The nutritional value of fruit and vegetables begins to decline from the moment of harvest. Vitamin C, folate, and B vitamins are particularly vulnerable to degradation during storage. Produce that has been picked unripe and transported over long distances before sale will have measurably lower nutrient content than locally grown, recently harvested produce eaten in season. A study comparing the vitamin C content of spinach found that spinach stored for seven days at room temperature retained only 39 percent of its initial vitamin C, while refrigerated spinach retained 74 percent.
Seasonal Eating and Microbiome Diversity
Research on the Hadza hunter-gatherer population of Tanzania found dramatic seasonal variation in gut microbiome composition that correlated precisely with seasonal variation in the foods available. Species that were abundant in the wet season were nearly undetectable in the dry season, then re-emerged the following wet season. This suggests that the human gut microbiome evolved to cycle through seasonal food variation, and that the year-round homogeneity of modern food availability may be a driver of reduced microbiome diversity.
Practical Seasonal Eating on the Isle of Man
- Spring: asparagus, peas, spring onions, spinach, radishes, and new potatoes provide fresh nutrition after the root vegetable-dominated winter
- Summer: courgettes, tomatoes, cucumber, lettuce, runner beans, and all summer fruits provide maximum polyphenol and vitamin C content
- Autumn: butternut squash, pumpkin, apples, pears, and root vegetables provide beta-carotene and prebiotic fibre
- Winter: dark leafy greens including kale and cabbage, leeks, celeriac, and fermented vegetables provide micronutrients through the low-sun months