The Question of Seasonality in Fructose Availability

Let’s continue the discussion from last time. Again, I apologize for any meandering. This is a big topic, and I think it helps to leave no stone unturned.

Seasonal eating is currently pretty popular, perhaps even trendy in some circles. You’ve got the locavores, folks who only dine on meat and produce grown and harvested within a certain radius (generally fifty or 100 miles). They don’t necessarily set out to eat by the seasons, but that’s how it works out when you’re only eating local stuff. Others are committed seasonalists (yeah, I may have made that term up), specifically choosing foods that would only be available that time of year. There are even a small number of strict ancestral seasonalists, who only eat those foods which were seasonally available to their ancestors. A lot of Primal dieters fall into this category, and they generally do it for health.

The vast majority of seasonal eaters and locavores are motivated by environmental or social concerns. By eating seasonal, local food, they’re trying to reduce their carbon footprints or stimulate the local economy. I’m all for keeping things local, but I’m really interested in seasonal eating for health reasons. Does seasonal eating optimize health?

It’s a tricky question, and I’m not sure there’s a definite answer. You’d have to establish the definitive seasonal diet, and I’m not even sure such a thing exists. There’d have to be a single global seasonal cycle, but that’s obviously not the case. Seasons change, roughly in accordance with latitude, or distance from the equator. Regions close to the equator tend to be warmer year round, with wet and dry seasons, while regions further from the equator tend to have higher temperature variations. As I mentioned last week, we evolved in a mostly temperate climate studded with intense periods of drought and moisture. The landscape was varied (grasslands, forests, shrubby desert), but the warm weather allowed a fairly steady supply of plant and animal life. Wild plants, edible tubers, small lean game, large fatty game, fruits, and nuts were all available.

Okay. Let’s get this started. I’m just going to let loose with some stream-of-consciousness style speculation. I’ll try and throw in some links where they’re applicable, but I ain’t making any promises. (Hey, I just reread “On the Road” and Coltrane is on, so I’m in that mood). This isn’t to be confused with medical advice or scholarly prose.

Cold Weather and Fructose Availability

My initial thought was that fruit (and therefore fructose) availability historically meant winter was coming. For more northern climes, like in, say, prehistoric Europe, this was definitely true. Let’s look at berries, everyone’s favorite Primal source of fructose. When are wild berries available? European wild berries flourish in the sun and are generally picked in late summer or early fall (according to this guide to the wild berries of Finland, where summers are short and warm, and the winters are long and cold), right as the weather begins to turn cold. In European forests, there are several species of naturally occurring wild fruit trees. The malus (apple family), prunus (plums and apricots), pyrus (pear family), and sorbus (rowanberry) all grew and still grow in Europe, and their fruit all ripens in late summer and early fall. If Euro Grok was eating fruit, it’s pretty clear he ate it seasonally.

We all know what a high fructose intake can promote: insulin resistance, weight gain, metabolic syndrome. Sounds pretty bad, right? In northern climates, however, a little bit of seasonal metabolic syndrome accompanied by a nice layer of adipose tissue might have been protective against the cold and the coming dearth of edibles. It wasn’t the chronic metabolic syndrome of the industrialized nation. It was seasonal, and it probably made a lot of sense for cold weather humans to eat as much fruit as they could to prepare for the winter.

But wait – if you add tons of Omega-6 fats to lots of fructose, metabolic syndrome gets even worse (or “better,” depending on how you look at it I guess). I wonder if polyunsaturated fat availability was seasonal, too. Since Grok wasn’t extracting oil from seeds using industrial processing, he had to get his PUFAs from whole foods, like nuts, seeds, and fowl. Nuts are certainly seasonal, and, at least in the US, they’re harvested mostly in fall. For cold weather Grok, this would place his greatest nut consumption in early fall, right in line with his elevated fructose intake. The combination of Omega-6 and fructose would represent a potent cocktail for pre-winter weight gain. (Before they hibernate, bears gorge on nuts, honey, berries, and fruit. Their metabolisms slow and they enter what might be described as a pretty intense bout of metabolic syndrome. I bet their triglycerides are sky high!)

What about today? Is there still an advantage to getting pudgy for the winter by overloading on fructose? I’m not sure, but I doubt it. We generally stay warm with clothing and heaters, and most people have access to plenty of food throughout the winter without needing to truck around a couple dozen pounds of fat energy on their person. I tend to think that it was an adaptive behavior, a cultural (albeit unwitting) reaction to seasonal changes. It conferred external benefits to humans living in cold climates (without steady food or access to shelter) but I don’t think the same thinking necessarily applies to humans (even descendants of Euro Grok) living today with plenty of food, shelter, and warm clothing. Remember, as far as we know Homo sapiens have only lived in cold climates with distinct seasons (like northern Europe) for 40,000 years, while the bulk of our genome was established in the 200,000 years spent in central and east Africa in temperate climates with wet and dry seasons, so if we’re genetically adapted to any seasonality, it’s going to be that one. We can’t fall into the trap of looking only to the prototypical hairy Grok stalking mammoths across frozen tundra. You can’t forget about the tropical, warm-weather Grok, with whom we all arguably share far more commonalities, regardless of ethnic background.

Vitamin D, the Seasons, and Fructose Availability

That brings up another point: cold weather humans were eating fructose and polyunsaturated fats in the relative absence of sunlight. That means little to no Vitamin D (whatever we could wrest from dietary sources). What do we know about Vitamin D and fructose? Well, when compared to glucose, increased intake of dietary fructose inhibits calcium absorption and induces Vitamin D “insufficiency.” You eat a ton of fructose – you need more Vitamin D to make up for it… unless the goal is to get insulin resistant, put on some weight, and stock up your energy stores for the coming winter.

Maybe seasonal (“protective”) metabolic syndrome is the result of eating fructose (along with PUFAs) without Vitamin D to quell the effects. We already know that European hunter-gatherers were under pressure to wring every last drop of Vitamin D from their environment, which is probably why they have white skin. Vitamin D wasn’t readily available, and for at least half the year it was unobtainable for lack of sun. If you look at our earliest tropical forebears, however, they had year round access to sun. They also had greater access to fructose.

That’s how tropical Grok enjoyed his fruit – with the sun blazing overhead. In fact, any traditional hunter-gatherer group that consumed fruit or fructose year round did so in a temperate, “seasonless” climate. Take the Efe, from the Democratic Republic of Congo’s Ituri Rainforest (average temperature: 88 degrees F), who can derive up to 42% of their caloric intake from raw, wild honey. The Efe also happen to exhibit the L1 haplotype, long considered to be the oldest genetic haplotype, and the 90,000 year-old Semliki harpoon, one of the earliest known Homo sapien tools, was discovered in traditional Efe hunting grounds.

What does this all mean to us modern humans? I think it means that strict (European) paleo reenactment (thanks to Kurt Harris for that term) by avoiding the sun for half the year and gorging on supersweet fruit in the fall is unnecessary, or even harmful (unless we need metabolic syndrome’s “protection”). Are you holing up in some hut out in the tundra this winter? Are you a black bear with the ability to read? If so, then go ahead and avoid sun and fill up on fructose and nuts, because you’ll probably need the body fat. For the rest of us, however, we just need to be aware of the interplay between the seasons, fructose, and our metabolisms. Low sunlight and low vitamin D coupled with high fructose intake tells the body that winter’s a’ coming. If we want to eat fruit, it probably makes sense to get plenty of Vitamin D, too.

Cold weather fructose consumption patterns weren’t ideal; they were just optimized to make the best of a tough situation. I’d argue that eating fructose the cold weather way (intermittently, with low Vitamin D levels) doesn’t make sense for most people today, and it may even be a big cause of modern obesity levels (instead of gorging on wild raspberries and walnuts while huddled in freezing caves, we guzzle soda and eat PUFA-laden French fries while sitting in air-conditioned homes).

What do you think? Is there something inherently beneficial to intermittent reenactment of northern European fructose consumption patterns, or do you agree that they are cultural adaptations to the realities of harsh winter conditions? Next week, I’ll continue the discussion.

TAGS:  Grok

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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66 thoughts on “The Question of Seasonality in Fructose Availability”

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  1. How does this square with the recent discovery (sorry don’t have the link handy right now, I’ll dig it out later) in a 40,000 year old cave in france that shows paleolithic humans (in europe at least) snorted refined fructose (through hollowed bones if I remember right) on an almost daily basis?

    1. I’d really like to see that link…
      How did they conclude that “refined” fructose was “snorted”??

      1. Yes, this is definitely interesting. Maybe the hollow bones were a primal form of straws and they were used for drinking fruit juice (hence leaving traces of fine fructose inside them).

  2. I’m sure this seasonal eating ties in to the seasonal hormonal changes that are triggered by changes in the number of daylight hours. Maybe that should read WOULD be triggered if we didn’t have artificial light sources to get us to midnight. I would love to know about this in more depth, but am still just starting to take it all in.

    Keep it coming, Mark!!

  3. I live in the north (Chicago) and come from southern California. After 10 years in Chicago I still get seasonal depression come February. I just can’t be away from warm weather that long as a modern Grok.

    I supplement with vitamin D and generally avoid fruit. Had no depression or seasonal down feelings this winter (and lost 25 pounds going primal!).

    So, I’m a believer in the need for paleo Grok, but this neo Grok likes his supplements and the science that helps him stay warm, positive, and healthy.


    1. i come from townsville, north queensland which probably gets as cold as 60F in the winter (thats as cold as it will get) and year round its always someplace between 80-90F. Now I live in northern california and granted its not as cold as chicago, but i miss my year round warm weather!!!
      i can totally relate to seasonal depression

  4. I came to that conclusion too before reading this artcle. Natural selection selects, not for the one who will live to 100 and still have a kickass jump-shot, but for the one who survives long enough to propagate one’s genes. So although Grok was doing himself some long-term harm, much of which would be mended in the winter, he was surviving another year by doing it.

    So consumption of lots of fructose at any time makes little sense for us, and it may even be a good idea to take a couple months a year off of fruit.

  5. I think it is very tempting to try to recreate the ultimate “primal” conditions, but it just isn’t possible. There are just too many variables that change from area to area, and year to year. Even if you pick a single point on the planet, and look at the temperature/precipitation over several years, you’ll notice that it is constantly changing. Even before global warming, there were shifts into and out of ice ages.

    I think the strength of our species comes from our adaptability. People could survive in areas where fructose abounded or was virtually non-existant and still be successful in either environment. I don’t think there is anything wrong with the idea that we live in a global world, where we have access to fructose year round. We are not the first civilization to do so, and I think it is counter-productive to pretend that we can’t find a berry in our local grocery store year round (aside from the other benefits of supporting local growers). I personally will enjoy fruit throughout the year, and get sunshine when i can and not feel the slightest bit guilty/unGrok-like for it.

  6. You mention Kurt Harris. Something that both you and he really push for, that I like, is the idea that we should not be asking “is this primal?” Instead we should be asking “is this healthful?” So we look to paleo/primal principles for guidance, but we glean from them what works best for the health of modern man. Well done.

  7. I moved from Southern California to New Zealand about 8 years ago. I definitely notice the changes in seasons a bit more here. The push for “comfort foods” which are generally fructose and carb laden are definitely cultural.

  8. Loading up on fruits in the fall and avoiding the sunlight seems very unreasonable. I say eat what you want when you want. But, eat foods that are locally grown as much as possible. This will make you eat a good chunk of your foods while in season.

  9. An interesting book by Dr. Sharon Moalem – Survival of the Sickest, hypothesizes that diabetes is an adaptation to extreme cold.

    Makes sense that the on switch for excess sugar in the blood to keep it from freezing would be seasonal variations in sunlight and food availability.

  10. “The malus (apple family), prunus (plums and apricots), pyrus (pear family), and sorbus (rowanberry) … all ripen in late summer and early fall.”

    Hi Mark,

    We grow all of these fruits and more in our backyard here in Nor Cal and our plums and apricots are ready to eat in early June. We’ll have peaches and nectarines in mid July. Apples and pears of course come fall.

    So I would imagine that parts of Europe might have had fructose spring through fall.

    btw just finished all of our home grown spinach for the season. Should be another month for the broccoli and kale and then we’ll have to wait until late summer for the squash. We also grow a variety of green-leafies throughout the year.

    Cheers, love the site!

  11. This is completely fascinating – it certainly seems to make sense to me that eating seasonally in northern climates (I’m at 57 north with the obivous likelihood of fat gain in the Autumn)only makes true sense if you are experiencing the other seasonal changes that go with it, ie sub zero temperatures and low light levels – down to 6 hours here in deepest winter.

    The fact that my house is electrically lit and heated during the winter (and this last winter has been the hardest for nearly 50 years) means that I’m not actually living the climate in any sense, even at night when the house probably falls below 10 degrees I’m still wrapped up in a big duvet with an electric blanket!

    Brilliant piece, look forward to the rest.

  12. I don’t pursue local or seasonal eating — the more good healthy food I can eat 365 days a year, the better off I figure I will be. Personally, I eat fruit daily but in moderation and with either protein and/or fat to slow the entrance into the bloodstream. In the winter (live in Michigan), I eat apples (they keep a long time so even a seasonalist could legitimately eat them) with weekend treats of strawberries or blueberries whenever they show up at Trader Joe’s. I wonder how many Groks stayed put in the winter and how many migrated to stay in tune with the readily available food sources.

  13. The adverse health effects of fructose that you are describing only result from the use of industrially refined high fructose corn syrup, and refined high fructose sugars from other sources such as agave.

    Fructose in its natural form as found in fruit is consumed along with the fiber of the fruit and doesn’t cause the obesity, insulin resistance, and consequent development of diabetes that so many people suffer from today.

    The unnaturally concentrated fructose, refined from corn is the main culprit of the current “diabesity” epedemic affecting consumers of industrially produced refined foods.

    Lumping all forms of fructose together is a mistake, and leads to bizarre conclusions like the one you’re presenting here as the reason for Grok’s stored fat for the winter.

    1. I kind of agree. How can fructose, as contained in a whole food, compare to HFCS or other fructose-enhanced non-foods? If we can argue that it’s not the grass-fed beef that causes the problems that grain-fed, hormone-laced beef does, then why aren’t we making the same differentiations for whole fruits vs. extracted, isolated components of fruits? (Or not even a fruit – in the case of HFCS.)

    2. Date palm fruits (Dates), due to the concentrated sugar, when fully matured (the usual) are very problematic to body chemistry (diabetes symptoms and such) for most people, unless one is only eating no more than somewhere 2 and 7 dates of average size (although yes, medjools are XXL, so on the lower side with them).

  14. Great post. Could fat burned during the winter months be a source of vitamin D? I’ve heard this hypothesis before, and it makes sense as Vitamin D is fat soluble. Fructose + sunshine during the summer could conceivably lead to vitamin D-rich fat stores.

    1. I also wonder if fat storage in winter is really ‘Vitamin D’ storage?

  15. I gorge on fruit, and don’t plan on stopping anytime soon. While I’ll grant that many seem to function quite nicely on low carb intakes, I need ~100g day to perform the kind of workouts and physical activities I enjoy. It would be way, way too difficult to consume that many carbs eating only vegetables. I tried, and felt stuffed, bloated, and generally unpleasant. Since adding ~2-3 servings of fruit a day, my workouts have been much better and I’ve had a much higher level of energy. There’s also the not insignificant fact that fruit tastes great. My feeling is that, provided you’re physically active enough to use the carbs, it’s quite difficult to eat too much fruit. And for what it’s worth, I maintain a bf% of ~8% with no trouble at all, so I don’t think the fruit is adding any fat to me.

  16. I think it’s silly to follow primal living that closely. Modern technology has allowed us to control our environment in ways that we need to take into consideration. Not getting vitamin D, or getting cold in the winter, just doesn’t have the impact it would have had on our ancestors.

    We can take supplements, have the warmth of the indoors. Having some fruit on a daily basis is fine. Some say it’s not essential, but just because it’s not essential doesn’t mean it’s not healthy.

  17. This is discussed in Lights Out: Sleep, Sugar and Survival by TS Wiley, a great book that actually brought me to the primal way of eating.

    1. Lights Out started me on this path several years ago, also! Great book.

  18. Hey Mark,

    Heard Art Devany interview on EconTalk yesterday.

    Art seem to say that seasonal foods such as honey and tubers(simple carbs) were signals to the body to turn our bodies to reproduction and away from repair and maintance to economize on resources.

    Wonder if the introduction of grains into our diet keeps us on the reproduction cycle all the time?

    Heck. It’s hard to see ourselves any different?

    1. Interesting point, I know oestrogen/progesterone hormones are involved with fat storage – very low body fat in female athletes can lead to a cessation of their cycles, equally though obesity affects reproductive cycles too, seems like this is probably a ‘Goldilocks’ one, it needs to be ‘just right’!

  19. Though it’s not a hut, I am holed up on the tundra all winter (except for a week for Christmas break and spring break, where it’s off to Mexico), but I have been wondering about how this location changes needs. I’ve also been wondering about seasonal sleep here. I’ve heard elders say they remember their parents only sleeping 2-4 hours a night in summer because thats how much sunlight there is. Then of course its like 13 hours of sleep in the winter. Interesting.

  20. I would argue that the changes following the departure from Africa are the most recent significant changes in our evolution as a species. The various ethnicites we see today largely formed during this period. If we view ethnicity as regional adaptations, it makes sense that nutritional adaptations would be included. The epicanthic fold, for instance, exists as a result of climate. It is an example of regional adaptation. Another notable adaptation are many Northern Europeans inability to process beta-carotene into vitamin A. In an environment where little meat / dairy is consumed, such a trait could be bad for survival, however in colder climates this gene has persisted. As such, one could be on a low-fat, vegetarian diet rich in fruits and vegetables and still be deficit in vitamin A. Thus the importance of nutrigenomics. Rosacea, another Northern European disease, is now thought to be related to fructose / carbohydrate mal-absorption (being that large fruits were historically limited to these regions) via SIBO.

  21. I know this probably goes against most peoples perceptions, but you know, the Grok family didn’t actually *have* to eat all their food on the spot. Berries and nuts are very amenable to drying and storing in baskets/bags. And I don’t know about Mrs. Grok, but I think I would have wanted to hole up in a cave for the winter, rather than wandering around in snowstorms looking for daily food. So, let’s see…nice cave, baskets of nuts and dried berries, chunks of meat that would keep well in the cold outer part of the cave, nicely tanned furs, a good woodpile…much more the ticket, I think. Yep, those fruits and nuts would have come in right handy.

    1. From my summer on the Yukon/Alaska border: Athabaskan traditional foodways include drying and fermenting lots of berries in the summer, as well as drying and fermenting fish and moose. There are big feasts on these items while they are being gathered, but they are also eaten throughout the rest of the year.
      Berries also very big commodity in the Columbia River Gorge/Mt Hood area, with huge annual gatherings during berry season.
      Year round fresh berries? Maybe not. Preserved, dried, and fermented fruits (and everything else)? Much more likely.

  22. i love eating seasonally! fruit aside b/c i dont eat it, vegetables home grown in the garden in season taste a ZILLION times better than anything from the farmer market or grocery store.

    hands down, the “fruits of your labor” taste awesome.

    we do collards in the winter and lots of fresh tomatoes, squash, broccolli, peppers, jalepenos in the summer… homemade salsa…

  23. When you eat mostly at your local food co-ops and farmers market, you are eating seasonally whether you want to or not. My local co-op only stocks vege/fruit from local farms. They just don’t have fruit this time of year. They don’t have many vegetables other than potatoes. There are a few hothouse things, but the taste is blah. The farmers market is only open from late april until novemeber. For the first few months, they don’t really have a lot of food other than salad greens. There are plenty of starts though.

    Sure, I could go to the chain store in town and get any fruit I wanted to eat year round, but it’s flown in from somewhere where the organic standards are often much more lax than in my own country. I don’t know what I could be eating. Plus, the food doesn’t taste right, it’s often very underripe or extremely overripe. As in, I buy it and bring it home and it’s conveniently mouldy by dinnertime. With local food, it was probably picked at most 3 days ago. Farmers markets? That morning.

    But I personally plan on gorging when it comes to be peach season again. And strawberry season. For about one month in August, I think I eat a peach or three a week. But that’s pretty much the only time I eat fruit.

  24. “Remember, as far as we know Homo sapiens have only lived in cold climates with distinct seasons (like northern Europe) for 40,000 years, while the bulk of our genome was established in the 200,000 years spent in central and east Africa in temperate climates with wet and dry seasons, so if we’re genetically adapted to any seasonality, it’s going to be that one.”

    I think you need to recheck your understanding of the location of the temperate zone, which generally lies between the Tropics of Cancer and Capricorn and the Artic Circle. Central and East Africa lie in the tropics. I do not know much about the vegetation of Central and East Africa, but in the tropics of Asia and Central America, fruit is available all year round, and the sugar content is generally higher than that of temperate fruits.

  25. One great thing about eating locally and seasonally (especially if you shop farmer’s markets) is that you get produce that was harvested recently and allowed to mature on the plant.

    This is definitely better than fruit that was picked unripe, shipped halfway around the world and chemically force-ripened at its destination.

    That’s reason enough for me to eat seasonally and locally (of course, it’s pretty easy to do in northern california).

  26. great article. i grew up in the tropics and we didn’t have the four seasons. we had rainy and dry. however, i remember the seasons split up differently. we had orange season, avocado season, “pisquette” season (they were a teeny tiny fish that we would fry up with tomatoes and onions and garlic), grapefruit season, etc. i think one of the greatest things about eating seasonally is an imposed diversity in our food choices. eating an apple a day every day just doesn’t cut it, i think. in a different vein, as an herbalist, one cool observation is that certain plants come into bloom or usefulness at the same times that our bodies need them. there is a definite co-evolutionary relationship that i find fascinating and worthy of deeper exploration.

  27. This is making my head spin! So, are we or aren’t we supposed to eat fruit?
    How much? When? I thought I knew, but now I’m doubting myself. I have 1/3 cup blueberries daily. Is that wrong?

    1. I’m wondering that myself, and frankly, nuts as well….we know O-6 is not good and nuts are loaded with O-6.Is Mark changing the blueprint a bit?

    2. How about fresh blueberries in season, other fruits when they are in season, and dried blueberries etc the rest of the year?

  28. Interesting Mark because I am living in the North of Europe (Sweden) and last month before i start eating primal I test my blood values and the results were that I was low on vitamin D. Here now is not a little sun light (sad) during the winter but summer it will be the opposite. Should we North European take some vitamin D supplements? The most sad thing of all is that our seasonal food is difficult to find and very expensive when you find it. I choose most frozen berries and the fruit that I get from the foodstore. Any tips?

  29. Hmm this is a little confusing. I think in general it’s probably something I’m not going to worry about. I’ll eat some nuts sometimes, when I want to, and I’ll eat some fruit sometimes, when I want to. I think it’s more important to just listen to your body than to freak out about the how much and when of each primal food. This is supposed to be an easy and enjoyable healthy lifestyle! Let’s not ruin it by worrying and being restrictive on the foods that are primal, as well as the stuff that isn’t! I think it’s great to know about the science and specifics, without getting too hung up.

  30. is everyone really this retarded?

    HUMANS EVOLVED IN A YEAR-ROUND TROPICAL, WARM, GREEN CLIMATE>.. only later on did we get the hair brained idea top migrate to cold and far reaching climates, a result of “culture”….

    so fruit availability through evolution and the majority of homo sapiens 2+ million year evolution was in an tropical, plant laden environment…


    1. If a MICRO nutrient requirement (e.g. Vitamin D) had “time enough” to selectively drive skin pigmentation, then game-on in terms of questioning regional environmental selective-effects on any other biological process.

  31. I can’t recall all the chronology but our hair-brained trek to northern climes was possibly due to population pressures caused/enhanced by the introduction of agriculture and the ‘abundance’ of all those starchy carbs!

    I’m sure someone will come along and shoot down that theory … what a great debate.

    1. My knowledge of human anthropology is minimal, but I do recall that Neanderthals co-existed alongside early humans in Europe, so the northern migration started way before the agricultural revolution.

      Human groups don’t pack up and undertake long, arduous journeys to unfamiliars lands for the sake of ‘culture’ (as per Lee’s comment). A lack of food and water and/or threats to safety like unfriendly neighboring tribes, dangerous predators and pests, or severe natural disasters would have driven early human migration the way it continues to drive a lot of modern migration.

    2. the migration was because of a climate change, i’ve been taught. i don’t remeber in which way this worked, if more people could survive because of better climate for finding food so that eventually there were too many people? northern europe was also warmer than it is now, during the viking age in scandinavia for example. at some point you could harvest grapes, don’t know when that was… Knowing that, it makes more sense that anyone would want to go north to find food.

      Also, it would be interesting to see these theories on northern indigenous people! Inuit sure, but sami for example used to be less depending on keeping their own animals historically and lived side by side with nomadic people that later chose to farm land instead of collecting etc.

      i would like to see an analysis starting from what mark is writing about here, compared to platectonics/climate and anthropology. *dreaming*

  32. Mark, I like term you used – “seasonal metabolic syndrome”, or SMS for short. It could apply to something I’m interested in, which is if/how SMS works once we get deeper into the winter months. It seems the danger of weight gain, for me at least, is much greater in Jan-Feb than it is during the Holiday Season of Nov-Dec. Does our body sense the lean/starvation months of deep winter and go into a protective mode? How does it know – via reduced levels of sunlight or cold temperatures or what? I believe SMS does kick in in the deep of winter and have had to do into intervention phase just to maintain my weight until the climate warms up. I’m wondering if others have found this same phenomenon?

  33. Funny. I’d been thinking this very thing. That’s basically how I relate it to people – the best way to get fat is to eat fruit & fruictose and con your body into thinking that it’s time to bulk up for winter. Not only do you store more fat, but you also get hungrier – your body forces you to overeat.

    I don’t know about you, but I get hungry as I eat a pear or apple.. and for a little while afterwards.. then I get sleepy. Fruit in the afternoon is great for nap time.

  34. Anyone have any resources on doing primal on a budget. I found eating healthy for P90X was hard on the pocketbook. As i read Mark’s books I can only see our grocery costs going up. Any thoughts on primal on a budget?


    1. I don’t have any resources to share, just some tips for maximizing nutrition on a limited budget.

      1. Eat eggs. They are the cheapest source of animal protein at 50 cents per serving of 2 conventional and about twice that for local farmers’ market eggs from pastured hens. I buy pastured but would eat conventional if I had to.

      2. Buy bone-in meats. Chicken is cheapest. Simmer the bones in a crockpot for 24 hours with a little vinegar added to the water to draw the minerals out of the bones. Broth is outstanding for cooking eggs and greens. Right now I am on a eggs poached in broth kick.

      3. Browse the meat aisle for meat marked down for quick sale. While the nutritional value of produce declines rapidly, I’ve not heard the same about meat.

      4. Browse the bargain shelves, too, if your store has one. I recently got organic roasted peppers for 50% and they won’t expire for another 6 months. Stocked up on canned organic pumpkin last winter. The process of canning increases the available beta carotene, so it’s actually nutritionally superior to fresh. Sometimes grocers close out unexpired items to make room for new products.

      5. Highly nutritious and affordable green cabbage, brussel sprouts, broccoli, and cauliflower have low pesticide residues, so no need to spend on organic. Don’t overlook tasty onions, also safe to eat, as a source of trace minerals.

      6. Broccoli sprouts have 10x the anti-oxidant power of mature broccoli. Brocco-sprouts cost $3.60 a package where I live. I put a handful on my salad, and the package lasts more than a week because the sprouts are densely packed. Among the lettuces, romaine has the lowest pesticide residues.

      7. The produce at my local farmers’ market is more expensive than conventional but cheaper than organic. I stick to greens as a staple and the first fruits of the season as a treat.

      8. Spend money on food before supplements. The only supplements I take are D3 and cod liver oil.

  35. I am fruit intolerant, my body simply does not digest fruit at all so it rots in my colon and makes me sick. I haven’t eaten any for about 7 years now. I have often wondered if I descend from people who did not have access to fruit so maybe that’s why I am genetically deficient in this area?? As for eating seasonally, my family does because it tastes SO much better and is more cost effective. Also better for local economy, supports small farmers, and good for the environment:)

  36. Anyone who’s taken a basic anthropology course knows that hunter-gatherers ate seasonally and would have stuffed themselves with any and all fruits, nuts, etc. that they would have come across. The reality is that in cold climates, Grok pretty much starved in the wintertime. Therefore, it would have been important to lay on as much fat as possible when the foods were available. As to sugar, I’m sure that as soon as he figured out how to get a honey hive he did it whenever possible. Nomadic Indian tribes in North America subsisted in the winter on dried meat and not much else.

  37. “Are you a black bear with the ability to read?”

    Literally made me laugh out loud with that one Mark; a great, humorous way to put the whole issue into context.

  38. Well, if the world does run out of oil for food transport, the fatties will live the longest.

  39. People in the UK are rather keen on seasonality. I think it makes sense to buy in season since the non-seasonal fruit will be subprime quality if organic, or pumped full of GMO and God knows what else if not to make it palatable.

  40. I didn’t have a chance to read all of these comments, but from a clinical standpoint I would say this: I live and practice in MN and there is great evidence of lowered Vit. D levels and MS. I think the advancements of modern science allow us to experience benefits our ancestors did not have. Certainly the case could be made for a more paleolithic seasonal eating, but I would suggest that it be done with caution. Great post, I would agree with your conclusions.

  41. “Remember, as far as we know Homo sapiens have only lived in cold climates with distinct seasons for 40,000 years, while the bulk of our genome was established in the 200,000 years spent in central and east Africa in temperate climates with wet and dry seasons, so if we’re genetically adapted to any seasonality, it’s going to be that”

    Bone to pick with this point: You’re ignoring the fact that those 40,000 years are more recent, and hence, more relevant to our current genome (provided you have European ancestry). You can say we had less time to adapt, sure, but to the extent we DID adapt, it was away from a tropical metabolism and towards a seasonal metabolism.

  42. Hi Mark,

    great post. I lost weight without trying on tons of fruits in a tropical climate but never did during a European winter… now I know why. dyou know if is this specific to fructose or do other carbohydrates exhibit a similar relationship with vitamin D?

  43. i dont see the connection between avoiding sun and eating fruit at the same time. how is that natural? who says that is natural? does fruit even last into the cold weather? did our ancestors walk around in the snow picking berries? i cant see what youre saying, though I think you are describing and refuting others’ point of view- im just confused that other point of view