There was this chap, Stanley Green - you might have heard of him - who trudged the West End of London for more than two decades carrying a placard that advocated Less Lust From Less Protein.
His wacky theory, outlined in the booklet he sold, was that protein made people aggressive. Stanley died in 1993, and his placard is now in the Museum of London. But it seems his argument lives on.
Last month the Government announced new health guidelines that we should all eat no more than 1lb of red meat a week, due to cancer risks. That's about one 8oz steak and two pork chops.
Critics rightly voiced concerns that this would mean many of us would not be getting the protein the human body needs for growth and maintenance.
The Food Standard Agency currently recommends that around 15 per cent of our daily diet should be protein-containing foods.
So how do we make up the shortfall without eating more meat?
Well, for a start, don't ditch your weekly steak. Just add some of the wide range of non-animal sources of this vital nutrient.
Don't ditch your weekly steak. Just add some of the wide range of non-animal sources of protein
Proteins are broken down in the stomach to provide amino acids, which in turn do everything from forming skin, organs, blood cells, and the immune system, to creating hormones and neurotransmitters.
There are 23 different types of amino acid, found in all foods. Eight of these, known as essential amino acids, must be obtained from food.
The body breaks these down to manufacture the remaining 15, which are called nonessential.
The protein containing foods that provide essential aminos are known as complete proteins, and the others as incomplete. All animal proteins are complete, but there are alternatives.
Here I outline my top 10 non-meat sources that I recommend to patients. A typical portion or serving is 3oz (80g).
Now available from most supermarkets, quinoa is a wholegrain that is a good source of protein and is rich in fibre, too. Unusually for a grain, quinoa offers an impressive 13 per cent of complete protein.
When buying uncooked, simmer in water like you would with rice - adding some vegetable or chicken stock enhances the nutty flavour. Quinoa can also be found ready-cooked, making an excellent fast food. Just two and a quarter portions contains a chicken fillet's worth of protein.
Avocado is two per cent complete protein and it also contains fibre, which aids healthy digestion
Unusually for a fruit, avocado does contain protein as well as carbohydrates and omega 6 essential fats, which can help reduce low-density lipoprotein, the unwanted type of blood cholesterol.
Avocado is two per cent complete protein - only a little less than whole milk - and it also contains fibre, which aids healthy digestion. In terms of protein content, 15 avocados equal one chicken fillet.