Sleepiness and Brain Fog on Soylent

Hello! I’ve been on Soylent for about 2 weeks now for 100% of my meals. The first couple days I didn’t notice much difference, but on day 3 I started feeling really run down and tired. My thinking and ability to focus also declined. I had a hard time staying awake while trying to read a book a couple days ago. My eyes glazed over with dizziness and I wanted to sleep right then and there are my desk!

I tried to pass it off as a fluke. That maybe I was having an “off day”.I didn’t give it much attention, so I kept on drinking the soylent. After a couple more days I couldn’t ignore it anymore. Yesterday at work I had a soylent meal and about 15-20 minutes later all I wanted to do was sleep! I have found it a struggle to go for my daily walks these last two weeks and just stay awake in general! I was yawning and feeling very heavy with sleepiness and felt dizzy. I’ve been having 4-5 of the meals per day and plenty of water. I also added a multivitamin to fill in any gaps in case I was missing something on those 4 meal soylent days.

Most people report boosted energy on soylent, but I have had the exact opposite effect. Has anyone else experienced the sleepiness on soylent? What have you done to counteract this? If someone has advice, I’d be very happy to hear it!

1 Like

Two things to try: Drink more water, and eat some salt.

In my not-medically-trained opinion, your symptoms could be caused by dehydration or by low sodium in your diet. Soylent on its own definitely has too little water, and for some people the sodium level seems to be too low also. If you eat any typical American food you’ll probably get enough sodium to cover it up, but in your case that might not be happening.

If either of those is the problem, you should know a few hours after you start drinking water and/or eating salt.


I have been drinking a gallon of water a day in conjunction with soylent. Before I went on soylent I was on a whole food plant based diet with very little added salt and I didn’t feel this way. I’ll try adding a little salt into my next soylent meal. I shall be back to report :slight_smile: Thanks for the tip!

1 Like

Similar thing has happened to me. About 80% Soylent for 3ish weeks. Some days I feel fine, other days I feel pretty drowsy.

My first theory was that my body was missing the carb spikes from my typical diet. But I don’t think my energy level was spikey/crashy before I started getting most my calories from Soylent, so that theory doesn’t feel likely.

At this point, my best guess is that it’s unrelated to Soylent and is from getting worse sleep or spending more time in the sun starting around the same time as Soylent. I don’t remember those things changing at that same time, but I’m not very observant, so maybe they did.

Maybe it could be that I’m having a calorie deficit now vs. calorie neutral before. I haven’t heard of a moderate deficit causing a problem like this though.

I obsessively drink water most days, including the days when I have low energy. I doubt that too little water is my issue.

Sodium could be related. Unlike OP, I traditionally eat random crap much of the time, so my body is probably used to high sodium. I drank some salt water last week to try to get that extra sodium, but just ended up feeling sick. This is a good reminder to try supplementing my sodium intake in a moderate way.


I just decided not to use soylent as much and only have it a few times a week since it makes me feel really tired when I am straight on it. Yesterday I didn’t have any soylent and switched back to my “pre-soylent” diet and I felt a lot better.

I had a similar experience where I started to feel tired and lacking energy after being on the newer versions of Soylent for a period of time. I didn’t have this feeling when I was on 1.5 which contained more oat flour and zero soy and was a completely different recipe. I’ve been off of it for a while now and started making my own powder with oat flour and protein and MCT oil and it’s been fine. I think if you had a healthy, plant based diet you should keep part of that going. There are chemicals in plants that are beneficial to your body that Soylent won’t have. I think the people that benefit the most are people who replace unhealthy food and see a big difference in their energy because of the things they’re cutting out.

1 Like

Yeah, I went back to my pre-soylent diet yesterday and felt loads better on a high carb, low fat , whole foods plant based diet. I felt like walking arounf and being very active, not tired or clouded thinking at all! I think I will still be a customer of soylent, but only use it on occassion such as when I am traveling out of town. (I travel on troad trips out of town 2-3 days a month.) I’ll make those my “soylent days.” I’m sorry to hear that you experienced the sleepiness on the newer version as well >,< My body also isn’t used to having over 10g of fat on a day to day basis. I think that my have to do with it as well. Whenever I used to eat peanut butter I would get hot and feel my heart pound and feel sleepy, soylent also has the same effect. I think I will go back to my wfpb (whole food plant based) diet. I never had any added oils or fats either beforehand >,< Thank you for the reply.

I think @wms might have the right idea about sodium. When I first started Soylent, I wouldn’t get sleepy but I would have headaches with crazy brain fog. I started supplementing with extra salt and they went away, and then I seemingly acclimated and didn’t need the salt anymore (so the salt might or might not have been the fix). Some folks on this board speculated that similar issues could be related to the sodium/potassium balance in Soylent.

A related thought: I’m not a nutrition expert, but I wonder if the issues with sleepiness/brain fog could have been related to the drastic reduction in carbohydrates from your pre-soylent diet. I know that many people temporarily experience sleepiness and brain fog as part of so-called “keto flu” if they abruptly cut carbs out of their diet, largely because the decrease in carbs/insulin causes the body to flush out electrolytes and water. Soylent has too many carbs to allow for ketosis, but you had mentioned that your pre-Soylent diet was very high-carb. I wonder if maybe you experienced similar symptoms because 100% Soylent was such a reduction in carbs compared to your body’s usual fuel.

“Keto flu” is generally temporary and goes away once the body gets used to a low-carb diet. Its symptoms can be mitigated by supplementing with electrolytes (sodium, potassium, calcium, magnesium). But again, since Soylent isn’t keto, I’m only speculating that the problems you’re describing could have similar origins.

Anyway, it sounds like you decided Soylent (or using it exclusively, anyway) wasn’t for you. But if you do decide to try it again and have similar sleepiness/brain fog, one potential option to try might be supplementing electrolytes and seeing if the problem goes away after a little while. Best of luck.


I’m still using soylent, just not 100%. I had two meals today in conjunction with lots of fruits and vegetables and rice! I feel much better and energetic now! I think it may be the “keto-flu” thing that you described before! Thank you for all the details and helpful reply! I think I will still have frequent soylent meals throughout the week, but mix them with my regular diet. I had the soylent at work and it fit in quite nicely. Soylent has a place in my life, but not just exclusively hehe! I love this product and will continue to update and do more research <3

1 Like

I believe it is due to your blood running to your stomach and away from your brain(that happens when you have a heavy meal). You may be able to lessen the effects by spacing out your meals. For instance if you drink 6 servings a day instead of consuming them evenly in three meals , turn it into 6 meals.

Thank you for this, but there’s one problem. If this is the case, why have I never been sleepy after eating my normal pre-soylent diet? This only happens with soylent for some reason, but other foods. It happens if I have soylent all day. For example, I can have one serving and be okay, but if I have it day in and day out, I feel run down :frowning: any thoughts on this? I have a perosnal theory that it has to do with the high fat content of it. What do you think about that?

You could have an allergy or intolerance to a specific ingredient in Soylent. Have you tried the ready to drink ones?

Yes, I had a couple , but did not find them filling at all :frowning: I only tried a couple, so I wasn’t able to try them long enough to figure out if they made me sleepy :frowning:

There was a point in time when I did a full week on Soylent and water only. But this was back around the 1.4 powder days. When I did that, I felt AMAZING and an energy boost when I hit the 3rd day, and cravings for other food went away. Lately, the ready-to-drink version, which I love for its convenience, does make me feel like I’m having a “sugar crash” and want to sleep quite frequently. But I haven’t attempted to go 100% in a while, so I was considering this to be inconclusive before reading this thread. I also agree that they don’t seem filling. When I did 100% soylent powder, I felt like my body naturally regulated my soylent intake to a healthy level. Now, I wonder how many drink bottles I would go through a day if I didn’t regulate it in an exact way. Maybe I’ll experiment for a few days and see.

1 Like

I have been using the powder 100% the last couple weeks, but I stopped and returned to my normal pre-soylent diet. I feel much better and alert on real food. When on soylent I didn’t crave for a bunch of “traditional foods”, but I was always feeling unsatisfied and tired… Very “sugar crashy” This was on the soylent 1.8 powder (original). I will still keep soylent in my life and maybe replace a couple meals a week with it, but not as a sole source of nutrition. I’ve noticed that if I only replace a few meals with it, I don’t feel as bad. It seems that after I do it for more than 2 consecutive days in a row, that the brain fog and fatique take place. I will be doing 100% soylent this Wednesday, since I will be traveling and don’t want to be eating garbage gas station food and unhealthy restaurant food either. You’ll have to tell me how your experiment works out and post updates! What are you planning to do exactly for the experiment? Are you going to be using the bottles or powder? Currently I have only seen the v1.8 powder for sale on the Soylent website. Please keep me updated! <3

I have been eating Soylent for a couple of years now and have never felt the fatigue that you are talking about. But I’ve also never tried to go 100% Soylent. Here is an unscientific guess - when you suddenly change your diet, there is probably a “shock to the system” reaction. This happens with many things in life - if you change jobs, or travel, or have to deal with an entirely new group of people - there is usually some tiredness that goes along with things like that, right? It might be better to have it a few times a week to start. And remember to drink some water and sip it rather than gulp it down. And have some tea or coffee too.

1 Like

I drink 4-6 cups of tea a day :slight_smile:I gave up drinking soylent and don’t have it anymore , it just now sits in the cupboards for an emergency XD which kind of stinks, because there’s over $200 of the stuff just sitting there lol. Thank you for the reply :slight_smile: