Do plant-based diets prevent heart disease?
Only the ones built on whole plant foods. Among 14,776 US adults followed for more than a decade, those eating the most whole plant foods had about 28% lower risk of developing coronary heart disease (hazard ratio 0.72) than those eating the least. A broader score that counted white bread, fruit juice, and sweets as plant foods did not show the same protection, and no version of the diet score was linked to stroke.
The study drew on the REGARDS cohort, a long-running project that deliberately enrolled large numbers of Black Americans and people living in rural areas. Both groups carry a heavy burden of heart disease, and both have been thinly represented in earlier plant-based diet research. Participants filled out a food frequency questionnaire at the start, between 2003 and 2007, and researchers tracked their health through 2019.
From those questionnaires, the team built three separate diet scores. The plain plant-based diet index (PDI) rewarded any plant food. The healthy plant-based index (hPDI) rewarded whole grains, fruits, vegetables, nuts, and legumes. The unhealthy plant-based index (uPDI) rewarded refined grains, juices, and sweets. Everyone was ranked into fifths on each score, and the top fifth was compared with the bottom fifth.
What the Data Show
Over the follow-up period there were 700 strokes, 1,047 new cases of coronary heart disease, and 944 deaths from coronary heart disease.
The clearest result came from the healthy plant-based score. People in the top fifth had about 28% lower coronary heart disease incidence than people in the bottom fifth (hazard ratio 0.72). The true size of that benefit is very likely somewhere between 10% and 42% lower (95% confidence interval 0.58 to 0.90), and the pattern across all five groups was unlikely to be a fluke, with roughly a 3 in 100 chance of coincidence (p-trend 0.03).
The plain plant-based score behaved strangely. It was tied to about 27% lower risk of dying from coronary heart disease (hazard ratio 0.73), very likely between 10% and 41% lower, with about a 1 in 1,000 chance of coincidence (p-trend 0.001). Yet the same score was tied to about 60% higher risk of developing coronary heart disease in the first place (hazard ratio 1.60), very likely between 9% and 133% higher, with roughly a 9 in 1,000 chance of coincidence (p-trend 0.009).
The unhealthy plant-based score was not linked to coronary heart disease incidence or death. And none of the three scores was linked to stroke at all. Results did not differ by race.
Why one score pointed in two directions
A score that treats every plant food as a point in your favor will reward a diet of soda, white rice, and pastries just as readily as one built on lentils and greens. That is the design flaw the plain plant-based index carries, and it likely explains why higher scores lined up with more new heart disease while also lining up with fewer heart disease deaths.
Two other patterns are worth noting. The link between a higher plain plant-based score and more new heart disease showed up only among adults living outside rural areas (interaction p=0.006). And the healthy plant-based score was tied to lower heart disease death only in women (interaction p=0.03). These are subgroup signals inside a single observational study, not settled facts, but they suggest the same diet score can mean different things in different populations.
Dr. Kumar’s Take
The headline here is not “eat plants.” It is that the word “plant-based” has almost no nutritional meaning on its own. Potato chips are plant-based. So is white bread. A scoring system that cannot tell those apart from beans and broccoli produced contradictory results in the same cohort, and that contradiction is the most useful thing in the paper.
The null result on stroke deserves attention too, given that this cohort was built specifically to study stroke. Diet quality clearly matters for the heart in this data. For stroke, over sixteen years and 700 events, none of the three scores moved the needle.
I would also temper the effect sizes. These are relative comparisons between the top and bottom fifths of a diet score measured once, years before most events happened. People eat differently over sixteen years, and food questionnaires capture intentions as much as habits.
How strong is the evidence?
This is an observational cohort study, so it can show that patterns travel together but cannot prove that food caused the outcomes. People who eat more whole plant foods also tend to smoke less, move more, and have more money for groceries. The researchers adjusted for demographics, health risk factors, and calorie intake, which helps, but adjustment never fully removes those differences.
The strengths are real. The sample was large, the follow-up ran roughly sixteen years, and the deliberate inclusion of Black and rural Americans fills a genuine hole in this literature. The finding that associations did not differ by race is itself worth knowing.
Practical Takeaways
- Judge a plant food by how close it is to its original form, not by whether it came from a plant, since refined grains, juice, and sweets all qualify as plant-based.
- Build meals around the five food groups the healthy score rewarded: whole grains, fruits, vegetables, nuts, and legumes.
- Treat “plant-based” labels on packaged food as marketing rather than a health claim, because the score that counted those foods equally showed no benefit for new heart disease.
- Do not expect a diet change alone to protect against stroke based on this study, since none of the three diet scores was associated with stroke risk.
Related Studies and Research
- Ultra-processed foods linked to 47% higher heart disease risk
- A plant-based diet lowered heart disease risk over 20 years
- Sugary drinks linked to 34% higher anxiety risk in teens
- Long daytime naps linked to higher death risk in older adults
Frequently Asked Questions
Does going vegetarian or vegan lower heart disease risk?
This study did not compare vegetarians to meat eaters. It scored how much of each person’s diet came from plant foods, on a sliding scale, so even the highest-scoring group included people who ate animal products. The lesson that transfers is about composition rather than labels: a vegan diet built on refined grains and sweets would score well on the plain plant-based index, which is the score that produced the confusing results. Cutting out meat and cutting down on refined carbohydrates are two separate decisions.
Why did the same diet score predict fewer heart disease deaths but more heart disease cases?
Incidence and mortality are different outcomes, and a diet can plausibly affect them differently. Incidence counts who develops the disease. Mortality counts who dies of it, which depends on severity, medical care, and survival after diagnosis. In an observational study, an inconsistency this large is more likely a sign that the plain plant-based score is measuring something muddled than proof that plant foods cause heart disease and prevent heart deaths at the same time.
Should I change anything if I live in a rural area?
The rural finding here was an interaction, meaning the link between the plain plant-based score and new heart disease appeared only among adults outside rural areas. That is a difference in a statistical pattern, not a dietary instruction, and subgroup results from one cohort need replication before anyone acts on them. What did hold across the whole sample, including rural participants, is that the healthy plant-based score tracked with less heart disease.
The Bottom Line
In 14,776 US adults followed for about sixteen years, eating more whole plant foods was linked to roughly 28% lower coronary heart disease risk, while a diet score that counted refined grains, juices, and sweets as plant foods showed no such benefit and pointed in contradictory directions. Neither score, nor a score built on unhealthy plant foods, was linked to stroke. The category “plant-based” is too broad to be useful. What is inside it is what counts.
