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The Science of Higher Protein

After my post about the importance of protein to ensure a healthy old age, I came across a talk by Prof. Stuart Phillips. He is a professor in Kinesiology (the study of the anatomy, physiology and mechanics of movement) at McMaster University in Canada. His research focuses on how the way the human body uses skeletal muscle protein is affected by nutrition and exercise. He is specifically interested in how diet and exercise can change body composition, particularly in older people.

The takeaway from this talk in 2019 is that the best way of making the most of the protein one eats is to combine it with regular, daily exercise, and not just any exercise, but resistance training, for example weight training. He recommends a daily intake of a minimum of 1.6 g of protein/kg of body weight. In this talk he also addresses the myth that a higher protein diet might be detrimental to kidney function.

So you may ask what to eat for a higher protein diet. The good news is that it doesn’t have to be just meat.

To know how much protein a food contains, the concept of protein percentage is used. This reflects how much the protein in a food contributes to a food’s total calories (excl. calories from fibre).

Animal protein is known to have the highest protein percentages:

  • shrimp (97%)
  • egg whites (85%)
  • white fish (82%)
  • chicken breast with skin (63%)
  • chicken drumstick without skin (65%)
  • wild salmon (69%)
  • chicken liver (60%)
  • steak (60%)
  • lean minced beef (54%)

It may come as a surprise that the protein percentage of vegetables may be as high as 50+% (these numbers from dietdoctor.com):

  • spinach (57%)
  • arugula or rocket (42%)
  • asparagus (53%)
  • mushroom (52%)
  • romaine lettuce (40%)
  • kale (41%)

The best plant-based protein can be found in

  • lentils (42%)
  • edamame beans (40%)
  • lupini beams (55%)
  • sunflower seed protein powder (66%)
  • pea protein powder (79%)
  • tempeh (40%)
  • tofu (48%)
  • seitan (77%) – this is a form of vital wheat gluten considered to be an good substitute for meat
  • nutritional yeast (72%)

The protein powders included above may be used to supplement a plant-based diet as otherwise it might be difficult to meet protein needs.

Lastly, dairy is also a good source of protein:

  • plain non-fat Greek yogurt or Skyr (80%)
  • low-fat cottage cheese (65%)
  • reduced-fat Swiss or cheddar cheese (60%)
  • plain low-fat Greek yogurt or Skyr (57%)

With non-fat or low-fat yogurt it is important to check that there is no sugar added, as this will only push up the calorie count with no nutritional benefit.

Obviously, as an omnivore/carnivore I prefer to get my protein from animal sources, but with vegetables and dairy it means it won’t be as expensive as what might be the case otherwise.

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Why eating too little protein may set us up for poor quality of life in old age

In the UK & US it is recommended that people’s daily intake of protein should be 0.8 gram of protein per kilogram of body weight or ~50 grams (i.e. the RDA is ~50g).

However, what is less known is that RDA values are meant to be sufficient to meet the nutrient requirements of ~97% of healthy people. What this then means is, if anybody has any health issues, they should consider increasing their protein intake, unless they have known kidney disease. (Anyone who has any concerns about their kidney health, do consult your medical professional before eating more protein).

So why is protein intake important?

Proteins are the building blocks of our bodies. They are required for the structure, function and regulation of the body. Proteins are included in:

  • cell membranes
  • the cellular structure of skin, hair, muscle & bone
  • hormones
  • enzymes

Proteins consist of amino acids chained together to form the different proteins. Amino acids are divided into three categories: essential amino acids, conditionally essential amino acids and non-essential amino acids.

Essential amino acids are ones that must be included in the diet. Non-essential amino acids are ones that the body is able to build from other amino acids if needed. Some amino acids are considered “conditionally essential”, meaning that for most people they are not required in the diet because the body can make them from other amino acids. But for some populations who don’t make them in sufficient amounts, they may become essential, i.e. they had to be specifically included in the diet.

Non-essential amino acids are especially important to vegetarians and vegans, as many of the essential amino acids the body needs are contained in animal protein, which are considered as “complete” protein.

Increasing protein intake to 1.2-2 gram per kilogram of body weight has been shown to preserve muscle mass and improve body composition. There are multiple apps and websites which give an indication of the actual amount of protein in the chosen food. As a rough guide 100 g of meat contains ~20-25 gram of protein.

From the third decade onwards, muscle protein synthesis declines, and declines even faster from the age of 60 onward. For older adults, international consensus now recommends protein intake of 1-1.2 g/kg per day.

Sarcopenia is a condition primarily seen on older people. It is characterised by progressive loss of skeletal muscle mass and strength and it correlates with physical disability, poor quality of life and death. Increased protein intake at a younger age may prevent this debilitating condition in old age.

People who are underweight or healing from illness, injury or surgery may temporarily increase their intake to more than 2 g/kg per day, to aid and accelerate healing and recovery. Increased protein intake during time of illness or recovery makes sense knowing that protein are the building blocks of our body.

Anecdotally, too high an intake of protein has been linked to kidney failure, especially in athletes/body builders. Thus there is a perception that too much protein is bad for one’s kidneys. However, the question here may not be protein itself, but the quality of protein, e.g. artificial protein shakes vs. protein from real food.

As I have experienced the benefits of a higher-protein diet, I will continue eating this way for a healthier old age.