Danger of Low-Carb Diet: Not Enough Vitamin C

I eat a low-carb diet for reasons that have nothing to do with weight loss: To keep my blood sugar down. I am sure high blood sugar is bad. A few months ago, I noticed that my lips were chapped, which was unusual. I suspected it was due to lack of Vitamin C. About two months before that, I had stopped doing two things that I usually did: taking a multi-vitamin pill (which had Vitamin C) and eating fruit. I don’t know if the Vitamin C in the pill is absorbed but I’m sure the Vitamin C in fruit is. I started eating kumquats — the skins of four kumquats/day. (One kumquat contains about 15% of the recommended daily allowance of Vitamin C). My lips returned to normal.

Paul Jaminet, author of Perfect Health Diet, had a similar experience, which I knew nothing about when I noticed my chapped lips. While eating “a lot of vegetables but no starches and hardly any fruit,” he developed outright scurvy, including wounds that wouldn’t heal.  This happened while he was taking a multi-vitamin pill with 90 mg Vitamin C (my four kumquats contain only 35 mg Vitamin C). “Four grams a day of vitamin C for two months cured all the scurvy symptoms,” he found.

Why do we like sweet foods? The usual answer (so that we will eat more calories) is nonsense (except for children). The striking thing about our liking for sweetness is that it disappears when we are really hungry, which is the opposite of what the calorie-seeking explanation predicts. Desserts are served at the end of a meal because they taste much better then. But our liking for sweetness (when we’re not hungry) is so strong and obvious it must mean something important. I think it is pushing us to eat more fruit so that we will get enough Vitamin C. Fruits are much sweeter than other food groups and they are much higher in Vitamin C. We don’t like sweet things when we are hungry because a high-fruit diet is terrible (it is low in omega-3, other necessary fats, several minerals, and microbes, for example). But a small amount of fruit may be a big help. Paul and my experiences suggest it may be hard to get enough Vitamin C in other ways.

More Paul has a different idea about why we like sweetness.

38 Replies to “Danger of Low-Carb Diet: Not Enough Vitamin C”

  1. Not sure why that would be – lots of vegetables are loaded with vitamin c, more so than most fruits – bell peppers, broccoli, cabbage, garlic, etc.

  2. Green chillies are rich in Vitamin-C and are very low-carb.
    Far superior to fruit in this respect in my opinion. And
    one can easily eat 3-4 whole green chillies in a meal. That should
    provide more than sufficient Vitamin-C.

  3. Given that arctic explorers used fresh meet to avoid scurvy with great effectiveness, I find this odd.

    I have not eaten fruit in many months and show no signs of vitamin C deficiency. I’ve been eating only meat.

    How do you square Stefansson’s all-meat 1 year trial with this idea that low carb creates vitamin C deficiency?

    Perhaps in your case the problem was something other than lack of vitamin C, and in that other guy’s case, he wasn’t eating enough fresh meat.

  4. It’s true that fruits are sweeter than other foods (but keep in mind sugar cane, sugar beets, honey, stevia, etc.), but one perspective I’ve read is that modern man has bred fruits for sweetness, and ’twas not always so. I’m not sure I agree with this; breeding for sweetness doesn’t necessarily lead back to the idea that fruits were sour before that.

    I’m sure there is a bit more personal science you might do to test the theory that you were lacking vitamin C, v. something else that showed up in the kumquat skins. 130mg isn’t much, after all.

  5. Paul Jaminet developed outright scurvy while taking a multivitamin pill that contained 90 mg Vitamin C? That can’t be right. It seems much more likely that they were mislabeled or defective. Did he have a lab test done to confirm that they contained what they’re supposed to?

  6. Thanks for the link, Seth!

    Jim, vitamin C needs are highly variable — they rise from mg to grams per day during infections, cancer, or other severe stresses. The point of bowel intolerance of vitamin C can be as low as 2 g/day or as high as hundreds of grams/day depending on C needs. C needs also depend on the presence of other antioxidants (glutathione/zinc/copper/selenium) which are needed to recycle C. Oxidized C is degraded and excreted, reduced C is conserved.

    I had severe chronic infections at the time and was probably deficient in selenium and copper as well.

    Seth, fascinating point about the craving for sweets following rather than preceding dinner. Very true but I hadn’t thought of it before.

    Best, Paul

  7. Others have questioned Jaminet’s “zero carb” experience. Personally, I can only say that I was plant-free for one year, didn’t get scurvy or any other deficiencies, and had no problems whatsoever. The only organs I ate were beef liver once or twice a month and heart and tongue less frequently.

  8. Another n=1 experience on the appetite – vitamin C association:

    When I had scurvy I was always ravenously hungry. I ate 5,000 calories a day but was losing weight.

    As soon as I started supplementing vitamin C, my appetite dropped back to normal.

    I didn’t notice a specific craving for sweets, but it’s clear that vitamin C deficiency can induce hunger.

  9. Joseph, I ate/eat a lot of butter and roast pork. The roast pork is a few days old, at least. So I suspect it is low in Vitamin C. Vitamin C in meat may degrade much faster than Vitamin C in fruit — especially when the meat is cooked. Vitamin C is water-soluble, whereas I eat a great deal of fat. Because I eat so much fat relative to other foods and almost never eat fresh meat cooked rare, I suspect it is harder for me to get enough Vitamin C without eating fruit.

  10. As a type II diabetic, I also eat a low-carb diet, but certainly make sure to eat plenty of fruit and vegetables with vitamin C. I’m curious about your reasons for eating low-carb, though. You say “I am sure high blood sugar is bad” but what makes you think your glucose level is high? Do you monitor it with a meter? Just as dangerous — and *more* dangerous in the immediate sense — is allowing your blood sugar to drop too low. Don’t mess around with it unless you’re under the supervision of a doctor.

    And I’m also confused by your statement that fruit is sweet because it contains vitamin C. That’s just not true. Fruit is *tart* because it contains vitamin C. It’s *sweet* because it contains fructose and other sugars, of course!

  11. Richard, I think fruit trees have a different strategy than other plants. Fruit wants to be eaten; this is why it is colorful, not just sweet. Being eaten causes the seeds to move further from the tree, reducing competition and increasing diversity of habitat. Perhaps high Vitamin C content made them more attractive.

  12. Those wondering about the variability of vitamin C needs may be interested in reading about Dr. Cathcart’s experiments with vitamin C supplementation during different infectious conditions: http://perfecthealthdiet.com/?p=636

    In some infections, such as mononucleosis and pneumonia, the rate of vitamin C loss can go as high as 200 g/day. The normal whole-body vitamin C pool is only a few grams. It doesn’t take long to create a deficiency during infection!

  13. Scot, I believed my blood glucose was high because I measured it every morning. I fail to understand why eating a low-carb diet might cause my blood sugar to become too low. In any case, that has never happened, according to my measurements. I didn’t say fruit is sweet because it contains Vitamin C — I said that perhaps people like sweetness because a liking for sweetness would have pushed us to eat more fruit. Which contains Vitamin C, which we need. Our food preferences are obviously a guide to what we need to be healthy; I am trying to fill in the details.

    vic, when I said fruit is “almost necessary” to get enough Vitamin C I should have emphasized I meant under Stone-Age conditions. Nowadays of course fruit isn’t necessary. You can take a Vitamin C pill, for example. If you don’t want to eat green peppers. If you are simply following your natural preferences, eating what tastes good, I think you are unlikely to swallow a Vitamin C pill or eat green peppers or green chilis or other high Vitamin C vegetables. Whereas you are likely to eat fruit.

  14. I’ve been on a low-carb diet for a while now, but haven’t had any issues with this. Looking back at what I’ve been eating, though, I’ve been snacking on a lot of carrots, and the water I’m drinking has a bit of lime juice in it, so I think I have my bases covered. Unless I start seeing symptoms of deficiency, then I’d re-evaluate my diet.

  15. Oh, yes. Sorry for misquoting you about the sweetness of fruit. Still, I think it’s a likely a mistake to attribute preference for sweets to vitamin C requirements. People do need glucose as fuel for the brain. It uses no other compound for this purpose. Well, for that matter, neither do the rest of the cells in your body, but you’ll notice it pretty damn quickly if your brain fails to receive enough glucose.

    And yes, you can experience low blood sugar levels by eating insufficient levels of carbohydrates. You can’t rely on your stored glycogen as your sole source of glucose. Now, of course, you say you’re on a low-carb diet, not a no-carb diet. And you’re using an objective measure of your blood glucose level. Just would hate for someone without your commitment to scientific principles to attempt otherwise.

  16. Seth,

    I have read several books on the Traditional Chinese Medicine and they attributed that increased craving for sweets is in fact signalling some serious nutritious deficiencies. They said that it’s in fact meat or starches or other nutritionally dense foods that will soothe the craving, but sweets are more readily available. The taste of meat is in fact sweet as well.

    In my experience this seems (the TCM view) to be true. I always have been very skinny, but eating enormous amounts of sweets. After I switched to a proper, paleo-like diet, the situation changed in many aspects and I no longer have such strong cravings and slowly I am gaining some weight.

    So to sum it up, I think that taste for sweetness might mean more than taste for vitamin C

  17. Can someone here explain to me why humans, unlike a lot of animals, don’t create their own vitamin C endogenously?


    I don’t agree with this. It doesn’t fit with my experience, and I suspect it is a cultural phenomenon. Most of us were told as youngsters that we had to eat our dinner first if we wanted a sweet. The idea was that we WOULD eat the sweet first, if we could, and that might destroy our appetite so that we wouldn’t eat the other nutritious food.

  18. Thomas, you disagree that “we naturally won’t eat sweets when we are hungry.” There have been a bunch of studies showing that hunger reduces preferences for sweets, done I think by Elizabeth Capaldi. An article about this phenomenon mentioned among other things that in the Nazi concentration camps, where people were starving, a candy bar had zero barter value. Perhaps children are different than adults, I don’t know.

    Tomas, that’s an interesting point. Greater-than-usual desire for this or that food generally signals a nutritional deficiency, yes, as far as I know. Do you know what deficiencies causes greater-than-usual desire for sweetness?

  19. Kevin and others who have brought up the point that certain non-fruits are high in Vitamin C, I am wondering what you conclude from that about the evolutionary reason for our preference for sweetness. How would you explain our preference for sweetness?

    Look at the same thing in a different domain: our preference for sour foods. It’s strong and obvious, just like our preference for sweet foods. Lemons are sour. Does that mean we like sour things so that we will eat more lemons? Probably not because there is a bigger picture to consider. A much wider range of facts supports the idea that we like sour foods (such as yogurt) because we require plenty of microbes in our diet to be healthy. Microbes often make food sour.

  20. Interesting stuff.

    I’m on a low carb diet. But I take an Emergen-C every 2 days. A big part of me doubts if it’s improving my health. But it is a cheap and more healthy alternative to Coke.

    And after reading this, perhaps it is beneficial.

  21. Seth, since you eat a lot of animal fat, have you ever looked into the theory that animal fats are sources of lipid-soluble toxins? And China is rumored to have a serious problem with industrial pollutants.

  22. Well, I also wonder how a human living here (in the Pacific Northwest) would get his or her vitamin c before agriculture and the advent of shipping foods around the country. Like Native Americans. We can’t grow citrus fruits up here, and I don’t thing peppers grow naturally, either. I’ve heard that pine needles have a lot of vitamin c, but I can’t imagine they’re very agreeable?

    So what flavors would a tribe living here in Washington have to be attracted to in order to get their vitamin C?

    As for the evolutionary preference for sweetness, do you know for sure that there is a universal human preference for sweetness? Are there always sweet dishes in the pre-westernized cultures of the world? I’m not saying there aren’t, and you may know more about it than I do.

  23. I thought vitamins are stored in animal bodies, too. Mainly in some glands, but live might contain some, too.

    So if you eat the right parts of the animal you’ll get your vitamins.

  24. But don’t eat the wobbly bits.

    It seems to me this is really jumping to conclusions. Yes, we need vitamin C, but we need lots of other things too. Maybe the chapped lips were the result of some other deficiency, and the actual fruit countered the other deficiency. Fruits are made of a lot of compounds other than vitamin C.

  25. Nathan, do you have any specific nutrient in mind? Lack of Vitamin C unquestionably causes connective-tissue problems. Paul had bad gums, for example. With other necessary nutrients, such as magnesium, sodium, and many others, a connection with connective-tissue problems isn’t clear.

    Is there a universal human preference for sweetness? Well, very young babies like sweet things. Long before they could have been taught to like them. In children, the conventional explanation for sweetness preference (sweet foods are a source of calories) makes sense. They haven’t yet learned flavor-calorie associations that make food (containing calories) taste better than non-food (without calories), so a preference for sweetness helps them (because sweet things do usually have calories–extractable energy).

  26. Seth,

    sorry, I don’t remember and I am not even sure the books went deeper than just covering this general concept. I’ll try to find the corresponding passages, but first I need to find the book…

  27. Preference for sweetness is equivalent to preference for ripeness, in fruit. The learned association between sweetness and color makes this a very adaptive trait, because climbing a tree after fruit must be worth the risk.

    Plants convert starches to sugar in ripe fruit when the seed is viable and, perhaps, some environmental condition favoring germination is satisfied. This also is very adaptive, within the environment of animals that have been trained to recognize the ripeness they are encouraged, by the sweetness, to prefer. Co-evolution.

    I don’t know of any specific nutrient that may be in fruit that counters chapped lips. But then, I don’t believe we have identified every important substance we get from food. It certainly seems plausible that people who indulge in unusual diets (as defined by American custom of the mid 20th century), “unusual” activities (e.g. smoking, pregnancy, childhood, grave injuries, infections, starvation), or (particularly!) normal genetic variation seem likely to require substances not readily noted in lab testing, or much larger amounts of certain familiar substances. It has been suggested that autism, schizophrenia, and epilepsy are sometimes examples of such cases. I understand that some (of the terrifying variety of) mitochondrial genetic illnesses are known examples. Any drug that must be consumed daily to maintain normal health may be counted as such a substance. Just as several drugs may treat one condition, a variety of carotenes satisfy our need for vitamin A. The only difference, really, is how widespread the need is.

    Our need for vitamin C started as an example of normal genetic variation, and is now universal among primates, making it a proper vitamin. Including the rest of Mammalia in the population preserves its status as “needed for certain genetic variations”.

  28. Seth, are you buying the roast pork already cooked or cooking it yourself?

    Plus you’re in Beijing… which is a pretty tough environment on the lips anyway.

    It’s pretty much an article of faith for me at this point that eating the meat of any animal sufficiently large & fatty monotonically supplies all nutrients necessary for life, if not the optimal balance.

    I tried butter in a tiny quantity by the way, and it obliterated me.

  29. Anyway I’m almost always eating meat packed the same day. I don’t exactly cook it rare, as in still pink, but I don’t char it either… just quit when the ground beef changes color or the fish gets soft. So there’s no overcooking.

    So I’m probably getting a lot of Vit C… If you can trust the Chinese on meat freshness at MNC supermarkets. Which I think you can, ironically enough… meat freshness is something they’re culturally very particular about, and as far as I know they don’t employ the chemical treatment techniques designed to make meat look fresher longer used in the US.

  30. Joseph, the roast pork I eat is roasted by others.

    About your idea that eating enough of a sufficiently fatty animal supplies all necessary nutrients: That doesn’t explain why we like sweet things so much (except when we’re hungry). In spite of what Tomas says, meat isn’t significantly sweet. (One indication of this: Koreans marinate meat in a sauce that contains sugar.) And I’m sure we need plenty of microbes, which fresh meat doesn’t supply.

  31. I’ve always believed that we like sweets at the end of the meal (along with a nice cup of coffee) to counter-act the sluggish feeling we get from a big dinner. The sugar and caffeine perk us up a bit, so we can drag ourselves from the table….

  32. If sweet foods are craved after a ‘regular’ meal, it’s possibly because too much protein was eaten at that meal. That’s at least the theory in TCM.

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