In 1988 the BMJ published data from the Intersalt study suggesting that populations with high average intakes of salt were likely to have higher average systolic blood pressures and that salt intake predicted rise in blood pressure with age.4 The salt producers' international trade organisation, the Salt Institute, criticised the study, particularly the methods used to relate blood pressure to age, and asked the investigators to hand over their raw data for reanalysis. The investigators instead performed the reanalyses themselves: these appear on p 1249,5 confirming the previous findings. The Salt Institute sent the BMJ a letter in response to the reanalysis, and this appears on p 1 283,6 along with a commentary from an independent expert (p1284; and an answer from the Intersalt investigators (p1285).8
The Salt Institute's letter is the latest volley in a 20 year campaign by the food industry, waged since the role of diet in heart disease first became a public health issue. The aim is to promote the view that data from population studies have little bearing on individual patients and, in the case of salt, no basis in human physiology. This individualist view has influential proponents, including the current director of NHS research and development, Professor John Swales,9 and it currently guides government policy in Britain. Because of it the government's strategy for health, Health of the Nation, gives no target for dietary salt reduction (although it does ask food manufacturers to explore the development of products with less salt).10 Also because of it, the recommendations on salt from a major review of diet and cardiovascular disease2 have been ignored.
In 1994 the third review from the cardiovascular review group of the government's advisory committee on medical aspects of food policy recommended that people should reduce their salt intake by a third, from a daily average of 9 g (150 mmol) to 6 g (100 mmol).2 While endorsing the group's other recommendations at the launch of the report in November 1994 Britain's chief medical officer, Sir Kenneth Calman, specifically cast doubt on the evidence linking salt and blood pressure and emphasised that this recommendation was not part of government policy.
The food industry has everything to gain from keeping controversy alive.11 Common salt is the main source of flavour in processed foods. Tasting panels show that low salt foods are often unappetising, and there is currently no good alternative to sodium chloride. Improving flavour by adding more natural ingredients (such as fruit and vegetables) would be expensive.
The food industry has lobbied fiercely against the threat to its profits. In June 1994, after confidential drafts of the cardiovascular review group's report were circulated to the government's nutrition task force (which included at least one consultant to the food industry), representatives of Britain's four major manufacturers of sweets and snacks-Cadbury Schweppes, Tate and Lyle, United Biscuits, and Mars-demanded a meeting with the Department of Health. The department made no concessions. That year United Biscuits stopped its contributions to the Conservative party and Tate and Lyle shifted nearly half its annual donation to the opposition parties.
In May 1995 industry representatives on the government's nutrition task force declined to participate in discussions on how to reduce the salt content of their products.11 In October the task force was disbanded on the grounds that its terms of reference had been fulfilled even though its remit was to implement healthy eating into the next century.
The tactics over salt are much the same as those used by other sectors of industry. The Sugar Association in the United States and the Sugar Bureau in Britain have waged fierce campaigns against links between sugar and obesity, and dental caries. Publication of a report from the World Health Organisation on diet and chronic disease15 was delayed by representations from the sugar industry and 40 ambassadors from sugar producing countries who had been alerted by the industry. A delay in the introduction of regulations on salt in Britain is perhaps the best that salt producers can expect. Elsewhere they have already lost the battle. The United States departments of agriculture and health have recently recommended a daily average salt intake of no more than 6 g for the general population16 despite representations from the Salt Institute and other bodies. Scandinavian countries have also adopted lower salt programmes. In Finland doctors only receive full reimbursement for antihypertensive drugs if they have given patients a six month trial of weight loss, alcohol restriction, and salt reduction (J Huttunen, personal communication).
But delay has its cost, to commercial interests as well as the public's health. While the Salt Institute fights, other players in the food industry are changing. Many manufacturers have already diversified into low salt products, while others such as Heinz have been reducing the salt content of their products. The sodium content of 100 American foods monitored by the Centre for Science and the Public Interest has fallen by 10-15% over the past 12 years.
Despite these trends, governments have a tough job ahead. The world's food and soft drink industry spent over £55Om on advertising in 1994, compared with less than £5m on promoting fresh fruit and vegetables.18 In Britain, basic cooking skills are in decline19 as processed foods make up more of the average diet. To counter these forces governments will need to invest substantial resources in health education. The British government should be congratulated on the achievements of the Health of the Nation. But if it is serious about reducing premature deaths from cancer and heart disease it will need to ignore the voices of vested interest and listen to the advice of its independent expert advisors
Fiona Godlee Assistant editor, BMJ, London WC1H 9JR
2 Nutritional aspects of cardiovascular disease. Report of the cardiovascular Review Group, Committee on Medical Aspects of Food Policy. London HMSO, 1994
3 Gregory J Forster K, Tyler H, Wiseman M. The dietary and nutritional survey of British adults. London: HMSO, 1990
4 Intersalt Cooperation Research group. Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium. BMJ 1988;297:319-28
5 Elliot P, Stamler J, Nichols R, Dyer AR, Stamler R, Kesteloot H, et al for the Intersalt Cooperative Research Group. Intersalt revisited: further analyses of 24 hour sodium excretion and blood pressure within and across populations. BMJ 1996; 312:1283-4
6 Hanneman RL. Intersalt: hypertension rise with age revisited. BMJ 1996;312:1283-4
7 Law M. Commentary: evidence on salt is consistent. BMJ 1996;312:1284-5
8 Stamler J, Elliott P, Dyer AR, Stamler R, Kesteloot H, Marmot M for the Intersalt steering and Editorial Committee. Commentary: Sodium and blood pressure in the Intersalt study and other studies-in reply to the Salt Institute. BMJ 1988;312:1285-7
9 Swales J. Salt saga continued BMJ 1988;297:307-8
10 Secretary of State for Health. health of the nation: a strategy for health in England. London : HMSO, 1992:54
11 Blackburn h, Jacobs D, Sources of the diet-heart controversy: confusion over population versus individual correlations. Circulation 1984;70:775-80
12 Marks K, Coming soon: what you can and can't eat. Daily Telegraph 1994 Aug 9 1994
13 Anderson D. Take nanny's latest menu with a large pinch of salt. Daily Telegraph. 1994 Aug 9
14 Department of Health. A progress report from the Nutrition Task Force on the action plan to achieve the Health of the nation targets on diet and nutrition. London DoH, 1996
15 World Health Organisation. Diet, nutrition and the prevention of chronic diseases. Geneva: WHO 1990.
16 US Department of Agriculture, US Department of Health and Human Services. Dietary guidelines for Americans. 4th ed. Washington DC: US Government Printing Office, 1995
17 Jacobson MF, Liebman BF. Sodium in processed foods. Am F Clin Nutrition 1996:63:138
18 Dibb SE, Castell A. Easy to swallow, hard to stomach. London: National Food Alliance, 1995
19 Caraher M, Dixon P, Lang T, Buying and eating and cooking food: a review of the national data set on food attitudes, skills and behavioural change. London: health Education Council, 1996