Conventional wisdom, as dispensed by most endos today, appears to say that bedtime snacks help in preventing nighttime hypoglycemia, and that snacks including protein are better because the effect lasts longer.
But @MM2 recently cited a 2000 article that debunked many protein myths (Protein Controversies in Diabetes: debunking myths in diabetes). This very interesting article concluded, among other things, that protein ingestion does not increase blood glucose, and that nighttime snacks with protein are not better than carb-only snacks, except in increasing calory count. Intrigued, I decided to review the primary evidence.
I viewed every source to the original article to which I could gain access, or its summary when I could not get to the full article. I was somewhat disappointed to find that much of the research listed was a bit weak, due to low numbers of participants. It appears from some of the research that:
glucose normals do not react to protein ingestion the same way as T1s, or T2s
it is possible that, for T2s with significant insulin-producing capability, adding protein to a carb meal generates more insulin production ( Nuttall et al, : Effect of protein ingestion on the glucose and insulin response to a standardized oral glucose load, Diabetes Care, 7:465-70, 1984)
the amount of insulin additionally used by a glucose normal in the presence of protein represents 25% of that required by the same weight of carbs ( Krezowski et al, The effect of protein ingestion on the metabolic response to oral glucose in normal individuals. Am J Clin Nutr 44:847-56, 1986)
a solid study, but with few participants, which specifically reviewed carb vs carb+protein snacks, found zero protective effect from the additional protein ( Gray et al, RO, Comparison of the ability of bread versus bread plus meat to treat and prevent subsequent hypoglycemia in patients with insulin-dependent diabetes., J Clin Endocrinol Metab 81:1508-11, 1996)
in another solid study, also with few participants, the addition of protein to carb meals marginally increased the glucose response (and significantly increased the insulin requirements) ( Peters et al, Protein and fat effects on glucose responses and insulin requirements in subjects with insulin-dependent diabetes mellitus, Am J Clin Nutr* 58:555-60, 1993)
When I reviewed more recent research, I found a disappointingly small number of relevant studies. The most convincing one was also the most recent (2014), and concluded that post-dinner protein intake was inversely associated with nighttime hypoglycemia ( Desjardins, Katherine, et al, Association between post-dinner dietary intakes and nocturnal hypoglycemic risk in adult patients with type 1 diabetes, Diabetes research and clinical practice 106.3 (2014): 420-427). Unfortunately, the same authors, in an article submitted in the same year ( Desjardins, K., et al. Are bedtime nutritional strategies effective in preventing nocturnal hypoglycaemia in patients with type 1 diabetes?, Diabetes, Obesity and Metabolism 16.7 (2014): 577-587), concluded that…
Overall, the level of evidence was low. Results indicated that a calibrated bedtime snack based on bedtime blood glucose (BG) level could be effective to reduce NH occurrence for patients treated with human or animal insulin (short‐acting combined with lente, ultralente and/or intermediate‐acting insulin), but there is no evidence for patients treated with insulin analogues as part of multiple daily injections or insulin pump regimen. […] On the basis of the available evidence, a bedtime snack cannot be recommended systematically but it might be useful if prescribed in an individualized fashion; further research is needed to evaluate these strategies.
As for us:
we find no additional benefit to protein to sustain nighttime BG levels when comparing skim milk (carbs + protein) to candy (Skittles)
we also find no additional benefit to a bedtime snack when compared to starting the night at the same BG level that follows the bedtime snack
In other words, for us, the only significant factor is how high your BG is at bedtime. As always, a big YDMV.