Milk-and-Dairy-Products-in-Human-Nutrition-FAO

Chapter 5 – Dairy components, products and human health 209
5.2 Dairy components
5.2.1 Milk fat and human health
Milk fat is highly complex, consisting of a large number of fatty acids and other
lipid molecules that have various effects on human health. For example, cow milk 44
contains approximately 3.3 g of fat/100 g. This consists primarily of triacylglycerols
(97–98 percent of total lipids by weight), which are composed of fatty acids of
various lengths (4–24 carbon atoms) and levels of saturation. More than 400 fatty
acids have been identified in milk fat. Whole milk contains approximately 1.9 g
of saturated fatty acids (SFAs)/100 g. The monounsaturated fatty acid (MUFA)
oleic acid (C18:1 cis-9) is the most abundant unsaturated fatty acid in milk (about
0.8 g/100 g of whole milk). Whole milk contains approximately 0.2 g of
PUFA/100 g (Haug, Høstmark and Harstad, 2007). Up to five percent of the fatty
acids in cow milk may be ruminant-derived trans fatty acids (TFAs), which are
different from industrially-produced trans fats with respect to health outcomes
(FAO and WHO, 2010a).
Concerns about obesity and cardiovascular disease (CVD) in developed and
developing countries have increased public interest in minimizing the consumption
of fats. Such concerns have prompted the dairy industry to develop technologies to
modify milk fat content, which is evident from the range of liquid milk varieties that
are available. While there may be a need for populations in high-income countries
to reduce overall fat and calorie intake to avoid the risk of developing diet-related
chronic diseases such as diabetes and CVD, many developing countries face the
challenge of increasing fat consumption in populations with low-fat and overall
low-energy intakes (FAO and WHO, 2010a).
Individual fatty acids
The relationship between milk fat intake and health impact is complex (German et
al., 2009) and much has been written on the association between dairy and CVD
risk factors. As reported in the FAO and WHO expert consultation on fats and
fatty acids (FAO and WHO, 2010a), it is recommended that total intake of SFAs
should not exceed 10 percent of energy intake and SFAs should be replaced with
PUFAs in the diet to reduce the risk of coronary heart disease (CHD). Individual
SFAs have differing impacts on blood lipids. For example, lauric (C12:0), myristic
(C14:0) and palmitic (C16:0) acids are associated with elevated serum levels of
low‐density lipoprotein (LDL)-cholesterol, whereas stearic acid (C18:0), which
is poorly absorbed in the gut, has no effect on LDL-cholesterol (Shingfield et al.,
2008; FAO and WHO, 2010a; Gibson, 2011).
Cholesterol is an important component of cell membranes and is a precursor of
bile acids, vitamin D and adrenal and gonadal steroid hormones (Berg, Tymoczko
and Stryer, 2002; Lecerf and de Lorgeril, 2011), and thus is needed by the human
body. When dietary cholesterol intake is low, the human body is capable of synthesizing
cholesterol to maintain constant levels of cholesterol. Although altering the
diet may reduce the cholesterol level in some people, dietary changes alone rarely
44 Composition of milk from other species is detailed in Chapter 3.