A new study involving the University of Otago, Christchurch, has found that people with higher body weight may not be getting enough vitamin C under current health guidelines. This discovery could have serious health implications as obesity rates continue to rise worldwide.
The research, published in Critical Reviews in Food Science and Nutrition, shows that people who weigh more need a higher daily intake of vitamin C to stay healthy. But most public health recommendations are based on an average 70-kilogram male, with only a small 10% adjustment meant to cover almost everyone.
According to lead researcher Professor Anitra Carr, this doesn’t reflect the reality of today’s population, where many people weigh much more than that.
Professor Carr, who leads the Nutrition in Medicine Research Group at the University of Otago’s Christchurch campus, said, “Our data suggests current vitamin C recommended daily allowances internationally are severely underestimated.”
She explains that heavier people need more vitamin C because their bodies go through it more quickly, likely due to ongoing inflammation and higher oxidative stress linked to obesity.
For every 10 kilograms of extra body weight, the study found that people need an additional 17 to 22 milligrams of vitamin C each day. In New Zealand, for example, the recommended intake is just 45 milligrams per day—one of the lowest in the world. This means many people may be falling short, especially those who are overweight or obese.
To reach these conclusions, Professor Carr and her colleagues from the Universities of Copenhagen and Aberdeen analyzed two major health studies: the US National Health and Nutrition Examination Survey (NHANES) from 2017–2018 with 2,828 adults, and the EPIC-Norfolk study from the UK, which followed over 20,000 people between 1993 and 1997.
The results showed that only about two-thirds of participants met what’s considered an “adequate” vitamin C level based on current guidelines. When the required intake was increased by just 10%, only one-third to half of participants still had enough vitamin C in their systems.
Vitamin C is important for many reasons. Most people know it prevents scurvy, but it also supports the immune system, helps the body heal wounds, reduces inflammation, and protects against diseases like cancer and heart disease. Low vitamin C levels are also linked to fatigue, higher infection risk, and even mood problems like depression.
People with obesity are at greater risk of vitamin C deficiency, partly because of inflammation and stress inside the body. These same individuals are also more likely to develop chronic conditions like type 2 diabetes and fatty liver disease, which are also linked to low vitamin C levels.
So, what can people do? Professor Carr suggests making simple changes to the diet. For someone who weighs 70 to 80 kilograms, just one or two extra apples a day could help. A medium apple has about 10 milligrams of vitamin C.
Heavier individuals might benefit more from fruits with higher vitamin C content—like an orange (about 70 milligrams) or a kiwifruit (around 100 milligrams).
Supplements can also help, but Professor Carr warns that some multivitamins have very low vitamin C doses, so it’s important to check the label. In many cases, adjusting your daily food choices is a simple and effective way to improve your vitamin C intake.
This study highlights the need to update vitamin C recommendations worldwide, not just for the average-sized person but for everyone. As obesity becomes more common, ensuring that people get the right amount of essential nutrients—like vitamin C—could play an important role in preventing disease and improving overall health.
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