Results of study on trans fatty acids in local foods

The Centre for Food Safety (CFS) today (July 8) released results of the third study on the levels of trans fatty acids (TFA) in local foods.

"The study aimed to examine the nutrient contents of some common local foods, especially their TFA content, and to formulate advice to the trade and the public on the basis of the fat content in foods measured in this study and two previous ones," the Centre's Consultant (Community Medicine) (Risk Assessment and Communication), Dr Ho Yuk-yin, said.

Fat plays an important role in our diet. It is a concentrated energy source (1 gram (g) fat equals to 9 kilocalories (kcal)), which also aids in the absorption of fat-soluble vitamins (i.e. vitamin A, D, E, and K) and provides essential fatty acids that are not produced by our body. When eaten in moderation, it promotes maintenance of good health. Excessive fat intake, however, has been linked to major health problems, such as increased risks of heart disease, obesity and certain types of cancers.

TFA are unsaturated fats that exist naturally in milk, cheese, butter, and meat and meat products of ruminants (such as cattle and sheep). They can also be generated during the industrial hydrogenation and deodorisation of vegetable oils, and heating and frying of oils at extremely high temperatures.

Intake of excessive TFA increases the risk of coronary heart disease and its effect is considered to be even greater than saturated fatty acids (SFA) because TFA not only raise the level of low density lipoprotein cholesterol ("bad" cholesterol) but also reduce the high density lipoprotein cholesterol ("good" cholesterol).

The World Health Organisation and the Food and Agricultural Organisation of the United Nations recommend that daily energy intake from TFA and SFA should be less than 1% and 10% respectively of the total energy intake. Using the conversion factor of 1g fat equals to 9kcal of energy, an adult with a daily energy intake of 2,000 kcal should limit TFA and SFA intakes to less than 2.2 g and 22.2 g per day respectively.

Sampling from food premises and supermarkets, the Centre analysed the levels of TFA in 59 food items in six groups, comprising snacks, bakery products, other ready-to-eat foods (including fast food and dim sum), milk and milk products, oils and fats, and beverages.

The results showed that, on a per 100g basis, about 30% of foods had TFA of more than 0.3g. The highest TFA (mean) content was found in oils and fats (2.3g), followed by bakery products (0.48g), milk and milk products (0.3g), other ready-to-eat foods (0.13g), snacks (0.073g), and beverages (0.02g).

On a per unit basis, foods with puff pastry were high in TFA levels. A bowl of cream soup with puff pastry (total 315g) had 1.6g of TFA, 1.1g of which came from the puff pastry. The total TFA equals to 73% of an adult's daily TFA intake limit while the amount in the puff pastry alone amounts to 50% of that limit.

The four types of liquid vegetable oils tested contained TFA ranging from 0.11g to 0.97g per 100g.

"The results showed that TFA levels of the foods tested varied greatly. In general, oils and fats (especially margarines) as well as bakery products (especially puff pastry products) had high TFA content. All vegetable oils tested contained TFA. Besides having high TFA content, some dairy- or cheese-containing foods also contained high SFA content per unit," Dr Ho said.

"The food trade is advised to modify the manufacturing process to lower TFA content in foods and oils/fats. The TFA amounts should be stated in the nutrition labels of pre-packaged foods to enable consumers to make an informed choice. They can refer to the Centre's ‘Trade Guidelines on Reducing Trans Fat in Food' (www.cfs.gov.hk/english/food_leg/files/trans-fats-guide-e.pdf) for alternatives to provide healthier food choices to consumers."

Members of the public are advised to:
* maintain a balanced diet and avoid excessive intake of certain types of food;
* consume infrequently foods that contain a high level of TFA, such as foods with puff pastry;
* reduce the use of oils and fats in preparing foods;
* use liquid vegetable oils rather than animal fats;
* choose foods on the basis of their overall nutrient profile, including the TFA and SFA amounts; and
* use margarines and butter sparingly.

Members of the public can refer to the information in the food labels (including the ingredient lists and the nutrition labels) and food composition databases, such as the Centre's Nutrient Information Inquiry System (www.cfs.gov.hk/english/nutrient/index.shtml), to make healthier food choices.

Ends/Wednesday, July 8, 2009