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

106
Milk and dairy products in human nutrition
may arise as a result of different populations consuming different types of dairy
products; for example, low-fat vs high-fat milk, or cheese vs milk.
4.1.2 Interpreting study results
Interpreting results and formulating recommendations must take into account factors
such as age, gender, health status, level of physical activity and genetic background
of the targeted population. It is also important to keep in mind that the limited
sensitivity of dietary assessment instruments may prevent detection of an effect of a
single food in a mixed diet on clinical outcomes (Gibson et al., 2009). The cultural
and geographical context is also an issue because of the wide variation in the average
intake of dairy products; a high consumer in one context could be a low consumer
in another (Alvarez-León, Román-Viñas and Serra-Majem, 2006). This highlights the
need to express dairy consumption in consistent units: current expressions include
pints, frequency per week, times per day and servings per week. Serving sizes differ
between countries (Elwood et al., 2010; Soedamah-Muthu et al, 2011) and the
nutrient composition of dairy products may also vary between countries, depending
on factors such as species and breeds of dairy animals (see Chapter 3) and different
fortification policies.
4.2 Milk as a source of macro- and micronutrients 17
Milk intake may be a marker for diet quality because of its high nutrient content
(Barger-Lux et al., 1992; Fulgoni et al., 2007). The macro- and micro-nutrient composition
of whole (full fat) milk and skimmed cow milk are given in Table 4.1 and
those of other dairy products are given in Table 4.2. 18
Milk fat contributes about half of the energy in whole milk. For this reason,
animal milk can play an important role in the diets of infants and young children in
populations with a very low fat intake (Michaelsen et al., 2011a), where the availability
of other animal-source foods (ASF) is limited. However, it should be kept
in mind that breast milk is also a key source of energy and essential fatty acids, and
it is recommended that breastfeeding is continued, along with appropriate complementary
foods, up to two years of age or beyond (WHO, 2003). Milk lipids are
carriers of fat soluble vitamins. Milk fat contains approximately 400 different fatty
acids, which make it the most complex of all natural fats (Månsson, 2008). The milk
fatty acids are derived almost equally from two sources: the feed and the microbial
activity in the rumen of the cow. Approximately 60 percent of the fatty acids are
saturated. The effects of fat and fatty acids in milk on human health are reviewed
in Section 4.7 et seq. and Chapter 5. Milk contains high-quality protein, defined as
including all the essential amino acids needed by humans. Some milk proteins have
been associated with allergies (see Section 4.10.2). Lactose, the principal carbohydrate
in milk, will be discussed in Section 4.10.1.
17 This section covers milk as a source of nutrients. Health implications, both positive and negative, are
discussed elsewhere in this chapter and in Chapter 5.
18 Although data are presented per 100 g, portion sizes will differ between foods; for example, a serving
of milk or yoghurt may be 1 cup (250 ml = 250 g, since both milk and yoghurt have a density
of ~1 g/ml), whereas a serving of cheddar cheese may be about 40 g. Both portion size and nutrient
content need to be considered when making comparisons between foods.