When I walk through the vegetable garden, I pick whatever is ready â€“ a collard leaf, snap pea or cherry tomato — and devour it on the spot. The flavor is intense – crisp, fresh and satisfying. In contrast, the produce from the supermarket seems second-rate with limp texture and insipid taste. I recall from my childhood the sharp sweet crunch of the Pippin apples straight off my grandmotherâ€™s tree. If I hope for a similar experience with the bloated Gala, Fiji or Golden Delicious, I am destined for disappointment and indigestion.
Why do homegrown fruit and vegetables taste so different from commercial produce? Has the quality of our food declined? What are my taste buds trying to tell me?
Our ancient ancestors had to rely on taste to tell them what to eat. They gathered roots, leaves, and fruit as the main bulk of their diet; a small nibble had to signal whether a new plant was edible or not. With five differing chemical sensors â€“ salt, sweet, sour, bitter and umami (the savory protein flavor in cheese, meat and beans) — the human tongue is able to distinguish thousands of different tastes. Over the millennia, the human tongue evolved to become the gatekeeper of nutritional health.
When I put something in my mouth, unknowingly my taste-buds check out the food value of what I am about to swallow. As I chew, my tongue investigates all the different components, looking for those substances that provide both pleasure and nourishment. Depth and intensity of flavor indicate that a broad variety of vitamins and minerals are concentrated in the mouthful. If, on the other hand, the taste is bland or overly sweet or salty, I am probably not getting much dietary benefit.
Plants are mostly made of organic compounds, arrangements of carbon, hydrogen, oxygen, and occasionally nitrogen. About 5% of the plant structure is inorganic minerals. Humans have co-evolved with these plant substances; we need all their nutrients to build our bodily structure and keep us alive. We are what we eat and we know what to eat because it tastes right!
Looking for data to test whether my taste buds were on track, I purchased a brix refractometer. This simple instrument is designed to measure the total dissolved solids in the sap of a plant. You squeeze the plant juice onto the plate, look through the eyepiece, and read off the percentages. Traditionally, brix readings are taken to gauge the sugar content of fruit juices, particularly grapes. However, brix seems to actually measure a complex combination of sugars, amino acids, oils, proteins, flavonoids, minerals, and other good things flowing through the plant. Brix levels approximate the concentration of nutrients.
Curious about the value of those flavorless â€˜organicâ€™ tomatoes sold in a leading supermarket, I checked the brix level. It measured at 4.5. According to a brix chart, this is well below the average of 6 for ordinary tomatoes. In comparison, the rather neglected yellow cherry tomatoes I over-wintered, came in at 9. Similarly, a nice looking store-bought lettuce tested at 3, while my own lettuce came in at around 6. My taste buds and brix testing seem to agree that something is wrong with the way food is grown commercially. As the scientists put it, the nutrient density of conventionally grown food is not up to scratch.
Nutrient density is a measure of the quality of nutritional substances in a food, compared to the number of calories it contains. Nutrient-dense food provides essential nourishment â€“ vitamins, minerals, amino acids, fats, etc. Nutrient-poor, high-calorie foods such as soda and potato chips contain little else than corn syrup and salt and do nothing to promote health.
Research over the last 50 years shows that the nutrient density of food has steadily deteriorated. Michael Pollanâ€™s bestseller, In Defense of Food, cites studies that show losses of between 10% and 40% of essential nutrients in commercially grown fruit and vegetables. As he puts it, â€œâ€¦you now have to eat three apples to get the same amount of iron as you would have gotten from a single 1940 apple.â€
Pollan blames a lot of this nutritional decline on the overuse of chemical fertilizers and neglect of the soil. A 4-year study published in 2007 by the European Union shows extraordinary differences between organic and conventional farming. Organic fruits and vegetables have as much as 40% more antioxidants and higher levels of minerals such as iron and zinc. Harmful elements — lead, mercury, aluminum, and nitrates — were significantly lower. Good soil grows better produce that supports enhanced human well being.
Growing for Nutrition
If we want our food to be health giving, we have to be mindful of our cultivation methods. To ensure fruit and vegetables are nutritious it is necessary to take care of both the biological and mineral health of the soil. Here are some rules of thumb that help to grow healthy fruits and vegetables with high brix levels and exceptional taste:
- Think in terms of balance and relationships rather than deficiencies. We cannot add substances to the soil in isolation without thinking of the whole soil ecology. For example, Neal Kinsey in Hands-On Agronomy tells us that unless calcium and magnesium are available in particular proportions, neither becomes fully available.
- Over-simple growing methods based on NPK fertilizers do not produce superior foods. As Pollan says, â€œPlants can live on this fast-food diet of chemicals, but it leaves them more vulnerable to pests and diseases and appears to diminish their nutrition quality.â€ Use chemicals, particularly nitrates and phosphates, very sparingly.
- The foundation of healthy soil is carbon rich humus. Add compost, organic matter, green manures, and organic mulches regularly to your soil. Aim to achieve humus levels between 5% and 10% of your soil structure.
- Plants absorb micro-nutrients more easily when they have been pre-digested by the â€œstomachâ€ of the soil food web. Stock the soil with life using microbial products such as compost tea.
- Occasionally feed the soil food web with complex organic and inorganic materials. Use sea minerals, kelp, rock dust, fish protein, bentonite clay, wood ash, diatomaceous earth, alfalfa, etc. Use everything sparingly.
- Grow for quality and diversity as well as quantity. Experiment with a wide range of plant varieties. Restrict over-bred hybrids that perform well but have little taste or nutritional value.
- Trust your tongue to tell you the value of your food. Eat whatever is most ripe and ready; eat it young and fresh; eat it until it becomes old and tough.
Michael Pollan: In Defense of Food.
Neal Kinsey & Charles Walters: Hands-On Agronomy