Are plant-based diets healthy?

Author: Donna Jiang, Dietitian in Training

When peering into your oatmeal bowl, you could hardly be blamed for not seeing it as a breakfast abundant in protein. In the recent past, protein meant meat and meat meant protein - and this notion is still common nowadays!

According to a 2010 analysis of protein intake in U.S. adults, “the percentages of total protein intake derived from animal, dairy, and plant protein were 46%, 16%, and 30%, respectively” [1], which means that animal products still dominate daily protein consumption in the U.S. and other countries with similar diets.

However, plants such as grains, legumes, nuts and seeds are getting increasing recognition for their protein content.

 

The Essentials

Protein is one of three mactronutrients (the other two being carbohydrate and fat) that provide us with energy; in addition, it constitutes our muscles and other tissues and is in charge of many important functions in our bodies.

Protein molecules are chains of amino acids strung together in different combinations. Out of 20 amino acids, nine are called “essential”, because our bodies cannot synthesize them internally. We have to get them from food.

 

The Animal vs Plant Protein Dilemma

High consumption of meat has been linked to cardiovascular disease and hypertension [2], implying that we could benefit from reducing meat and seeking protein elsewhere. Yet anyone who begins exploring a plant-based diet will soon learn that animal and plant protein aren’t created equal, leading to the common concern: can plants provide enough protein?

These two worries can push us in opposite directions, turning our daily food choices into a struggle. In fact, it doesn’t have to be that complicated!

 

What’s the Difference?

Both animal protein and plant protein have their virtues:

• Animal protein is rich in all nine essential amino acids, and it comes with abundant vitamin B12 and zinc, which help to maintain nervous and immune system functioning.
• Plant protein comes with lots of folate and potassium, antioxidants, phytochemicals and fibre, which reduce the risk of heart disease and cancers [3]. It also tends to be more affordable and friendlier to the environment.

Animal products, especially processed meat, are related to many chronic diseases when their consumption exceeds a moderate level, while the concern with plant protein is its amino acid profile.

Unlike protein from meat which resembles the protein composition of our own muscles, plant protein doesn’t come with all the essential amino acids in the right amounts in one single source (except for soy beans!). Despite this, over the last decade protein adequacy has been proven to not be a problem for a plant-based diet [4]. How so?

 

Essential Amino Acids in Plants

Legumes, nuts, grains and seeds are popular plant protein choices. They each have a shortage in either methionine, tryptophan, lysine and threonine (essential amino acids). The table below illustrates how perfectly these foods compensate for each other’s shortcomings and together give us all the amino acids we need for biological functions.

	methionine	tryptophan	lysine	threonine
Legumes	x	x	√	√
Nuts	x	x	x	√
Grains	√	x	x	x
Seeds	x	√	x	√

 

For example, a breakfast of oatmeal topped with chia seeds and almonds and a lunch like bean chili with rice provides all the required amino acids. Note that you don’t have to eat all of these foods together at every meal! Our bodies are able to process the amino acids coming in from different meals throughout the day to build the proteins we need.

When you eat a variety of plant foods, protein won’t be a concern.

 

How Much Protein is in Plants?

Now that we’ve done away with the concern of plant protein quality, what about quantity? The recommended protein intake for the average adult is at least 0.8 g per kg of body weight, which means that if you weigh 60 kg (132 pounds), you need about 48 g of protein daily.

For reference, one cup (250ml) of chicken breast is 24 g of protein and about 433 calories.

Let’s compare this to plants (per cup).

              

Tofu (soybeans)                                      Oats

25 g protein, 405 calories                        16 g protein, 452 calories

 

            

Kidney Beans                                        Chia Seeds

16 g protein, 238 calories                       30g protein, 438 calories

        

Lentils                                                    Chickpeas

18.87 g protein, 243 calories                  15g protein, 284 calories

This brief list of popular plant protein choices shows that plants are comparable or lower in calories compared to meat, but they are equally abundant in protein!

 

Conclusion

You can replace animal protein with plants worry-free. You’ll benefit by avoiding the dangers of excessive meat intake, by reducing calories and increasing fibre, as well as gaining variety in your diet!

 

References:

1. Stefan, M.P.,Sanjiv, A.,Harris R.L., &Victor, L. F. (2015). Sources and Amounts of Animal, Dairy, and Plant Protein Intake of US Adults in 2007–2010.Nutrients. 2015 Aug; 7(8): 7058–7069. Retrieved from

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4555161/

1. Pan A, Sun Q, Bernstein AM, Schulze MB, Manson JE, Stampfer MJ, Willett WC, Hu FB. Red Meat Consumption and Mortality Results from 2 Prospective Cohort Studies. Arch Intern Med. 2012;172(7):555–563. doi:10.1001/archinternmed.2011.2287
2. Gary E Fraser. (2009). Vegetarian diets: what do we know of their effects on common chronic diseases?Clin Nutr. May 2009. vol. 89 no. 5 1607S-1612S. doi: 10.3945/​ajcn.2009.26736KAm J
3. Millward, D. (1999). The nutritional value of plant-based diets in relation to human amino acid and protein requirements. Proceedings of the Nutrition Society, 58(2), 249-260. doi:10.1017/S0029665199000348