What is the purpose of eating an adequate level of protein?
Protein is necessary to maintain good health and vital organ functions.
Much information is available including (as an example) from wikipedia.
All words below in italic are quoted from the wikipedia source unless otherwise stated.
Protein is a nutrient needed by the human body for growth and maintenance.
The adequacy of the protein intake varies depending on the food source:
Meat, eggs and fish are sources of complete protein. Milk and milk-derived foods are also sources of complete protein. [...]
Whole grains and cereals are another source of proteins.
However, these tend to be limiting in the amino acid lysine or threonine, which are available in other vegetarian sources and meats. [...]
Vegetarian sources of proteins include legumes, nuts, seeds and fruits.
Legumes [...] have higher concentrations of amino acids and are more complete sources of protein than whole grains and cereals.
A good source of protein is often a combination of various foods, because different foods are rich in different amino acids.
What is a reasonable daily intake of protein?
According to US & Canadian Dietary Reference Intake guidelines, women aged 19–70 need to consume 46 grams of protein per day,
while men aged 19–70 need to consume 56 grams of protein per day to avoid a deficiency.
The generally accepted daily protein dietary allowance, measured as intake per kilogram of body weight, is 0.8 g/kg.
However, this recommendation is based on structural requirements, but disregards use of protein for energy metabolism.
This requirement is for a normal sedentary person.
Several studies have concluded that active people and athletes may require elevated protein intake (compared to 0.8 g/kg)
due to increase in muscle mass and sweat losses, as well as need for body repair and energy source.
Suggested amounts vary between 1.6 g/kg and 1.8 g/kg, while a proposed maximum daily protein intake would be
approximately 25% of energy requirements i.e. approximately 2 to 2.5 g/kg.
However, many questions still remain to be resolved.
In our experience...
Based on our 50+ years old bones living on the land where there is no strenuous activity on a daily basis.
Each day we keep the body moving whether to handle livestock, or work on the vegetable garden or maintenance of the infrastructure.
Additional physical activities: Four times per week at least a brisk 30mns walk and once a week a 70 to 100 kms slow bicycle ride.
What works for us is: 1g of protein per kilogram of our body weight. So if I weigh 50kg, I need 50g of protein each day.
Each food brings a different quantity of protein. This may be displayed on the pack or you may need to refer to other sources (example: [WFIT])
Example: On a tin of tuna chunks in springwater protein per 100g is listed as: 25.8g
So if that was the only food I was eating on a given day, I would need roughly 200g of this drained tuna to satisfy my daily requirement.
Obviously we do not get fanatical about it. But early on when we changed our diet, we realised how low our protein intake was.
This seems to work for us.
Try and find out what works for you given your weight, activity level, and the type of protein you eat.