By Rebecca Rullo, A Nutrition Communication Student at Arizona State University
Many of us understand that fruits and vegetables are important for optimal health, but we may not understand how they are related to the seasons of the year. We might buy the same foods year round, thinking we have our healthy diet nailed with the food that’s available year-round. Seasonal eating is becoming more popular, but we might question its legitimacy. Can we take in sufficient nutrients while eating only what is available at particular times of the year, and is doing so better than eating out-of-season? Seasonal eating may prevent some of the prevalent nutrient deficiencies today by leading to consumption of more variety and more whole foods.
The World Health Organization states that we should consume “a minimum of 400g of fruit and vegetables per day”. This recommendation may give people the message to avoid potatoes and root vegetables, or the message that all spring and summer produce is healthier than all fall and winter produce, regardless of the season. Rather than recommending that we avoid eating potatoes and tubers, maybe we should be emphasizing eating them at certain times of the year.
Seasonal foods have higher nutrition content and their composition may match our bodily needs in different weather. During winter, if citrus fruits are out of season, potatoes may be a better source of vitamin C than the citrus. Switching from citrus to other fruits and vegetables creates more variety in the diet. For instance, fall foods may contain nutrients that are particularly beneficial for that season and may require a cooking method that suits the colder weather, according to the George Mateljan Foundation.
Some say that nutrient differences between in-season and out-of-season foods are minor and that even seasonal food quality is decreased through soil depletion, processing, handling, and cooking. A study comparing the amount of vitamin C in broccoli in season and out of season showed the in-season broccoli to have a higher vitamin C content. The author notes that eating produce that is out of season is better than not eating any. However, eating out-of-season produce replaces in-season produce like eating empty-calorie foods replaces energy-dense foods, which can add up in overall nutrient consumption to a more significant difference in nutrient intake.
Seasonal eating is neither easy to define nor easy to implement without knowledge of seasonal foods, agriculture, and climates. Seasonal foods change as frequently as each month, not necessarily lasting an entire three months of a season. They also vary by region. Familiarity with cold weather and warm weather crops helps generalize what types may be available in certain seasons. If we think seasonal eating may be limiting, our lack of knowledge in these areas and our abundant variety of out-of-season foods is actually more limiting. The frequent change up of diet allows more variety of produce to be consumed and places a focus on whole foods and produce over processed and convenience items. The better taste of in-season foods may lead us to choose more of them and fewer calorie-dense options. Regardless of any differences between in-season and out of season produce, eating seasonally helps us eat whole foods that are much more nutritious than processed foods.
Nutrient deficiencies can occur under any condition where a person is unable to take in a variety of foods. Eating seasonally may appear to limit variety until we understand how each season presents its own variety. All food groups can be consumed in each season, and foods contain varying combinations of micronutrients. As long as we consume a variety of food groups through the year, we don’t have to rely on a summer source of vitamin C through the fall and winter, when it probably doesn’t contain the proper amount of the vitamin anyway.
While scientific studies on the comparison of seasonal diets in the United States with non-seasonal diets are lacking, nutrient deficiencies do not appear to be caused by seasonal eating. Studies have been done comparing nutrient intakes among individuals at different seasons in the year. Intakes are usually similar in spite of different seasons, which shows that we are able to get adequate nutrients. The similarity may be minimum in countries that have fewer resources, such as in the case of one study where animal sources were unavailable, resulting in low calcium, iron, and B12.
The lack of animal sources was not related to seasonal eating. In the United States, we have a wider selection of seasonal foods. Nutrient deficiencies that occur in the United States today are because of poor diet and poor food quality, neither of which is indicated by seasonal eating. For countries that still eat seasonally, other deficiencies occur because of agricultural difficulties and economic status rather than from eating foods by the season.
As nutrition science advances and we find out more about the best foods to consume for optimal health, the health disparities among different regions with similar dietary intakes appear harder to explain. We know that humans have survived on many diets in many climates, but to what extent their health was affected is not really clear. Evaluating whether seasonal eating is important is hard when we have little details from history of the effects when people had no choice but to eat seasonally, because of other factors contributing to the countries that still eat seasonally, and because of a lack of research studies comparing seasonal and non-seasonal diets in the United States.
What is clear is that eating seasonally in the modern day supports other healthy habits and a higher nutrient consumption is likely. The connection with our environment through seasonal eating could be fulfilling psychologically, as well.
As the United States Department of Agriculture suggests, what we know about nutrition in some aspects is very clear: Work to eat a balanced diet full of fresh fruits and vegetables (50% of your plate), a variety of proteins including red meat, dairy, grains, and eggs.
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