Is seaweed alone sufficient to ward off scurvy?

Picture a small, densely populated archipelago. The level of technology is roughly medieval, and the sea is the primary source of food. Arable land is nonexistent, as the society needs to keep the islands forested with pine to sustain its navy and fishing fleet in the long term. Could scurvy be addressed solely by seaweed?

There are several different enzymes involved in vitamin C synthesis and the majority of them function just fine in humans.

There are two steps in the pathway to produce Vitamin C that are damaged in humans. The first is universally prevalent. The second error is known to be totally eliminated in some populations.

The error is in the gene for L-gulono-gamma-lactone oxidase. This is the last enzyme in the ascorbic acid synthesis pathway. The reaction L-GLO catalyzes (production of 2-keto-gulono-gamma-lactone) will also occur spontaneously on its own, so humans do in fact produce small amounts (15-20mg per day) of vitamin C. L-GLO is pseudogenetic in humans- no alternative product occurs.

The second error deals with lactonase. Lactonase is the enzyme preceding L-GLO in the chain. If functional it would dehydrate and cyclise L-glulonic acid to produce L-gulono-gamma-lactone. Mutants of this second type produce no ascorbic acid and must get it from external sources lest they develop a health threatening deficiency.
Quite predictably, the prevalence of lactonase dysfunction can be highly correlated with the availability of vitamin C. In certain tribes of desert nomads the dysfunction is totally absent. It has been predicted that historical seafaring communities would have also had a higher percentage of functional lactonase enzymes due to the disproportionate loss of sailors with the malfunctioning allele because of scurvy.

Reused with permission.

The U.S. RDA for vitamin C is about 60 milligrams per day.
Common seaweeds contain between 0.04 and 0.55 mg vitamin C per gram wet weight.

Depending on the weed, that means you’d have to eat between 110g and 1.5 kg to get your RDA. That’s doable, but perhaps not pleasant.

From cite:

Thank you for the information.

Another question: how long does it take for an initially healthy adult to die from scurvy?

If they have to use pine forests for the ships [and by the way they will also need something like oak for the hulls… so they would get a lot of use of acorn for flour mast and leached and roasted for coffee surrogate…] they can use the pine needles in tea to prevent scurvy.

Forested by pine trees, you say?

From Wikipedia.

Yes, pine needle tea (made from the very youngest msot tender needles) is also not bad tasting. But they have to remember to let the water cool a bit as boiling will destroy part of the vit C.

The problem with the seaweed is only a few are palatable, and they’d eat their way through those pretty fast without serious conservation efforts.

Here is a good link:

"Vitamin C
Algae provide a worthwhile source of vitamin C (Qasim et Barkati 1985). The levels of
Vitamin C average between 500 to 3000 mg/kg of dry matter for the green and brown algae (a
level comparable with that of parsley, blackcurrant, and peppers), whereas the red algae contains
vitamin C levels of around 100 to 800 mg/ kg. "

Many types of fresh food (not just fruits and veggies) were found to combat scurvy (or at least to signficantly delay its onset). I don’t know if fresh fish was among them, but it’s certainly plausible.

Death by scurvy:

You could live up to two years as your body fell apart from lack of vitamin c.

I’m not convinced you need the USDA amount of vitamin C to prevent scurvy. I bet lots of Americans don’t get the RDA, and I’ve never seen a case.

I suspect this is the answer. After all, these peoples survived for thousands of years. Anyhoo, I base this suspicion on what I’ve read about the even more remarkable survival of peoples in Arctic regions. Apparently, they got their vitamin C from animal sources. Scurvy was a problem for European/American sailors because they dried their meat for long voyages, in the process destroying the vitamin. If one subsisted entirely on fresh meat, however, there was enough C to get by. IOW, E/A’s who “went native” did okay; those who clung to the old ways did not.

They did, but maybe not 100%. Even in the tundra there are small plants that are good sources of Vit C, and the natives have also been known to eat some of the stomach contents of herbivores, too.

But you’re right, raw meat does contain Vit C.

You might not notice low level cases of scurvy- weak gums, wounds that heal slowly, etc.