Vegetables on a plant based diet: what the doctors say

Our view

No doctor on this site argues against vegetables; the questions are how much of the plate they should take, whether to cook them and whether a salad needs added fat¹²³. Greens matter most to Caldwell Esselstyn, who has asked his heart patients to chew a small portion of cooked leafy greens six times a day⁴, and Peter Rogers eats some every day and explains the same nitrate pathway Esselstyn teaches⁵⁶.

We give most weight to the low-fat clinicians who have fed thousands of patients for decades, and on the size of the vegetable share they line up: non-starchy vegetables hold so few calories that they cannot carry a diet, so starches do the feeding and vegetables fill the plate around them⁷⁸⁹. Where an added fat for salads is debated, we follow the doctors who use no oil, since Jeff Nelson points out that years of very low-fat diets heavy in colorful vegetables produced no known wave of vitamin A shortage¹⁰¹¹.

Where they agree

They agree that vegetables are the least calorie-dense food a person can eat: Novick put them at about 150 calories a pound in 1999, Goldhamer gave salad about 100 in 2025, and Rogers said greens carry roughly a tenth of the calories of starches¹²⁸¹³. Doug Lisle drew the practical lesson in 2019: a pound of lettuce stretches the stomach while supplying only about 100 calories, so it cannot by itself keep someone full for long¹⁴.

From that follows a second point of agreement, that vegetables work as company for starches rather than as the base: McDougall in 2011 said that living on them would take bushels of broccoli daily, and Goldhamer in 2026 said it would take some 20 pounds of raw vegetables¹¹⁵. Lisle, looking at human history in 2021, found no people anywhere whose main calories come from raw fruit and vegetables¹⁶.

Esselstyn and Rogers describe the same mechanism for leafy greens: mouth bacteria turn their nitrate into a compound that the stomach converts to nitric oxide, which relaxes the arteries⁴⁶. Both caution that fluoride mouthwash and antacid drugs can interrupt it¹¹¹⁷. T. Colin Campbell adds a case for whole vegetables over isolated nutrients: he recalled that smokers given beta-carotene pills in large trials ended up with more lung cancer, not less¹⁸.

Where they differ

The differences are about proportions and preparation: how large a share of the diet vegetables should be, raw or cooked, and whether a salad needs fat to be absorbed¹⁹²⁰³.

How much of the plate

McDougall in 2022 put non-starchy vegetables at about a tenth of a usual diet, said people seeking faster weight loss could raise them to a quarter, and set half as the ceiling, past which he said hunger comes back¹⁹. Novick’s 2012 advice for a stalled weight loss was similar, with vegetables filling a third to a half of what the eye sees on each plate²¹. Chef AJ in 2021 asked her clients for at least a pound of vegetables at every meal, breakfast included, before starch²². Goldhamer in 2026 went further, saying raw fruit and vegetables can be most of the volume and perhaps 40 to 50 percent of the calories², while Rogers said greens give him only about 5 percent of his calories⁵.

Raw or cooked

Esselstyn’s greens are cooked by steaming or boiling for around six minutes until tender⁴, and Barnard said in 2020 that people whose digestion objects to raw cabbage-family vegetables can cook them a bit longer²³. Campbell said in 2023 that salads are very good but that he knows of no evidence an all-raw diet is better, and that cooking does no real harm²⁰. Goldhamer added in 2026 that raw food diets tend to drift toward fruit, nuts and avocado because vegetables alone supply too few calories, and that some of his raw food patients developed depletion²⁴.

Fat on the salad

Rip Esselstyn in 2022 allowed a quarter to half an avocado on a salad as a condiment²⁵, while Lisle said in 2026 he would not pour olive oil on his own salad because it is pure fat²⁶. Nelson in 2026 challenged the idea, which he said Michael Greger among others repeats, that a salad needs fat for its carotenoids²⁷. He granted that adding fat lifts carotenoid levels in the blood for a few hours, but noted that one early study was paid for by Procter and Gamble to test a full-fat dressing and that the avocado industry funded later work³.

Which vegetables

Esselstyn names the leafy greens, from kale and collards to chard and bok choy²⁸, while Barnard stresses the cabbage family, citing sulforaphane, which he said pushes the liver to produce extra detox enzymes²⁹. Asked to pick one favorite in 2021, Barnard declined and said he rotates spinach, broccoli, Brussels sprouts and kale³⁰. Rip Esselstyn’s PLANTSTRONG site argues for variety by color, since different colors bring different vitamins and plant compounds³¹.

What each expert says

JM

John McDougall

McDougall warned in 2011 that a diet of green and yellow vegetables alone is too bulky and too low in calories, and that people who try it often get cramps and tire easily¹. He wanted starches at the center and vegetables beside them for color, interest and vitamins such as A and C⁷. In 2022 he allowed a larger vegetable share for faster weight loss, but never more than half¹⁹.

John on vegetables and greens: the full summary on John McDougall's page

CE

Caldwell Esselstyn

Leafy greens are a signature of Esselstyn’s heart program, and his 2014 paper on 198 patients describes generous daily servings of them³². In a 2014 lecture he asked for a fist-sized cooked portion with balsamic vinegar six times a day, and by 2023 the portion he named had shrunk to about a quarter of a fist, still six times daily³³⁴. A talk posted in 2011 has him describing an Okinawan trial where women given extra local greens showed more of the cells that mend the artery lining³⁴.

Caldwell on vegetables and greens: the full summary on Caldwell Esselstyn's page

TC

T. Colin Campbell

Campbell uses vegetables to make his case against single-nutrient pills: when beta-carotene was taken out of vegetables and given to heavy smokers, their lung cancer risk rose¹⁸. In 2023 he said salads at lunch had become his favorite meal³⁵, while doubting that an entirely raw diet has any advantage²⁰.

Colin on vegetables and greens: the full summary on T. Colin Campbell's page

NB

Neal Barnard

In his 2024 Power Foods talk Barnard ranked cabbage-family vegetables second and other greens third in the Harvard weight data he cited³⁶. He said a serving of broccoli brings about 5 grams of fiber for some 55 calories, along with sulforaphane²⁹. For sensitive stomachs he suggested cooking those vegetables a little longer²³.

Neal on vegetables and greens: the full summary on Neal Barnard's page

DO

Dean Ornish

In a 1999 radio interview Ornish grouped vegetables with fruit, grains and beans as complex carbohydrates whose fiber slows absorption and keeps blood sugar from spiking³⁷. Eating out in 2019, he said he asks the kitchen for its freshest vegetables cooked without oil, butter or salt³⁸.

Dean on vegetables and greens: the full summary on Dean Ornish's page

AG

Alan Goldhamer

Goldhamer often uses salad to explain calorie density: at about 100 calories a pound, he said in 2025, living on it would take some 20 pounds a day⁸. In 2026 he still wanted raw fruit and vegetables to make up most of the volume on the plate, with potatoes, rice and beans supplying much of the rest². He finds vegetables easier to eat in quantity once cooked¹⁵.

Alan on vegetables and greens: the full summary on Alan Goldhamer's page

PR

Peter Rogers

In a 2026 video Rogers told people trying to lose weight to eat their greens first, since their low calorie density fills the stomach early¹³. He explained the nitrate route to nitric oxide and warned that fluoride mouthwash and acid blockers interfere with it⁶¹⁷. He eats greens daily, though they supply only a small share of his calories⁵.

Peter on vegetables and greens: the full summary on Peter Rogers's page

JN

Jeff Novick

Novick wrote in 2010 that many people who call their diet vegetable based actually get most calories from nuts, fruit or starches, because non-starchy vegetables average about 100 calories a pound⁹. He liked to note that a tablespoon of olive oil holds nearly the calories of a whole pound of broccoli³⁹. In 1999 he reported a Harvard study of more than 114,000 adults, observational and without a comparison diet, in which five or six daily servings of fruit and vegetables went with a 31 percent lower risk of ischemic stroke than fewer than three⁴⁰.

Jeff on vegetables and greens: the full summary on Jeff Novick's page

JN

Jeff Nelson

Nelson argued in 2026 that people eating low-fat plant diets full of carrots, sweet potatoes, squash and greens are anything but short of carotenoids²⁷. He asked where the patients are who lost vitamin A or their sight by skipping oil on their vegetables, and said he had never seen one¹⁰.

Jeff on vegetables and greens: the full summary on Jeff Nelson's page

RE

Rip Esselstyn

In a 2018 talk Rip Esselstyn said the calcium the body absorbs best comes from leafy greens and beans rather than dairy⁴¹. He treats avocado on a salad as a condiment, a quarter to half at most²⁵, and his PLANTSTRONG site encourages eating many colors of vegetables³¹.

Rip on vegetables and greens: the full summary on Rip Esselstyn's page

A

Chef AJ

Chef AJ places non-starchy vegetables at the bottom of the calorie density scale, about 100 calories a pound, as she said on a 2022 podcast⁴². In 2021 she replaced the half-and-half plate with a simpler rule for her clients: a pound of vegetables at each meal, then as much starch as they can manage²².

Chef AJ on vegetables and greens: the full summary on Chef AJ's page

NP

Nathan Pritikin

After his heart disease diagnosis, Pritikin told McDougall in 1982, he switched to whole grains, beans, peas, potatoes, fruit and vegetables⁴³. In the same conversation he agreed that starches, vegetables and fruit make the diet that best supports health⁴⁴.

Nathan on vegetables and greens: the full summary on Nathan Pritikin's page

DL

Doug Lisle

Lisle explains that romaine lettuce does not excite us because it holds hardly any calories, unlike a candy bar⁴⁵. In his account of human evolution, cooked starches and some animal food supplied most calories, with raw fruit and vegetables as a garnish⁴⁶. He said in 2026 he would not dress his own salad with olive oil if weight loss is a goal²⁶.

Doug on vegetables and greens: the full summary on Doug Lisle's page

What we do in practice

We eat vegetables and leafy greens every day, alongside the starches that carry most of the calories, as McDougall, Goldhamer and Novick describe⁷²²¹. How large the vegetable share should be, raw or cooked, and whether to add fat are the points where these doctors differ, so questions about your own health belong with your own doctor. This page is education, not medical advice.

Each small number links to its reference below: the video at the exact second, or the page where it was said.