Overweight people lack vitamin C, study finds

An international study involving the University of Otago in Christchurch has found that vitamin C deficiency is significantly linked to weight gain, which is a growing public health concern given the growing obesity epidemic around the world.

The results were published in the journal Food Science and Nutrition ReviewHeavier people require significantly more Recommended Daily Allowances (RDA) of essential vitamins to maintain health, and a large portion of the world’s population has been shown to not meet current vitamin C recommendations.

“Our data indicate that current internationally recommended daily intakes of vitamin C are significantly underestimated,” said lead researcher Professor Anitra Carr, director of the Nutritional Medicine Research Group at the Christchurch campus.

“Currently, all recommended international daily intakes of vitamin C for men, women and children are calculated for a healthy, young, 70kg man, with a 10 percent deviation allowed – this is a guideline that covers 97.5 percent of the population,” Prof Carr says.

“Clearly, with weight increasing worldwide, a significant proportion of the world’s population is no longer meeting these recommended intakes.”

New Zealanders are currently advised to consume 45 milligrams of vitamin C per day, in line with the World Health Organisation’s recommendation, which Professor Carr says is currently one of the lowest recommended intakes in the world.

She said the new findings estimate that a 70-kg person would need to take in an extra 17 to 22 mg of vitamin C per day for every 10 kg of body weight to reach adequate vitamin C levels.

“We believe this new evidence highlights the need to update the recommended daily intakes of vitamin C nationally and internationally to help guide future public health recommendations,” she says.

The study, co-authored by researchers from the Universities of Copenhagen and Aberdeen, analyzed two large international datasets: the 2017-2018 US National Health and Nutrition Examination Survey (NHANES), which included 2,828 adults, and the 1993-1997 Norfolk European Prospective Investigation into Cancer (EPIC) study, which included 20,692 participants.

Results showed that only about two-thirds of both cohorts achieved “adequate” vitamin C plasma concentrations by consuming the recommended daily allowance or more, while only one-third to one-half of the cohorts achieved an “adequate” status by consuming the RDA plus or minus 10 percent.

According to international studies, obesity may affect the relationship between the dose and concentration of vitamin C in the body as a result of low-grade inflammation, which may result in increased oxidative stress and increased metabolism of vitamin C in the body. Obesity is also known to increase the risk of type 2 diabetes and non-alcoholic fatty liver disease, both of which are associated with reduced vitamin C status.

The study authors suggest that additional vitamin C intake can be easily achieved through diet or supplements.

“An average-sized apple contains 10 milligrams of vitamin C, so if you weigh 70-80kg, eating one or two extra apples to get an extra 10-20 milligrams of vitamin C a day would be enough to achieve your body’s optimum vitamin C needs. If you weigh more than this, an orange, which contains 70 milligrams of vitamin C, or kiwifruit, which has 100 milligrams, may be the simplest solution,” Prof Carr says.

“My advice to anyone who chooses to get vitamin C from a multivitamin is to check the exact amount of vitamin C per tablet. Some multivitamins contain only very low doses of vitamin C.”

She says there is growing evidence worldwide that vitamin C is essential for disease prevention.

“Although vitamin C was originally thought to be useful only in preventing scurvy, there is now compelling evidence that consuming sufficient amounts of vitamin C may play an important role in reducing the risk of more common diseases, such as heart disease and cancer.”

“Other studies have shown that symptoms associated with vitamin C deficiency – such as increased risk of infection, poor wound healing and risk of depression and fatigue – increase in prevalence with weight gain,” Professor Carr says.