Are organic vegetables better for your health?

Researchers explore the nutritional value and antioxidant potential of organic and conventional vegetables of the genus Allium – which include garlic, leek and onions.

Allium L. vegetables are a valuable source of a variety of health-promoting substances – including those with antioxidant properties such as polyphenolic compounds and vitamin C. But unfortunately, these vegetables can also contain chemical pollutants such as pesticide residues and nitrates. For this reason, organically grown plants – which are perceived as healthier and free of this type of contamination – are becoming increasingly popular.

According to the principles of organic farming, mineral fertilisers and chemical pesticides are not used. This cultivation method may therefore positively affect the levels of basic nutrients, mineral elements and biologically active substances in fruit and vegetables.

But there is currently no conclusive evidence that organically grown products are of higher nutritional value - or that consuming them has greater health benefits – compared with those grown using conventional methods.

A battery of tests

In a new study, published in Scientific Reports, researchers compared the antioxidant capacity and nutritional value of four species of Allium L. vegetables obtained from organic and conventional production.¹

The researchers collected samples of garlic, leek, yellow and red onions that were grown on two organic and two conventional farms in Poland. After washing and homogenisation, they used a variety of analytical techniques to determine their basic nutrient levels and mineral composition – as well as their content of bioactive substances and antioxidant potential.

Comparison of the organically grown vegetables with conventional ones in terms of their content of dry matter, crude protein and crude fibre revealed no general trend indicating the superiority of one method over the other.

However, all organic vegetables analysed were more abundant in minerals (Ca, Mg, Fe, Zn, Cu and Mn) and bioactive compounds. They also had higher antioxidant capacity as measured by FRAP (ferric-reducing antioxidant power) and DPPH (free radical scavenging activity) tests.

Species differences

The species of Allium L. vegetable influenced the content of bioactive substances. Among those tested, garlic had a significantly higher content of dry matter, total protein and minerals (Mg, Ca, Fe and Zn).

In the case of compounds with potential antioxidant activity, garlic was the most abundant in total polyphenols, red onion in vitamin C – and leek showed the highest FRAP and DPPH values.

The researchers used water generated from an ELGA PURELAB® Classic laboratory water purification system to minimise the risk of introducing contaminants that may affect the results of their experiments.

Potential health benefits

The results of this study confirm the influence of the cultivation method on the nutritional value and antioxidant capacity of Allium L. vegetables. Vegetables from organic cultivation had a much higher content of minerals, as well as compounds with antioxidant properties – such as polyphenolic compounds and vitamin C – compared to conventionally grown ones.

Overall, these results provide evidence in support of the idea that consuming organically grown Allium L. vegetables may help strengthen the body’s natural antioxidant defences – which, in turn, could provide potential health benefits.

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Reference:

1. Czech A, Szmigielski M, Sembratowicz I. Nutritional value and antioxidant capacity of organic and conventional vegetables of the genus Allium. Sci Rep. 2022;12(1):18713. doi: 10.1038/s41598-022-23497-y.

Dr Alison Halliday

After completing an undergraduate degree in Biochemistry & Genetics at Sheffield University, Alison was awarded a PhD in Human Molecular Genetics at the University of Newcastle. She carried out five years as a Senior Postdoctoral Research Fellow at UCL, investigating the genes involved in childhood obesity syndrome. Moving into science communications, she spent ten years at Cancer Research UK engaging the public about the charity’s work. She now specialises in writing about research across the life sciences, medicine and health.