Nutrition Science and Everyday Application - beta v 0.1

SOURCES OF VITAMINS AND MINERALS 449
foods to communities increases access to a variety of foods. Preservation techniques like
canning and freezing extend the shelf life of foods and increase their availability outside
of their peak harvest season. In fact, because fresh foods can deteriorate rapidly, food
processing techniques may result in better nutrient retention over time when compared to
fresh items. However, some vitamins are more stable than others, and the amount retained
depends on the specific vitamin and the processing technique. Water-soluble vitamins are
the most susceptible to the effects of processing, though other nutrients can be impacted as
well.
Method of
Processing
Air exposure
and time
Temperature
Water
Canning
Freezing
Refining of
grains
Effect on Nutrient Retention
Enzymes present in foods and exposure to air can destroy
nutrients, because as soon as the food is harvested, the food
begins to slowly decompose.
Cooking helps kill bacteria, makes foods more appealing, and
in some situations improves bioavailability of nutrients. But
high temperatures for prolonged amounts of time can destroy
some vitamins.
Minerals and water-soluble vitamins can leach into the water.
High temperatures may be used, which can destroy watersoluble
vitamins, but commercial techniques usually use rapid
heating, which helps to reduce nutrient loss.
Freezing does not reduce nutrient content, but if foods are
blanched prior to freezing it may slightly reduce levels of watersoluble
vitamins.
Many B vitamins, minerals, and phytochemicals, as well as
fiber, are lost when whole grains are refined.
How to Minimize Nutrient Loss
Purchase fresh items in quantities
that can be used as soon as
possible.
Cut up foods only when ready to
use.
Buy local produce to cut back on
transport time and air exposure.
Use fast cooking methods like
microwaving, steaming, or stirfrying.
Don’t soak produce in water.
Limit the amount of water used to
cook foods (e.g., steam vegetables
rather than boil them).
Use cooking water in food
preparation.
Choose a variety of canned goods
that don’t have added sugars or
sodium to maximize nutrient
density.
Choose a variety of frozen goods
that don’t have added sugars,
syrups, or sauces to maximize
nutrient density.
Choose whole grains whenever
possible.
Table 8.2. The effects of processing on nutrient retention. 1
There is a notable exception to the effects of processing described here. In contrast to
most vitamins, the bioavailability of beta-carotene, a precursor to vitamin A, and similar
phytochemicals called carotenoids is actually increased by the cooking process, because
cooking, chopping, and homogenizing releases carotenoids from the plant matrix. Thus,
cooked carrots can be a better source of vitamin A than raw carrots. However, overcooking
transforms some of the carotenoids into inactive products, and in general it is best to
chop and lightly steam vegetables containing carotenoids to maximize their availability from
foods.
VITAMIN SYNTHESIS IN THE BODY
In addition to getting vitamins from the foods we eat, there are some vitamins that can be