I. 22 Swiss Chard
The nitrate-betalain-magnesium triad – a colorful leafy green that brings the NO axis and antioxidant matrix together.
Swiss Chard in 1 minute
What does it provide? Nitrate concentrate (200–400 mg/100 g – on par with spinach and beetroot), betalain pigments (betacyanin in red-veined leaves, betaxanthin in yellow ones), high magnesium (81 mg/100 g – 20% of adult daily requirement), folate (14% RDI), vitamins K and A [2764].
How much? 50–75 g raw or lightly steamed leaves/day. The multicolored "rainbow chard" provides the maximum betalain matrix [2765].
When to avoid? Kidney stone predisposition (moderate-to-high oxalate ≈ 645 mg/100 g – soaking and boiling reduce it). Warfarin (vitamin K – constant intake). Infants under 6 months: nitrate-methemoglobinemia.
Swiss chard is the leaf-developed variant of wild beet (Beta vulgaris) – a Mediterranean vegetable cultivated already in the time of Aristotle and Theophrastus. Italian "bietola" and French "blette" were woven into the dietary traditions of the Roman Empire, and by the Renaissance gardening books the multicolored "Swiss chard" had appeared. At the end of the 19th century, Adolf von Baeyer (1879) isolated the betalain pigments – research continues today on their polyphenol-like health effects.
Scientific Background
Swiss chard's nitrate content is similar to that of spinach and beetroot (200–400 mg/100 g fresh weight) – it is also a member of the Bondonno 2016 J Nutr "nitrate-rich vegetable portfolio" [2748]. Activation of the oral nitrate → nitrite → NO pathway lowers blood pressure and improves flow-mediated dilation [912].
The betalain pigment (betacyanin + betaxanthin) has strong antioxidant capacity – according to Clifford 2015 Nutrients review, in vitro inhibition of lipid peroxidation by betalain is comparable to that of anthocyanins, but it acts through different pathways [854]. Small-sample human RCTs have documented decreased plasma malondialdehyde and inhibition of LDL oxidation [2762] [2763].
The magnesium content is clinically relevant: 81 mg/100 g – magnesium deficiency is common across Europe (according to Schiopu 2022 review, 25–40% of the adult population). Magnesium is a cofactor for insulin sensitivity, NMDA receptor modulation, and vascular function.
- + Olive oil + lemon: classic Mediterranean "chard sauté" – fat enhances carotenoid and vitamin K absorption.
- + Beetroot + walnut: dual nitrate matrix + omega-3.
- + Eggs (omelet, frittata): classic Italian "frittata di bietole" – protein + iron + fat.
- + Citric acid (in the cooking liquid): reduces oxalate content.
- + Trout or salmon: Mediterranean omega-3 + nitrate combination.
- Very long boiling (> 10 min): partial loss of nitrate + vitamin K.
- Iron supplement at the same meal: oxalate chelation.
- Dairy + high-oxalate context: calcium-oxalate formation.
- Calcium-oxalate kidney-stone predisposition: high oxalate content (≈ 645 mg/100 g) – soaking + boiling in plenty of water reduces it.
- Warfarin: vitamin K (≈ 830 µg/100 g!) – strictly constant intake.
- Infants under 6 months: methemoglobinemia risk.
- Active Crohn's disease, IBD: high oxalate + nitrate to be avoided.
- Hashimoto + high raw dose (≥ 200 g/day): moderate goitrogenic potential as a Brassica relative.
References
[854] Clifford T et al. The potential benefits of red beetroot supplementation in health and disease2015;7(4):2801–2822. Nutrients. 2015. Link
Review article (Nutrients) on the potential health and disease benefits of red beetroot supplementation.
[912] EFSA Panel on Contaminants. Nitrate in vegetables — scientific opinion. EFSA Journal 2008;689:1–79. EFSA Journal. 2008. Link
At the request of the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) performed a scientific risk assessment of nitrate in vegetables. The opinion reviews the sources of nitrate exposure and its possible health consequences, weighing the risks associated with nitrate intake against the beneficial effects of vegetable consumption. The document was published in the EFSA Journal (2008; 689:1-79).
[2748] Bondonno CP, Croft KD, Hodgson JM. Dietary nitrate, nitric oxide, and cardiovascular health. Journal of Nutrition. 2016.
Review of human studies on the cardiovascular effects of nitrate-rich vegetables (including arugula, spinach, beetroot, watercress). Daily nitrate intake is converted via oral-microbiota nitrate reduction into systemic nitric oxide, improving vascular function and reducing blood pressure.
[2762] Pyo YH, Lee TC, Logendra L, Rosen RT. Antioxidant activity and phenolic compounds of Swiss chard (Beta vulgaris subspecies cycla) extracts. Food Chemistry. 2014.
Study of the antioxidant activity and phenolic compounds of Swiss chard (Beta vulgaris var. cicla). It documents the antioxidant capacity of the leaf's betalain and polyphenol fraction.
[2763] Ninfali P, Angelino D. Nutritional and functional potential of Beta vulgaris cicla and rubra. Fitoterapia. 2013. Link
Review of the nutritional and functional potential of Beta vulgaris cicla (Swiss chard) and rubra (beetroot). It summarizes the distribution of betalain pigments, vitamins, and minerals and their potential health effects.
[2764] . Chard, Swiss, raw (NDB 11147). USDA FoodData Central. 2019. Link
Entry from the USDA FoodData Central nutrition database for raw Swiss chard, documenting macro- and micronutrient composition (including magnesium, folate, vitamins K and A). A reference source for the nutrient values reported in the chapter.
[2765] . Swiss chard — low FODMAP serving guidance. Monash University FODMAP. 2023. Link
Classification from the Monash University FODMAP database placing Swiss chard in the low-FODMAP category (green up to a 75 g serving). It provides a practical basis for the safety of consuming 50—75 g daily.