Smoking, weight affect daily vitamin C needs

Aug 05, 2023

People who smoke need to consume twice as much vitamin C per day as non-smokers, new research shows.

The University of Otago, Christchurch study analysed about 3,000 participants in the US National Health and Nutrition Examination Survey (NHANES 2017/2018) to investigate what demographic, lifestyle and health factors impact vitamin C levels.

Results, published in the international journal Nutrients, show males need about 20 per cent more vitamin C to reach the same circulating level as females.

Associate Professor Anitra Carr

Lead author Associate Professor Anitra Carr, of the Department of Pathology and Biomedical Science, says this isn't due to gender; it is because, on average, males weigh and smoke more.

"When we looked at smokers, there was a dose dependent decrease in vitamin C levels with increasing number of cigarettes smoked per day.

"Furthermore, smokers needed to consume twice as much vitamin C than non-smokers to reach adequate circulating levels of the vitamin.

"And these weren't necessarily heavy smokers, as the average number of cigarettes smoked per day was less than 10."

Smoking is known to deplete vitamin C levels because of the enhanced oxidative stress it causes in the body. Since vitamin C is a potent antioxidant, it can scavenge oxidants generated in cigarette smoke, but the vitamin becomes consumed in this process.

Associate Professor Carr says body weight impacts vitamin C levels in similar ways to smoking.

"When we looked at the impact of body weight, there was a decrease in vitamin C levels with increasing weight.

"Of note, it was primarily people who weighed less than 60kg who were able to reach adequate circulating levels of the vitamin.

"And, like smokers, people with higher body weight need to consume twice as much vitamin C than people with lower body weight. This is particularly important in view of the looming global obesity pandemic."

When people have a higher body weight, the vitamin is diluted into a larger volume. Additionally, obesity is associated with enhanced inflammation and oxidative stress, both of which can further deplete the vitamin.

"If an intake of 100 mg/day – which is approximately the average New Zealand intake of vitamin C – is sufficient for non-smokers and people of lower body weight to reach adequate circulating levels of the vitamin, then smokers and people of higher body weight should aim to consume at least 200 mg/day of the vitamin."

One hundred milligrams of vitamin C is the equivalent of about 1 gold kiwifruit or 1.5 oranges.

Eating more vitamin-rich foods is an easy way for people to increase their vitamin C consumption. Otherwise, supplements are readily available and relatively inexpensive.

"They are safe to take orally because the body can only absorb a certain amount at any one time and any excess that is absorbed but is not needed is excreted in urine."

Associate Professor Carr says vitamin C helps enzymes in the body to work optimally, which impacts collagen synthesis, cellular energy production, hormone and neurotransmitter synthesis, and metabolic regulation.

The research findings have important implications for the public health guidelines around recommended dietary intakes, which are often one size fits all.

"Our research shows that there are certain vulnerable groups within our population who may be consuming inadequate vitamin C, even when following current guidelines."

Factors Affecting the Vitamin C Dose-Concentration Relationship: Implications for Global Vitamin C Dietary Recommendations.

Anitra C. Carr, University of Otago, Christchurch, and Jens Lykkesfeldt, University of Copenhagen.

Nutrients

DOI: 10.3390/nu15071657