Cooked fruit and veg get a raw deal, research finds

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A new study indicates that it’s not about how many fruit and vegetables you eat, but rather the way in which you eat it.

The research from the University of Otago in New Zealand discovered raw fruit and vegetables may be better for your mental health than cooked, canned and processed fruit and vegetables.

The study surveyed 422 people aged 18 to 25 living in New Zealand and the United States. The particular age group was chosen as young adults typically have the lowest fruit and vegetable consumption of all age groups and are at high risk for mental health disorders.

The consumption of raw fruits and vegetables cooked and processed were assessed, along with the subjects’ mental health status. Lifestyle and demographic factors were also assessed to determine the association between fruit and vegetable intake and mental health.

Factors included exercise, sleep, unhealthy diet, chronic health conditions, socioeconomic status, ethnicity, and gender.

The results found that consumption of raw fruits and vegetables differentially predicted better mental health than the consumption of processed fruits and vegetables.

Lead author, Psychology PhD student Kate Brookie, said public health campaigns have historically focused on aspects of quantity for the consumption of fruit and vegetables (such as 5+ a day).

“Our research has highlighted that the consumption of fruit and vegetables in their ‘unmodified’ state is more strongly associated with better mental health compared to cooked/canned/processed fruit and vegetables,” Ms Brookie said.

However, the study showed that for mental health in particular, it may also be important to consider the way in which produce is prepared and consumed.

Co-author, Psychology Senior Lecturer Dr Tamlin Conner, believes this could be because the cooking and processing of fruit and vegetables has the potential to diminish nutrient levels.

“This likely limits the delivery of nutrients that are essential for optimal emotional functioning,” Dr Conner said.

“Controlling for the covariates, raw fruit and vegetable consumption predicted lower levels of mental illness symptomology, such as depression, and improved levels of psychological well-being including positive mood, life satisfaction and flourishing. These mental health benefits were significantly reduced for cooked, canned, and processed fruits and vegetables.

“This research is increasingly vital as lifestyle approaches such as dietary change may provide an accessible, safe, and adjuvant approach to improving mental health,” Dr Conner added.

What fruit and veg should you eat?

According to the study, the top 10 raw foods related to better mental health are:

  • Carrots
  • Bananas
  • Apples
  • Dark leafy greens such as spinach
  • Grapefruit
  • Lettuce
  • Citrus fruits
  • Fresh berries
  • Cucumber
  • Kiwifruit

According to Australian Dietary Guidelines, there is increasing evidence that whole foods such as fruit are more effective in reducing the risk of cancer than specific vitamin and mineral supplements. There is also supporting evidence that some risk factors for cancer can be avoided by eating fruit and vegetables during childhood and early adult life. The health benefits of eating vegetables have been reported for decades and continue to be strengthened, in particular for cardiovascular disease.

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