Protein needs

Where do you get your protein from?

Answer: plants and fungi

Animals cannot synthesize amino acids. Even the non-essential amino acids, they can only make from other amino acids. All dietary protein originates in plants (and fungi). Livestock are sentient food processing machines – they take plant protein, remove the fibre and phytonutrients, concentrate it, and repackage it with saturated fats, cholesterol and other components that are harmful to human health.

Protein is essential but it is not the limiting factor for the human food supply. The limiting factor has always been energy (calories/ kilojoules). Adequate calories of whole foods provides adequate protein. Food supply or production costs should therefore be expressed per kilojoule rather than per unit of protein, as is often the case.

How much protein do we need?

Answer: humans have very low protein requirements

This can be expressed as grams per day or as a percentage of daily energy intake. Note that the recommended intake is not the minimum requirement, it’s already adjusted upwards to cater for individuals who might have higher than average requirements. No additional adjustment factors are necessary for vegan diets. A high carbohydrate diet may reduce protein requirements by reducing the need for gluconeogenesis (one-way conversion of amino acids into glucose).

Recommended intakes per kilogram of body weight: The calculation is based on a non-overweight body (lean body mass or ‘fat free mass’), and requirements are not increased by obesity:

  • 0.8g/kg – Light to moderate level of physical activity
  • 1.2g/kg – High level of physical activity. Endurance athletes and maintenance phase of strength training.
  • 1.7g/kg – Early stages of strength training (with rapid increase in muscle mass)

Protein requirements may be increased in old age. However, much of the evidence has been tainted by meat and dairy industry funding. A macronutrient ratio of 10% energy from protein meets the needs of most individuals and does not require adjustments for body size or activity level because larger or more active people consume more calories and therefore more protein. Diets based on whole grains, legumes, vegetables, and fruits typically come in at 12% protein.

The following chart lists the protein content of whole plant foods. Note that expressing protein content in this way corrects for energy density, giving what we consider a fairer ranking of the protein content of nuts, grains, and other items.

Protein in food – expressed as a % of calories and per 100 calories

It is interesting that human breast milk is so low in protein yet provides adequate protein for our most rapid period of growth.

Do plants provide quality protein?

Answer: Yes

What is meant by ‘quality protein’ is that every essential amino acid, the ones our bodies cannot make out of other amino acids, is present in at least the proportion our body needs for protein synthesis. Plants contain all essential amino acids, but some plants have a lower proportion of one or other of these. This led to the idea of protein complementarity, combining two of more plant protein sources at each meal to match our bodies requirements for full utilisation of dietary protein, an approach that has been abandoned for several reasons. Our bodies maintain a small store of amino acids that balances out the intake of essential amino acids across each day. Even if protein quality were to fall short of 100%, it would not matter as plant-based diet protein intakes are typically well in excess of minimum daily requirements. The ‘quality protein’ in animal products contributes to human health problems. High levels of sulphur containing amino acids create an acid load on the body. High levels of branched chain amino acids upregulate mTOR, driving cancer and cellular aging. Animal protein increases IGF-1 hormone levels which promotes cancer growth, acne and other health problems. Rat feeding studies suggest that animal protein but not plant protein is a potent cancer promoter, backing up human studies that observe an association between animal protein intake and cancer incidence.

Are protein supplements healthy?

Answer: no

Plant protein supplements are processed foods, comparable to other macronutrient food extracts like sugar and vegetable oil.

Taking protein supplements worsens nutritional status through displacement of nutrient rich whole plant foods. A 50g protein powder serve has 200 calories but none of the fibre, iron, vitamins and phytonutrients that could have come from an equal calorie serve of a whole plant food, for example 200g of legumes. In most situations, dietary protein is sufficient to meet our needs and the extra protein in the supplement is converted to glucose and fats, contributing nothing but nutrient poor calories to our day. Its’s ironical that some nutritionists recommend olive oil (zero protein), protein supplements (zero nutrients), and then suggest a nutrient supplement to compensate. The full array of plant phytonutrients, only found in whole plants, would still be missing. We say “Eat peas not pea protein.”

Which whole plant foods are proteins?

Answer: all of them

Whole plants cannot be neatly divided into carbohydrates and proteins to match the classic plate model of a quarter protein, a quarter carbohydrate, and half vegetables. Legumes are classified as protein, but most contain far more carbohydrate than protein. Whole grains are classified as carbohydrate but are moderately high in protein. Nuts have a similar protein content to whole grains (on a per calories basis) but are classified as protein. Even potatoes, a vegetable that is typically described as a ‘starch’ has a protein content equal to the % calories recommended. However, non-starchy vegetables, despite having a high protein macronutrient ratio, contribute little to daily protein intake because of their very low energy density. Our take home message is that one’s plate does do not need a ‘protein’ group to meet one’s protein requirements – adequate calories of whole plants provides adequate protein.

See also:

Resources

Peer reviewed articles

Page created 24 June 2013
Page last updated 16 May 2022 (major update)