Cooking and Nutrient Loss

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While most animals thrive on diets consisting almost exclusively of raw, uncooked food, few human cultures have evolved or been sustained without incorporating some aspect of cooked food into their eating practices. At the WHF, we encourage inclusion of both raw and cooked foods into the daily meal plan. We believe there is every reason to make the most from the nourishment available in both types of food.

The way that food is cooked is absolutely essential for avoiding unnecessary nutrient loss. Five minutes can make an enormous difference in the nutritional quality of a meal. (This is about the time it takes to walk away from the stove, answer the phone, and say that you can’t talk right now because you are in the middle of cooking). In addition, every food is unique and should be treated that way when it comes to cooking temperatures and times. We refuse to simmer spinach for more than 2-3 minutes. But we know that kale needs to steam for 6-8 minutes. Head over to our Good Tasting Healthy Recipes to get all the details about each food and the unique cooking approach it deserves.

The traditional rules about heat, water, time, and nutrient loss are all true. The longer a food is exposed to heat, the greater the nutrient loss. Being submersed in hot water (boiling) creates more nutrient loss than steaming (surrounding with steam rather than water) if all other factors are equal. The lower nutrient loss from steaming is the main reason we recommend it so often in our recipes. We just can’t think of any valid reason to expose a food to high heat and boiling water for any prolonged period of time, for example, more than twenty minutes. We even get our butternut squash steamed in that length of time!

With our very precise and short cooking times, you’re unlikely to get a nutrient loss of more than 30% with most nutrients. In general, you’re likely to get nutrient losses in the 5-15% range. This range is dramatically lower than the losses than occur in food processing, or in many cafeterias and restaurants where food is routinely overcooked (in Table 1, you will find a presentation of research results that have looked at how various cooking and preparation methods may impact nutrient loss from select foods). Processed foods often have nutrient losses in the 50-80% range - as much as ten times the amount that occurs with the World’s Healthiest Cooking. The 5-15% nutrient loss that occurs with careful, minimized heat and water exposure is often a worthwhile loss, because it is accompanied by other changes in the food that can support out health. These other changes include improved digestibility, and the conversion of nutrients into forms that are more easily absorbed.

Table 1

Food

Nutrient

Method

% Nutrient Loss

broccoli

vitamin C

blanch

47%

carrots

folate

boiling

79%

carrots

beta-carotene

canning

27%

cauliflower

folate

boiling

69%

grapefruit juice

folate

canning

<5%

milk

vitamin B12

boiling (2-5 minutes)

30%

mixed vegetables

vitamin C

blanching (3-5 minutes)

25%

mixed vegetables

vitamin C

boiling (10-20 minutes)

55%

mixed vegetables

vitamin C

canning

67%

mixed vegetables

pantothenic acid

canning

20-35%

mixed vegetables

vitamin B6

canning

40-60%

navy beans

calcium

cooking

49%

navy beans

copper

cooking

59%

navy beans

iron

cooking

51%

navy beans

magnesium

cooking

65%

navy beans

manganese

cooking

60%

navy beans

phosphorus

cooking

65%

navy beans

potassium

cooking

64%

navy beans

selenium

cooking

50%

navy beans

zinc

cooking

50%

onions

flavonoids

boiling

30%

peanuts

lysine

cooking at 150ºF (90 minutes)

20%

peanuts

lysine

cooking at 150ºF (150 minutes)

40%

soybeans

thiamin

boiled

48-77%

spinach

calcium

blanching

spinach

flavonoids

boiling

50%

spinach

magnesium

blanching

36%

spinach

phosphorus

blanching

36%

spinach

potassium

blanching

56%

tomato juice

folate

canning

70%