Probably a question for @JamesCollier. I am into my second week now and have not replaced all meals. Mainly because of the social aspect of eating but also because of my concerns around the effects of a liquid only diet.
James, do you have and info on this? Will having three Huels a day for an extended period of time have any negative effects on digestion or anything else? Surely, if your stomach does not see solids for a while it may change digestive behaviour?
Also, i heard that eating solid food burns more calories because of the effort it takes for your body to break down the food. I also see this as a positive to eating only a proportion of a Huel diet.
There have been concerns that long term liquid only diets can cause peristalsis to become ‘lazy’. Peristalsis is the movement of the digestive system to puch food along. With fluids it has less work to do. However, there are a large number of long term enterally tube fed patients who are fed in this way due to a medical condition. Some have been enterally fed for years and have successfully gone back to a solid diet with no adverse effects. This is because of fibres used in their formulas.
When we developed Huel, we took this on board and ensured that the mixture of soluble and insoluble fibres was at amounts to keep peristalsis working well. Remember, Huel is primarily based on natural foods - just in minute forms. Our main ingredients is fine milled oats. Oats don’t dissolve, they just suspend in water.
Solid food does burn more calories, but how much more? A very small amount. The thermic effect is the total number of calories in digestion, absorption, metabolism and excretion. This may be 10% of total daily energy expenditure, but liquid diets still use a major chunk of this 10%. The difference between calories expended between digesting a solid food only diet and a liquid diet are only a few and the equivalent to walking up and down the stairs at best.
In theory shouldn’t all food be chewed and mixed with saliva so it is pretty much a liquid when it reaches the stomach? Of course in practice I don’t chew each mouthful 20 times or whatever it’s supposed to be though my stomach might be happier if I did!
Digestion does begin with chewing; it starts the breakdown of solid food to increase the surface area and there’s also one enzyme - salviary amylase, which breaks down the polysaccharide starch into the disaccharide maltose.
However, with liquid diets, this has already been done for you and salivary amylase has very little effect on total starch digestion - it merely kick starts cab digestion as, in the stomach, it itself is broken down (remember, enzymes are proteins). It’s sister enzyme pancreatic amylase which acts in the intestines has a more pronounced effect where even previously solid food is liquid chyle. Huel has fine milled oats as the carb source and these are a lot easier to break down further than whole oats.
Really, the only minor concern with liquid diet is the ‘lazy’ peristalsis and we’re addressed this with soluble and insoluble fibres as described above. And this issue has been shown to be minimal and of no issue when peopel revert back to sold diets.