PROTEIN QandA: OUR EXPERTS ANSWER YOUR QUESTIONS
Prof Jennie Brand-Miller and Dr Alan Barclay answer the most common questions we are asked about protein.
WHAT IS PROTEIN?
People talk about “protein”, but in fact there are many proteins. They
are chemical compounds made up of chains of smaller building blocks
called amino acids. There are about 20 different amino acids that come
together in different combinations to make up the millions of proteins
found in nature. A protein can consist of between 50 and tens of
thousands of amino acids.
WHAT ARE AMINO ACIDS? An
amino acid consists of a central carbon atom, linked to an amino group
(an atom of nitrogen + hydrogen atoms), a carboxylic acid group (an atom
of carbon + oxygen atoms), a hydrogen atom, and a distinctive R group,
which is referred to as the side chain. The unique composition of the R
group is what makes all of the amino acids different.
In addition to being the building blocks of proteins, the cells
of our bodies use amino acids to form nerve transmitters and hormones
(e.g. adrenalin and insulin). They can also be used as an energy source,
particularly when carbohydrate and fat are restricted. Amino acids are
generally divided into two broad classes – those that our bodies can
make (non-essential amino acids), and those we have to get through our
diet (essential amino acids).
WHY DO WE NEED PROTEIN? We need to consume protein for the
growth, development and maintenance of our body tissues because it’s an
essential part of the structure and function of every cell in our body.
Consuming protein brings a couple of bonus side-effects. First up,
protein-rich foods are more appetite satisfying compared with carb- and
fat-rich foods and can reduce those pesky hunger pangs between meals. In
addition, protein increases our metabolic rate for one to three hours
after eating. This means we burn more energy by the minute compared with
the increase that occurs after eating carbs or fats.
WHERE DO WE GET IT?
Protein is widely available in our food supply. And while people talk
about “protein foods”, no food is all protein and most of us eat a
variety of foods containing many different proteins. We are often asked
what are the best sources. The answer is easy: whole foods which provide
us with other things our bodies need such as vitamins, minerals and
dietary fibre. As Dr David Katz says: “Dietary protein does not require
animal foods, and does not require any specific food combinations.
Wholesome foods in any balanced, sensible assembly – even a strictly
vegan assembly – will readily provide it.”
Animal sources:
• Meat, poultry, and seafood
• Eggs
• Milk, cheese and yoghurt.
Plant sources:
• Beans, chickpeas or lentils (legumes/pulses)
• Nuts and seeds
• Grains, especially whole grains
• Starchy veggies
HOW MUCH DO WE NEED?
Because our bodies don’t stockpile large amounts of protein from one
day to use up the next, we need to top up the protein tank every day. We
don’t need a lot – in fact, the average adult needs less than 1 gram of
protein per kilogram of healthy body weight a day. So, it isn’t hard to
do and most of us living in developed nations get more than enough.
Children, teenagers, pregnant women and women who are breastfeeding need
more as do people recovering from an injury or a major illness.
Athletes, weekend warriors and people who work out vigorously also need
more for building and repairing muscles. People with diabetes do have an
increase in protein turnover because of their high blood glucose levels
and this increases the body’s protein needs slightly. However, because
most people are already consuming much more protein than necessary,
eating more is not usually recommended. Remember, excess calories from
protein are still excess calories and they will do what all excess
calories do, turn into stored body fat.
WHAT ABOUT PROTEIN AND BLOOD GLUCOSE? Up
to half the protein we eat will eventually be converted to glucose via a
process called gluconeogenesis (which literally means the creation of
new glucose). However, our glucose concentrations do not rise and fall
in any marked way after we eat a protein-rich meal because our bodies
balance the rate of glucose production with the rate of glucose burning.
While protein does not directly affect blood glucose levels, it does
stimulate secretion of significant amounts of insulin depending on the
protein source. Research to-date suggests whey protein (often used in
protein-supplemented foods) is the most potent insulin stimulator,
followed by fish, beef, eggs and chicken.
WHAT ARE PROTEIN SUPPLEMENTS? These
are the high protein balls, bars, shakes and powders you’ll find in
gyms, health food stores and supermarkets. Consuming them is not the
same as eating protein-rich wholefoods such as a piece of meat, a
handful of nuts or a tub of yoghurt, as they provide few nutrients apart
from protein. They are typically highly processed made with either soy
or whey protein such as:
- Soy protein isolate, which is extracted, refined protein from the soy bean.
- Whey protein concentrate, which is extracted protein from whey (the leftover liquid from milk formed during the production of cheese). It retains many of the bioactive compounds of the whey, along with small amounts of fat and lactose.
- Whey protein isolate, which is further refined so that it is almost entirely protein.
- Whey protein hydrolysate which is where the proteins have been partially broken down for quicker digestion and absorption.
WHO NEEDS PROTEIN SUPPLEMENTS? No one really needs supplemental protein says the American College of Sports Medicine. Athletes do require more protein than the rest of us, but can generally get it from a good mixed diet. However, consuming protein right after a vigorous workout can help you recover and gain muscle mass. “A good choice for the post workout would be a whey-based protein shake or a home-made protein shake made with milk, yoghurt and fruit as it will be absorbed more quickly than solid food and this is key for timing,” says dietitian and nutritionist Dr Joanna McMillan.
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