Nutrition Meets Food Science


Protein is an important macronutrient that is required in all stages of life of an individual. Our country has overcome protein deficiency to some extent but at the same time, there is a common opinion that animal proteins are superior to plant proteins. With environmental issues such as global warming, and agricultural activity leading to greenhouse effects it would be prudent to weigh the pros and cons of both plant and animal sources of proteins and wisely decide on an environmentally friendly as well as highly nutritious option.

Let’s take a look at the different Protein Sources:

Animal Sources of Protein Plant sources of protein Neither Plant nor Animal
Milk, Yoghurt / Curd, Cheese
Beef (Red)
Goat and Lamb (Red)
Pork (Red)
Fish and other seafood
Whole grains
Seeds (sunflower, flax seeds)
Vegetables and other plant
Algae – Red, Brown and
Green Micro and Macro
Macro- Seaweed
Protein content- 5 to 47%
(in red varieties)
Source of all amino acids – As good as egg white

Plant sources are good sources of proteins and are good for vegans too. Algal and seaweed sources of proteins could be the best among the three sources as they contain all the amino acids and high protein content.

PER is one of the important methods of estimating Protein quality and indicates the requirement of protein to be consumed for an increase in body weight. It has been noticed that when animal protein is consumed PER ranges from 3.1 to 3.7 (i.e., 1 gm of protein increases body weight by 3 gms). On consumption of plant protein PER ranges from 1.2 to 2.4 (i.e., 1 gm of protein increases body weight by 2gms). The lower PER in plant proteins is because of two reasons. They lack certain essential amino acids. They have lesser digestibility because they are enmeshed in plant and other plant components, and antinutrients.

To avoid using animals for testing an alternate method using PDCAAS (Protein Digestibility Corrected Amino Acid Score) is used to derive PER values using a simple conversion as follows:

PER=PDCAAS X2.5 (as given by Health Canada, 2020)

Plant Protein sources can have lower levels of some of these amino acids despite having a good PDCAAS value which can be seen in the following table: (FAO 1991)

As per this table, milk has a good PDCAAS value and has all amino acids in the required levels, whey though has the same PDCAAS value as milk but has lower levels of histidine. Similarly, other plant protein sources have good PDCAAS values but have low levels of sulphur-containing amino acids and some essential amino acids.

There are different ways by which Essential Amino Acid intake can be improved by consuming predominantly plant protein sources:

  • By increasing the quantity of protein consumed to compensate for lower digestibility
  • By consuming plant protein isolates or concentrates which can provide 20 gms per serve and also are more
  • By consuming plant protein from different sources, a combination of roti/rice and dhal balances both lysine (that is absent in rice /roti) and methionine (that is absent in dhal).


Soy Protein is one of the best vegetarian protein sources as it provides all nine essential amino acids, 100gms of raw soy beans provides around 37gms of protein and also records a high digestibility.

PDCAAS of Soy protein is almost equal to that of milk (around 1.0) and higher than other vegetarian sources like pea, potato, legumes.

Effect of food produce on Environment

Food production leads to production of greenhouse gases namely carbon dioxide, methane, nitrous oxide, fluorinated gases and according to Emissions Database of Global Atmospheric research (EDGAR) these emissions are highest while rearing lamb, goat and beef, intermediate during production of milk, cheese, pork and poultry and lowest while producing eggs, nuts, rice, lentils and millets. In addition, 6 kg of plant protein is required to produce 1 kg animal protein. Food related emissions make up for 34% of total greenhouse gases (around 35% of this comes from livestock and rice cultivation)

Disadvantages of Animal Protein

Consumption of animal protein leads to higher risk of

  • Heart diseases due to saturated fat content in red meat
  • Type 2 diabetes though not directly related but maybe due to obesity related to saturated fat consumption
  • Strokes
  • Developing certain types of cancer due to saturated fats in red meat

Poultry (lean meat) and fish (contains omega 3 fatty acids) are exceptions to these disadvantages

Advantages of Plant Protein

  • Relatively less expensive
  • Lower emission of greenhouse gases thereby it is sustainable
  • A balanced diet that includes plant proteins can lower risk of non-communicable diseases like heart attack,
  • Plants contain phytonutrients like soy isoflavones and carotenoids which are beneficial to health
  • Beneficial for chronic kidney disease patient as they are put on a diet that avoids animal protein, so plant protein comes to their rescue as it is not as damaging to the kidneys as animal
  • Studies are on to see a direct effect of plant protein in reducing the risk of Type 2 Diabetes
  • Longevity and mortality reduction can be attained by consuming plant proteins

It should be noted that health benefits of plant protein are for the whole plant as food and not for isolated proteins.

Potential Negative effects of Plant proteins

  • Certain antinutrients in plants (e.g., lectins and some saponins), can cause adverse effects- e.g. leaky gut and autoimmune effects
  • Protein maldigestion can occur due to trypsin and protease inhibitors
  • Carbohydrate maldigestion can happen due to alpha-amylase inhibitors, mineral malabsorption can happen due to phytates, tannins, and oxalates
  • Interference with thyroid iodine uptake (goitrogens), gut dysfunction, inflammation is possible
  • Behavioural effects due to conversion of cereal gliadins to

All these negative effects can be eliminated by proper processing of the food, so it is practical to cook the plant protein source and reap its benefits.

Allergenicity of proteins

All proteins both animal and plant can have allergenic epitopes. Allergens are thermal resistant and may not be eliminated by processing. So it would be wise to maintain Allergen databases and warning labels should be made mandatory.

In case of known allergies, protein can be replaced by protein hydrolysates which are known to be less allergenic.

So, plant protein matches up to the animal proteins enabling people who consume only plant proteins to lead a healthy life. Also considering the environmental aspects and sustainability it would be prudent for all to shift from animal proteins to plant proteins or partially replace animal proteins.

Dr. B. Sesikeran

Chairman - Scientific Advisory Committee, Hon. Scientific Director, PFNDAI, Former Director, NIN (ICMR)

Dr. Shashank Bhalkar

Executive Director, PFNDAI

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