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Evidence Based

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Weighing the Pros and Cons of a Plant-Based Diet

Written by Dr. Ruscio on August 24, 2023

Written by Dr. Ruscio on August 24, 2023 — Reviewed by Aimee Gallo

Plant-Based Doesn’t Suit Everyone. Find Out if it’s Right for You.

• What is Plant-Based Eating|
• Plant-Based Health Benefits: An Overview|
• Higher in Plant-Based Proteins|
• No or Low Oily Fish|
• Higher in Some Micronutrients (and Lower in Others)|
• High in Fiber|
• Find the Level of Plant-Based that Works for You|
• Plant-Based Diets Have Upsides and Downsides|

As more of us make more space for veggies and non-animal proteins in our diet, “plant-based” has become one of the most popular buzz-words in nutrition.

But while eating more plant-based food is generally a good thing, that’s not to say that it is always better for everyone.

In fact, a plant-based diet can be healthy or unhealthy, depending on the mix of foods you eat. Also, what might be an ideal plant-based diet for you might not be for someone else, depending on how well your gut can tolerate different types of plant fiber.

Let’s use this article to do a deep dive into the various health pros and cons of a plant-based diet.

First, let’s look at exactly what “plant-based” means.

What is Plant-Based Eating?

Plant-based can mean anything from a balanced diet that contains some meat and fish to one that is fully vegan. Other ways you may have heard plant-based described, include “plant-forward”, “plant-rich” or “flexitarian”.

These diets can all be quite different, but the defining factor is that plant foods, such as veggies, fruits, beans, nuts, and plant proteins are the main focus. In a traditional American diet, animal products are usually the prominent feature, with vegetables being more of an afterthought.

Whatever terminology you use, more and more American adults are embracing some form of plant-based eating. For example [1]: 

• 39% say they are actively trying to eat more plant-based foods
• 44% are seeking to reduce their meat intake
• 80% are “open” to trying plant-based substitutes for meat and/or eating less meat 

Plant-Based Health Benefits: An Overview

Observational research has linked plant-based diets with a reduced risk of heart disease and cardiovascular diseases, as well as a lower risk of type 2 diabetes, diverticular disease, kidney stones, cataracts, and possibly some cancers [2, 3, 4, 5]. 

Remember, however, that observational research can only really tell us that specific reduced health risks seem to coexist with a plant-based diet. Though it’s tempting to say plant-based diets cause these effects, we can’t make that leap from the data. It’s possible that people who tend to eat plant-based diets also lead generally healthier lives by exercising regularly and taking steps to relieve stress. 

The science on plant-based diets and health is a bit more solid when it comes to 

• Managing obesity and helping with weight loss [6]
• Reducing high blood pressure (hypertension) [7]
• Keeping cholesterol levels healthier [8]. 

In this case, there are multiple clinical trials (a more solid type of research) showing plant-based diets are better at improving these health measures than more meat-heavy diets.

However, a flexitarian approach (plant-based but with some animal products) may actually be the optimal one for most people.

For example, a meta-analysis of clinical trials found that the plant-based diets with the best effects on blood pressure contained some animal products, such as eggs, fish, and dairy [7]. 

On average, populations of people who eat a balanced plant-forward diet but who don’t cut out animal products completely (the Mediterranean diet is a good example) seem to do the best healthwise. 

The data is strong enough that many of the world’s public health bodies recommend a largely, plant-based diet for most people.

However, what works as a broad brushstroke recommendation for populations of people may not work for each individual. In my clinical experience, the pros and cons of a plant-based diet will weigh differently for different people. 

To look at this in an even-handed way, let’s dig into the typical features of a plant-based diet and the potential pros and cons of each, including who is most and least likely to benefit. 

High in Plant-Based Protein: Pro and Con

Compared with a heavily meat-based diet, you will be getting more of your protein from non-animal sources when you eat a plant-based diet. These proteins are not naturally as rich in the full range of essential amino acids, especially leucine, needed for vital anabolic (muscle-building) effects. However, if you are careful with your meal planning and eat enough varied plant protein sources every day this is not of concern.

In my very interesting interview with nutrition scientist Dr. Stephan van Vliet we drilled down into exactly what constitutes enough plant protein to overcome the effect of lower amino acid quality. The answer is that for the average person (including people who exercise regularly) 1.6g of plant protein per kilogram body weight (or 0.7g per pound bodyweight) is sufficient. 

For most people, this equates to around 30g protein per meal. As a guide:

• A can of chickpeas (253g drained) has 17.8g of protein
• 2 tbsps peanut butter contain 8g of protein
• A cup of cooked quinoa has 8.1g of protein
• A 3oz serving of firm tofu supplies 8g of protein
• A 4oz serving of Beyond Beef has 20g of protein

There are also smaller amounts of plant protein in many cereal grains and vegetables so eating 30g protein per meal could be easier than you think. 

However, for people who struggle with smaller appetites, or who are old, frail, or coming back from injury or illness, it’s much harder to take in enough protein of the right quality just from plant sources [9]. The same applies to serious endurance athletes or bodybuilders who need to significantly bulk up, and to pregnant or breastfeeding women [10]. In this case consuming at least some higher-quality animal protein like chicken, meat, or fish, is a good idea. 

If you are in one of the above categories and want to be a strict vegan for ethical reasons you could consider supplementing with pea protein powder, or consuming one of the processed meat substitutes like Impossible or Beyond Beef.

I personally prefer to get a high protein intake from an ancestrally focused diet such as the Paleo diet, which focuses on quality unprocessed protein sources, like grass-fed meat, along with nuts, seeds, and lots of non-starchy vegetables. 

To reach high protein intakes on a purely plant-based diet you may end up eating too many processed sources (like man-made “meats”) than is ideal, but of course it is your call to make. 

Some trial and error may be needed to see what levels of plant protein intake versus animal protein intake feels good for you.

Low in Oily Fish: Con

Oily fish deserve a separate look when considering the pros and cons of a plant-based diet.

If you aren’t eating oily fish you’ll likely be getting very few of the long-chain omega-3 fats, especially DHA (docosahexaenoic acid), which can help manage moods and is anti-inflammatory [11]. 

In fact, the average vegan consumes just 31 mg of EPA and DHA combined a day, whereas a meat-eater will have 266 mg a day and a pescatarian (a vegetarian who eats fish) consumes in excess of 287 mg a day [9].

On the plus side, your body can make EPA and DHA from the essential fat alpha-linolenic acid (ALA) found in some plant source oils, but it’s an inefficient process. Balancing out your essential fat intake so the proportion of omega-6 to omega-3 fats isn’t too high can help in this regard [12]. 

Plant-based foods with a lower omega-6 to omega-3, which may convert more efficiently into EPA and DHA in the body include:

• Flaxseeds and flaxseed oil
• Chia seed
• Cold pressed canola
• Camellia oil
• Walnuts and walnut oil

Our bodies are pretty remarkable and will adapt to making more DHA when we stop eating animal products. So if you are long-term plant-based and include plenty of the omega-3-rich seeds and oils from the list above you are likely getting enough EPA and DHA for your needs.

However, if you are newer to plant-based eating, and especially if you are a woman planning a pregnancy, already pregnant, or are breastfeeding a baby, you’re definitely going to benefit from a direct intake of DHA and EPA [10].

The best way to do this is by relaxing your plant-based diet and including some oily fish like fresh or canned salmon, mackerel, or sardines. Taking a supplement of algae-derived DHA is another option if you want to avoid animal products.

Higher in Some Micronutrients: Pro (but Lower in Others: Con)

A plant-based diet tends to be high in [9]:

• Folate
• Antioxidants such as Vitamin C and vitamin E
• Magnesium

However, it can also be low in [9]:

• Vitamin B12
• Vitamin D
• Iron
• Zinc
• Iodine
• Calcium

When we look at some of the nutrients that a plant-based (particularly vegan) diet is lower in, it’s an unfortunate fact that females can be more strongly impacted.

For example, up to 40% of young women and girls may have low iron levels, which can cause suboptimal physical and mental performance, and around 6% are actually anemic [13]. These statistics could get worse if the push towards cutting out animal foods continues. That’s why I caution women to be really careful about proper planning if they choose to go plant-based. Some plant foods that are high in iron include cashew nuts, leafy veg, and legumes (peas, beans, and lentils), but none of these are as well absorbed as the iron in red meat. 

Low levels of calcium and zinc can also impact women, in this case, their bone health [14]. Dairy products are the richest source of calcium for most Americans, while red meat is the best source of zinc. While it’s not impossible to get enough zinc and calcium from a plant-based diet, you’ll need to do your homework on good sources of both. 

Some of the better plant-based sources of zinc include

• Beans
• Nuts, especially pumpkin seeds, pine nuts, and pecans 
• Whole grains, including whole wheat and rye flours, quinoa
• Wild rice 
• Wheat germ

Richer plant-based sources of calcium include:

• Sesame seeds and tahini
• Almonds and brazil nuts
• Green leafy leafy veg especially kale, arugula, and spinach
• Fortified plant milks

On average, plant-based diets are also lower in iodine (as dairy and seafood are the best sources). Low iodine intake can have a negative impact during pregnancy, slowing the infant’s growth rate, and affecting brain development [5] .

Low iodine intake can be easily fixed if you use sea vegetable flakes or iodized salt for seasoning your food. 

Keep in mind that it’s possible to overdo iodine intake from some seaweed sources (kelp for example), so always check how much you are taking on board to keep within the recommended daily intake.

If You’re Fully Plant-Based, Try Vitamin B12 and Vitamin D Supplements

Two nutrients you won’t get at all from a purely plant-based diet are vitamin D and vitamin B12. You can take care of vitamin D by getting some regular sun exposure (for example spending 20 minutes outside on a sunny day). But in less sunny climates, especially during the winter, it’s a good idea for all plant-based eaters to take a daily vitamin D supplement.

The same also applies to vitamin B12, which only occurs naturally to any significant degree in animal products. Vitamin B12 supplements are effective and inexpensive and I’d recommend anyone who is eating a vegan diet (no animal products or dairy of any sort) to take one. Alternatively, you can look for products such as plant milks that are fortified with vitamin B12 (always check the label).

High in Fiber: Pro and Con

In most discussions of the pros and cons of a plant-based diet, a high fiber content usually features as one of its biggest advantages. However, from a clinical perspective, I would say that the high fiber provided by a plant-based diet can be either a benefit or a drawback, depending on the health of your gut.

If you have a healthy gut that does well digesting and absorbing nutrients from plant-based foods then the high level of plant and prebiotic fibers you get from a plant-based diet can be a boost to the health of your microbiome.

Prebiotic fibers found in many plant foods including beans and lentils, asparagus, leeks, Jerusalem artichokes, and the onion family are a preferred food for gut bacteria — including beneficial bacteria. Good bugs such as Bifidobacteria can ferment these prebiotic fibers and are able to thrive and multiply as a result. 

In turn, good bacteria produce short-chain fatty acids (SCFAs) that can benefit gut health. For example, SCFAs have been linked with [15, 16, 17]:

• Preventing leaky gut
• Mucus production to maintain a healthy intestinal barrier 
• Protection against inflammation 

However, for people who have a sensitive gut, too many prebiotics from a plant-based diet may also cause a flare-up of symptoms because of their fermentable nature. Most prebiotic foods are also FODMAPs, where the “f” stands for “fermentable” carbs that can create uncomfortable gas, bloating, and diarrhea for people with IBS [18]

A high-fiber plant-based diet can be a disadvantage (increasing gut symptoms) if you have: 

• Irritable bowel syndrome (IBS) or small intestinal bacterial overgrowth SIBO [19, 20, 21, 22].
• Generalized digestive symptoms including gas, bloating, abdominal pain, cramping, heartburn, nausea, and constipation [21, 22, 23, 24].
• Active inflammatory bowel diseases [24]

In these cases, I wouldn’t advise a heavily plant-based diet. Instead, many of my patients do better with a somewhat lower-fiber diet.

Find the Level of Plant-Based that Works for You

Finding your ideal intake of carbohydrates and prebiotics is one of the four pillars of healthy eating that I focus on any time I help a patient with gut health issues (along with eating to control inflammation, controlling blood sugar, and identifying any food sensitivities).

When you’re struggling with an unhealthy gut or unbalanced microbiome your tolerance level for a wholly or mostly plant-based diet may be relatively low but is likely to get better over time. 

If a plant-forward Mediterranean-style diet (veggies, fruit, whole grains, lean proteins) is too hard for you to tolerate, you could try a paleo-style diet (veggies, lean protein, limited grains) instead. If your gut sensitivities are more complex a low FODMAP diet (free from most fermentable carbs) is likely a better option to start out with.

Taking a quality probiotic supplement to assist your microbiome health is also a good idea, and may make it easier for you to reap the benefits of a plant-based diet, without the digestive downsides.

Plant-Based Diets Have Upsides and Downsides

After weighing up the pros and cons of a plant-based diet, you’ll come to your own decision on how to proceed depending on your own circumstances and preferences. 

Plant-based definitely has some health benefits but that doesn’t mean to say that animal foods are bad — in fact, a whole food omnivorous diet can provide an optimal nutritional balance and may be better for people who have gut issues (as well as being better than plant-based diets that feature a lot of highly processed meat alternatives).

If you have dietary intolerance or gut health issues, you’ll find more details on the diets and supplements that can help in my book Healthy Gut, Healthy You. You can also contact us at the Ruscio Institute for Functional Medicine if you’d prefer a personal consultation. 

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.