Whether for health, ethical, environmental, or spiritual reasons, plant-based diets continue to grow in popularity, with nearly 10 million Americans adopting one. Here's what you need to know about plant-based diets and their potential risks and benefits.

What is a plant-based diet?

A plant-based diet consists of mostly plant-based food sources like fruits, vegetables, beans, legumes, whole grains, nuts, seeds, and oils. However, some plant-based diets still include small amounts of animal products. 

"A key point for those contemplating a plant-based diet is that it does not have to be an all or nothing proposition. Each change one is able to make - whether it's eliminating some type of animal-based food or just reducing its frequency - can have significant health impact when done the right way," says Mindy Haar,  RDN, a clinical associate professor and chair of Interdisciplinary Health Sciences at New York Institute of Technology. 

Types of plant-based diets

• Lacto-vegetarian. A diet that excludes red and white meat, fish, eggs, and poultry but allows for dairy products like butter and milk. 

• Ovo-vegetarian. A diet that excludes red and white meat, fish, poultry, and dairy products but allows for egg and egg products. 

• Lacto-ovo vegetarian. A diet that excludes red and white meat, fish, and poultry, but allows for egg and dairy products. 

• Pescetarian. A lacto-ovo vegetarian diet with the addition of fish

• Flexitarian. A lacto-ovo vegetarian diet with occasional meat intake 

• Vegan. A diet without any animal products including eggs, dairy, meat, or honey. 

What do you eat on a plant-based diet?

Plant-based diets require a diverse variety of foods in order to meet nutrient needs. 

"Vegans who consume no animal products at all may be at risk for vitamin B12 deficiency and may consider supplementing this vitamin. Those who eliminate dairy products can still get enough calcium from fortified plant-based milks, calcium-fortified orange juice, and tofu," Haar says.

On a plant-based diet, you should eat foods like:  

• Calcium-enriched and fortified products (juices, cereals, soy milk, tofu)

• Dark green vegetables (spinach, kale, collard greens, broccoli)

• Fruits (berries, bananas, citrus fruits, apples)

• Legumes (lentils, chickpeas, beans)

• Nuts and nut butter (peanuts, peanut butter, pistachios, cashews, almonds, pecans, walnuts) 

• Seeds (pumpkin, hemp, sunflower, flax, chia) 

• Whole grains (brown rice, quinoa) 

• Meat 

• Fish and seafood

• Eggs 

• Dairy 

• Bee products 

• Gelatin 

The benefits of a plant-based diet 

Following a plant-based diet can be beneficial to both your health and the health of the environment. 

1. Plant-based diets can help you lose weight

Research has found following a plant-based diet can decrease obesity risk and aid in weight loss. 

Animal foods including meat and dairy products are often high in saturated fat and low in fiber. Research indicates consuming foods high in saturated fat is linked to obesity and heart disease. Meanwhile, high fiber foods - like vegetables - can help with weight loss. 

"When one moves to a more plant-based diet, the animal-based foods are typically replaced with legumes, whole grains, and more fruits and vegetables. As these foods are filling, higher in fiber and nutrients, and lower in fat there is potentially reduced calorie intake leading to weight loss," Haar says. 

What the research says: A small 2018 study found overweight people who followed a plant-based vegan diet for 16 weeks saw an improvement in body weight, fat mass, and insulin resistance markers compared to a control group. The decrease in fat was associated with an increased intake of plant protein, and decreased intake of animal protein.

2. Plant-based diets can reduce your risk of diabetes 

Research has found plant-based diets are effective in reducing the risk of type 2 diabetes. 

A large 2009 study found the prevalence of prediabetes and type 2 diabetes is significantly lower among people following plant-based eating patterns compared with those who eat meat.

The prevalence of type 2 diabetes decreased with a reduction in animal products: from 7.6% in non-vegetarians, 6.1% in semi-vegetarians, 4.8% in pesco-vegetarians, 3.2% in lacto-ovo vegetarians, and 2.9% in vegans.

Plant-based diets are typically full of high-fiber foods like vegetables, legumes, and fruits which Haar says can reduce glucose intolerance - the high blood glucose levels seen in pre-diabetes and type 2 diabetes. 

3. Plant-based diets can reduce your risk of heart disease 

Coronary heart disease, the leading cause of death in the US, occurs when plaque builds up in the walls of arteries. 

 "Animal meats and processed snacks are notorious for being high in saturated fat, sodium, and cholesterol which can cause plaque buildup in arteries," says Kelly Springer, RD, the founder of nutrition program Kelly's Choice. 

However, not all plant-based diets are created equal. A large 2017 study found those who followed a plant-based diet rich in "healthier" plant-based foods like whole grains, fruits, vegetables, nuts, and legumes and low in "less healthy" plant-based foods like refined grains, potatoes, sweetened beverages, and desserts had lower rates of coronary heart disease (CHD). 

Those who followed plant-based diets that emphasized "less healthy" plant foods experienced a significantly increased risk for CHD.  

The risks of going on a plant-based diet 

Plant-based diets are beneficial to all people, but experts warn that it's important to make sure you're consuming enough nutrients that are more commonly found in animal products like protein, vitamin D, and vitamin B12.

To make up for these discrepancies, people following plant-based diets should integrate fortified foods like almond milk or talk to their doctor about taking a multivitamin supplement. 

Additionally, those recovering from eating disorders should avoid following a plant-based diet while still in the recovery process. 

"Plant-based diets are restrictive and can limit the recovery process of someone learning that all foods fit in a healthy and balanced diet," Springer says. 

Environmental impact of a plant-based diet 

A 2020 survey found 48% of people choose to follow a plant-based diet for environmental reasons, an increase of 17% since 2018. 

Avoiding meat and dairy products is one of the most substantial ways to reduce your carbon footprint. Livestock production is responsible for 14.5% of greenhouse gas emissions - the gases that trap heat in the atmosphere and contribute to climate change. 

Animal products, particularly meat, are also significantly more resource-intensive to produce than plant-based foods. One pound of beef requires between 2,000 and 8,000 gallons of water to produce, while one pound of tofu requires 302 gallons. Therefore, cutting back on animal-based food can help prevent further water scarcity. 

Insider's takeaway 

Plant-based diets are beneficial to most people and can help prevent chronic diseases, but changing your diet doesn't have to be an all or nothing operation. Integrating more fruits, whole grains, and vegetables into your diet while decreasing your consumption of animal products is a low-risk way to improve your overall health and reduce your carbon footprint.

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