Food Structure for Nutrition - Food Colloids: Self-Assembly and Material Science - page 4

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2.5

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1.5

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Low versus High GI Low versus High CHO

Figure 1 Relative probability of developing premature macular degeneration (P) as
affected by the glycemic index (GI) and the total carbohydrate (CHO) of
reported habitual diets in the Nurses' Study population 7

glycemic index. 6 Numerous studies have documented the effect of glycemic
index in accounting for variations in metabolic response to particular diets.
Even more impressively, as glycemic index has been included as an independent
variable in larger health issues, this simple surrogate reflection of food structure
is being recognized as important to many end points that are not typically
thought of as being related to food structure. For example, Taylor and
co-workers 7 have shown that glycemic index as a dietary variable was associ-
ated with an almost threefold increase in risk of macular degeneration in the
Nurses' Health Study population (Figure 1). Though many more studies have
documented the effects on health of the rate of absorption of glucose as
glycemic index, as reviewed by Dickinson and Brand-Miller, 8 little research
has been pursued to extend these observations into a more precise understand-
ing of the role of food structure in the dynamics of glucose delivery.

1.3 Food Structure and Bioavailability
Bioavailability is defined 9 as the difference in delivery to blood between an oral
dose and an injected dose. It is determined experimentally by measuring the
dose-corrected area under curve (AUC) of a substance administered orally (po)
divided by the AUC intravenous (IV):

F ¼ ([AUC] po dose IV )/([AUC] IV dose po ) (1)

If 100% of an ingested dose of a nutrient or a compound reaches the blood, the
bioavailability (F) is considered to be 1. From the perspective of essential
nutrients - especially when considering the risk of deficiency - the greater the
bioavailability, the better the nutrient. Hence, food matrices promoting rapid
and complete absorption were judged to be superior in their ability to deliver