Jim OwenA 2019 Stanford lab study found that flavored e-cigarette liquids damaged the cells that line human blood vessels, an early step toward heart disease. Research since then has not cleared vaping. A 2022 analysis found that adding e-cigarettes to smoking does not lower heart risk, while long-term data on heart attacks are still thin.
Updated October 11, 2026.
I have read health headlines for a long time, and vaping stories follow a pattern. A lab study comes out, the headline says vaping wrecks your heart, and the paper turns out to be about cells in a dish. So I read the methods before I trust the summary. Here is what the 2019 paper actually tested, and what it didn’t.
What the 2019 vaping study tested
The paper ran in the Journal of the American College of Cardiology on June 4, 2019. Won Hee Lee was the first author, and Joseph C. Wu of Stanford was the senior author. The team grew endothelial cells from stem cells donated by three healthy people. Endothelial cells form the thin inner lining of every blood vessel, and they help keep blood pressure in check.
The researchers then exposed those cells to six store-bought e-liquids. Each liquid was tested at 0, 6 and 18 milligrams of nicotine per milliliter. That design let them separate the effect of the flavoring from the effect of the nicotine.
Which vape flavors did the most damage
A cinnamon-flavored liquid was the most toxic of the six, according to the JACC paper. A menthol tobacco liquid also hit the cells hard. The flavored liquids lowered cell survival and raised reactive oxygen species, a chemical marker of cell stress. They also weakened the cells’ ability to move and to form the tube shapes that stand in for new vessel growth in a lab dish.
Nicotine strength mattered less than flavor in these tests. That finding is the part of the study most often left out of news coverage. A zero-nicotine flavored liquid was not shown to be harmless.
The blood test in people who vape
The team also drew blood from five nonsmokers, five cigarette smokers and four e-cigarette users. Blood nicotine peaked at 12.3 nanograms per milliliter after vaping and 12.6 after a cigarette, so the two delivered nearly the same dose. Serum from the vapers raised cell-stress markers and impaired tube formation in the lab-grown cells.
Inflammation markers rose after use as well. However, those increases lost statistical significance once the authors corrected for running many comparisons at once.
Limits the study’s authors named
The authors listed the gaps themselves. They tested liquids, not heated vapor, so the chemistry of heating was missing. Real vapers do not puff on a fixed schedule. Six flavors cannot stand for every product on the market, and the blood samples were small. Their conclusion was that flavored e-liquids and vaping worsen endothelial dysfunction, which often comes before heart disease. They called for long-term clinical studies.
In other words, the 2019 study was a warning sign from cells in a dish. It did not count heart attacks or strokes in people.
What later research found on vaping and heart health
Counting real cardiovascular events takes years. A 2022 research letter in Circulation by J.B. Berlowitz and colleagues used the national PATH Study, which followed American adults from 2013 to 2019. The authors concluded that combining smoking with e-cigarette use does not reduce cardiovascular events. Quitting both products, they wrote, is what lowers risk. They also called for larger studies with longer follow-up.
The CDC’s health effects page adds detail on what is in the vapor. E-cigarette aerosol can contain cancer-causing chemicals, heavy metals such as nickel, tin and lead, fine particles and volatile organic compounds. It generally has fewer harmful chemicals than the roughly 7,000 in cigarette smoke. Even so, the CDC states that this does not make e-cigarettes safe. Using both products may also expose a person to more toxins than using either one alone.
Does vaping help people quit smoking?
This question has a clearer answer now than it did in 2019. The Cochrane review published August 26, 2026, covers evidence up to January 1, 2026. It found that 8 to 10 of every 100 people using nicotine e-cigarettes quit smoking for at least six months. With nicotine patches or gum, the figure was 6 in 100. Reviewers rated that finding high certainty.
Serious side effects were rare in the trials. The most common complaints were throat or mouth irritation, headache, cough and nausea, and these tended to ease over time. Still, the reviewers said longer and larger trials are needed to judge long-term safety. The CDC frames any benefit narrowly: it applies to adults who smoke, are not pregnant and switch completely away from smoked tobacco.
Vaping among teenagers in 2025
Youth vaping has dropped since the original post ran. The FDA’s 2025 National Youth Tobacco Survey found about 1.44 million middle and high school students currently using e-cigarettes. That is 5.2% of all students. Among high schoolers, the rate was 7.1%, or about 1.13 million teens.
The CDC notes that nicotine can harm the developing brain, which keeps maturing until about age 25. It can affect attention, learning, mood and impulse control. Younger children face a different danger. More than 80% of calls to US poison control centers about e-cigarettes involve children under 5.
What the vaping evidence means for heart health
For someone who does not smoke, the CDC’s position is plain: e-cigarettes are not safe, and starting brings risk with no offsetting benefit. For an adult who smokes, the picture is different. Nicotine e-cigarettes can help some people quit, per Cochrane. But the Circulation analysis suggests the heart gains little if vaping is added on top of cigarettes instead of replacing them.
The 2019 lab result still stands as an early signal. Later studies have filled in the quitting question faster than the heart question. Anyone weighing vaping as a way off cigarettes should talk it through with a doctor, who can also lay out patches, gum, prescription options and the broader lifestyle changes for better health.
Is vaping bad for heart health?
Does vaping damage blood vessels?
In lab tests, yes. The 2019 Stanford study in the Journal of the American College of Cardiology found that flavored e-liquids lowered the survival of blood vessel lining cells and raised markers of cell stress. Blood drawn from people who vape had similar effects on those cells. The study used cells in a dish, so it did not measure heart attacks or strokes in people.
Is vaping safer for heart health than smoking?
The CDC says e-cigarette aerosol generally has fewer harmful chemicals than cigarette smoke, but that this does not make vaping safe. A 2022 Circulation analysis of the PATH Study concluded that using e-cigarettes alongside cigarettes does not reduce cardiovascular events. Quitting both products is what lowers risk, according to those authors.
Do flavors make vaping worse for the heart?
In the 2019 JACC study, flavoring mattered more than nicotine strength. A cinnamon-flavored liquid was the most toxic of the six tested, and a menthol tobacco liquid also caused strong damage to the cells. The authors noted that six flavors cannot represent every product sold, so the ranking applies only to the liquids they tested.
Can e-cigarettes help someone quit smoking?
For some adults, yes. The 2026 Cochrane review found that 8 to 10 of every 100 people using nicotine e-cigarettes quit for at least six months, compared with 6 of 100 using nicotine patches or gum. Reviewers rated this high certainty. The CDC adds that any benefit depends on switching completely away from smoked tobacco.
This article is for general information only and is not medical advice. Talk to a licensed clinician about your own situation.
Tami Benedict
Madeline Marshall