Should you trust what a vegan doctor says about protein in a vegan diet?
When I carried out the nutritionional analysis on the McDougall starch – vegan diet, I found the protein amount to be adequate as long as a large amount of higher protein plant foods like legumes and lentils were eaten.
The McDougall starch diet – a nutritional analysis
However, reading Dr McDougall’s and other vegan websites and the information presented on protein, what did concern me is some of the misinformation around protein recommendations, and the justifications for these. (You can read the sources of information here and here)
I will briefly address some of the statements made which misrepresent human protein requirements, and nutrition science as it applies to humans.
Herbivores get all the protein they need from plants, so we can too
From this video Dr Neal Barnard (Physicians Committee for Responsible Medicine or PCRM) for tells us that protein is abundant in plants, and uses the fact the herbivores get a lot of protein through eating a diet of plants like grass. (PCRM Protein)
However – ruminents digest their food completely differently to humans – they have large rumens full of bacteria and other microbes that digest the indigestible cellulose and convert to amino acids. The microbes are eventually digested in the true stomach – the abomasum to give protein and nutrients to the cow. In fact if a cow does not have microbes in its rumen to break down plant material and provide nutrients it will die of starvation (Source).
Let’s take a quick look at the cows digestive system (source) compared to ours (source). Note the very large fermentation chamber (rumen) in the cow, and none in a human:
Although humans do have a microbiome, and it appears they may be able to make some amino acids (source) it is not on the scale that ruminents do, and we must eat protein for our needs or we will become protein deficient.
Dr McDougall bases his original plan on an ancestral Hawaiian diet – is this diet vegan?
Dr. McDougall saw the devastating effects of a Western diet in the younger Asian populations compared to the older people eating their Ancestral diets. (John McDougall’s Story)
Despite all the ‘junk’ that was added to young people’s diets, he decided that meat and dairy were solely to blame.
An ancestral Hawaiian diet is high in starches, AND it includes animal protein.
The traditional native diet was high in fibre, high in complex carbohydrates, high in polyunsaturated fatty acids, low in saturated fats, and low in fat. It was estimated to contain, by calories, < 10% fat, 12 – 15 % protein and 75 – 78% carbohydrate.
Typical foods eaten: taro, poi (a mashed form of taro) sweet potato, yams, breadfruit, seaweed, greens (fern shoots and leaves of taro, sweet potato, and yams), fruit, fish and chicken.
In studies where Hawaiians resumed their native diet, diabetes was reversed and people lost signifant weight:Obese Hawaiians Learn From Thin Ancestors : Diet: Nutritionists offer plan featuring food ancient islanders ate. Natives–many of whom are at high risk for heart disease and other ailments–are losing weight.
Of note: There is no evidence that any ancestral Asian or Pacific diets are vegan, all ancestral diets include animal protein and fat.
Vegan recipes often provide inadequate levels of protein
If a vegan diet includes protein rich sources of plant foods (legumes, lentils, tofu, Quorn) it might provide adequate amounts of protein. However, a vegan diet comprised of grains, fruit and vegetables will be unlikely to provide enough. An analysis of many meals from Dr Barnard for example, show they provide only 10 – 15 grams of protein (Dr. Neal Barnard recipes).
Dr. McDougall says 5% of calories from protein in our diet is adequate, and this advice is from WHO
You can download the latest World Health Organisation (WHO) report on protein here: Protein and amino acid requirements in human nutrition. Report of a joint FAO/WHO/UNU expert consultation (WHO Technical Report Series 935)
McDougall refers to the WHO recommendations and says the WHO recommends men, women, and children get five percent of their calories from protein.
What the WHO actually says about protein requirements:
The WHO report does not mention percentages at all. Dr McDougall’s information appears to be out of date.
The current report from WHO says an adult human needs 0.66g/kg/day which is for a 70 kg person is 46.2 grams per day, or nearly 9.2% of calories. The safe requirement for humans is a recommended 0.83g/kg/day, 58 g per day for 70kg person and 11.6% calories. Both calculations are far from 5%. In fact WHO does not even talk about percentage of calories in the latest report – they only talk in terms of grams protein per kg per day.
Using McDougall’s calculation an adult would be protein deficient by WHO standards
It we take the standard diet of 2000kcal, 5% of that is 100 kcal which is 25 grams of protein. For a 70kg human this is just .36g/kg/day. This amount is considered by the WHO to be inadequate. Even using In McDougall’s example above: 38 grams of protein for a male and 29 for a female in higher calorie diets still fall well short of WHO recommendations.
Dr McDougall says Americans are getting 6 – 10 times the protein they need
How much protein would a person eat if they consumed 6 – 10 times the RDA?
According to WHO an adult of 70 kg requires 58 g per day (.83g per kg/ day). If they are getting 6 to 10 times that amount – that would be 336 to 580 grams of protein per day. Is this true?
Let’s take a look at how much meat you would need to eat to get this amount of protein.
500 grams of protein has a total of 2000kcal, it takes 2 kg of meat to provide 500grams of protein. Where are the people eating 2kg of meat a day? (And that would be eating very lean meat or poultry). In pounds that would be 4.4 pounds, which is 70 oz.
A 12 oz steak is pretty damn huge, is the average person really eating nearly 5 x 12 oz steaks a day? An average chicken is is 1.5 kgs, are people eating an average 1.5 chickens a day? Even at the lower amount of 336 grams a day that would be an entire chicken per day.
How much protein do Americans actually eat each day?
According to the Current protein intake in America: analysis of the National Health and Nutrition Examination Survey, 2003–2004 the highest intake was of ≈91 ± 22 g/d in adults aged 19–30. This works out to 1.3g per kg/day if you weigh 70kg. Not even 2 times the WHO recommended amount. In older people the intake was decreased to ≈66 ± 17 g/d in the elderly, or close to the required WHO amount.
So where on earth does McDougall get his data from?
McDougall bases protein recommendations on breast milk
Breast milk. How much protein does it actually contain?
| Component | Mean value for mature breastmilk (per 100mL) |
| Energy (kJ) | 280 |
| Energy (kcal) | 67 |
| Protein (g) | 1.3 (7.8% kcal) |
| Fat (g) | 4.2 (56% kcal) |
| Carbohydrate (g) | 7.0 (41% kcal) |
According to the Infant nutrition council of AU and NZ Breast milk contains almost 8% kcal from protein. Colostrum the first milk a mother produces is even higher in protein. Again incorrect ‘facts’ from Dr McDougall.
Dr. McDougall uses breast milk as an example of protein requirements, yet despite the fact that 56% of kcal come from fat, this is what he says about fat in the diet:
How much protein do children and babies actually consume from breastmilk?
Again we need to look past the percentage of protein in breast milk to the actual amount of protein a baby consumes i.e. grams per kg body weight per day.
This from WHO document:
Actual protein intakes of breast-fed babies range from 1.5 to 2.5 grams protein per kg body weight a day. This is higher than the average adult American eats, and is actually in line with current optimal protein requirements.
Protein requirements and animal protein dangers – links to current research
Protein requirements in humans have been under a lot of investigation in the last 20 years. Proported damaging effects have also been investigated. Much of what Dr McDougall and other vegan proponents say is not in line with current research.
Here are links to a few well researched recent articles and reviews.
The WHO report on protein contains a complete section on protein and health adressing kidney, bone, and other concerns raised by many (Download link). Go to page 223.
Examine.com have a well researched review on optimal protein levels. Here is a graph from their post. How much protein do you need per day? Optimal protein levels are significantly higher than many vegan proponents recommendations.
One argument for removing meat and dairy from our diets is the saturated fat content. Another article from Examine looks at the research on this topic Is saturated fat bad for your health? Here is the final overview from their extensive look at the research – for detail – read the entire review!
On a final note:
Be wary of any ‘facts’ presented as truth from people on nutrition (yes – even me!) Question ‘facts’ and look at the whole of the research. More importantly work out what is right for you – this is a slide I present in my nutrition talks:
First – the number of calories would be insuffient to maintain this persons weight. Protein is only just over the minimum required as suggested by the RDA. Carbohdyrates – despite having a high percentage is 283 g per day, not particularly high. Nutrients- many exceed daily requirements, especially fibre, vitamin C and folate, which are rich in plant foods. However there are clear nutrient deficiencies.
Two things which Dr McDougall states stand out:
As you would expect carbohydrates are high – however not overly high, with net carbs at 283 grams and fibre and hefty 52 grams. Sugars are relatively low and fructose only 9 grams. A person switching from a standard American diet onto the McDougall diet would likely decrease carbohydrates with the switch to high fibre, high water content, high nutrient and low density carbs.
