- Mark's Daily Apple - http://www.marksdailyapple.com -

Dear Mark: Am I Eating Too Little Food or Too Much Iron?

For today’s edition of Dear Mark [7], we’ve got a two-parter. First, Mathilde wonders whether she’s eating too little food. A high-fat, nutrient-dense Primal way of eating can have the effect of maximal satiation on fewer calories, and that’s usually fine, but there are instances where too few calories can have negative health effects. I tell her what symptoms to watch out for. After that, I discuss the issue of too much iron in the diet. It may be a concern for people with genetic tendencies to store excessive amount of iron, but what about regular people without those genetic variants?

Let’s go:

Dear Mark,

I will be as brief as possible ūüėČ I know we shouldn’t count calories when eating primal/paleo, but when I’m eating this way, I find myself not managing to eat more then 1000 maybe 1100 calories and that is by adding coconut and olive oil to my meals. Is so little calorie intake just fine if I’m not more hungry or will it spoil my effort by putting my body in a kind of “common restriction diet state”?

Thank you so much for all your eye opening information!

Best regards,


For the most part, I see the inadvertent reduction in calorie intake as a good thing. A feature of a nutrient-dense, satiating Primal way of eating. Many of us, particularly if we have excess fat to lose, are consuming more food than we require. It can go the other way, though. It can get messy and unpleasant and begin to have a negative effect on your health and quality of life.

Unfortunately, hunger isn’t always a reliable barometer to decide whether you’ve gone too low. During a calorie restricted diet, in fact, hunger doesn’t necessarily even increase [8], probably due to a reduced energy expenditure to match the reduced energy intake. If your body perceives the reduced calorie intake as the new normal, you’re not going to feel very hungry – even if you would be better served by more food. That’s not necessarily a bad thing, of course, and there’s some evidence that a slightly slower metabolism is optimal for longevity, but when you start seeing decidedly negative symptoms along with the reduction in hunger, it might herald a problem. After all, you want to enjoy your life, not live out a miserable, lengthy existence. Compression of morbidity, not extension, is what we want [9].

You might want to try eating more calories if:

You find yourself developing a newfound sensitivity to cold. Long term calorie restriction is a fantastic way to lower your core body temperature [10]. Higher body temperatures act as a buffer against the elements; if your body temperature drops, you will be more sensitive to cold weather and you may perceive otherwise moderate temperatures as uncomfortably chilly.

Sex doesn’t interest you as much as it used to.¬†In males, calorie restriction lowers testosterone [11], sexual impulses, and attraction to otherwise fetching females (albeit rodent females). Human calorie-restricted males also have lower testosterone [12]. Since leptin lowers with calorie restriction [13], and libido is intimately tied to leptin levels, the same holds true for women as well. A loss of libido [14] is a common side effect of chronic calorie restricters.

You never feel like doing anything. Since we need fuel to power our body to perform mental and physical tasks, under-eating can leave us listless.

You get dizzy when you stand up quickly. Calorie restriction is usually quite effective against hypertension [15], but if taken to the extreme it can lead to electrolyte imbalances/deficiencies and cause orthostatic hypotension, or postural hypotension. A common symptom is dizziness/head rushes upon standing.

Your performance in the gym is suffering. Interestingly enough, calorie restriction paired with resistance training prevents muscle atrophy (PDF [16]), while calorie restriction paired with inactivity increases it [17]. In other words, you gotta use it or lose it. Unfortunately, given the common side effect of not wanting to do anything at all, you might find it difficult to maintain a regular workout schedule [18].

Your wounds are taking longer to heal: Caloric restriction has been shown to impair collagen synthesis [19], which is how new skin forms as a wound heals.

You feel depressed (or worse). For a nice rundown on the possible psychological effects (including depression and suicidal thoughts) of super low-calorie intakes, check out this post [20] by Dr. Emily Deans [21].

That last bit of belly fat just isn’t disappearing and even appears to be growing.¬†Long term inadequate intake of food is, in essence, a major stressor [22] on your body. It’s a mild form of starvation. And when your calories get too low,¬†cortisol – one of the main stress hormones – goes up [23]. Cortisol [24], as you probably know, is strongly associated with abdominal fat.

These are basically warning signs that your body is perceiving the chronically low calorie intake as a signal of famine. If none of this bothers you, or you find the tradeoffs to be worth the benefits, go ahead and keep going. But if the benefits aren’t worth it – or they’re increasingly nonexistent – you should probably eat more food. It’s a roundabout way of saying: do you feel good? If so, keep on keepin’ on.

Hi Mark,

My question is with regards to iron intake when eating Primal – I’m concerned I’m actually getting too much. After plugging my daily stats into Cronometer – I was constantly getting in excess of 500% my iron RDI, or close to 50mg/day. This was through eating very Primal friendly foods – red meat, and organs like hearts and liver (which seem to have the highest iron content of any foods).

So my question is, even though I’m pretty sure I don’t have haemochromatosis, is consuming this amount of iron on a daily basis safe? I’ve read that iron overload symptoms can be very similar to iron deficiency symptoms.


Should you worry? Well, iron¬†is¬†highly reactive. Its inherent proclivity for electron exchange can create free radicals that damage DNA, cells, and blood lipids [25]. And observational studies [26] linking iron intake and stored iron to diseases like¬†type 2 diabetes [27], heart disease [28], and cancer [29]¬†do exist. Heme iron, the most bioavailable type and the easiest to absorb [30], is found exclusively in animal sources. Meanwhile, humans don’t absorb non-heme iron, found in plant foods like spinach, raisins, dried apricots, and lentils, nearly as efficiently.

Assuming you don’t have hemochromatosis, however, iron shouldn’t pose a problem, as humans have built-in mechanisms that regulate iron absorption [31]. If you have low iron stores, you will absorb more from your food. If you have elevated iron stores, you will absorb less. It fluctuates on an as-needed basis. In hemochromatosis, this regulation gets thrown out of whack, but it works well in most people – provided they’re getting sufficient amounts of dietary iron. Most people don’t need to worry about their iron intake.

So first off, get tested for hemochromatosis. According to Chris Kresser [32], even heterozygous carriers (with only one copy of the gene) may still have an elevated risk of several disease states (especially if you’re eating lots of iron). Your doctor may not be aware of this, as the conventional wisdom is that only homozygous carriers (two copies of the gene) are at risk for iron overload-related conditions. If you are a carrier, you may have to reduce iron intake (although one study [33] found no consistent connection between iron intake and ferritin levels in homozygotes), get regular phlebotomies, and stay up to date with your iron panels. Getting an iron panel done is a good idea regardless.

Second, what exactly are you eating to hit 50 mg of iron a day? That’s a lot of iron. A pound of steak has around 10 mg, depending on which cut. Are you eating five pounds? Liver [34] and other offal [35] will get you there faster, but you shouldn’t be eating liver every day anyway because of the vitamin A content. Remember, each animal has but a single liver. Shellfish [36] also run pretty high, especially clams. Unless you’re eating a chicken liver, lamb spleen, and pork lung stir-fry for dinner every other day, a clam smoothie for breakfast, and a five pound chuck roast [37] for lunch on the other days, though, it’s gonna be hard to hit 50 mg.

However, there are other things to consider when considering the possible danger of iron:

The unhealthy user effect: Strangely, when you differentiate between the various sources of heme iron,¬†research [38] suggests that only heme iron from red meat is associated with type 2 diabetes. This means one of two things. Maybe something about heme iron from red meat [39] is particularly lethal. Or maybe, because red meat is universally considered to be unhealthy [40], those people who care the least about their health and show it by smoking more, drinking [41] more, exercising less, and so on are more likely to eat more red meat. Even though studies try to account for the unhealthy user effect by adjusting for variables like tobacco and alcohol, they can’t adjust for everything that unhealthy people do. For instance, if data on “time spent sitting” was never even gathered, the researchers couldn’t have adjusted for it – even though sitting is a big predictor of type 2 diabetes risk [42]. I’d imagine people who eat the most red meat also sit [43] the most, while folks who eat lentils and chicken and wild salmon [44] tend to walk more [45].

Inflammation: Another study [46] found no link between heme iron (and total iron, for that matter) and pancreatic cancer, except in female smokers. If that link is causal, it could indicate that dietary iron only becomes carcinogenic in the presence of inflammation (from smoking, in this instance). Other research has found that inflammation increases ferritin levels [47], suggesting that elevated iron could be an indication of disease rather than a cause of it.

Interaction between iron and other nutrients. You might be aware of the various interactions between dietary minerals. For example, manganese competes with iron for absorption [48]. Dietary calcium also reduces iron absorption [49]. If you’re eating plenty of other nutrient-dense foods along with your sources of iron, iron absorption will be modulated.

Does that mean you, a healthy Primal eater, are out of the woods? Not necessarily. The connections between excess iron and various diseases warrant caution, and 50 mg seems unnecessarily high to me. Here’s what I’d do:

First, establish your hemochromatosis status.

Second, get a full iron panel from your doctor or other health professional.

Third, don’t eat 50 mg of iron a day, particularly heme iron. How do you manage that, anyway? Heck,¬†I’m not even mad. That’s amazing! [50]

Fourth, eat from a diverse swathe of the plant and animal kingdom. Eat red meat, white meat, fish meat, shellfish meat, nut meat, and the fibrous flesh of leafy greens [51]. This will help you get plenty of nutrients that normalize your iron absorption.

And finally, consider giving blood on a regular basis, especially if you’ve established that your ferritin levels are higher than you’d like. It’s highly likely that humans evolved to regularly endure small amounts of blood loss, whether through parasites or cuts, scrapes, and wounds, and this would have provided a way for men to shed excess iron and prevent overload. That could be why regular blood donation is associated with a lower risk for both heart disease [52]¬†and cancer [53]. Donating blood is a good move anyway, without accounting for potential health benefits.

That’s it for today, folks. Thanks for reading and be sure to chime in with your thoughts, experiences, stories, and comments!