has the nutrient composition of foods changed in the period of agricultural industrialisation? What could be the causes of any differences? What are the potential consequences for human nutrition?
History of British Composition of Foods Editions 1936 Nutritive value of Fruits, Vegetables and Nuts 1940 Chemical Composition of Foods 1946 Composition of Foods II 1960 Composition of Foods III 1978 Composition of Foods IV 1991 Composition of Foods V 2002 2013 Composition of Foods VI Nutrient Analysis of Fruits and Vegetables
Historical changes in the mineral content of fruits and vegetables Anne-Marie Mayer Historical changes in the mineral content of fruit and vegetables. AB Mayer, British Food Journal 1997 99(6) 207-211
Original Comparison UK Average a percentage change over 50 years (1936 to1985) in mineral content of 20 vegetables and 20 fruits b Ca Mg Fe Cu Na K P Dry matter Water Vegetables % change -19% -35% -22% -81% -43% -14% -6% -3% -0% p value c 0.014 * 0.000 ** 0.088 0.000 ** 0.013 * 0.090 0.487 0.53 0.872 Fruits % change 0% -11% -32% -36% -10% -20% -1% -9% +2% p value 0.957 0.016 * 0.002 ** 0.006 ** 0.561 0.000 ** 0.903 0.023 * 0.006 ** a Geometric mean, the antilogarithm of the mean of the logarithm of the ratio of 1980s to 1930s values b Vegetables:- beetroot, brussel sprouts, cabbage - winter, carrots - old, celery, lettuce, mushrooms, mustard and cress, onions, parsley, parsnips, peas, potatoes - old, pumpkin, runner beans, radishes, swedes, tomatoes, turnips, watercress. Fruits: apricots, bananas, blackberries, cherries, cooking apples, eating apples, grapes, grapefruit, lemons, melon cantaloupe, nectarines, oranges, passion fruit, peaches, pears, pineapple, plums, raspberries, rhubarb, strawberries c Probability that average ratio of new:old is statistically different from 1 by t-test. * = significant at the 5% level ** = significant at the 1% level.
Other historical changes in the composition of foods: meat and dairy products (UK) 1936 to 1985 Ca Mg Fe Cu Na K P Meat (10 cuts) Milk (whole) Cheese (cheddar) -41-10 -54-24 -30-16 -28-4 -21-38 - +10-12.5-3 -11-47 -47 nc - -34-10 David Thomas 2001 Mineral depletion in foods over the period 1940 to 1991. The nutrition practitioner (3.2) 27-29
Other sources of data on historical changes in the composition of garden crops: USA 1950 to 1999 Ca Mg Fe Cu Na K P Dry matter Water USDA data -23% - -27% - - - -14% -3% +1% P value 0.0005 ** - 0.0004 ** - - - 0.01 * 0.287 0.043 Donald Davis Melvin Epp and Hugh Riordan. Changes in USDA Food Composition Data for 43 garden crops 1950 to 1999. Journal of the American College of Nutrition 2004 23(1) 38 vegetables 5 fruits included in the analysis. Corrected for changes in the water content
Mineral contents of historical and modern varieties of wheat Murphy Reeves and Jones. Relationship between yield and mineral concentrations in historical and modern spring wheat cultivars, Euphytica (2008) 163:381 390
Has the nutrient composition of foods changed in the period of agricultural industrialisation? What could be causing the declining nutrients?
The Composition of foods Fifth Edition 1991 The nutritional value of many of the more traditional foods has changed. This can happen when there are new varieties or new sources of supply for raw materials; with new farming practices which can affect the nutritional value of both plant and animal products Holland, B. Welch, A.A. Unwin, I. D. Buss, D.H. Paul, A.A. and Southgate, D.A.T., McCance and Widdowson s Composition of Foods fifth edition, HMSO, London, 1991
Possible Reasons for the reduced levels of minerals 1. Changes in varieties/ cultivars genetic dilution Wheat, maize, broccoli 2. Changes in the methods of agriculture dilution effect related to increased yield 3. Other environmental changes, e.g. CO2 levels Small reductions in mineral content related to increased CO2 4. Soil mineral and microbiological changes Mycorrhizal symbiosis providing minerals from soils 5. Changes in the food systems Sources of foods, storage methods 6. Changes in methods of analysis of food samples
Latest data UK Average a percentage change in mineral content (1985 to 2012) of 13 vegetables Ca Mg Fe Cu Na K P Zn Dry matter Water % change +2% +25% -34% +85% -7% -0.7% -16% +0.3% -16% +1.5% P values 0.81 0.07 0.01 * 0.01 * 0.81 0.92 0.04 * 0.98 0.09 0.09 These results are broadly similar to existing data held. There is no evidence of major changes in the nutrient content of fruit and vegetables based on this survey and any changes are unlikely to be nutritionally significant in a varied diet Department of Health UK (2013). Nutrient analysis of fruit and vegetables. a Geometric mean, the antilogarithm of the mean of the logarithm of the ratio of 1980s to 1930s values b Vegetables Broccoli, cabbage, carrots, cauliflower, cucumber, lettuce., mushrooms, onions, peas, pepper red, potatoes, runner beans, tomatoes c Probability that average ratio of new:old is statistically different from 1 by t-test. * = significant at the 5% level ** = significant at the 1% level.
What are the potential consequences for human nutrition?
Percentage of respondents with average daily dietary intakes of minerals below the Lower Reference Nutrient intake in the UK 1-3 4-10 11-18 19-64 65+ % % % % % Iron 6 1 26 12 2 Calcium 1 2 14 7 4 Magnesium 1 2 40 14 13 Potassium 1 0 25 17 14 Zinc 5 9 17 7 5 Selenium 1 1 33 38 42 Iodine 1 3 16 8 2 Bases (unweighted) 604 1277 1497 2697 753 National diet and nutrition survey 2012 table 5.35
Essential Nutrients- there are many Macronutrients Carbohydrates Proteins Fats Water-soluble vitamins Vitamin C Thiamin (B1) Riboflavin (B2) Pyridoxin (B6) Cobalamin (B12) Folate/ Folic acid Panthothenic Acid Niacin Biotin Minerals Calcium Phosphate Magnesium Sodium Chloride Potassium Fat-soluble vitamins Vitamin A & carotenoids Vitamin D Vitamin E Vitamin K Trace Elements Iron Zinc Iodine Selenium Chromium Copper Boron Manganese Molybdenum some others
Nutrient interactions and interdependencies Red blood cells require iron, vitamin A, vitamin B12, folic acid, zinc, copper, cobalt Carbohydrate metabolism requires vitamins B1, B2, B3, B5, B6, B12, folate, biotin plus chromium, cobalt Bone health requires calcium, protein, magnesium, phosphorus, vitamin D, potassium, manganese, copper, boron, iron, zinc, vitamin A, vitamin K, vitamin C, and the B vitamins
Comments on historical changes in food composition Response has been. To market dietary supplements Plant breeding approaches including biofortification with Fe, or Zn or Vitamin A Single micronutrient soil or plant fertilisers e.g. Zn What about. Use of traditional plant varieties and agro-biodiversity? Soil health > Plant health > Human health connections Agro-ecological approaches to increase a whole range of nutrients
Recommendations More frequent monitoring of the nutritional quality of foods with annual publication of results Partnerships between agriculture and nutrition to research quality of foods related to breeding and agronomic trials with agreed protocols. A rethink on the productionist paradigm with its possible trade-offs for nutrition particularly in very poor countries. Dilution effect- can it be overcome? Nutritionists to work on increased understanding of the inter-relatedness of nutrients for health, thus encouraging more holistic solutions rather than single nutrient solutions to malnutrition Consumers keep eating fruit and vegetables (organic if possible) and diversify. Also to consider post harvest and processing losses..
Anne-Marie Mayer https://annemariebmayer.wordpress.com/