Should your diet change with the seasons?

Seasonal eating is the idea that our body craves certain food based on the time of year. But is that accurate?

There's more to this than 'no carbs before Marbs'. Are we evolutionarily attuned to eat what's in season? And do we need different nutrients at different times of the year?

“Advocates of the diet say that in summer months, due to increased perspiration, we naturally look for hydrating foods such as melons, berries and peaches,” explains Dr Mike Molloy, founder of M2 Performance Nutrition. “In the cooler months [the theory argues] we start to crave more veggies, grains and fat rich foods perhaps to increase body fat stores.”

As anyone who’s felt the urge to nail a whole pack of biscuits on a cold winter evening knows, there is some truth in this. But what does ‘seasonal eating’ actually mean?

What is Seasonal Eating?

“When people talk about eating in season, they’re also talking about eating locally too– it’s eating in season for where you live,” explains Daniel Clarke, sustainable nutrition manager at Huel. This sounds simple, but doesn’t really gel with modern life. Clarke continues:

“What happens when your parents come from Japan but you live in Italy or you decide to go on holiday to the Caribbean for two weeks? Do you have to eat seasonally based on our genetics or where you live at the time? How do you even go about determining that? How long do you have to be living in a country to stop eating seasonally based on where you came from and start eating based on where you live?”

Clearly, humans don’t live like that and the definition of what is a seasonable crop is flexible across different countries  – especially so considering that thanks to science we can pretty much grow anything at any time.“Are we evolutionarily attuned to eat what's in season? No. Humans are adaptable and have been able to live from the Arctic down to Tierra del Fuego,” says Clarke.

So, what does science say?

The Science Behind Eating Seasonally

“There is a lack of studies looking at this approach overall which makes examining it from an evidence-based perspective difficult,” explains Malloy.

However, a 2018 study looking at seasonal diets in older adults in Turkey discovered some interesting results. In the study, men and women over the age of 65 recorded their food intake across the seasons. Both sexes reported an increase in calorie intake, including carbohydrates, vegetable protein, n-3 fatty acid and sodium intake. For the women in particular, vitamin C, iron and zinc intake was highest in spring, and cholesterol, retinol, vitamin D and niacin intake highest in fall, suggesting different biological needs in different seasons. The problem was, while the study noticed this, it couldn’t say if there was a benefit, concluding: “ It is not clear if nutrition plans in older adults will benefit from consideration of seasonal changes in eating habits.”

Clarke agrees that evidence in favour of seasonal diets is scant. He points to a Journal of the Academy of Nutrition and Dietetics study and a European Journal of Clinical Nutrition study, both of which conclude that while people may eat slightly more in the winter than the summer, it isn’t especially significant.

The Benefits of Seasonal Eating

The evidence suggests there is very little benefit in eating with the seasons. Is there anything to be gained at all? “The only nutrient that we need to keep an eye on through the seasons is vitamin D,” explains Clarke. “Our body can make vitamin D by utilising sunlight, which means it can be difficult to get enough vitamin D in the winter months. Does eating seasonally solve this issue? Not really. Oily fish contains vitamin D, which doesn’t really change with the seasons – the solution is to take a vitamin D supplement.”

The Takeaway

As far as science is concerned, eating specific foods at certain times of year seems to offer no nutritional benefit.

“That said,” Malloy continues, “one major benefit to eating seasonally is that locally produced, seasonal foods are amongst the best sources for vitamins and minerals comparative to foods that are picked thousands of miles away, well before reaching full ripeness (and micronutrient density).”

According to data from Michigan State University “Local food has a shorter time between harvest and your table, and it is less likely that the nutrient value has decreased. Food imported from far-away states and countries is often older, has traveled and sits in distribution centers before it gets to your store.”

The lesson? Your health won’t improve by just eating nuts and apples in fall or lamb in spring, but by eating locally you’ll be able to get the most from your good, simply because it will be fresher. The choice, then, becomes less about seasonality, and more about opting for local, good quality produce where you can.

Want to read more about seasonal eating? Here's how the changing seasons can affect skin health.