Food Safety Focus (33rd Issue, April 2009) – Food Safety Platform
Nutrient and Health – Cholesterol
Reported by Ms. Jacqueline FUNG, Scientific Officer
Risk Communication Section, Centre for Food Safety
We examined different types of fat in the last issue. This time, we will explore another common lipid - cholesterol.
Sources of Dietary Cholesterol
Dietary cholesterol is found in most animal foods, with egg white being an exceptional case. Often, people think that foods containing high saturated fat have significant amount of cholesterol. The truth is that there is no link between saturated fat and cholesterol contents in foods. For example, shrimps have high cholesterol (180mg cholesterol per 100g) and low saturated fat (0.4g saturated fat per 100g) contents.
|Illustration: Egg and cuttlefish have high cholesterol content|
Dietary Cholesterol and Lipoprotein
There is confusion about the difference between dietary cholesterol and blood cholesterol. Dietary cholesterol in food is a lipid compound and cannot be separated into "good" or "bad" ones, whereas the commonly known blood cholesterol in the body is a lipoprotein, which is a complex of lipids and proteins. Lipoprotein carries lipids from liver to cells and vice versa. In other words, lipoprotein is responsible for transporting triglyceride and cholesterol in the body.
The so called "bad" cholesterol and "good' cholesterol in blood are the low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), respectively. Generally speaking, individuals with higher level of "bad" cholesterol (i.e. LDL-C) and/or lower level of "good" cholesterol (i.e. HDL-C) will have higher risk of heart diseases.
Sources of Cholesterol in the Body
The relationship between dietary cholesterol and cholesterol in the body is rather intricate. Simply speaking, dietary cholesterol only contributes a small portion of the cholesterol in the body. Majority of the cholesterol found in the body is made by our own liver. For healthy individuals, there is a self-regulatory mechanism in our body to help control the level of cholesterol.
Functions of Cholesterol
Cholesterol is an important part of the cell membranes. Besides, it is the material for synthesising vitamin D, bile and some hormones, such as sex hormones (e.g. testosterone) and adrenal hormones (e.g. cortisol).
Health Effects of Cholesterol
Many people think cholesterol is the "bad" guy as it increases the risk of cardiovascular diseases. In point of fact, cholesterol is vitally important in the body and its adverse health effects are found only if the level exceeds certain limit.
Cholesterol is carried by lipoprotein in the body. While flowing in the bloodstream, some cholesterol forms deposits in the walls of the blood vessels which may lead to atherosclerosis (hardening of the arteries) and in turn increases the risks of developing heart attacks and strokes.
It is worth noting that some evidence shows that intake of saturated fat and trans fat are more critical than dietary cholesterol in terms of the risk of cardiovascular diseases. In particular, some findings indicate that increasing intake of saturated fat may increase the production of cholesterol in the body. Therefore, reducing the intake of dietary cholesterol alone may not help lower the blood cholesterol level. For heart health purpose, besides dietary cholesterol, we should pay more attention to the saturated fat and trans fat intake.
Intake of Dietary Cholesterol and Saturated Fat
According to the Chinese Adequate Intake (AI), less than 10% of energy contribution should come from saturated fat, which means that there should be less than 22g of saturated fat from all food sources in a 2 000-kcal diet. As for dietary cholesterol, the reference intake is not related to the energy requirement (i.e. the amount of kcal in the diet) as it does not contribute to energy production in the body. It is suggested that an adult should consume less than 300 mg (a much lower order than saturated fat) of dietary cholesterol daily.
Cholesterol Contents in Foods
|Food (per 100g, unless otherwise stated)||Dietary Cholesterol (mg)|
|Chicken egg (1 piece ； ~50g)||293|
Please visit the Nutrient Information Inquiry System at the CFS's website for more information.
In the next issue which will be the last in this "Nutrient and Health" series, we will take a look at sodium, another nutrient that is related to heart health.