Preparation & Everyday Use

Fresh, frozen and canned

A University of California, Davis study compared eight fruits and vegetables kept refrigerated or frozen and measured four vitamins. The authors concluded that vitamin content of the frozen produce was comparable to and occasionally higher than the fresh counterparts, but that beta-carotene fell drastically in some of the foods. [3] The NHS counts fresh, canned and frozen fruit and vegetables toward a portion, and suggests choosing canned types packed in juice or water with no added sugar or salt. [4] FDA advises choosing low-sodium or no-salt-added canned vegetables. [5]

Proper evidence not found in the sources we read for a broad nutrient comparison of canned produce with fresh or frozen. We searched PubMed for canned-versus-fresh nutrient comparisons and read the NHS and FDA pages above. Details: fresh, frozen and canned produce.

Raw and cooked

Raw is not always safer or healthier, and cooked is not always worse. FDA says cooking produce thoroughly kills harmful bacteria and reduces the risk of illness. [6] On the nutrient side, one review of broccoli-family vegetables reported that boiling and blanching caused the largest losses of glucoraphanin and sulforaphane (compounds studied for their chemistry), while short steaming or microwaving favored conversion to sulforaphane. [7] That is a laboratory review of one vegetable family, not a rule for every food, and it does not show a health outcome. We did not find a source in this session that settles raw versus cooked for all produce: proper evidence not found.

Whole fruit and juice

A meta-analysis of 14 prospective cohort studies found non-100% fruit juice was linked to a higher risk of type 2 diabetes (relative risk 1.15), while 100% juice showed no significant link, and the authors noted that unlike whole fruit, 100% juice had no beneficial effect. [8] These are observational findings. See fruit juice versus whole fruit.

Pasteurized and unpasteurized

FDA explains that pasteurization kills harmful germs by heating milk to a specific temperature for a set time. [9] Pasteurizing does not remove every risk: a systematic review of dairy outbreaks in Canada and the United States found outbreaks linked to both raw and pasteurized products. [10] In one crossover trial, pasteurized sauerkraut still changed some gut measures in healthy adults. [11] More: pasteurized versus unpasteurized foods.

Storage and handling

FDA advises keeping the refrigerator at or below 40°F (4°C). [12] Its produce guidance also covers washing, separating raw produce from raw meat, and cooking. [6] See food safety basics.

Home fermenting and home canning

We do not give home-fermentation or home-canning instructions or methods. Risks are described on our page about fermented foods safety. Home canning guidance from a food-safety authority was not read this session, so we say nothing about it beyond pointing you to such an authority.

Where this fits

Preparation changes a food's safety and some of its nutrients; it does not turn food into medicine. For medicines and food questions, ask a pharmacist; see food and medicine interactions.