Effects of Cooking on Vitamins (Table)

(Looking at the Science on Raw vs. Cooked Foods--continued, Part 2E)

Effects of cooking on vitamins

Vitamin loss can be induced by a number of factors. Obviously, losses of vitamins depend on cooking time, temperature, and cooking method. Some vitamins are quite heat-stable, whereas others are heat-labile. From textbooks in nutrition, such as Kreutler et al. [1987], many other factors than heat can destroy (some) vitamins, such as: solubility in water, exposure to air (oxidation), exposure to light (UVs), heat, acid and alkaline solutions, storage losses, etc. Here is a tabular summary:

FACTORS THAT CAN INDUCE
VITAMIN LOSS

Nutritional Element	Is substance susceptible to losses under given condition?
Nutritional Element	Soluble in Water	Exposure to Air	Exposure to Light	Exposure to Heat
Vitamin A	no	partially	partially	relatively stable
Vitamin D	no	no	no	no
Vitamin E	no	yes	yes	no
Vitamin K	no	no	yes	no
Thiamine	highly	no	?	> 100°C
Riboflavin	slightly	no	in solution	no
Niacin	yes	no	no	no
Biotin	somewhat	?	?	no
Pantothenic Acid	quite stable	?	?	yes
Folate	yes	?	when dry	at high temp
Vitamin B-6	yes	?	yes	?
Vitamin B-12	yes	?	yes	no
Vitamin C	very unstable	yes	yes	yes

(table, continued)

Nutritional Element

Is substance susceptible to losses
under given condition?

Acid
Solution

Alkali
Solution

Other

Vitamin A
?

?

--

Vitamin D
?

?

--

Vitamin E
?

?

contact with iron or copper

Vitamin K
strong acids

yes

--

Thiamine
no

yes

--

Riboflavin
no

yes

long cooking in large volume of water

Niacin
no

no

--

Biotin
strong acids

yes

oxidizing substances

Pantothenic Acid
yes

yes

--

Folate
heat-labile

?

storage

Vitamin B-6
no

yes

--

Vitamin B-12
strong acids

yes

contact with iron or copper

Vitamin C
?

yes

--

Significance of losses depends on a given food's context in the overall diet. Of course, not all vitamin losses have detrimental consequences, since some vitamins are widely available (such as pantothenic acid). The vitamins in which some deficiencies are occasionally observed are: A, D, E, thiamine, riboflavin, niacin, folate, and B-12. Of those, only thiamine, niacin, and folate would be destroyed significantly by excessive exposure to heat and/or water. It also appears from the above that many other factors than heat can destroy vitamins. Recommendations to preserve vitamins include: utilizing foods when fresh; using steaming in preference to boiling; and avoiding overly long cooking times.

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(Comparison of Vitamin Levels in Raw vs. Cooked Foods)

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SEE REFERENCE LIST

SEE TABLE OF CONTENTS FOR: PART 1 PART 2 PART 3

GO TO PART 1 - Is Cooked Food "Toxic"?

GO TO PART 2 - Does Cooked Food Contain Less Nutrition?

GO TO PART 3 - Discussion: 100% Raw vs. Predominantly Raw

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