What are the possible health benefits of a vegetarian diet? On the downside might you be missing out on important nutrients?

This article looks at the different kinds of vegetarian diets and at the evidence for their benefits to our health.

• What healthy nutrients does a vegetarian diet contain?
• Is what a vegetarian diet excludes also important?
• What is the evidence for health benefits?
• Are all vegetarian diets the same?
• Are there possible deficiencies in a vegetarian diet?
• Conclusions 

What healthy nutrients does a vegetarian diet contain?

 

Each of the food types in the vegetarian diet pyramid provides us with essential nutrients for healthy eating. Here are the five main sources of those nutrients: 

Food type	Essential nutrients
Nuts and seeds	Rich sources of Vitamin E and essential fatty acids. The US Food and Drug Administration has granted tree nuts a qualified health claim for cardiovascular disease risk reduction.
Vegetables and fruits	Contain fibre, as well as vitamins such as A, C and E. Eating more fruit and vegetables is associated with a lower risk of death from all causes, in particular cardiovascular causes (e.g., heart attack and stroke) and cancer. That’s according to a review of 95 different studies published in 2017.
Wholegrain	Wholegrain products contain vitamin B, potassium, magnesium and zinc. They are associated with a range of health benefits, including a reduced risk of heart disease, cancer, and type 2 diabetes.
Pulses, legumes and soy	This group includes beans, lentils and peas, all of which are a good source of protein, fibre, and minerals such as iron, zinc and magnesium.

 

The Healthy Eating Plate

Harvard School of Public Health’s interactive ‘Healthy Eating Plate’ helps you build a healthy, mostly vegetarian, balanced diet, while it also suggests that we limit dairy products like milk, cheese and butter.

 

 

Is what a vegetarian diet excludes also important?

Red meat and processed meats

The NHS advises people who consume large quantities of red and processed meat to cut back, as this diet probably increases the risk of bowel cancer and cardiovascular disease (CVD). However, they do not indicate a similar risk from eating poultry (chicken, turkey, duck or goose).

Saturated fatty acids (SFA)

For many years consuming saturated fatty acids (i.e., animal fats, meat, milk, cheese, butter and cream) was believed to increase the risk of cardiovascular disease. However, this is currently being contested. Some countries like France consume quite high levels of saturated fats, although the French generally have low levels of cardiovascular disease.

In 2020, the Journal of the American College of Cardiology concluded that the most recent meta-analyses of randomised trials and observational studies found no beneficial effects of reducing SFA intake on cardiovascular disease (CVD) and total mortality, although the studies found protective effects against stroke. The Journal also concluded that whole-fat dairy, unprocessed meat, and dark chocolate are SFA-rich foods with a complex matrix are not associated with increased risk of CVD.

This suggests that what vegetarian diets exclude may be less of a factor than assumed.

Research continues to indicate that a diet with high levels of processed meat (such as sausages, bacon and ham) increases the risk of CVD.

 

Fish and eggs

According to the Harvard School of Public Health, on balance, fish and moderate egg consumption (provided the eggs are stored and cooked properly) can form part of a healthy diet. 

What is the evidence for health benefits?

Some indicators of poor health

Here is a short list of indicators that help us to identify risks to our health. Below this list, we look at how eating more healthily can reduce these risks. 

The positive effects of a vegetarian or vegan diet

An analysis of 96 different studies, published in 2017, showed that vegetarians and vegans have significantly reduced levels of LDL cholesterol, blood glucose, and Body Mass Index (BMI – an indication of being overweight), as well as a reduced risk of heart disease and cancer.

Research from the USA suggests that vegetarian diets are associated with lower deaths from all causes – particularly from heart attack and stroke, kidney failure, and diabetes. These reductions were larger and more significant in men than in women.

To identify the specific effects of diet, this research took account of other lifestyle factors such as smoking, alcohol, exercise, education, and sleep.

Vegetarianism and all-cause mortality 

A long-term study of over 130,000 nurses in the USA, published in 2016, found that plant protein was associated with lower death rates from all causes, where participants had at least one health risk factor, such as smoking, high alcohol consumption, obesity or physical inactivity.

Conversely, a 2021 analysis of published research, based on ‘very low certainty of evidence’, concluded that, although a vegetarian diet was associated with a reduced risk of death from coronary heart disease, it did not appear to influence all-cause mortality.

Type 2 diabetes 

Three long-term studies in the US, collectively with over 200,000 health professional participants, suggested that plant-based diets (especially when rich in high quality plant foods like whole grains, vegetables, fruits, nuts and pulses) were associated with a substantially lower risk of developing type 2 diabetes.

A 2019 review of published research supported these findings, concluding that the evidence supported the value of including vegetarian dietary products to help manage diabetes. 

Are all vegetarian diets the same?

If we leave out diets that include fish or meat, there are four main types of vegetarian diet: 

These four vegetarian diets have different nutritional consequences, as outlined in the next section. 

Are there possible deficiencies in a vegetarian diet?

Yes: animal proteins (i.e., from eggs, dairy products, fish, and meat) tend to provide all the amino acids we need. In contrast each type of plant-based protein (from pulses, seeds, nuts, grains, fruit and vegetables) typically lacks one or more of the essential amino acids.

For example, beans on toast provides pulses (beans) and cereals (bread). Adding a glass of soya milk, some nuts and a banana would add soya, nuts and fruit i.e., three additional and different types of plant based protein. Soya and quinoa are also said to be the best plant-based sources of essential amino acids. 

Sources of essential nutrients

The main nutrients vegetarians and vegans need to ensure that they get enough of are iron, selenium, vitamin B12 and omega-3 fatty acids. Potential sources for these essential nutrients are:

• Iron and absorption of iron: pulses, green vegetables, wholemeal bread, dried fruit, nuts, seeds and eggs (for iron) – ideally with fruit, to help increase the absorption of iron.
• Selenium: Brazil nuts, cashew nuts and pecans.
• Vitamin B12: yeast extract and some fortified breakfast cereals.
• Omega-3: tofu (‘bean curd’), flaxseed, eggs, walnuts and walnut oil. 

Vegetarianism around the world

Vegetarian diets from around the world provide interesting alternatives to the diets we are used to in the UK. Examples include: tortillas, beans, avocado and salsa (from Mexico), and Chana Masala (chickpeas stewed with onions, tomatoes and spices, and eaten with rice), from India. 

Conclusions

• Vegetables, fruit, pulses, whole grains, nuts and seeds contain a range of health-enhancing nutrients.
• Most research suggests a vegetarian diet reduces the risk of heart attack and the risk of becoming overweight.
• Research is divided as to whether a vegetarian diet reduces death from causes other than heart disease.
• The stricter the vegetarian diet the more important it is to eat a wide range of sources of plant-based protein to get all the nutrients needed (i.e., the nutrients that non-vegetarians get through meat, fish, eggs and dairy products).

Reviewed and updated by Harrison Prince February 2023. Next Review date January 2027.