Honestly? I'd see this as a fluke or, perhaps, a virus.

You seem to be doing everything by the book. This seems like an abberation. I mean, it's only been a few DAYS.

the Paleo lifestyle takes several weeks / months to really settle in with some changes and adjustments in between.

I think you just got hold of some food that didn't agree with you or have nabbed a passing gastro-intestinal bug. Hang with it for a bit and see how it goes. :)

Sounds like you ate some food that had gone bad. If it were a virus, I would expect there to be more episodes. I makes no sense to me that it would have anything to do with not eating whole grains or other complex carbs.

I've had oxidized (overcooked) salmon make me sick. I get sashimi salmon and eat it raw or lightly seared.

I highly incredibly doubt you got sick because you aren't eating something like grains...

Hi, April. It came out in the comments to Austin's answer that you had been significantly increasing your fat intake. I can say from my own experience that it took me a while to get better at consuming fat; I experienced a lot of nausea when I first started eating paleo. I have even thrown up, and could tell that it wasn't food poisoning, since I felt better immediately afterwards.

I've seen a lot of other anecdotal evidence of this in paleo circles, people getting gradually better at digesting fat. The obvious thought is that your body can get better at producing bile. Bile is a major player in digesting fats: it breaks down big units of fat into smaller little droplets so the enzymes in your small intestine can have at it. Consider this discussion from way back when on Dr. Harris's forum, about eating paleo without a gall bladder (which stores and concentrates bile). Consider also the case of the 88-year-old guy who ate 25 eggs a day, much quoted for pro-cholesterol reasons because he had pretty good blood cholesterol levels. But the interesting thing I just noticed about that article is that he had double the rate of bile-acid synthesis compared to normal subjects. The authors obsess over the fact that bile acids help regulate cholesterol, but bile acids also help digest fat -- and a high-egg diet is also a high-fat diet. So maybe he also increased his bile production in response to all the fat. Anyhow that's the best I could come up with in tonight's research for finding some evidence other than anecdotal that we can get better at digesting fat. But the anecdotal evidence is pretty strong.

There are too many variables to blame that on paleo. In time, you too will be eating previously disgusting foods even for breakfast without batting an eye. Take my breakfast this morning for example: mackerel fried last night with buttered yams and natto.

My transition was also rough in that I experienced about 2 weeks of diarrhea, during which my immune system was very weak (as gauged by swollen lymph-nodes, oral cold sores, etc).

Barring the possibility that we got something like food poisoning, rapid changes in gut flora might help explain our rough transitions. Different bacteria populations thrive on different inputs or diets. When they cannot properly break down the inputs, the system responds with a 'flush,' which is what I understand diarrhea to be. Things stabilize once the appropriate bacteria have come to dominate the population.

Don't forget that during this period your body is forming new chemical pathways for burning energy. Until this happens, the lack of carbs is a deficit shock, while the larger amounts of fat and protein are surplus shocks. Also, your brain has to adapt to using glucose that is internally produced. All of these processes help explain why in the beginning many of us experience 'low carb flu.' I think that this term encompasses a phenomenon that has many dimensions - cognitive, digestive, energy-burning, immunity, etc.

Importantly, though, none of this suggests that what carb flu symptoms are indicative of a dietary change that is unnatural in any sense. Rather, it merely indicates a radical change to which the body's systems need time to adjust.

As for me, since those initial two weeks, which was over three months ago, I haven't gotten sick once. This is quite miraculous considering that I spent the past 3 winters sick in bed almost every other week.

I can't really answer your question but I've noticed that salmon can make me queasy. I had some for breakfast this morning and walking to work I thought for a minute that it was going to come back up. I also couldn't finish the fillet that I had cut for myself - I almost started gagging. Too much on an empty stomach? I'm not sure what the problem is but I'm going to be cautious with salmon for awhile.

If you've ruled out things like food poisoning or a virus, then think about your fat intake. When I first started upping my fat intake, I felt like I had indigestion (probably my gallbladder wasn't used to dealing with that level of fat). My husband will throw up if he goes way over his body's capacity for dealing with butter or cream, which has happened a handful of times when something was really yummy and he didn't pay attention to his body's signals (and if you're new to paleo, you might not know the signals at all). The vomit was always barely digested, even if it had been hours. And when I had morning sickness I felt like I absolutely couldn't digest any fat without something sour like vinegar or lemon juice to help emulsify it, as though my body just couldn't produce enough bile. It felt just like going paleo again, except I knew how to deal with it by then.

So if you think that might be the issue, go back to the amount of fat you used to eat, and SLOWLY build up from there. Sour things seem to help, too.

I have no idea why this happened but I can say that my digestion of meat - and likely fat - was greatly helped after a short course of hydrochloric acid (HCl) to assist my stomach acid production.

S&C coach Charles Poloquin has an article about it here:

http://www.charlespoliquin.com/ArticlesMultimedia/Articles/Article.aspx?ID=27

Even if you don't have any of the symptoms he lists, I think it's worth a shot as I find his arguments for better digestion pretty compelling.

HTH

You may have experienced ketoacidosis. If that's the case, you need to eat more carbohydrates. I had a similar reaction 4 days after going strictly paleo. I felt the same burning, like the worst heartburn I'd ever had, headache, and aching, though no vomiting. I kept myself from vomiting so I could keep down the carbs I knew I so desperately needed. I had been eating a lot of grains prior to going paleo as well.

Try eating some grains with every meal and gradually reduce the amount of grains you eat to nothing over one to two weeks. Make sure that while you're decreasing your grain intake, you're greatly increasing the amount of vegetables you're eating with every meal to keep your carb intake up.

When your body metabolizes lipids, ketone bodies are created as an intermediary, which are then broken down to create energy. This process is ketosis. However, when your body is relying too heavily on lipids, ketone bodies build up in your blood to the point where your blood pH drops. This is ketoacidosis. Your body is more susceptible to ketoacidosis when you suddenly decrease your intake of carbs. You may be eating a perfectly balanced paleo diet, but if your body hasn't had time to adjust, you'll experience ketoacidosis.

Sources: http://www.livestrong.com/article/297064-low-carb-diets-ketoacidosis/

To specifically answer your question, throwing up is not "normal" under any circumstance, Paleo diet or other. That said, four days? I encourage you to be a little more patient. Most reliable sources say to try it for thirty days. If you keep throwing up, then maybe you should consider whether this is the correct option for you.

Vomiting could be a sign of protein toxicity. When people say to eat "lean meats", they are giving bad advice. You can't have a sustain protein intake of over 30-40% of your caloric intake. Review what you have eaten and see if you didn't have enough carbs and fat to balance it out. Seafood is 60-90% protein by calories and will be a problem if you eat it at most meals. If you eat lean meats, you have to add in fat (olive oil, coconut oil) and/or carbs (sweet potato, potato, parsnips, fruit).

Ground beef is good paleo staple. Get 75-82% lean and you won't run into protein toxicity. Chicken and turkey can be too lean to use as a staple.

I didn't have issues with vomit- but I definitely had issues with diarrhea. This took care of me super quick:

http://www.amazon.com/Barleans-Organic-Oils-Greens-Container/dp/B0009ET4KE

many times when I eat and I start getting an upset stomach its mainly because it isn't digesting properly. I drink a tablespoon of raw apple cider vinegar with an 8oz glass of water and usually it helps to bring the PH in my stomach back to a stable level and digestion resumes as normal.

I'm also going to cast my vote for food poisoning here. Happened to me last month; I remember reflexively licking the spoon I was using to cook dinner and thinking, "That was just sitting in raw hamburger; I shouldn't have done that." And sure enough, that night (or hours later, early the next morning, after a very painful night), I had the same experience you did - right down to the texture of the puke. Hope you feel better now. Stay hydrated!

I got that exact same thing day 5, I was rendered useless throwing up all day, I am 99% sure it was a severe wheat withdrawal. I've read something like wheat activates the same receptors in the brain as heroin and alcohol so the withdrawal process (sickness, headaches, sweats, vomitting) can be a milder version. I realise this is purely anecdotal, but it was my experience anyway.