Phytonutrients: Nature’s Protective Compounds

Hi I’m Sammy,

Your Good Farm in-house nutritionist. Here to bring you essential information on nutrition, diet and permaculture gardening - in a bite size, easy to understand, science-backed way.

About ten years ago, I listened to a podcast with Chris Kresser interviewing Jo Robinson, a food writer and researcher known for her work exploring how modern agricultural practices have altered the nutritional profile of fruits, vegetables, and animal products, particularly through selective breeding, feed, and farming methods. At the time I was midway through my health science degree, and I was completely absorbed in what she was sharing. Before the episode had even finished, I had bought her book, Eating on the Wild Side, and went on to read it multiple times.

Around that same time, I was working for organic growers at farmers markets across Sydney, one of which was Carriageworks Farmers Market. Unlike most markets, it operates as a true farmers market, meaning every stallholder must be the grower or the maker. That direct connection to the source of food shaped how I understood quality, and ultimately what constitutes a healthy diet. It was not just about what something looked like, but how it was grown, when it was harvested, and how quickly it reached the person eating it.

Once I began to understand phytonutrients, I started seeing plants completely differently. I no longer viewed vegetables as just the parts commonly eaten, but as the entire plant from root to leaf, including flesh and skin. At the markets, it was common for customers buying a bunch of beetroot to ask for the leaves to be removed, leaving only the roots. That moment often became an opportunity to explain that the leaves are frequently more nutrient-dense than the root itself.

Phytonutrients, also known as phytochemicals, are compounds produced by plants to protect themselves. They defend against pests, UV exposure, and environmental stress. The parts most exposed to the elements often contain the highest concentration of these protective compounds. Beetroot leaves, the dark green tops of leeks, pumpkin skin, and citrus peel and pith are all examples. In many cases, however not all, the darker, more deeply coloured parts of a plant are the most nutrient dense.

These compounds contribute to antioxidant activity, support inflammatory balance, influence detoxification pathways, and interact with the gut microbiome. Diets rich in a wide variety of plant foods, and therefore a broader spectrum of these compounds, are consistently associated with reduced risk of chronic disease and improved long term health outcomes. Traditional diets naturally contained far greater diversity than what is typically consumed today.

The presence of these compounds in food is influenced by several factors.

Freshness is one of the most important. From the moment a plant is harvested, nutrient degradation begins. The longer the time between harvest and consumption, the greater the loss. Food that moves through extended supply chains may appear visually appealing but can be significantly reduced in nutrient density, including both phytonutrients and micronutrients such as vitamin C, by the time it is eaten. There are some exceptions to this rule. Fruits such as watermelon and tomatoes can increase in certain nutrients as they continue to ripen after harvest.

Growing conditions are equally important. Once you understand that phytonutrients are compounds produced by plants as part of their natural defence system, it changes how you view farming practices.

When a plant is routinely exposed to herbicides or pesticides, its own defensive pressures may be altered. As a result, the plant may not need to produce the same level of protective compounds. Some research has suggested that conventionally farmed produce can contain lower levels of certain micronutrients compared to plants grown under more challenging or less protected conditions, including organically farmed systems, where plants may be exposed to different environmental pressures and therefore maintain stronger internal defence responses.

This is where the conversation around organic food often lacks nuance. Choosing organic produce from large supermarket chains can reduce exposure to synthetic chemicals, but it does not address the length of time between harvest and consumption. Food that has travelled long distances or been stored for extended periods will be lower in nutrient density. In this context, it is possible to have food that is free from certain inputs yet lacking in the compounds that contribute most to its nutritional value.

How food is prepared also plays an important role in nutrient availability, including both micronutrients and phytonutrients. Some compounds only form through preparation. For example, allicin, one of the most active compounds in garlic, is only created when garlic is chopped or crushed. It then needs a short period of time, around 10 minutes, to fully develop and become more stable to heat. In other cases, cooking increases nutrient availability. Cooked carrots, for instance, provide more accessible beta-carotene than raw carrots. Fat also plays a key role, as many of these compounds are fat soluble and are better absorbed when consumed with dietary fat.

Another factor is how plants have been bred over time. Many modern varieties have been selected for sweetness, size, and shelf stability. In doing so, some of the more bitter and protective compounds have been reduced. Wild and traditional varieties often contain higher levels of phytonutrients, even if they are less familiar in taste or appearance.

When food is grown and sold within the same region, freshness is more within reach. The shorter the time between harvest and consumption, the more likely the food is to retain its nutritional value.

Helena Norberg-Hodge, a pioneer of the localisation movement and founder of Local Futures, highlights that local food systems are not only about reducing distance, but about restoring relationships between people, land, and food. Localisation strengthens communities, supports small-scale farmers, and reconnects food systems to place in a way that is both ecological and economic.

If you are looking for a starting point, visit a local farmers market and take the time to speak with a grower. Start to include a portion of your weekly shop from there where possible. Alongside this, include a new plant food each week and begin eating parts of the plant that are often discarded, such as leaves and stems. Aim for variety and use the whole plant from root to leaf where possible. Grow something yourself, even a single plant in a pot. Use it fresh, eat it fully, and include the flowers where they are edible.

The act of reconnecting with food, how it is grown, and the people behind it offers great benefits that extend well beyond nutrition.

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Further Reading & Listening

• Eating on the Wild Side by Jo Robinson
• Why Grassfed Is Best! by Jo Robinson
• Cooked: A Natural History of Transformation by Michael Pollan
• The Dorito Effect by Mark Schatzker
• Dirt to Soil by Gabe Brown
• What Your Food Ate by David R. Montgomery and Anne Biklé
• Local Is Our Future by Helena Norberg-Hodge
• Call of the Reed Warbler by Charles Massy
• Chris Kresser with Jo Robinson, Could ‘Eating Wild’ Be the Missing Link to Optimum Health?

References

Liu RH (2004) American Journal of Clinical Nutrition
Slavin JL & Lloyd B (2012) Journal of Nutrition
Kalt W (2005) Critical Reviews in Food Science and Nutrition
Brandt K et al. (2011) Journal of the Science of Food and Agriculture
Barański M et al. (2014) British Journal of Nutrition
Lee SK & Kader AA (2000) Postharvest Biology and Technology
Dewanto V et al. (2002) Food Chemistry
Song L & Thornalley PJ (2007) Journal of Agricultural and Food Chemistry