Hana Kahleova

What Hana says, topic by topic

Vitamin B12

In a 2020 Exam Room Live episode on her metabolism trial, Kahleova said the vegan participants’ diets were nutritionally adequate, with enough protein and essential amino acids, and that B12 was the one nutrient that needed real attention, so the trial supplied it as a supplement¹. She added that absorption declines with age and with some drugs such as metformin, and that since B12 is water soluble she saw no downside to supplementing it¹.

In another 2020 episode, asked about B12 in pregnancy, she put the amount needed at about 100 micrograms a day and advised against high-dose products, which she said have been linked to other problems². The Swedish study she was presenting had found that higher B12 levels in the mother went with shorter telomeres in the placenta³.

What all the experts say about vitamin B12

Vitamin D

Presenting the same Swedish pregnancy study in 2020, Kahleova said higher vitamin D levels in the mother went with longer telomeres, and drew from it that women should get enough sun and take vitamin D during the winter months⁴.

What all the experts say about vitamin D

Oil

In a 2024 Exam Room episode Kahleova said her team’s analysis found that oil, like any other added fat, slowed weight loss, so in her view it does not belong among the healthy plant foods⁵.

Her trials ask for it to be cut. Presenting a 2023 cost analysis of one of them, she said the low-fat vegan group had been told to keep oil to a minimum, which even trimmed a few cents a day from the grocery bill⁶.

What all the experts say about oil

Protein

A 2026 PCRM release on a study she led in postmenopausal women reports that those who swapped animal protein for soybeans, beans and grains lost weight while their total protein stayed the same⁷. She said the finding questions the idea that all protein is alike, and that the source matters for weight⁷.

The release ties part of the effect to less methionine, an amino acid more plentiful in meat, eggs and dairy⁸. Kahleova added that public advice tends to push more protein without saying which kind⁹.

What all the experts say about protein

Calcium, dairy and bones

Kahleova’s comments on dairy focus on cheese. In a 2021 talk on dietary acid load she ranked cheese above meat as an acid-forming food, with parmesan at the top of the list¹⁰. She explained that cheese is concentrated protein and phosphorus, the two inputs that raise acid load most, so the harder and more concentrated the cheese, the higher it scores compared with milk¹¹.

In 2022, discussing her rheumatoid arthritis trial, she said people who were not breastfed and were given cow’s milk early in life may react more strongly to dairy later, and she urged parents to be careful about which foods babies get and when¹².

What all the experts say about calcium, dairy and bones

Calorie density

A 2026 PCRM release on another of her trials reports that a low-fat vegan diet cut the energy density of what people ate by about 30% over 16 weeks, while the weight of food they ate stayed the same¹³. She said this explains weight loss without counting calories, since plant foods carry a lot of water and fiber¹³.

She also said that a drop that size would be very hard to reach by shrinking portions alone¹⁴.

What all the experts say about calorie density

Nuts, seeds and avocado

Describing a PCRM trial in 2022, Kahleova said participants could choose any fruit or vegetable but were asked to be careful with avocados and nuts, and to pick packaged foods with no more than 3 grams of fat per serving, about 30 grams a day in all¹⁵.

In 2024 she repeated that the low-fat vegan diet in their studies meant keeping oil, nuts and avocados to a minimum¹⁶.

What all the experts say about nuts, seeds and avocado

Soy

Her 2026 analysis drew on a 12-week trial of a low-fat vegan diet with daily soybeans in postmenopausal women⁷. The PCRM release says moderate to severe hot flashes fell by 88% in that trial and credits soy isoflavones for part of the relief¹⁷.

What all the experts say about soy

Sugar

In 2022 Kahleova said the PCRM trial she was describing never banned sugar or salt; its only two rules were vegan foods and low fat¹⁸. Asked which single food raises diabetes risk most, she named processed and red meat rather than sugar¹⁹.

In 2024 she said sweets did slow weight loss in their analysis, but probably because cookies and chocolate pair sugar with fat²⁰.

What all the experts say about sugar

Starches

In a 2020 PCRM release on two type 1 diabetes case reports, Kahleova said the findings counter the belief that carbohydrates are the enemy in diabetes²¹.

In her type 1 diabetes trial, described in 2024, the vegan group ate no animal products, kept fat to about 30 grams a day and favored low glycemic foods such as pumpernickel and brown rice²². Their carbohydrate intake rose, and their daily insulin dose fell by about 12 units on average²³.

On potatoes, she said in 2024 that observational studies rank them as unhealthy largely because fries are eaten with burgers, and that potatoes eaten with beans are a different matter²⁴.

What all the experts say about starches

Fasting

A 2017 PCRM release on her analysis of about 50,000 Seventh-day Adventists (Adventist Health Study 2) reports that those who gained the least weight ate breakfast, made it their biggest meal, skipped snacks and fasted longer overnight, up to 18 hours²⁵. She suggested two meals five to six hours apart, breakfast and lunch, while granting that such long fasts do not suit everyone every day²⁶.

In 2025 she described an earlier trial in type 2 diabetes comparing two meals a day with six of the same calories. On two meals people lost about half again as much weight, lost more liver fat, improved insulin sensitivity more and felt less hungry²⁷.

What all the experts say about fasting

Iron

In a 2021 talk Kahleova listed heme iron, the form found in meat, among the dietary risk factors for type 2 diabetes and heart disease, next to cholesterol, saturated fat and animal protein²⁸. She counted it among the strengths of a plant-based diet that its iron is all of the non-heme kind, without the heme form she described as harmful for the heart and for diabetes²⁹.

What all the experts say about iron

Fish and eggs

Reviewing a PCRM trial in 2022, Kahleova said the strongest predictor of weight loss on the vegan diet was eating no meat, poultry or fish, with eating beans second³⁰.

What all the experts say about fish and eggs

Fiber

In 2025 Kahleova said complex carbohydrates come packaged with fiber, and that fiber feeds gut bacteria that make short chain fatty acids good for the brain and metabolism³¹. She cited a study in which only about 21 grams of fiber a day went with 63% less depression, and noted that some participants ate under 10 grams³².

What all the experts say about fiber

Fruit

In a 2025 Exam Room episode on diet and mood, Kahleova singled out flavonoids, plant pigments with antioxidant and anti-inflammatory effects found in berries, citrus and apples³³. She cited Nurses’ Health Study data in which women eating at least two servings of citrus a day had an 18% lower risk of depression than women eating less than one serving a week³⁴, and she closed by urging listeners to favor these colorful, flavonoid-rich fruits³⁵.

In 2021 she noted that citrus, despite its sour taste, counts as alkalizing in terms of acid load³⁶, and that participants in her vegan trial ate fewer sweets once they ate more fruit³⁷.

What all the experts say about fruit

Vegetables and greens

In her 2021 talk on dietary acid load, Kahleova placed potatoes, carrots and above all spinach and other leafy greens at the alkalizing end of the scale, calling the greens the champions³⁸. As an example she compared a ham and cheese sandwich, which adds acid, with a baked potato and spinach, which removes it, a gap of more than 60 units³⁹.

In a 2022 episode on diet and COVID-19 she cited a study of nearly 600,000 people in which people with the highest intake of healthy plant foods, above all fruits and vegetables, were 41% less likely to fall severely ill⁴⁰.

What all the experts say about vegetables and greens

Beans and lentils

Beans are the food Kahleova singles out most often. In 2022 she reported that in her 16-week trial, eating beans, lentils and peas was the second strongest predictor of weight loss after avoiding meat, and on that basis she called them a superfood⁴¹. She put the target at a minimum of half a cup a day, an amount she said most people do not eat even in a month, which may be why adding them made such a difference⁴². Some people get gas at first, she said, but it settles within a few weeks⁴³.

Co-authoring a 2019 review on legumes and heart health, she described beans as a cheap, easy to find staple that could help cut the toll of heart disease⁴⁴.

What all the experts say about beans and lentils

Whole grains, bread and flour

In 2023 Kahleova said whole grains fill people up so well that they leave little room for the refined grains they used to eat⁴⁵. In her type 1 diabetes trial she asked participants to favor low glycemic choices such as pumpernickel and brown rice over white bread and white rice²².

She is not strict about white bread, though. In 2024 she said her trial data suggest that a vegan sandwich on white bread, when that is all that is on offer, matters more than holding out for whole grain⁴⁶. In 2021 she said bread sits slightly on the acidic side but that this is no reason to avoid it; the reason to lower acid load is to drop animal products⁴⁷.

What all the experts say about whole grains, bread and flour

Potatoes

Kahleova defends potatoes. Asked in 2025 whether she would include them in her diet, she said she absolutely would⁴⁸. She traced their bad name to Nurses’ Health Study data that counted fries, chips and mashed potatoes but left out boiled ones⁴⁹, and cited a later analysis of three US cohorts with over 200,000 people that found no link between boiled, baked or mashed potatoes and diabetes⁵⁰. In her words the potato is “a good kid in a bad crowd”, blamed for the burgers and cheese served with it⁵¹; she made the same point in 2024²⁴.

On blood sugar she said the glycemic index can be lowered by choosing red, purple or sweet varieties, by cooling cooked potatoes so resistant starch forms, by keeping the skin on and by eating them with beans and vegetables⁵². In 2020 she presented an Australian trial in people with type 2 diabetes in which potato dinners led to lower overnight glucose than basmati rice, roasted potatoes doing best⁵³, and she described potatoes as rich in fiber, vitamin C and potassium and low in sodium⁵⁴.

On weight she cited a satiety study of 38 foods in which potatoes were by far the most filling⁵⁵. She added that this is no endorsement of chips, and that potatoes should be prepared without excess oil⁵⁶.

What all the experts say about potatoes

Meat

Kahleova argues that junk food from animals and from plants is not equivalent. In 2024 she cited data in which each extra half serving of red meat a day went with a 48% higher risk of type 2 diabetes, while she described the risk from so-called unhealthy vegan foods as small by comparison⁵⁷. In 2022 she named processed and red meat as the single food that raises diabetes risk most¹⁹, and reported that cutting out meat, poultry and fish was the strongest predictor of weight loss in her trial³⁰.

A 2022 PCRM release on her research reports that replacing fatty meat and dairy with a low-fat plant diet sharply cut dietary advanced glycation end-products, inflammatory compounds more common in animal foods, and that the drop went with weight loss and better insulin sensitivity⁵⁸. In 2021 she also named meat, cheese and eggs as the main acid-forming foods⁵⁹.

What all the experts say about meat

Low-fat eating

Kahleova’s case for low fat is metabolic. In a 2020 talk she said a Western diet supplies more fat than fat tissue can hold, so the excess spills into the liver, muscles and pancreas, where it impairs the mitochondria and disturbs metabolism⁶⁰. Presenting a 2017 trial, she said that clearing fat out of muscle cells lets insulin work again⁶¹.

Her trials therefore pair a vegan diet with a fat limit: no added oils, very few nuts and seeds, packaged foods with no more than 2 to 3 grams of fat per serving, and 20 to 30 grams a day in total⁶². In 2022 she added that a high-fat diet is pro-inflammatory and weakens immune defenses⁶³, and in 2025 she cited a study in which a single drink with 100 grams of fat lowered BDNF, a brain protein linked to mood, by 28% within six hours⁶⁴.

What all the experts say about low-fat eating

Saturated fat

In a 2017 statement on the PURE study, Kahleova rejected its call to lift limits on saturated fat⁶⁵. She argued that in poorer countries only the well-off can afford fatty animal foods, so a high saturated fat intake marked wealth and access to medical care rather than causing longer life⁶⁶.

In 2025 she cited a three-week trial in young adults in which replacing saturated fat with monounsaturated fat from plants, at the same total fat intake, left people less angry and in a better mood⁶⁷.

What all the experts say about saturated fat

Cholesterol

In her 2024 type 1 diabetes trial, Kahleova reported that total cholesterol fell more on the low-fat vegan diet than on the portion-control diet, and LDL cholesterol fell only on the vegan diet⁶⁸. She estimated that the roughly 20% LDL drop would correspond to about a 20% lower risk of cardiovascular disease⁶⁹.

Her 2021 head-to-head trial with the Mediterranean diet showed the same pattern: total and LDL cholesterol dropped on the vegan diet and did not change significantly on the Mediterranean diet⁷⁰. In 2018, as a co-author of a meta-analysis of the Portfolio diet (nuts, soy or pulse protein, sticky fiber and plant sterols), she said some plant foods are particularly strong at lowering cholesterol⁷¹.

What all the experts say about cholesterol

Carbohydrates and low-carb diets

Kahleova rejects the idea that carbohydrates drive disease. In a 2017 statement on the PURE study, which had tied very high carbohydrate intake to higher death rates, she argued that such intake marked poverty and poor living conditions, and that the study lumped soda together with sweet potatoes⁷².

She is critical of ketogenic diets. In 2020 she asked people considering keto for weight loss to think twice, citing a trial in which keto produced more weight loss than a low-fat plant diet but little of it was fat, while most of the plant-based loss was fat⁷³. The same year she discouraged keto diets in pregnancy, citing research on a higher risk of birth defects⁷⁴. In 2025 she described two year-long trials in which keto and high-carbohydrate diets gave similar weight loss, but depression, anxiety and hostility scores ended lower on the high-carbohydrate diet⁷⁵.

What all the experts say about carbohydrates and low-carb diets

Juicing and smoothies

Kahleova takes a middle position on fruit juice. In 2022 she said freshly squeezed orange juice is very different from a sugary drink with 12% juice, but warned that people tend to drink too much and that most store-bought juice has lost its fiber, pulpy brands being better⁷⁶. The best options, she said, are juice made at home or a smoothie of whole fruit that keeps the fiber⁷⁷.

In 2024 she questioned whether 100% fruit juice belongs among unhealthy plant foods at all, noting studies in which it lowered cardiovascular risk and might even help weight loss⁷⁸.

What all the experts say about juicing and smoothies

Mediterranean diet

Kahleova led the PCRM crossover trial comparing a low-fat vegan diet with a Mediterranean diet in overweight adults. The 2021 PCRM release reports an average loss of about 6 kg (13 lb) on the vegan diet against no mean change on the Mediterranean diet⁷⁹, while blood pressure fell on both, more on the Mediterranean diet⁸⁰.

In a 2024 follow-up analysis she said the results help bust the myth that the Mediterranean diet is best for weight loss, crediting the vegan diet’s lack of dairy and oil, which lowered harmful advanced glycation end-products⁸¹. In 2025 she added that even with refined grains and potatoes the vegan diet beat the Mediterranean one, because it leaves out animal products and added oils⁸². A 2024 cost analysis she led put the vegan diet’s grocery savings at over $870 a year compared with the Mediterranean diet⁸³.

She has not dismissed the Mediterranean pattern in every context: in 2020 she said reviews suggest both plant-based and Mediterranean diets work well in pregnancy⁸⁴.

What all the experts say about mediterranean diet

Weight loss

In her 2020 metabolism trial, presented on Exam Room Live, overweight adults on a low-fat vegan diet lost about 14 pounds in 16 weeks while their after-meal calorie burn rose by 14%⁸⁵. Liver fat fell by 34%, and her summary was that going vegan speeds up metabolism⁸⁶.

She stresses that leaving out animal foods matters most. In 2024 she reported that all plant foods, even the so-called unhealthy ones, were linked to weight loss in her trial, though less so than the healthy ones⁸⁷, and a 2025 PCRM release quotes her saying a bagel beats bacon at breakfast for someone trying to lose weight⁸⁸. In 2025 she also cited data that obesity and depression each raise the risk of the other by more than half⁸⁹.

What all the experts say about weight loss

Exercise

In 2025 Kahleova put exercise first among three ways to raise brain-derived neurotrophic factor (BDNF), a brain protein tied to mood, learning and appetite, especially endurance exercise such as running, swimming, cycling and rowing⁹⁰. She cited a study in which overweight sedentary men doing an hour of endurance training a day for three months quadrupled their BDNF levels⁹¹.

She also links diet to fitness. In 2021 she said diets low in animal products and rich in fruits and vegetables, which carry a low acid load, have been tied to better anaerobic and aerobic performance⁹².

What all the experts say about exercise

Heart disease

A 2018 PCRM release on a review she led reports strong evidence that plant-based diets can prevent and reverse atherosclerosis. Kahleova said such a diet can prevent, manage and sometimes reverse heart disease, “something no drug has ever done”⁹³.

In her 2024 type 1 diabetes talk she noted that people with that disease die early mainly of heart disease, and that higher insulin doses track with higher cardiovascular risk⁹⁴. She estimated that the vegan diet’s cuts in insulin dose, A1C and LDL cholesterol would translate into roughly 9%, 12% and 20% lower cardiovascular risk⁹⁵.

What all the experts say about heart disease

High blood pressure

Kahleova has addressed blood pressure mainly through reviews. Co-authoring a 2019 review of legumes, she said putting more beans on the plate could help bring blood pressure down⁹⁶. A 2018 meta-analysis of the Portfolio diet she co-authored found it lowered both systolic and diastolic pressure⁹⁷. In her 2021 trial, blood pressure fell on both the vegan and the Mediterranean diets, more on the Mediterranean⁸⁰.

What all the experts say about high blood pressure

Diabetes

Diabetes is the center of Kahleova’s research. In 2024 she said the usual advice in type 1 diabetes is to count carbohydrates and dose insulin to match, and that her trial showed a plant-based diet could be a breakthrough instead⁹⁸, cutting daily insulin needs by about 12 units on average²³. For type 2 diabetes she said a plant-based diet can reverse the disease in many cases by improving insulin sensitivity⁹⁹.

She co-authored the 2023 European (EASD) nutrition recommendations for diabetes. Presenting them, she said they put vegetables, fruit, whole grains and legumes first, with nuts and seeds in moderation, and advise keeping red and processed meat, sodas, salty foods such as cheese, and refined grains to a minimum¹⁰⁰. She contrasted this with US advice that still centers on cutting calories and watching carbohydrates¹⁰¹.

A 2026 PCRM release on her trial in type 2 diabetes reports that a low-fat vegan diet cut liver fat by a third and improved insulin production, and quotes her stressing that nobody had to count calories¹⁰².

What all the experts say about diabetes

Dementia and the brain

Kahleova’s comments on the brain come from a 2025 Exam Room talk on diet and mood. She explained that BDNF, a protein made in the brain, protects neurons and helps form the new connections needed for memory and learning, and that people with depression have lower levels¹⁰³. She cited trials in which flavonoid-rich fruits, vegetables or cocoa raised BDNF, with higher levels going along with better cognitive scores¹⁰⁴.

What all the experts say about dementia and the brain

Longevity and aging

Kahleova links aging to fat overload. In 2020 she said the underlying mechanism of aging is mitochondria overloaded with fat and energy, so clearing excess fat from cells should in fact make people metabolically younger¹⁰⁵. That year she also described telomeres as a marker of aging that can lengthen again after a switch to a plant-based diet¹⁰⁶.

In 2022 she pointed to Okinawa, a blue zone whose traditional diet is built on sweet potatoes, rice, soy and greens with only about 6% of calories from fat, and where centenarians are nearly twice as common as in the rest of Japan¹⁰⁷. A 2020 editorial she wrote with PCRM colleagues argued that plant-based diets promote healthy aging, and she said simple diet changes could help populations live longer and healthier lives¹⁰⁸.

What all the experts say about longevity and aging

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