Wow, in the back of the refrigerator you found an apple grown in Brazil that you bought last month from the grocery store. That should be nutritious, right? Not quite – though I have to admit, it’s probably better and definitely less harmful than the drive-through. Let’s see what we can do about getting the most nutrients out of our fruits and vegetables:
Harvesting a vegetable/fruit separates it from the source of nutrients.
The longer a food is separated from the soil, the more nutrients are lost. Leaving fresh foods sitting around leads to nutrient losses. Food washing, peeling and cooking can also lead to further nutrient losses.
By the time you pick up a fresh vegetable/fruit at the grocery store, it might have already lost between 15-60% of some vitamins (unless purchased and consumed within 72 hours of harvest). Canned/frozen varieties of the same vegetable/fruit usually have lost no more than 20% of these vitamins.
Check out this table comparing the vitamin C content of fresh and frozen peas, spinach, and French beans. Quantity of Vitamin C (mg/100g)
Freshly picked peas 22.1 Fresh peas (after 2 days) 14.1 Frozen peas 20.2
Freshly picked spinach 17.0 Fresh spinach (after 2 days) 4.1 Frozen spinach 14.0
Freshly picked French beans 16.4 Fresh French beans (after 2 days) 7.9 Frozen French beans 14.3
The nutrient content of preserved plant foods depends on four factors:
Time of harvest
Freezing is one of the best methods for preserving as many nutrients as possible. When plant foods are frozen, they are often blanched (briefly immersed in boiling water) to suppress the growth of microbes and retain color. Then they’re flash frozen (immediately taken in small batches to freezing).
Blanching can make some nutrients (including phytochemicals) more bioavailable. Some data indicate that certain nutrients are actually higher in frozen vegetables than in fresh or canned. Even in delicate blueberries, the antioxidants aren’t much different between canned, frozen, fresh, and dried.
Regardless of whether a food is canned, frozen or fresh, cooking can leach out nutrients, especially vitamins B1 and C, with vitamin C being the least stable. Don’t overcook foods if you want to maximize nutrient intake. Microwaving and steaming seem to help retain the most nutrients.
Vitamins A, D, and E, along with most carotenoids, are fat-soluble, making them resistant to degradation from blanching and washing. However, they’re still prone to oxidation with the presence of light, heat and oxygen. This can be minimized with canning/freezing (compared to purchasing fresh, storing at home, and then preparing).
Further, we tend to absorb carotenoids better after eating cooked foods rather than raw. So, canned/frozen foods might offer a better source for these nutrients.
Minerals are resilient. They’re not destroyed by light, heat, or oxygen. Thus, noticeable mineral losses from canned/frozen foods are rare.
Minerals are removed from foods by leaching into the cooking water (tends to be negligible) and mechanical processing (e.g., the stems of mushrooms are often removed before canning them).
Canned vegetables may have higher levels of calcium and other minerals due to the uptake from hard water during processing. Iron levels can increase and copper levels can decrease when foods are canned in tin-plated steel.
Fibre losses occur only when there is mechanical separation of the food (e.g., removal of peels, skins, stems, etc.), such as with canned asparagus and tomatoes. The fibre content in canned beans/legumes is the same as fresh.
What to do to prevent vitamin losses in food
To prevent losses of natural vitamins in food try to:
- Steam, not boil vegetables and fruit
- If you cook vegetables in water do it in a little amount of it, which can then be used for sauces or soups
- Prepare meals as late as possible before serving them
- Definitely choose frozen food when having frozen and canned food to choose
- Cook frozen food without defrosting
- Prepare salads from freshly cut vegetables, otherwise they lose vitamins B and C
- Use vessels made of stainless steel; cooking in copper pots make meals poorer in vitamin C, E and folic acid
- Always buy fresh products, especially vegetables and fruit – only such quantity which can be used within several days
- Washing/ rinsing for too long rinses out vitamins B and C; it is best to wash them using a brush in running water
- Do not expose milk and dairy products to the sun, because they lose vitamins A, D, B2
- Keep food requiring cooling in a fridge (at constant temperature up to 4°C) to prevent its going bad. In case of frozen food it is best to keep it at temperature under -18°C. Canned and dried food should be stored in a cool and dry place.
I try to do the following when I buying and storing food:
- I have a home delivery of just picked, farm fresh fruits and vegetables from http://www.abundantharvestorganics.com/
- I also shop at a Farmers’ Market because when you buy food there, you are buying just picked produce and you are buying food that was picked when it was actually ripe, as opposed to being picked too early
- I buy seasonal fruits and vegetables, not fruits and vegetables that are in season in another hemisphere and flown in
- I use frozen food over canned food because of the BPA in canned food
- I try to use my produce up quickly, so it doesn’t sit in my refrigerator, losing nutrients
- I buy special bags that help the food stay fresher longer: http://www.amazon.com/Evert-Fresh-Bag-Set-each-size/dp/B0009L8GHY
- I usually only steam or quickly stir fry vegetables. I never, ever use a microwave, I don’t care how many nutritients are preserved this way! Why? This is really a subject for another article, but quickly – in a Swiss Study it was found: Significant changes were discovered in the blood samples from the intervals following the foods cooked in the microwave oven. These changes included a decrease in all hemoglobin and cholesterol values, especially the ratio of HDL (good cholesterol) and LDL (bad cholesterol) values. Lymphocytes (white blood cells) showed a more distinct short-term decrease following the intake of microwaved food than after the intake of all the other variants.
These recommendations are for the reduction of stress only. They are not intended as treatment or prescription for any disease, or as a substitute for regular medical care.