Nearly every food preparation process reduces the amount of
nutrients in food. In particular, processes that expose foods to high
levels of heat, light, and/or oxygen cause the greatest nutrient loss.
Nutrients can also be "washed out" of foods by fluids that are
introduced during a cooking process. For example, boiling a potato can
cause much of the potato's B and C vitamins to migrate to the boiling
water. You'll still benefit from those nutrients if you consume the
liquid (i.e. if the potato and water are being turned into potato soup),
but not if you throw away the liquid. Similar losses also occur when
you broil, roast, or fry in oil, and then drain off the drippings.
The table below compares the typical maximum nutrient losses for
common food processing methods. This table is included as a general
guide only. Actual losses will depend on many different factors,
including type of food and cooking time and temperature
|
Typical Maximum Nutrient Losses (as compared to
raw food)
|
|||||
|
Vitamins
|
Freeze
|
Dry
|
Cook
|
Cook+Drain
|
Reheat
|
|
Vitamin
A
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Retinol Activity Equivalent
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Alpha
Carotene
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Beta
Carotene
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Beta
Cryptoxanthin
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Lycopene
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Lutein+Zeaxanthin
|
5%
|
50%
|
25%
|
35%
|
10%
|
|
Vitamin
C
|
30%
|
80%
|
50%
|
75%
|
50%
|
|
Thiamin
|
5%
|
30%
|
55%
|
70%
|
40%
|
|
Riboflavin
|
0%
|
10%
|
25%
|
45%
|
5%
|
|
Niacin
|
0%
|
10%
|
40%
|
55%
|
5%
|
|
Vitamin
B6
|
0%
|
10%
|
50%
|
65%
|
45%
|
|
Folate
|
5%
|
50%
|
70%
|
75%
|
30%
|
|
Food
Folate
|
5%
|
50%
|
70%
|
75%
|
30%
|
|
Folic
Acid
|
5%
|
50%
|
70%
|
75%
|
30%
|
|
Vitamin
B12
|
0%
|
0%
|
45%
|
50%
|
45%
|
|
Minerals
|
Freeze
|
Dry
|
Cook
|
Cook+Drain
|
Reheat
|
|
Calcium
|
5%
|
0%
|
20%
|
25%
|
0%
|
|
Iron
|
0%
|
0%
|
35%
|
40%
|
0%
|
|
Magnesium
|
0%
|
0%
|
25%
|
40%
|
0%
|
|
Phosphorus
|
0%
|
0%
|
25%
|
35%
|
0%
|
|
Potassium
|
10%
|
0%
|
30%
|
70%
|
0%
|
|
Sodium
|
0%
|
0%
|
25%
|
55%
|
0%
|
|
Zinc
|
0%
|
0%
|
25%
|
25%
|
0%
|
|
Copper
|
10%
|
0%
|
40%
|
45%
|
0%
|