Just how nutritious are home-canned goods anyway?
That’s a fair question to ask. After all, all home-canned goods have to go through some form of heat processing to make the jar safe. Food safety trumps food nutrition, every time. Still, would-be canners can be shocked at how long the processing times are for vegetables.
The take-away is that, if produce is home canned fairly soon after picking, the nutritional levels can be as good as if not higher than “fresh” produce you see at a supermarket, and will be better than anything frozen for a few months or more. The growing nutritional concern from healthy experts with home canned goods is more about what we add to them: salt and sugar.
Summary of what the experts say
- dehydrated food loses the most nutrients compared to canned or frozen;
- frozen foods will lose more nutrients during their frozen storage period than home canned goods will;
- home canned goods canned promptly after harvest can be more nutritious than fresh produce you buy at a supermarket except when it comes to the added sugar and sodium in them;
- sugar and salt only added for flavouring;
- completely fresh produce is best for vitamin C;
- can produce as soon as you are able to. Even in the refrigerator, half or more of some vitamins will be lost in a week or two;
- the heat of canning will destroy ⅓ to ½ of these 4 vitamins: vitamin A, vitamin C, thiamine, and riboflavin;
- other vitamins and minerals however are preserved close to fresh levels;
- after a year, vitamin loss of 5 to 20% per year, depending on what vitamin you are looking at.
Now, let’s let the various sources speak for themselves.
Compare like with like
The Hazel-Atlas Company had a great reminder of the results to expect from home-canned food:
Canning is a method of using heat and air-tight containers to preserve food as nearly as possible in the condition in which it would be served when freshly cooked.” Canning Helps. Hazel-Atlas Glass, Wheeling, West Virginia. msuspcsbs_atla_hazelatlas9.pdf
Note: “when freshly cooked.”
That is the nutritional value you need to compare home-canned goods with; not with a green bean that you picked in your back garden and ate raw on the spot.
What is the impact of processing on home-canned goods?
The USDA says,
Many vegetables begin losing some of their vitamins when harvested. Nearly half the vitamins may be lost within a few days unless the fresh produce is cooled or preserved. Within 1 to 2 weeks, even refrigerated produce loses half or more of some of its vitamins. The heating process during canning destroys from one-third to one-half of vitamins A and C, thiamin, and riboflavin. Once canned, additional losses of these sensitive vitamins are from 5 to 20 percent each year. The amounts of other vitamins, however, are only slightly lower in canned compared with fresh food. If vegetables are handled properly and canned promptly after harvest, they can be more nutritious than fresh produce sold in local stores.”  United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-5.
Utah State Extension says,
Salt or sugar are not necessary for safe canning and only added for flavoring.
Canned foods maintain mineral content for entire shelf life. Vitamins A and C will decrease rapidly after fruits and vegetables are picked and cooked. Vitamins are lost during heating processes; however, once canned, vitamin A and C loss slows to 5- 20% per year. Other vitamins remain close to fresh food levels. Salt or sugar are not necessary for safe canning and only added for flavoring. Be sure to label canned goods with ingredients when canning mixed foods such as sauces.”  Jahner, Brandon and Brian A. Number. Canned Goods. Utah State Extension. September 2008. Accessed July 2015. https://extension.usu.edu/foodstorage/htm/canned-goods
University of California-Davis researchers studied the issue in depth in 2007. They found:
Depending on the commodity, freezing and canning processes may preserve nutrient value. While the initial thermal treatment of canned products can result in loss, nutrients are relatively stable during subsequent storage owing to the lack of oxygen. Frozen products lose fewer nutrients initially because of the short heating time in blanching, but they lose more nutrients during storage owing to oxidation. In addition to quality degradation, fresh fruits and vegetables usually lose nutrients more rapidly than canned or frozen products. Other variables such as storage and cooking conditions will also influence the final nutrient content of a food.  References: Rickman, et al. 2007. Nutritional comparison of fresh, frozen and canned fruits and vegetables. Part I. Vitamins C and B and phenolic compounds. Journal of Science in Food and Agriculture. 87:942. Accessed June 2015. https://ucce.ucdavis.edu/files/datastore/234-779.pdf
A New York Times blogger, discussing the 2007 study, said:
Despite their reputation, canned fruits and vegetables retain many of their nutrients, in some cases better than fresh produce does.”  O’Connoer, Anahad. Really? The Claim: Fresh Produce Has More Nutrients Than Canned. New York Times Blogs. 27 May 2013. Accessed July 2015. https://well.blogs.nytimes.com/2013/05/27/really-the-claim-fresh-produce-has-more-nutrients-than-canned/?_r=0
Barb Ingham, Extension Agent at the University of Wisconsin, summed up the study for her readers:
Research supports the common perception that fresh is often best for optimal vitamin C content, but once harvested deterioration can be rapid. If storage is considered, canned and frozen fruits and vegetables are as nutritious in vitamin C content, and may even be higher than fresh. In fact, processing does not provide an overall positive or negative impact on nutrients except where sodium is added to canned vegetables. A quick rinse of canned vegetables before reheating can dramatically reduce sodium content. Consumers can comfortably choose canned, frozen or fresh as the season and their pantry allows.”  Ingham, Barb. Safe & Healthy: Canned, Frozen or Fresh? University of Wisconsin-Extension. 3 October 2013. Accessed July 2015. https://fyi.uwex.edu/safepreserving/2013/10/03/safe-healthy-canned-frozen-or-fresh/
In terms of long-term storage of food, many people feel that canning might just preserve the most nutrition of all the methods we currently have:
While some nutrients are lost during canning, recent research has shown that refrigerating fresh fruits and vegetables also results in nutrient losses, especially of fragile vitamins like vitamin C. for example, broccoli loses 50 percent of its vitamin C and Vitamin A (in the form of beta carotene) after five days of refrigeration, similar in scale to the loss of vitamin C during cooking and canning. This is because plant foods are alive and thus continue to metabolize nutrients during storage. It’s safe to assume that root cellar storage causes the same magnitude of nutrient loss. Frozen food lose more nutrients than canned food after six months of storage. Dried foods lose the most nutrients. With this in mind, canning is preferably done very soon after harvest, when nutrients are at their peak, thus preserving the most nutrients possible.“  Rayner, Lisa. The Natural Canning Resource Book. The Natural Canning Resource Book. Flagstaff, Arizona: Lifeweaver LLC. 2010. Page 17.
What’s the impact of additives on home canned goods?
The two most dominant additives currently used in home canned goods are sugar, and salt. They are, in fact, the first big jolt that modern would-be canners get when looking at home canning as a source of nutritious food, and they are the deal breaker that causes many people to decide against home canning.
The issues of produce having to sit in the fridge a day or two before you can can it, or of some vitamins leeching into canning water, seem paltry when compared to the cargo ship loads of refined white sugar and salt dumped into our Mason jars:
When we think of preserved food, however, we often conjure up thoughts of sticky, sweet jams and jellies and salty pickles and sauerkraut. The treats from the kitchen of a home food preserver are tasty, but it’s not exactly health food, right?”  Roche, Brenda. Home preserved foods: Nutrition friend or foe? http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=5849? Agriculture and Natural Resources, University of California blog. 27 September 2011. Accessed March 2015.
A Ball regular pectin recipe for strawberry jam actually calls for more sugar than fruit — 7 cups of sugar, but only 5 cups of strawberries.  Homemade strawberry jam recipe. Accessed August 2016 at https://www.freshpreserving.com/strawberry-jam-%7C-making-strawberry-jam-%7C-ball-fresh-preserving-br1265.html That’s not a fruit preserve: that’s candy.
The concern about sugar is, obviously, obesity levels and the ensuing health problems that causes. Currently Canada, the US, Australia, the UK, New Zealand and many other first world countries are classed as experiencing an obesity crisis. No one wants their home canning to be contributing to that.
The concern about sodium is actually a raft of problems. Here’s what the Dietitians Council of Canada says:
…Too much sodium can lead to health problems like high blood pressure, stroke, heart disease and kidney disease.
Eating less sodium can help you and your family stay healthy and feel your best. Even if you don’t have high blood pressure, you can still benefit from lowering the amount of sodium you eat. We all need some sodium, but most of us eat about 3400 mg per day. This is more than double the amount of sodium we need.
- Healthy adults need only 1500 mg of sodium per day.
- Healthy children need only 1000 to 1500 mg of sodium per day.
People with health conditions like high blood pressure or kidney disease may need to aim for lower sodium intakes and should follow the advice of their health care provider.”  Dietitians of Canada 2016. Cut out the salt. EatRigth Ontario web site. Accessed August 2016.
So, healthy adults really only need about 1500 mg of sodium a day. There’s a debate, for sure, about how much higher a day people can go – nutritional councils debate amongst themselves, and we’ll let those experts sort that out — but there’s little debate about the lower number 1500 mg.
But, you don’t have to can with all that salt and sugar – or any of it. You can make home canned goods nutritious again.
If you’ve been slow to embrace the [home canning] trend because of concerns about added sugar and sodium, you can relax. New ingredients and processing equipment mean you can make Grandma’s yummy preserves and jams without lots of sugar or salt but with equally tasty results.”  AARP Magazine. Healthy Home Canning. September 2011. Accessed July 2015. https://www.aarp.org/food/healthy-eating/info-08-2011/healthy-home-canning.html
All recipes on healthycanning.com give nutritional values, so you can look at them to see what the sodium and other levels are in them.
References [ + ]
|1.||↑||Canning Helps. Hazel-Atlas Glass, Wheeling, West Virginia. msuspcsbs_atla_hazelatlas9.pdf|
|2.||↑||United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-5.|
|3.||↑||Jahner, Brandon and Brian A. Number. Canned Goods. Utah State Extension. September 2008. Accessed July 2015. https://extension.usu.edu/foodstorage/htm/canned-goods|
|4.||↑||References: Rickman, et al. 2007. Nutritional comparison of fresh, frozen and canned fruits and vegetables. Part I. Vitamins C and B and phenolic compounds. Journal of Science in Food and Agriculture. 87:942. Accessed June 2015. https://ucce.ucdavis.edu/files/datastore/234-779.pdf|
|5.||↑||O’Connoer, Anahad. Really? The Claim: Fresh Produce Has More Nutrients Than Canned. New York Times Blogs. 27 May 2013. Accessed July 2015. https://well.blogs.nytimes.com/2013/05/27/really-the-claim-fresh-produce-has-more-nutrients-than-canned/?_r=0|
|6.||↑||Ingham, Barb. Safe & Healthy: Canned, Frozen or Fresh? University of Wisconsin-Extension. 3 October 2013. Accessed July 2015. https://fyi.uwex.edu/safepreserving/2013/10/03/safe-healthy-canned-frozen-or-fresh/|
|7.||↑||Rayner, Lisa. The Natural Canning Resource Book. The Natural Canning Resource Book. Flagstaff, Arizona: Lifeweaver LLC. 2010. Page 17.|
|8.||↑||Roche, Brenda. Home preserved foods: Nutrition friend or foe? http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=5849? Agriculture and Natural Resources, University of California blog. 27 September 2011. Accessed March 2015.|
|9.||↑||Homemade strawberry jam recipe. Accessed August 2016 at https://www.freshpreserving.com/strawberry-jam-%7C-making-strawberry-jam-%7C-ball-fresh-preserving-br1265.html|
|10.||↑||Dietitians of Canada 2016. Cut out the salt. EatRigth Ontario web site. Accessed August 2016.|
|11.||↑||AARP Magazine. Healthy Home Canning. September 2011. Accessed July 2015. https://www.aarp.org/food/healthy-eating/info-08-2011/healthy-home-canning.html|