Houston, Texas, USA : Vitamin C may reduce the harm done to lungs in infants born to mothers who smoke during their pregnancy, according to a randomized, controlled trial published online in the American Thoracic Society’s American Journal of Respiratory and Critical Care Medicine.
In “Oral Vitamin C (500 mg/day) to Pregnant Smokers Improves Infant Airway Function at 3 Months: A Randomized Trial,” Cindy T. McEvoy, MD, MCR, and her co-authors report that at three months of age, the infants whose mothers took 500 mg of vitamin C in addition to their prenatal vitamin had significantly better forced expiratory flows (FEFs). FEFs measure how fast air can be exhaled from the lung and are an important measure of lung function because they can detect airway obstruction.
The researchers also discovered an association between the infant FEFs and a genetic variant some of the mothers possessed that appeared to amplify the negative impact of nicotine on the babies before they were born. Other studies have linked this genetic factor, specifically for the α5 nicotinic acetylcholine receptor, to increased risk of lung cancer and obstructive lung disease.
“Smoking during pregnancy reflects the highly addictive nature of nicotine that disproportionately affects the most vulnerable populations,” said Dr. McEvoy, lead study author and professor of pediatrics at Oregon Health & Science University. “Finding a way to help infants exposed to smoking and nicotine in utero recognizes the unique dangers posed by a highly advertised, addictive product and the lifetime effects on offspring who did not choose to be exposed.”
In a previous study, the authors had shown that 72 hours after birth, babies of mothers who smoked had better lung function if their mothers were randomized to vitamin C (500 mg/day) during their pregnancies compared to those born to mothers who smoked and were randomized to placebo.
That study used passive methods to measure lung function, and the authors note that FEFs provide a more direct assessment of airway function and are similar to methods used to diagnose lung disease in adults and older children.
In the current study, 251 pregnant women who smoked were randomly assigned at 13 to 23 weeks of gestation to either receive vitamin C (125 women) or a placebo (126 women). Smoking was defined as having had one or more cigarettes in the last week. All participants received smoking cessation counseling throughout the study, and about 10 percent of the women quit smoking during the study.
The researchers wrote that study results support the hypothesis that oxidative stress caused by cigarette smoking reduces the amount of ascorbic acid, a component of vitamin C, available to the body. At the time they enrolled in the study, the women had lower levels of ascorbic acid than have been reported among women who do not smoke.
Those levels rose in study participants who received vitamin C to become comparable to women who do not smoke.
Infants in this study will continue to be followed to track their lung function and respiratory outcomes. The authors believe that future trials of vitamin C supplementation in pregnant smokers should determine whether the benefits are greater if the supplementation starts earlier and continues postnatally in the babies themselves.
Summing up the findings of the current study, Dr. McEvoy said that a relatively low dosage of vitamin C may present “a safe and inexpensive intervention that has the potential to help lung health of millions of infants worldwide.”
However, she added, helping mothers quit smoking should remain the primary goal for health professionals and public health officials. “Although vitamin C supplementation may protect to some extent the lungs of babies born to mothers who smoke during pregnancy, those children will still be at greater risk for obesity, behavioral disorders and other serious health issues,” she said.
A second study found that Vitamin C improves pulmonary function in newborns of pregnant smoking women.
Vitamin C improves pulmonary function in newborns of pregnant smoking women
Vitamin C supplementation in pregnant women who are unable to quit smoking significantly improves pulmonary function in their newborns, according to a new study.
“Smoking during pregnancy is known to adversely affect the lung development of the developing baby,” said Cindy McEvoy, MD, associate professor of pediatrics at Oregon Health & Science University Doernbecher Children’s Hospital. “We found that daily use of vitamin C (500 mg/day) by smoking pregnant woman significantly improved pulmonary function tests administered to their offspring at about 48 hours postpartum.”
The study enrolled the newborns of 159 smoking women and randomized them to daily vitamin C (500 mg) or placebo before 22 weeks gestation and treatment was continued through delivery.76 non smoking pregnant women were also studied. The primary outcome of the study was the measurement of the newborn’s lung function with a pulmonary function test at about 48 hours of life. This assessment included measurement of peak tidal expiratory flow to expiratory time (TPTEF:TE) and respiratory compliance (Crs).
Smokers treated with placebo had significantly lower levels of ascorbic acid than non-smokers, but levels returned to those of non-smokers in smokers randomized to vitamin C. Newborns of smoking women randomized to placebo had decreased TPTEF:TE and Crs compared to non-smokers. Both TPTEF:TE and Crs were significantly increased by vitamin C supplementation, returning them nearly to the levels seen in non-smokers.
“In our pilot study, we were able to show that babies born to smoking pregnant women who were randomized to daily supplemental vitamin C had significantly improved pulmonary/lung function tests compared to babies born to smoking women who were randomized to placebo,” said Dr. McEvoy.
“Moreover, although our study numbers were small, we found that one particular genetic variant that has been shown to increase the risk of smokers developing cancer and is associated with both a reduced ability to quit smoking and a high likelihood of relapse, also seemed to intensify the harmful effects of maternal smoking on babies’ lungs. Although the lung function of all babies born to smokers in our study was improved by supplemental vitamin C, our preliminary data suggest, importantly, that vitamin C may help those babies at the greatest risk of harm during their development from their mother’s smoking in pregnancy.”
“Getting women to quit smoking during pregnancy has to be priority one, but this study provides a way to potentially help the infants born to at least 12% of pregnant women who cannot quit smoking when pregnant.” said Dr. McEvoy. “Vitamin C supplementation may block some of the in-utero effects of smoking on fetal lung development.”
“Our findings are important because improved lung function tests at birth are associated with less wheezing and asthma in childhood,” concluded Dr. McEvoy. “Vitamin C is a simple, safe, and inexpensive treatment that may decrease the impact of smoking during pregnancy on the respiratory health of children.”
Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. Humans, unlike most animals, are unable to synthesize vitamin C endogenously, so it is an essential dietary component.
Vitamin C is required for the biosynthesis of collagen, L-carnitine, and certain neurotransmitters; vitamin C is also involved in protein metabolism. Collagen is an essential component of connective tissue, which plays a vital role in wound healing. Vitamin C is also an important physiological antioxidant and has been shown to regenerate other antioxidants within the body, including alpha-tocopherol (vitamin E). Ongoing research is examining whether vitamin C, by limiting the damaging effects of free radicals through its antioxidant activity, might help prevent or delay the development of certain cancers, cardiovascular disease, and other diseases in which oxidative stress plays a causal role. In addition to its biosynthetic and antioxidant functions, vitamin C plays an important role in immune function and improves the absorption of nonheme iron , the form of iron present in plant-based foods. Insufficient vitamin C intake causes scurvy, which is characterized by fatigue or lassitude, widespread connective tissue weakness, and capillary fragility.
The intestinal absorption of vitamin C is regulated by at least one specific dose-dependent, active transporter. Cells accumulate vitamin C via a second specific transport protein. In vitro studies have found that oxidized vitamin C, or dehydroascorbic acid, enters cells via some facilitated glucose transporters and is then reduced internally to ascorbic acid. The physiologic importance of dehydroascorbic acid uptake and its contribution to overall vitamin C economy is unknown.
Oral vitamin C produces tissue and plasma concentrations that the body tightly controls. Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1 g/day, absorption falls to less than 50% and absorbed, unmetabolized ascorbic acid is excreted in the urine. Results from pharmacokinetic studies indicate that oral doses of 1.25 g/day ascorbic acid produce mean peak plasma vitamin C concentrations of 135 micromol/L, which are about two times higher than those produced by consuming 200–300 mg/day ascorbic acid from vitamin C-rich foods. Pharmacokinetic modeling predicts that even doses as high as 3 g ascorbic acid taken every 4 hours would produce peak plasma concentrations of only 220 micromol/L.
The total body content of vitamin C ranges from 300 mg (at near scurvy) to about 2 g . High levels of vitamin C (millimolar concentrations) are maintained in cells and tissues, and are highest in leukocytes (white blood cells), eyes, adrenal glands, pituitary gland, and brain. Relatively low levels of vitamin C (micromolar concentrations) are found in extracellular fluids, such as plasma, red blood cells, and saliva.
Vitamin C Deficiency
Acute vitamin C deficiency leads to scurvy. The timeline for the development of scurvy varies, depending on vitamin C body stores, but signs can appear within 1 month of little or no vitamin C intake (below 10 mg/day). Initial symptoms can include fatigue (probably the result of impaired carnitine biosynthesis), malaise, and inflammation of the gums. As vitamin C deficiency progresses, collagen synthesis becomes impaired and connective tissues become weakened, causing petechiae, ecchymoses, purpura, joint pain, poor wound healing, hyperkeratosis, and corkscrew hairs. Additional signs of scurvy include depression as well as swollen, bleeding gums and loosening or loss of teeth due to tissue and capillary fragility. Iron deficiency anemia can also occur due to increased bleeding and decreased nonheme iron absorption secondary to low vitamin C intake. In children, bone disease can be present. Left untreated, scurvy is fatal.
Until the end of the 18th century, many sailors who ventured on long ocean voyages, with little or no vitamin C intake, contracted or died from scurvy. During the mid-1700s, Sir James Lind, a British Navy surgeon, conducted experiments and determined that eating citrus fruits or juices could cure scurvy, although scientists did not prove that ascorbic acid was the active component until 1932.
Today, vitamin C deficiency and scurvy are rare in developed countries. Overt deficiency symptoms occur only if vitamin C intake falls below approximately 10 mg/day for many weeks. Vitamin C deficiency is uncommon in developed countries but can still occur in people with limited food variety.
Groups at Risk of Vitamin C Inadequacy
Vitamin C inadequacy can occur with intakes that fall below the RDA but are above the amount required to prevent overt deficiency (approximately 10 mg/day). The following groups are more likely than others to be at risk of obtaining insufficient amounts of vitamin C.
Smokers and passive “smokers”
Studies consistently show that smokers have lower plasma and leukocyte vitamin C levels than nonsmokers, due in part to increased oxidative stress. For this reason, the IOM concluded that smokers need 35 mg more vitamin C per day than nonsmokers. Exposure to secondhand smoke also decreases vitamin C levels. Although the IOM was unable to establish a specific vitamin C requirement for nonsmokers who are regularly exposed to secondhand smoke, these individuals should ensure that they meet the RDA for vitamin C.
Infants fed evaporated or boiled milk
Most infants in developed countries are fed breastmilk and/or infant formula, both of which supply adequate amounts of vitamin C. For many reasons, feeding infants evaporated or boiled cow’s milk is not recommended. This practice can cause vitamin C deficiency because cow’s milk naturally has very little vitamin C and heat can destroy vitamin C.
Individuals with limited food variety
Although fruits and vegetables are the best sources of vitamin C, many other foods have small amounts of this nutrient. Thus, through a varied diet, most people should be able to meet the vitamin C RDA or at least obtain enough to prevent scurvy. People who have limited food variety—including some elderly, indigent individuals who prepare their own food; people who abuse alcohol or drugs; food faddists; people with mental illness; and, occasionally, children—might not obtain sufficient vitamin C [4,6-9,11].
People with malabsorption and certain chronic diseases
Some medical conditions can reduce the absorption of vitamin C and/or increase the amount needed by the body. People with severe intestinal malabsorption or cachexia and some cancer patients might be at increased risk of vitamin C inadequacy. Low vitamin C concentrations can also occur in patients with end-stage renal disease on chronic hemodialysis.
Vitamin C and Health
Due to its function as an antioxidant and its role in immune function, vitamin C has been promoted as a means to help prevent and/or treat numerous health conditions. There are four other diseases and disorders in which vitamin C might play a role: cancer (including prevention and treatment), cardiovascular disease, age-related macular degeneration (AMD) and cataracts, and the common cold.