Interesterified fats: Health effects of commercially relevant palmitic versus stearic acid rich interesterified fats

Random interesterification is extensively used by the food industry to create
fats with desirable functional characteristics for use in spreads and bakery
products without the use of trans fatty acids (FA) or animal fats and with a
lower saturated FA (SFA) content. Randomly interesterified (IE) fats rich in
palmitic and stearic acids are the most commonly used IE fats by the food
industry. Palmitic-acid rich IE fats are generally used by the European market
and derived from palm fruits and include palm oil fractions such as palm
stearines (PSt) (high in palmitic acid) and, in smaller proportions, palm
kernel oil (PK) or coconut oil (both rich in lauric acid). Stearic-acid rich IE
fats are generally used by the North American market and typically are derived
from fully hydrogenated soybean (FHS) IE with vegetable oils. Despite their
widespread use, there has been no published research on the cardio-metabolic
health effects of the most commonly consumed palmitic and stearic acid rich IE
fats.

To compare the effects of commercially relevant IE palmitic and stearic acid
rich fat blends on fasting and postprandial cardiometabolic risk parameters
after chronic exposure to these fats.

This is a double-blind, randomized, cross-over study with commercially relevant
palmitic and stearic acid rich IE fats. Subjects will receive both fats for 6
weeks with a wash-out period of at least 4 weeks in between. Contrast in the
intakes of the IE fats is 15% of energy. A postprandial test will be carried
out at the start and the end of each dietary period.

Following a 2-week run-in period, volunteers will be randomly allocated to test
diets providing 15% energy of the hardstock from test fats (palm stearin kernel
blended with rapeseed oil (PSKb) or a fully hydrogenated rapeseed oil blended
with sunflower oil and coconut oil (FHRpS)) for 6 weeks with a washout period
of at least 4 weeks. A subgroup will undergo postprandial test meal challenges
at the start and end of each 6-week intervention on the corresponding test fat.

Before the start of the study, subjects will be screened to determine
eligibility during one 15 min visit. During this visit, body weight, and height
will be measured and a blood sample (7.5 mL) will be drawn by means of
venapunction. Blood pressure will also be measured. Thereafter, subjects will
be asked to fill in a medical and general questionnaire, including information
on physical activity. During the study, subjects will receive products based on
the experimental fats. On 4 occasions a fasting blood sample will be drawn
(with a total of 76 mL spread over the four visits), body weight, fat
distribution (waist to hip ratio), and blood pressure will be measured. At the
start and end of each intervention period, a subgroup will participate in a
postprandial test. An intravenous cannula will be inserted in an antecubital
vein. Before and after meal consumption, 14 blood samples (4x130.5 mL) will be
drawn during an 8-hour period. During the test, subjects are allowed to drink
water and to walk freely around. In this subgroup, liver fat will be assessed
as well at the end of each experimental using magnetic resonance imaging
(MRI). Subjects may visit the research facilities in between to pick up the
experimental products. All subjects will be asked to complete a food frequency
questionnaire four times. Subjects will register daily the intake of the
experimental foods, and the remaining products in a diary, as well as any signs
of illness, medication used, and any deviations from the protocol. On rare
occasions, blood sampling might cause bruises or hematoma. Total time
investment for the subjects will be approximately 16 hours for those who do not
participate in the postprandial tests plus MRI measurements and 55 hours for
those who will participate in the postprandial test.