Attitudes have changed dramatically in the last thirty years because nutritionists now consider it highly improbable that anyone in an affluent country or even anyone in a developing country who is not starving will fail to get enough protein. This huge change of attitude has not come about because of higher intakes of protein but because our assessment of the protein needs of children and the practical significance of variations in protein quality have been reduced. The problem has not been solved but rather the experts probably got it very wrong and there never really was any “protein crisis” in the first place. Our estimates of the protein needs of young children are now less than half of what they were believed to be in the 1950s. The practical importance of differences in the quality of protein in different foods was also exaggerated because quality is really only an issue if you rely almost entirely on one low protein vegetable food to supply all of your protein. Quality is not really an issue when you eat several foods because any amino acids that are in short supply in one food will be plentiful in another and this will raise the protein quality of the whole diet.
There are many factors that contributed to this false crisis but one important one was our reliance on experiments with animals to study protein needs. Most animals grow much faster than children and so require much higher levels of protein in their diets. Rats, for example, double their birth weight in less than a week compared to several months for a breastfed baby; rat milk like cows’ and most animal milks have 3-4 times as much protein as human milk. If young rats are fed with diets containing a low quality protein like wheat protein then they need a lot of this protein in order to grow properly. Experiments such as these convinced many scientists that growing children like growing rats or pigs required large amounts of high quality protein. The experts jumped to conclusions that were not fully supported by evidence. Maybe we need to remember this lesson because almost all of the extravagant media health claims for specific foods and dietary supplements are also based upon similar very incomplete evidence.
What are the practical conclusions about protein for UK consumers? People require much less protein than most other animals and so protein is one of the least likely nutrients to be deficient in human diets. Provided children eat enough food to satisfy their appetite then they will almost certainly get enough protein; the diet would have to be very bizarre for this not to be true and other nutrients besides protein would almost certainly be lacking in such cases. Vegetarians and even vegans are not at risk of protein deficiency.
The last post on the topic of Protein from Dr Geoff but don’t forget to check out his previous posts on this topic! Next week Dr Geoff will cover another hot topic so watch this space!