Nutritional advantages of fat and oil
Fat is an efficient energy source capable of higher energy production than proteins and carbohydrates. Vegetable oils are mainly composed of oleic, linoleic and linolenic fatty acids making them an important source of essential fatty acids (linoleic and linolenic). When ingested together with various fat-soluble vitamins, fat also facilitates their absorption.
Increasing fat intake
According to a 2003 WHO Technical Report1), the average global supply of fat increased 20g per capita per day during the 30-year period of 1967-1969 to 1997-1999. The proportion of energy contributed by dietary fats exceeds 30% in the industrialized regions, and in nearly all other regions this share is increasing. Fat has a number of nutritional advantages, but ill-effects such as obesity and hyperlipidemia due to excess consumption aregrowing and becoming serious problems.
Increasing obesity
The prevalence of obesity is commonly assessed by using "body mass index" (BMI: body weight(kg)/height(m)2. The WHO assesses a BMI over 25kg/m2 as overweight and a BMI of over 30kg/m2 as obesity.2) In Japan, where even lower BMI values have been associated with an increased risk of obesity-related health problems, Japan Society for the Study of Obesity guidelines assess a BMI of over 25kg/m2 as obesity.3) According to a WHO report, globally, more than one billion adults are overweight, and at least 300 million of them are obese.4) The proportion of obese individuals in the USA has increased 2.6-fold among males and 2.2-fold among females over approximately 40 years since 1960, to a rate of 34.0%.5) In Japan, the number of obese males has shown an increasing trend, and in 2002, the rate of obesity, defined as BMI 25kg/m2 or greater, was 28.9% among males and 23.0% among females.6)
Considerations on diet for prevention of lifestyle-related diseases
Obesity is intimately related to the onset of lifestyle-related diseases such as hyperlipidemia, hypertension, and diabetes. Diet and exercise regimens play a crucial role in prevention and treatment of obesity. General considerations on diet include:
(1) |
The need for attention to quantity and quality of fat consumption |
(2) |
Adequate consumption of dietary fiber |
(3) |
Balance of vegetable proteins and animal proteins |
(4) |
The need for attention to excess sugar and alcohol intake. |
At the same time, restricting fat intake is difficult, and in reality, there is no progress at present. In recent times, the importance of "fat quality" and not simply "fat quantity" has been considered.
Applied research focused on nutritional characteristics of oils and fats
Active research on the composition of fatty acids, the components of oils and fats, is oriented as follows.
(1) |
Optimization of SMP ratio (SMP: Saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids)
(Saturated fatty acids include stearic acid; monounsaturated fatty acids include oleic acid; and polyunsaturated fatty acids include linoleic acid.) |
(2) |
Optimization of n-6 and n-3 unsaturated fatty acid ratio
(n-6 unsaturated fatty acids include linoleic acid and arachidonic acid; n-3 unsaturated fatty acids include a-linolenic acid and eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA.) |
(3) |
Influence of excess trans-fat consumption |
(4) |
Influence of EPA and DHA omega-3 fatty acids (n-3 unsaturated fatty acids) on coronary heart disease |
(5) |
Influence of monounsaturated fatty acids from olive oil on coronary heart disease |
In the field of edible oils, prevention of excess fat accumulation is guiding development of fat and oil substitutes and application of phytosterols possessing a cholesterol absorption-inhibiting effect.
Recently, attention has focused on the basic constituents of fats and oils themselves. With a principal component of diacylglycerol (DAG), one fatty acid removed from triacylglycerol (TAG) which is commonly present in many vegetable oil, "Econa" cooking oil has been developed. The nutritional characteristics of this oil have drawn attention.
References
1) |
Diet, Nutrition and The Prevention of Chronic Diseases, WHO Technical Report Series No. 916 (2003) |
2) |
Obesity: Preventing and Managing The Global Epidemic, WHO Technical Report Series No. 894 (2000) |
3) |
New criteria for ‘obesity disease’ in Japan, Examination Committee of Criteria for ‘Obesity Disease’ in Japan; Japan Society for the Study of Obesity, Circ J., 66, 987-992 (2002) |
4) |
Obesity and Overweight (2003), see WHO official web-site:
http://www.who.int/dietphysicalactivity/publications/facts/en/
|
5) |
Statistics Related to Overweight and Obesity, see Weight-control Information Network official web-site:
http://win.niddk.nih.gov/statistics/index.htm
|
6) |
The National Nutrition Survey in Japan, 2002, DAI-ICHI SHUPPAN PUBLISHING Co. LTD (2004), in Japanese |
