Epidemiological studies into changing patterns of food consumption and disease statistics can provide valuable insights into the relationships between diet and health. In Great Britain data from national statistics show that amount of fat consumed has fallen from 120gm/day in 1969 to 74gm/day in 2000. When expressed as a proportion of energy consumed the fat intake has decreased from 42.6% in 1980 to 37.7% Calories in 2010.At the same time there has been an increase in the energy as carbohydrate from 44.4 t0 47.4%. Consideration of the different types of fats shows that between 1969 and 2000 that the intake of saturated fat (SFA) has fallen from 56.7 to 29.2 g/day. In other words it has been reduced by almost half!
Healthy Eating has now been actively promoted in the UK for at least a quarter of a century. There is no question that one of the driving forces for these changes was the official UK Committee on Medical Aspects of Food Policy (COMA) in 1984 which recommended:
- Total fat as a percentage of total daily energy should be reduced from 42 to 31-35% calories
- Saturated fat should be reduced from 20 to 15% calories
- Polyunsaturated fat could be increased.
It is evident that the national diet has changed in accordance with these recommendations. The response from the food industry and from consumers has been very positive as demonstrated by the development of extensive ranges of low fat products. A good example of the success of these strategies is the growth in sales of semi-skimmed milk which is now the predominant liquid milk product. However it should also be noted that the reduction in total fat has been largely replaced by an increase in carbohydrates much of which consists of sugar.
Table 1 Changes in the intakes of fat in Great Britain
|Year||Total fat, g/day||Saturated fat , g/day||Monounsaturated fat, g/day||Polyunsaturated fat, g/day|
Source: National Food Survey.
Note: The National Food Survey was replaced by Family Food in 2000 so that data collected since then is not comparable.
. The justification for recommending a reduction in total fat was that as a concentrated source of calories it was a major contributor to obesity. As SFA were considered to raise the level of blood cholesterol (TC) it was concluded that reducing SFA would lower the TC with a consequential reduction in the risk of heart disease. Therefore it is highly relevant to see what has actually happened to some of the key indicators of public health.
The Health Survey for England is a valuable source of information on the state of public health and this has been used to prepare the following tables (1).
Table 2 shows that there have been large increases in the prevalence of obesity. The value for men has almost doubled since 1993.
TABLE 2 PREVALENCE OF OBESITY (BASED ON BMI>30)
|YEAR||ALL MEN ,%||ALL WOMEN,%|
In Great Britain the life-time risk of developing bowel cancer in men has increased from 3.5% in 1975 to 6.9% in 2008. In women there has been an increase from 3.9% to 5.4% over the same period. For females aged between 40 and 59 years the breast cancer rates have increased from 134/100,000 in 1979 to 215/100,000 in 2008 (2).
Table 3 shows that between 1994 and 2010 the incidence of diabetes has more than doubled for both men and women (1). The importance of these results cannot be underestimated. According to Diabetes UK there are 145,000 new cases of diabetes every year which means that the total number in the UK is about 2.6 million. In addition it is estimated that there are about 1 million people who have diabetes which has not been diagnosed and that 7 million people have pre-diabetes which means that they are up to 16 times more likely to develop diabetes than those who do not have the condition.
TABLE 3 PREVALENCE OF DIABETES
|YEAR||ALL MEN, %||ALL WOMEN,%|
However diabetes is in many ways just the tip of the iceberg because those who suffer from it are likely to experience further complications. These can include damage to small blood vessels which in turn leads to blindness, kidney failure and nerve damage. Deterioration of the larger arteries can contribute stroke and heart disease as well as difficulties in pregnancy and infection. The American Heart Association has concluded that adults with diabetes are two to four times more likely to have heart disease or a stroke than adults without diabetes.
EXPERIENCE OF OTHER COUNTRIES
The changes in food consumption patterns which have occurred in the UK over the past 25-30 years are in direct contrast with what happened in Spain between 1964 and 1991(3). Over this period the consumption of the main sources of carbohydrate in the diet: bread, pulses, pasta and rice declined from 43.8 to 20.4% of the total food intake. At the same time one of the main sources of fat, dairy products increased from 13.3 to 22.8% of food intake. Other important sources of fat including meat, fish and eggs increased from 10 to 19.7% (Table 4).
TABLE 4 CHANGES IN FOOD CONSUMPTION PATTERNS IN SPAIN BETWEEN 1964-65 AND 1990-1991
Between 1976 and 1990 the mortality rates from CHD declined from 126/100,000 to 110/100,000 in men and from 59/100,000 to 49/100,000 in women. The decline in deaths due to strokes was even more impressive. It fell from 171/100,000 to 104/100,000 in men and from 147/100,000 to 86/100,000 in women (Table 5).
The reduction in carbohydrates and the increase in fats would be expected to be accompanied by an increase in the death rate from heart disease if the rationale which underpins the dietary recommendations for the UK. In fact the reverse has actually happened with a decline in these death rates.
TABLE 5 CHANGES IN MORTALITY
|Coronary heart disease|
Essentially similar results have been reported for Japan. Between 1958 and 1995 the fat intake in the national diet increased by a factor of 4 due to the increased consumption of meat, eggs and dairy products(4). Inevitably much of the increased fat was saturated. Despite this change in the pattern of consumption there was no change in the incidence of heart disease. By contrast, the incidence of stroke fell by 85%.
- Health Survey of England 2010 Adult Trend Tables
- Cancer Research UK
- L. Serra-Majem et al (1995) American Journal of Clinical Nutrition 61 (supplement) pp. 1351S-1359S
- A. Okayama (1993) Journal of International Epidemiology 22 (6) pp 1038-104