Keto Experiment: Is a “Green Smoothie” Ketogenic?

Analysis: What Could Explain The Results?

We could just say the sweet bell pepper caused the glucose spike in experiment one and by removing it we no longer saw this spike in experiment two. But that may be overly simplistic. 

More likely it was also due to a number of factors. The differences in gut health between the experiments may have played the biggest role. 

Let’s assume for a minute that the sweet bell pepper was the glycaemic monster in the room. We would need to see if the pepper eaten with the same ingredients would cause the same result. 

Is Blending or Juicing Anti-Keto?

Green vegetables are a mix of carbohydrates and fibres. When you blend them to create a smoothie it breaks down the vegetable structure. This makes them much easier and quicker to digest. This also increases the number of nutrients available for you to absorb[note]van het Hof, Karin H., et al. (1999) Influence of feeding different vegetables on plasma levels of carotenoids, folate and vitamin C. Effect of disruption of the vegetable matrix. British Journal of Nutrition, 82.3(2): 203-212.[/note]. 

But, physically disrupting fibre can affect how fast the sugar from carbohydrates enters the bloodstream. In other words, blending impacts their glycemic impact. This has been shown in apples[note]G B Haber, K W Heaton, D Murphy, L F Burroughs. (1977).Depletion and disruption of dietary fibre. Effects on satiety, plasma-glucose, and serum-insulin. Lancet. Oct 1;2(8040):679-82.[/note]. So you would presume it might happen in higher sugar vegetables. Such as sweet bell peppers.

However, breaking down the food matrix in some fruits and vegetables has less of an impact than others. For instance, freeze-dried mangoes do not seem to cause a higher blood sugar response than fresh mango[note]S F Evans, M Meister, M Mahmood, H Eldoumi, S Peterson, P Perkins-Veazie, S L Clarke, M Payton, B J Smith, E A Lucas. (2014).Mango supplementation improves blood glucose in obese individuals. Nutr Metab Insights. Aug 28;7:77-84.[/note].

So what? The easier carbohydrates are to digest, the quicker they get into the bloodstream. When a whole smoothie does this it can increase glucose all in one go.

Compare this to the green vegetables in their original form – where the gut will digest them and release the glucose slowly over many hours. As a result, the increase in blood glucose is hardly noticeable if at all.

So this result is most likely driven by the ‘blending’ of the food.

The other question this raises is whether liquid foods are always ‘less ketogenic’? Maybe not anti-ketogenic, but just less ketogenic.

Does Adding Fat to a Food Always Improve its Ketogenic Profile?

In research carried out in 2015 by Eran Segal’s team, they established that fats in food affect people differently in terms of how it ‘inhibits’ increases in glucose[note]Zeevi D, Segal E, (2015). Personalized Nutrition by Prediction of Glycemic Responses[/note]. (Note: I discussed this research and its implications with him in this Quantified Body podcast episode).

So it is likely that for some people (perhaps you) fat can reduce glucose increases considerably. In the extreme, some people can eat ice cream without large blood glucose spikes due to the high-fat content. The only way to know – is to test your own response.

I have run microbiome tests like DayTwo to better understand my own situation. But to be frank, they have not provided clarity on this topic. So I currently believe my response to fat – is moderate. It may inhibit blood glucose somewhat, but not as much as others.

So for now – this point is inconclusive. I don’t know if the fat helped.

C8 MCT Increases Ketones: Are These Ketone Results Positively Biased?

The C8 MCT oil consistently increases my blood ketones. I know this from many previous experiments where I’ve tested different doses of it.

So we know that it would increase my blood ketones. But how did it impact this green smoothie and experiment?

My assumptions are that it did the following:

1. It increased my blood ketones within the first 30 minutes. This is the only explanation for the rise of around 0.25 mmol in that first half an hour.
2. It likely offset some of the drop in my blood ketones. With an increase in blood glucose of 30mg/dl in that first 30 minutes, I would expect a significant drop in ketones – perhaps 1 mmol or more.
3. Only a drop of 0.25 mmol from baseline ketones was seen. So my assumption is that the C8 MCT oil offset a lot of the drop in endogenous ketone production (the body’s own production of ketones).

In a way, I wish that I had not been adding ‘fat’ and ‘C8 MCT oil’ to my green smoothies. This would’ve helped me understand much clearer the impact of green smoothies on my ketogenic diet.

Satiety, does drinking a green smoothie make you more hungry?

According to the research, drinking calories leads to less satiety and fullness[note]M J Martens, MS Westerterp-Plantenga. (2012).Mode of consumption plays a role in alleviating hunger and thirst. Obesity (Silver Spring)., Mar;20(3):517-24.[/note]. Having the same meal blended also causes significantly less satiety and fullness

Liquid calories gulped down quickly can undermine our body’s ability to judge a healthy food intake[note]C de Graaf. (2011). Why liquid energy results in overconsumption. Proc Nutr Soc., 70(2), 162-70.[/note].

More greens = more fibre = more satiety. So would a green smoothie with more greens in it be more filling?[note]K Gustafsson, N G Asp, B Hagander, M Nyman.(1995).Satiety effects of spinach in mixed meals: comparison with other vegetables. Int J Food Sci Nutr., 46(4), 327-34.[/note]

According to the studies the thicker the smoothie the less hungry, you will be[note]R D Mattes, D Rothacker.(2001).Beverage viscosity is inversely related to postprandial hunger in humans. Physiol Behav., 74(4-5), 551-7.[/note]. So to reduce hunger after a green smoothie. Add a thickening ingredient such as ground flaxseed, coconut milk, or nut butter.