A week devoted to forgotten vegetables rarely collapses for lack of enthusiasm. It collapses because the Jerusalem artichoke turns up too early, in too generous a portion, often raw, and day three is spent regretting day two. The variable that decides everything is neither curiosity nor recipe count, it is how many grams of fructans land in each meal. A 150 g portion of Jerusalem artichoke supplies, by the calculation set out below, somewhere between 17 and 24 g of inulin, whereas the crossover trial published in 2010 in the Journal of the American Dietetic Association puts the comfortable ceiling at roughly 10 g of native inulin per day in healthy adults.

Three further points are worth settling before you start. Parsnips accumulate furocoumarins when whole roots sit in the fridge for weeks, and the concentrations involved are not trivial. The legal threshold that would let you call these vegetables a source of protein is technically cleared by Chinese artichoke, which says a great deal about how an energy percentage flatters low-calorie foods. And nearly every vegetable on this list is an autumn and winter crop, which makes the choice of week more decisive than the choice of recipes.

Why this kind of challenge usually stops on day three

Parsnip, Jerusalem artichoke, scorzonera and swede share a trait that carrots and courgettes do not have to the same degree: they store their reserves as fructans rather than starch. These fructose chains slip past human digestive enzymes and reach the colon intact, where they are fermented. That is precisely what makes them nutritionally interesting, and precisely what produces the bloating.

The 2010 trial cited above is useful because it puts numbers on both edges of the window. Twenty-six healthy adults aged 18 to 60 received blinded 5 g and 10 g doses of native inulin or oligofructose. Up to 10 g a day of native inulin and up to 5 g a day of oligofructose remained well tolerated. At 10 g of oligofructose, symptoms rose substantially, with flatulence reported most often and bloating close behind.

The other edge of the window comes from food law. For a product to claim an effect on stool frequency, Regulation (EU) 2015/2314 requires that consumers be told the benefit is obtained with a daily intake of 12 g of native chicory inulin. The useful dose and the uncomfortable dose almost touch. A challenge that stacks three portions of fructan-rich tubers into a single day sits well above both.

What a portion of Jerusalem artichoke actually contains

This calculation deserves to be spelled out, because it is the one argument that genuinely changes how the week should be organised.

The ANSES Ciqual table gives raw Jerusalem artichoke a water content of 80.1 g per 100 g, leaving roughly 19.9 g of dry matter. A 2025 study in Antioxidants, following eight cultivars through 60 days of cold storage, measured inulin contents of 582 to 810 g per kilogram of dry matter. Combining the two, a 100 g portion of fresh tuber holds on the order of 11.6 to 16.1 g of inulin, and a 150 g portion between 17 and 24 g.

Two caveats travel with that figure. It bridges two sources that do not cover the same cultivars, and the content varies with variety, harvest date and storage time. It also contradicts the Ciqual dietary fibre column, which credits raw Jerusalem artichoke with only 2.1 g per 100 g. That contradiction is instructive: standard fibre assays do not capture short-chain fructans properly, so a nutrition table can describe as fibre-poor a food that is in practice among the most concentrated dietary sources of inulin.

The practical consequence fits in one sentence. Treat Jerusalem artichoke as a supporting ingredient at 50 to 80 g per person, blended with a neutral vegetable, rather than as the base of a dish.

Composition of the seven vegetables, with numbers

The values below come from the Ciqual 2020 table, per 100 g of edible portion, raw unless stated. Raw carrot serves as a familiar reference point.

Vegetable	kcal	Protein	Fibre	Potassium	Vitamin C
Raw carrot	40.2	0.63 g	2.7 g	230 mg	2.05 mg
Raw parsnip	58.3	1.54 g	4.7 g	505 mg	11.5 mg
Raw Jerusalem artichoke	60.7	1.94 g	2.1 g	495 mg	5 mg
Raw swede	not reported	1.17 g	2.6 g	349 mg	33 mg
Raw celeriac	29.3	1.38 g	4.5 g	500 mg	2.87 mg
Raw scorzonera	not reported	3.13 g	3.3 g	387 mg	3 mg
Cooked Chinese artichoke	50.8	2.13 g	1.9 g	310 mg	not reported

A few readings are worth drawing out. Parsnip is the only member of the group carrying a meaningful amount of vitamin K1, at 22.5 µg per 100 g. The NHS puts adult requirements at roughly one microgram per kilogram of body weight per day, so 65 µg for a 65 kg person. A 200 g plate of parsnip therefore covers around two thirds of that benchmark, which is real without being spectacular, and a very long way from the 1220 µg per 100 g of fresh parsley.

Swede is the most interesting entry for vitamin C, at 33 mg per 100 g raw, sixteen times the carrot figure. That content does not survive long boiling, and the cooked Ciqual entry drops back to 18.8 mg. Celeriac, for its part, combines 4.5 g of fibre with only 29.3 kcal, giving it the best fibre-to-energy ratio in the group.

What the Swiss thresholds allow, and what they do not mean

Annex 13 of the Swiss ordinance on food information sets two routes for a fibre claim. A product is a source of fibre from 3 g per 100 g or 1.5 g per 100 kcal. It is high in fibre from 6 g per 100 g or 3 g per 100 kcal.

Applied to parsnip, that means 4.7 g per 100 g, a source of fibre by the weight route. But expressed against energy, parsnip reaches 8.1 g per 100 kcal, far above the 3 g demanded for the high-fibre claim. Celeriac climbs to 15.4 g per 100 kcal. Jerusalem artichoke, despite its 2.1 g by weight, reaches 3.5 g per 100 kcal. These vegetables clear the upper threshold through the energy door, simply because they contain a great deal of water.

The same mechanism produces a frankly misleading result on the protein side. The source-of-protein threshold is 12 % of energy value. Cooked Chinese artichoke reaches 16.8 %, raw Jerusalem artichoke 12.8 %. They clear it. And yet 100 g of Chinese artichoke delivers 2.13 g of protein, which changes nothing about a day’s intake. An energy percentage is a ratio, not a quantity. For protein you have to look elsewhere, and the guide to plant protein sources and portions answers that question better than any tuber.

Parsnip and furocoumarins, a genuine storage question

This is the only item in the file that concerns safety rather than comfort. Furocoumarins are natural constituents of the Apiaceae, present in celery, carrot and parsnip, with phototoxic properties.

Work published in 2002 in the Journal of Agricultural and Food Chemistry tracked how they behave under different storage conditions. In freshly harvested parsnips, the sum of five furocoumarins stayed generally below 2.5 mg per kilogram. Stored whole at 4 °C, the roots showed a two-stage rise, after 7 and then 38 days, up to around 40 mg per kilogram. Market parsnips left for 53 days at room temperature, with visible mould infection, reached 566 mg per kilogram. Storage at -18 °C for 50 days, by contrast, produced no marked increase in any form tested. Commercial baby foods containing parsnip, analysed alongside, stayed at 0.41 mg per kilogram or below.

The handling rules follow directly from those numbers. Buy parsnips in sensible quantities and eat them within a fortnight, not after six weeks in the vegetable drawer. A root showing spots, fuzz or a musty smell goes to the compost, even if the affected area looks contained. If you have more than you will use, the freezer is the right answer. The general rules for storing fruit and vegetables apply here with a specific reason behind them.

Oca and oxalates, what sunlight does

Oca, Oxalis tuberosa, takes its name from the botanical genus of sorrel, and like sorrel it contains oxalic acid. Andean communities do not leave this to chance: they expose freshly harvested tubers to sunlight before cooking them.

A 2025 study in Plant Foods for Human Nutrition, covering four cultivars, checked what that practice achieves. Sun exposure lowers oxalate content and raises sugar concentration substantially, while also enriching the tuber in polyphenols and carotenoids. Traditional dehydration, which yields the product known as khaya, likewise reduces oxalates, at the cost of some antioxidant capacity.

An oca bought in Switzerland has rarely had that treatment. Leaving it in bright light for a few days before cooking is therefore not folklore, it is the reason it becomes both sweeter and lower in oxalate. Anyone with a history of calcium oxalate kidney stones should treat oca the way they treat sorrel and spinach, meaning in moderation and alongside a calcium source in the same meal.

Chinese artichoke, a case of its own

Chinese artichoke, Stachys affinis, does not belong to the same family as the other tubers on this list. An analysis published in 2017 in Food Chemistry identifies stachyose and succinic acid as its compositional markers, with a profile dominated by carbohydrates at 36.9 % of dry matter and potassium at 2.36 %.

Stachyose belongs to the raffinose family of oligosaccharides, the same ones found in dried beans. Humans lack the enzyme that splits them, and they are fermented in the colon exactly as the fructans of Jerusalem artichoke are. Chinese artichoke therefore calls for the same caution over dose, however harmless it looks on the plate. Its cooked simple-sugar content in Ciqual, 0.2 g per 100 g, also explains its very discreet flavour: it compensates for nothing with sweetness and needs assertive seasoning.

One last practical detail: you do not peel it. Rub it in a tea towel with coarse salt, rinse, done. It is the fastest vegetable on the list to prepare.

A seven-day programme built around dose

The principle below inverts the usual logic. Instead of introducing a new vegetable at every meal, it spreads the fermentable load and gives the gut microbiota time to adjust. Each day carries a single discovery meal, the other two staying familiar.

Day 1, roasted parsnip. 200 g of parsnip in wedges, roasted at 200 °C with an oil that tolerates the heat, served with lentils. Parsnip is the gentlest of the group and the closest to a familiar vegetable. Oven caramelisation is what makes these roots immediately convincing.

Day 2, celeriac. Half raw as a remoulade, half mashed with potato. The contrast between two textures from the same root teaches more than an additional vegetable would.

Day 3, rest. No new vegetable. This day is not a concession, it is the part of the protocol that decides how the rest goes. The first two days have already lifted fibre intake, and the NHS notes that the average adult eats about 20 g of fibre a day against a 30 g target. Moving too fast has a cost.

Day 4, swede. 200 g in cubes in a curry with chickpeas and coconut milk. Swede holds up to long cooking without falling apart, and its faintly sulphurous note disappears behind the spices.

Day 5, Jerusalem artichoke, in small quantity. 60 g per person, sliced thin, mixed into 200 g of potato in a gratin. That is the sensible maximum for a first encounter. Jerusalem artichoke is never served raw and never on its own.

Day 6, scorzonera. Peel it under cold water, gloved if you can, because the latex stains fingers. As a velouté, or pan-fried after a brief pre-cooking. It is the messiest vegetable here to prepare and the most delicate to eat.

Day 7, Chinese artichoke and tuberous chervil. The two quickest, pan-fried with garlic and parsley. The closing meal should be easy, not ambitious.

A Sunday of preparation up front removes half the dropouts. Soup bases made ahead will absorb any root vegetable without a second thought on a weeknight.

The season decides more than the programme does

Parsnip, swede, celeriac, scorzonera and tuberous chervil are autumn and winter storage crops. Jerusalem artichoke is harvested from autumn to early spring, Chinese artichoke in an even narrower window, often November to March. None of these is a Swiss summer crop.

Launching this challenge in July therefore means buying long-storage roots, imported or held in store for months, which undercuts both the flavour argument and the environmental one. The useful window runs from October to March, with an optimum in November and December, when all seven are simultaneously available. The principle of adapting meals to the seasons applies more strictly here than elsewhere, because out-of-season supply is close to nonexistent.

For sourcing, farmers’ markets and seasonal veg boxes clearly outperform supermarkets on these species. Parsnip and celeriac appear on standard shelves, swede intermittently, and Chinese artichoke, oca and tuberous chervil almost exclusively through specialist growers or direct sales.

What the biodiversity argument is actually worth

This is where enthusiasm most often runs ahead of the data, and it deserves precision.

The figure quoted everywhere comes from the FAO: since the 1900s, some 75 % of plant genetic diversity has been lost, and 75 % of the world’s food is said to come from twelve plants and five animal species. That figure is attributed to a 1999 publication and rests on a methodological basis that has been debated since.

An analysis published in 2014 in PNAS, covering fifty years of national food supply data, gives a more nuanced and more interesting picture. The number of crop commodities contributing to national supplies actually increased, and the dominance of the largest commodities declined within each country. But national supplies became markedly more similar to one another. The food supply has become relatively species-rich nationally and species-poor globally. It is not the individual plate that grew narrower, it is the planet eating the same thing everywhere.

It is also worth separating two gestures that get conflated. Buying a parsnip supports a grower. Conserving a variety is a different job. In Switzerland that work is publicly documented: the National Gene Bank for plant genetic resources held 5319 accessions in 2016 and 6087 in 2025, a trajectory the Federal Statistical Office rates as positive, with an 11.3 % change between the 2016-2018 and 2023-2025 averages. The Federal Office for Agriculture’s PGRFA-NIS information system makes those varieties and collections freely searchable.

Cooking Jerusalem artichoke for a week conserves no variety at all. It does create demand, and demand is what allows a grower to keep cultivating a barely profitable species. That is a real effect, a modest one, and it is better stated at its true size than inflated.

Five mistakes that sink the week

Serving Jerusalem artichoke raw. It combines a high fructan dose with no cooking, and it is the advice most frequently given for this vegetable.

Putting fructan-rich tubers at breakfast. A digestive system on an empty stomach handles a fermentable load poorly, and the discomfort lasts all morning.

Stacking several new vegetables into one meal. If a reaction follows, there is no way to know which one caused it. One at a time makes the information usable.

Buying all seven on day one. Chinese artichoke and oca keep badly, and parsnip degrades over time as described above. Two shopping trips spread across the week beat a single one.

Treating swede like a potato. It contains far less starch and far more water, it releases liquid during cooking, and a mash run like potato mash ends up thin. Low-temperature cooking gives much better results on these watery roots.

Who should skip this format

People living with irritable bowel syndrome should avoid the challenge as described. In that context the NHS advises avoiding foods that are hard to digest and keeping a food diary to identify triggers. A week built on fructans is the opposite of that approach.

Anyone who has had calcium oxalate kidney stones should set oca aside, or include it in small amounts alongside a calcium source in the same meal.

People on vitamin K antagonists do not have to drop parsnip, but they do need a steady rather than fluctuating intake. Going from none to 200 g daily for seven days and then back to none is exactly the swing that therapeutic monitoring is designed to avoid. That question belongs with the clinical team, not with an article.

Anyone who has only recently increased their fibre intake will do better spreading the programme over two weeks rather than one, keeping the rest days.

What this article does not say

No trial has tested this specific programme. The tolerance thresholds quoted come from studies on isolated inulin given as a supplement, not on whole tubers eaten within a meal, and the food matrix probably alters the speed of fermentation. The conversion from inulin content to fresh portion bridges two sources covering different cultivars, which is why the range given is wide.

No average Swiss price is offered for these vegetables, because the gaps between direct sales, markets and supermarkets are too large for a single range to mean anything. Finally, Ciqual is a French table; Swiss production may diverge according to soil and variety, even if the order of magnitude holds.

Frequently asked questions

Do I need to peel Jerusalem artichoke? No, if the skin is thin and the tuber well scrubbed. The skin changes neither the inulin content nor digestive tolerance, mostly just the look of the dish.

Does cooking reduce fructans? It transfers part of them into the cooking water, which can then be discarded. Boiling in plenty of water, water not reused, does lower the load. Roasting or making soup keeps it entirely.

How much Jerusalem artichoke for a first attempt? 50 to 60 g per person, cooked, mixed with another vegetable. If tolerance is good, you can double it next time.

Is a parsnip that has darkened still edible? Light browning at the cut surface is harmless oxidation. Dark patches, a fuzzy appearance or a musty smell mean the root goes in the bin, consistent with what furocoumarin measurements on infected roots show.

Do these vegetables replace potatoes? Not in energy terms. Celeriac at 29.3 kcal per 100 g supplies about a third of the energy of a potato. A dish built on these roots alone leaves you hungry, which adding a pulse or a wholegrain corrects.

What do I do with the week’s leftovers? A single soup at the end of the week absorbs the tail ends of all of them. It is also the best moment to test the combinations you did not dare try.

Is this challenge suitable for children? Yes, in reduced portions and without Jerusalem artichoke at the start. NHS fibre benchmarks drop to 15 g a day between ages 2 and 5, which leaves little headroom. The gradual approach described in the advice on getting children to like vegetables remains more effective than a timed challenge.

Can I grow these myself? Jerusalem artichoke, yes, with a serious caveat: it is invasive and re-seeds from the smallest tuber fragment left in the soil. Parsnip and swede sow without difficulty. Preparing an autumn vegetable garden is the right moment to put them in.

Sources

• ANSES, Ciqual 2020 food composition table
• Bonnema et al., Gastrointestinal tolerance of chicory inulin products, Journal of the American Dietetic Association, 2010
• Regulation (EU) 2015/2314 on the native chicory inulin claim
• Inulin content and antioxidant capacity of eight Jerusalem artichoke cultivars, Antioxidants, 2025
• Effects of storage conditions on furocoumarin levels in parsnips, Journal of Agricultural and Food Chemistry, 2002
• Sunlight exposure and traditional dehydration of oca, Plant Foods for Human Nutrition, 2025
• Polar constituents and nutritional value of Chinese artichoke, Food Chemistry, 2017
• Khoury et al., Increasing homogeneity in global food supplies, PNAS, 2014
• FAO, What is agrobiodiversity
• Swiss Federal Statistical Office, plant genetic resources for food and agriculture, MONET 2030
• Federal Office for Agriculture, PGRFA-NIS national information system
• Ordinance on food information, SR 817.022.16, Annex 13
• NHS, how to get more fibre into your diet, vitamin K and diet and irritable bowel syndrome

To go further, the species-by-species guide to forgotten vegetables complements this programme on technique, and root vegetables through winter place these tubers in a full season.