Last review and update: January 30, 2020.
Stephen Phinney is wrong about the key aspects of the physiology of ketosis.
Stephen Phinney is a charismatic professor and an ardent proponent of a “well-formulated ketogenic diet”. However, Stephen Phinney is wrong about the key aspects of the physiology of ketosis.
In the 1980s, when Phinney first got interested in ketosis, he somehow missed a number of fundamental facts that had been already well established. Some of Phinney’s shortcomings are really strange.
For example, in his presentations, Phinney often mentions Arctic explorer Vilhjalmur Stefansson. Vilhjalmur Stefansson wrote extensively about Eskimo, our main reference group for a life-long zero carb diet. But Stephen Phinney did not read any of the books written by Stefansson.
Vilhjalmur Stefansson was a man of exceptional intelligence, a risk-taker, a skilled explorer and hunter capable to survive in extreme conditions. Vilhjalmur Stefansson was also a proponent of a zero carb diet “a la Eskimo”. Stefansson was biased at times. But this type of bias is common and is within the norm.
Phinney does not have his own opinion about Vilhjalmur Stefansson and repeats things that someone told him, e.g. “you can’t trust a single word that Stefansson said or wrote”. Strange.
Vilhjalmur Stefansson wrote in his books that Eskimo did not eat added salt at all. Eskimo tried tobacco, coffee, and tea, and loved them. But Eskimo persisted in rejecting added salt.
For example, here is one citation of Stefansson on salt and the Natives of America. Vilhjalmur Stefansson in “The Friendly Arctic”, 1921:
‘When a white man has been a year without salt it becomes almost as unpalatable to him as it is to the Eskimos or Indians who
have never used it; with this difference, that the white man knows
from experience he will come to like it again, but the native has
the opinion that he never will.
If Stephen Phinney had read Stefansson’s books, he would have known the fact that Eskimo did not consume any added salt. Phinney should have immediately seen a contradiction. Indeed, Phinney needed to supplement his ketogenic subjects with 5 to 7 grams of sodium a day (12.5 to 17.5 (!) grams of salt) to avoid “hypovolemic symptoms” characteristic of ketosis. Yet, Eskimo did not have any such symptoms on a diet without any added salt.
Here is how Phinney viewed salt on a ketogenic diet in 1983 and how he still understands it today. Phinney et al., 1983:
There was no brisk loss at the time of the EKD initiation (see Table 2). This lack of change suggests an absence of a profound diuresis associated with the onset of ketosis in this group of subjects, although they were given extra sodium chloride (up to a total of 7 g sodium daily) on beginning the EKD to avoid hypovolemic symptoms.
The first (and probably the most important) point is control of the salt intake of the subjects. Whereas other investigators had withheld, not controlled or not specifiedi adequate sodium intake, in this study subjects were encouraged to take salt and bouillon on a quantity sufficient to maintain a daily urinary sodium output of 200 mEq while on the EKD. This quantity, representing between 4 and 5 g daily, is not excessive relative to the average American intake. It is interest- ing to note, however, that the subjects had to be encouraged to take salt in quantities beyond their perceived need (taste) to maximally limit deficiency symptoms of lethargy or fatigue during exercise. This level of sodium supplementation was well tolerated by the subjects and appears to have been a critical factor in avoiding the nausea, fatigue, and orthostatic symp- toms that appear to have interfered with previous studies using low-carbohydrate eucaloric diets.
It is difficult to explain how highly trained cyclists from the 1983 study by Stephen Phinney could remain in a positive nitrogen balance on 131 grams of protein a day.
Many of Stephen Phinney’s misconceptions date back to his early studies. It is, therefore, informative to look into those early studies.
In the 1983 study by Phinney et al. (1), subjects consumed a eucaloric ketogenic diet (EKD) with 1.75 grams of protein per kilogram of ideal weight. In lean athletic subjects, the lean weight is roughly equivalent to the total weight. The average weight of the subjects can be approximated to 75 kilos. See the “Table 1” below.
Thus, we can estimate the average daily intake of protein as 75*1.75 = 131.25 grams. The eucaloric ketogenic diet (EKD) in Phinney’s study (1) was composed of 131.25 grams a day of protein, 20 grams of carbohydrates, with the rest of the calories coming from fat.
Phinney and colleagues (1) found that the subjects remained in a positive nitrogen balance.
Phinney et al., 1983 (1):
Nitrogen balance (N-Ball was regained after one week of the EKD.
Nitrogen is a proxy for protein. Being in a positive nitrogen balance is the same as being in a positive protein balance.
Interestingly, five of the subjects were competitive bicyclists. Phinney et al., 1983 (1):
all were physically active (one to five hours a week of sports activity). The last five subjects were specifically selected; all were competitive bicyclists at a stable level of training. All subjects kept a daily diary of physical activity, specifying the type, intensity, and any perceived limitations.
How likely is it that Phinney’s subjects, in particular, the competitive bicyclists who continued their regular training, remained in a positive protein balance on such a diet?
The subjects even gained 400 grams of lean mass. Phinney et al., 1983 (1):
The mean daily nitrogen balance for all nine subjects for the 35day balance period was 0.5 g/d. This implies an average net gain in lean body mass over the duration of the study of approximately 400 g.
Below, there is an extended citation from this study (1) that describes the diets.
Phinney et al., 1983 (1):
Beginning on the eighth day of the study, the subjects were given a eucaloric ketogenic diet (EKD), providing equal amounts of protein and calories as the EBD (1.75 g and 35-50 calories per kilogram daily, respectively), but containing less than 20 g of carbohydrate daily. Thus 83% to 85% of the total calories provided by the EKD came from fat.
The daily diet was composed of three meals and a snack. The subjects were given their choice from five meals prepared
from ground beef, breast of chicken, water-packed tuna fish, pow-
dered egg solids, and cheddar cheese. Mayonnaise, heavy cream,
sour cream, and cream cheese were used as the primary lipid sources.
All protein sources were subjected to acid digestion and Kjeldahl
analysis for nitrogen content multiple times to document uniformity.
The caloric contents of the fat sources were obtained from standard tables.” All food portions were weighed on an analytical balance, and all serving dishes were cleaned with rubber spatulas by the subjects to ensure quantitative accuracy of their intakes. The EKD was supplemented with the same multivitamin as the EBD, but in addition, the subjects received the following daily supplements: 600 mg of calcium; 300 mg of magnesium; 1 .O g potassium as bicarbon ate (in addition to the Ill.5 g provided by the protein sources); 5 g of sodium (minimum) as bouillon or salt in cooking; and a minimum of 2000 mL of noncaloric beverages daily.
The fluctuation of serum electrolyte and blood-formed elements is another interesting piece of data from the study.
The serum bicarbonate level dropped sharply with initiation of the EKD, from the EBD-1 level of 26 mEq/L to 22 mEq/L at EKD-2 (P < 0.01 compared with EBD-1). By the fourth week of the EKD, the serum bicarbonate level had risen back to 24 mEq/L (P < .05 compared with EKD-2). Thus, although there was a significant fall followed by recovery in the first four weeks of the EKD, serum bicarbonate levels remained in the normal clinical range, and hence the initiation of ketosis was not accompanied by acidosis.
Liver and renal functions are also of interest.
Triiodothyronine (T3) went down on the ketogenic diet EKD but remained above the low normal limit.
In the discussion part of the paper (1), Phinney provides some arguments to explain how a positive nitrogen balance could be maintained with 1.75 grams of protein per kilo of lean body weight a day (or 131 grams of protein plus 20 grams of carbohydrate a day in a 75-kilo lean male subject):
The protein level of the EKD, 1.75 g/kg/d, appears on the average to be adequate to allow nitrogen balance to be regained within a week after removing carbohydrate from the diet. This conclusion is based on the calculated nitrogen balance, weights, and 40K (potasium isotope) counting. The differences between the calculated slight overall positive nitrogen balance, as opposed to the slight decrements in weight and total body potas- sium can be explained by mild reductions in whole body water and glycogen. Thus the data are compati- ble with the subject group as a whole, being in slight positive nitrogen balance over the course of the four weeks of EKD. In the context of this return to nitrogen balance, the findings of Silwer15 are not readily explained. Utilizing diets with protein contents up to 2.3 g/kg/d and total caloric intakes and distributions comparable to those used in this project, he was unable to demonstrate a return of the 24-hour urine total nitrogen level back to baseline levels in most instances. The dichotomy in the results between Silwer’s study and this project might be explained by a difference as minor as a lack of adequate salt (Silwer noted that his subjects com- plained of fatigue and weakness), or the vitamin and mineral supplements used in the EKD may have allowed optimum use of the dietary nitrogen. Further, while Silwer was unable to demonstrate a decrease in nitrogen excretion with administration of a base load, a recent report by Fery and Balasse of reduced blood alanine levels after intravenous bicarbonate adminis- tration suggests the additional possibility that the base load given with the EKD supplements (calcium car- bonate, magnesium oxide, and potassium bicarbonate) contributed a minor protein sparing effect.
The verdict.
In other studies, and in relatively sedentary subjects, a positive nitrogen balance with similar micronutrient intakes was indeed observed. However, it is difficult to explain how the highly trained cyclists from the 1983 study by Phinney (1) could remain in a positive nitrogen balance. Ketone levels were high (see the table below). Still, there is an apparent contradiction with the basic physiology.
A Test of Physiological Literacy:
1.
Explain why hematocrit levels were lower in highly trained cyclists.
Phinney et al., 1983 (1):
“…highly trained cyclists have lower hematocrit values than untrained controls, which is analogous to a similar situation previously reported for elite runners.”
2.
A highly trained endurance athlete trains for two hours every day and follows a zero carb diet. How much protein and fat a day should he consume to cover his daily glucose expenditure?
Selected references:
1. Phinney et al., Metabolism, Vol. 32, No. 8 (August), 1983.
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