Incidence of adult obesity has doubled in the past 25 years, with almost 1 billion people worldwide—about 1 in every 8—classified as obese in 2022. And with nearly 50% of the global adult population meeting the clinical definition of overweight, those numbers don’t show any signs of decreasing.
This epidemic of excess weight has been linked to a host of chronic health problems, including increased risk of heart disease, type 2 diabetes, stroke, and some cancers. But beyond these well-documented issues, some researchers are concerned that other harmful consequences of overweight and obesity are being overlooked. And a new study published in Critical Reviews in Food Science and Nutrition would seem to confirm that idea, at least in the area of nutrient deficiencies.
The international study, led by Anita Carr, PhD, of the University of Otago, Christchurch, in New Zealand, focused on the recommended daily allowance (RDA) of vitamin C and whether the current guidelines were promoting an adequate intake of the vitamin to support optimum health.
“Current international vitamin C recommended daily allowances for men, women, and children are all extrapolated from calculations for a healthy, young, 70-kilogram male, allowing for a 10 percent deviation—a guideline that’s supposed to cover 97.5 percent of the population,” said Carr. But with the rampant increase in body weight worldwide, Carr and her team wondered whether those numbers are still relevant.
To determine the effects of obesity on vitamin C levels in the body, the researchers took a look at data from two large-scale studies, the 1993-1997 EPIC-Norfolk cohort conducted in Great Britain, and the 2017-2018 National Health and Nutrition Examination Survey (NHANES) conducted in the United States. Carr’s team analyzed data gathered from 18,185 non-smokers in the EPIC cohort who had vitamin C laboratory values available but didn’t take vitamin C supplements, and an additional 2,027 participants in the NHANES survey with the same restrictions.
Their results showed that only about two-thirds of both cohorts achieved an “adequate” vitamin C plasma concentration by consuming the recommended daily allowance or above, while only between one-third and half of the cohorts achieved “adequate” status with an intake of the RDA plus or minus 10 percent.
Extrapolating from these findings and the participants’ body weights, the researchers estimated that an additional 17 mg to 22 mg of vitamin C is needed daily per 10 kg of additional body weight to reach adequate vitamin C levels, as compared to a 70 kg individual.
Conclusions
“Clearly, with the global increase in body weight, a substantial and growing proportion of the world’s population are no longer covered by [the] recommended intakes,” said Carr. “We feel this new evidence highlights the need for an updated set of vitamin C recommended daily allowances…to guide future public health recommendations.”
Adequate vitamin C intake is important, said Carr, because this basic nutrient may be vital for disease prevention. “[E]vidence is now compelling that adequate levels of the vitamin may play an important role in risk reduction of more common diseases such as heart disease and cancer,” she said. “Other studies show conditions associated with vitamin C deficiency—such as increased infection risk, poor wound healing, risk of depression and fatigue—show an increased prevalence with increased weight.”
The good news, said Carr, is that additional vitamin C intake can be easily achieved through either diet or supplements. “My advice for those who choose to get their vitamin C from a multivitamin is to check the exact amounts of vitamin C per tablet,” she said, “as some multivitamin formulations may only contain it in very low doses.”
