DEAR DR. BLONZ: What makes a vitamin water-soluble? I know vitamins A, D, E and K are not water-soluble, and that B and C are. Does this relate to the fact that we do not store water-soluble vitamins in our body? -- H.T., Phoenix

DEAR H.T.: First, some history about what we now call vitamins. The work of Louis Pasteur (1822-1895) and Robert Koch (1843-1910) revealed that germs were responsible for diseases. Scientists then began working to identify the bugs behind every illness. Sanitation was found to be a key, and the “germ theory” of disease ruled the day. Some ailments, however, were found to persist even when sanitation was under control. The concept that what we ate, or failed to eat, was involved was not widely embraced, but as time went on, scientists began to investigate the role of diet.

The usual way to establish the essentiality of a nutrient is through an investigation of what happens when it is absent. Because vitamins are present (and needed by the body) in relatively small amounts, it was not until researchers had an ability to purify foods that they could know what, precisely, was being fed. Answers began to emerge when experiments started using purified diets that only contained protein, fat and carbohydrate. These nutrients, by themselves, did not support life; young animals failed to grow, and mature animals failed to maintain their body weight. It became clear that there were other essential substances.

As analytical procedures progressed, the different essential micronutrients were discovered. The first of these nutrients contained the element nitrogen, in the form of an amino group. It was assumed that all micronutrients would have a similar structure, and this new group was referred to as “vital amines,” or “vitamines” -- a word coined in 1911 by a Polish scientist named Casimir Funk. It was later determined that not all of these substances were built in the same way, but the name -- shortened to “vitamins” -- had already become part of scientific jargon.

An adult is about 60% water by weight. Water gets consumed, serves as the medium for biochemical reactions, then serves as the vehicle to help eliminate metabolic byproducts through the kidneys. By contrast, the body conserves fat by virtue of its role as the body’s concentrated source of metabolic energy.

When the vitamin discoveries began, it became convenient to classify these substances by whether they dissolved in water or fat. This classification was not based on whether the vitamins were stored; that was not known at the time. This system, however, has remained. Due to the constant turnover of water through the body, water-soluble vitamins are not effectively stored to any appreciable degree. Fat-soluble vitamins tend to get distributed in body fat, so they hang around for a while.

The fat-soluble vitamins include A, D, E and K, as you mentioned. The water-soluble vitamins include thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), ascorbic acid (C), vitamin B12, folate, choline and biotin.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I need a bit more info about an ongoing internet campaign against canola oil. There is a claim that this oil was developed as a name-change alternative to rapeseed oil, after that oil was found to cause health problems. A place where I buy some of my food (and whose advice I sometimes follow) rails about its use in prepared foods. The claim is that it is toxic, especially when used in cooking, and that it is produced from genetically modified grain -- stealthily imported from Canada behind the back of the Food and Drug Administration.

I am hoping for your assessment as to whether there is anything scientifically valid here, or if this just ongoing nonsense. -- T.S., Topeka, Kansas

DEAR T.S.: This is an issue that seems to emerge periodically, with its lease on life recycled through the communicative and archive powers of the internet and social media. One difficulty is that many people who maintain sites with dubious information don’t take down the inaccuracies when confronted with solid evidence to the contrary. Conspiracies do make for compelling postings, but this one is already a bit rancid. I wish that people would give it up, because it is confusing well-meaning, health-conscious consumers.

Perhaps we can all do a little community service and have some facts at the ready to put this nonsense to rest. Rapeseed (Brassica napus) is a member of the mustard family. It is known for its oil-rich seeds that are used in animal and human food.

Traditional rapeseed contains a toxic fatty acid compound known as erucic acid. This was used in animal feed, but did not appear to be associated with any problems with animals who have multichambered stomachs. The fermentation vat in such digestive systems, known as the rumen, appears to be able to detoxify erucic acid. For animals with a one-chambered stomach, like us, traditional rapeseed oil -- with its elevated content of erucic acid -- is to be avoided.

In the 1970s, using traditional plant-breeding techniques -- not genetic engineering -- rapeseed was successfully bred to reduce its erucic acid content. The erucic acid was replaced during breeding with oleic acid, the healthful fatty acid found in olives and other plants.

The name “canola” was originally a trademark standing for “CANada Oil, Low Acid,” which was deemed a more palatable name than “low-erucic acid rapeseed oil.” (The low-acid plant was bred in Canada.) The canola plant is now a different variety of rapeseed; think of it as a distant, younger cousin to traditional rapeseed. Organically grown canola, available in the marketplace, is a testimony that this type of oil can have a non-GMO pedigree.

Similar to any cooking oil, as long as canola oil is not overheated or otherwise abused, it will not become toxic when used in cooking. The smoke point for canola oil is over 400 degrees F, which is high enough for most types of cooking.

Bottom line: Be wary of advice from sites that continue to spread misinformation.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: Being a nut lover, I have a question after your recent column on the topic. Your information stated that nuts in their shells would keep for about six to 12 months if stored in a cool, dry place, but that shelled nuts only keep about half as long. I recently discovered an unopened 26-ounce container of lightly salted peanuts in the back of my kitchen pantry. The best-by date on the bottom was 2/26/2017, which means it is three years out of date. I assumed they would taste stale or whatever, but figured I’d give them a try. I recently opened it and found the taste and texture seemed like a brand-new container, fresh off the store shelf. The thing I do not know is whether the passage of time has affected the nutrients. Any thoughts? -- A.F., via email

DEAR A.F.: There are different methods of quality-control dating for foods. Different types of dating provide information on a range of issues, including a food’s loss of quality, the risk of microbial spoilage, and an increased risk of foodborne illness. (Check the information in an earlier column: blonz.org/we3wt.)

Nuts tend to use the “best if used by” type of freshness date, providing a date after which the contents would be expected to decrease in flavor and quality. The wild-card aspect is that one can’t accurately predict the lifespan for every product. The dates typically have a bit of a buffer, but three years seems like pushing it. My general advice is to toss out-of-date foods under the canon of “Why take a chance?”

You have sampled from that container and have found nothing wrong. Given that the peanuts show all signs of being unspoiled and edible, I would predict they would also still be nutritious. Oxidation is the main type of spoilage affecting nuts, occurring when nuts are in contact with the oxygen in the air. Vacuum-sealing keeps air away, so it limits this process. The nuts, however, continue to age as they are stored. They might taste and smell fine when first opened, even if their freshness date is history, but that quality will drop more rapidly in a long-stored package than in a container opened within its freshness period.

Fats are the most prevalent nutrient in nuts, and these suffer during oxidation. It is the short-chain fats that take the hit first. While there are not many of these in peanuts, when the nuts do turn, it makes them no longer pleasant to eat or smell. There will be an effect on some nutrients, especially those that act as antioxidants; it’s their job to react with oxygen, thereby protecting oxidizable substances such as fats.

Again, I do not advise eating out-of-date foods, but if you are going to continue eating from this particular container, consider storing it a well-sealed container in the refrigerator or freezer, as cold temperatures also help slow oxidation and other types of spoilage.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.