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Paleo and Seasonal Affective Disorder

Sad face

It’s more than the “winter blues.” It’s more than just feeling a little down because it’s cold and dark outside. Everyone can get a little down in the winter sometimes, but when it starts bordering on a case of major depression, it’s called Seasonal Affective Disorder (SAD, not to be confused with the Standard American Diet, which shares the same abbreviation), and it’s not just you. Symptoms of SAD include constant exhaustion, depression, overeating (especially carbohydrate cravings), and disinterest in sex. If all that sounds disturbingly like your mental state from November through March, you might have SAD.

SAD affects 5-10% of the population; it’s more common in women than men, but when men do have it, they tend to get it worse. Understandably, it’s more common the further north you go, and it tends to run in families. People who move from a sunny to a colder climate also seem to be affected more, which points to an environmental as well as a genetic origin.

The good news is that you don’t have to just put up with a total loss of interest in life for a third of the year: there are a lot of diet and lifestyle interventions that can help minimize symptoms and keep you going through the winter with your sanity intact.

What Causes SAD?

Since everyone lives through the winter, but not everyone gets SAD, there must be some kind of genetic or physiological difference between people who do and people who don’t. Unfortunately, we haven’t completely figured out what those differences are, but they seem to be connected to brain chemistry. People with SAD seem to be more sensitive to environmental changes, especially the darker winter weather.

On the most fundamental level, SAD is the result of seasonal changes in the circadian rhythms, the biological clock that synchronizes your body with the cycle of day and night. Perception of daylight and darkness regulate the complex network of hormones and neurotransmitters that tell your body to wake up in the morning and get tired at night. With longer nights and shorter days during the winter, a few things start to happen:

Taken together, the drop in serotonin and the rise of melatonin seem to be responsible for many of the chemical changes of SAD. This is only amplified by environmental factors: fewer opportunities to get out in the sun, less outdoor exercise, and the 6 weeks of intense holiday stress and generally poor nutrition surrounding Thanksgiving, Christmas, and New Year’s.

So what can you do to control this cycle of depression or better yet, stop it before it happens? As it turns out, there are actually several options.

Diet and SAD

The best way to learn about eating during a long winter is to take a look at the people who do it well – indigenous groups living in northern Canada and traditional diets in Scandinavia and Russia. These food patterns have been tweaked over hundreds of years to meet the challenges of very severe winters…so how do they do it?

The obvious common ground is fish. All these groups rely on seafood heavily as part of their diet. Even more specifically, recent epidemiological research has identified two countries that have much lower rates of SAD than their northern location would suggest: Iceland and Japan. Both of those countries have a comparatively high rate of fish consumption, even relative to other northern nations.

Specific nutrients in fish that appear to be protective against SAD include:

Vitamin D

Sun exposure

Fatty cold-water fish are among the few foods that provide Vitamin D. During the winter, this becomes especially important because the most powerful source of this vitamin – sunlight – is obviously in rather short supply. So when the days are short and the nights are long, food sources of Vitamin D become critical.

Vitamin D deficiency is strongly associated with depression and SAD (although this does not necessarily prove causation). Studies on whether or not Vitamin D supplementation actually helps are fairly scarce – this trial was very small, but found an improvement, while this larger experiment did not. However, considering that depression is hardly the only side effect of Vitamin D deficiency, and that deficiency is extremely widespread, taking appropriate steps to improve your Vitamin D status can’t possibly hurt.

One potential way of treating this is to brave the cold and spend more time outside. But unless you work outdoors, it’s difficult to get enough D from sunlight alone in the winter, because you’re only exposing a small amount of skin (usually just your face) to weak and indirect sunlight. And if you work a regular 9-5 job, it might not even be logistically possible to go outdoors while the sun is up.

Another solution, as mentioned above, is diet. Traditional diets in northern latitudes make up for inadequate sunlight with abundant food sources of Vitamin D, most notably fish. Values for the Vitamin D content in fish vary dramatically depending on where the fish were from and how they were raised, so it’s hard to give a basic value for “salmon” or “sardines,” but according to the USDA nutrient database, some of the fish highest in Vitamin D are:

That’s per 6-ounce serving, or about as much as you’d eat at a meal. It’s very important to get wild-caught fish for this: farmed fish has much less. In this study for example, farmed salmon only had 25% of the Vitamin D of wild-caught. A less tasty but more concentrated source is cod liver oil: just one tablespoon contains 1350 IU of Vitamin D.

Omega-3 Fats

Fish aren’t just good sources of Vitamin D; they come to the rescue again with high levels of anti-inflammatory, anti-depressant Omega-3 fatty acids. A very quick review of Omega-3 fats: they’re a type of PUFA, and unlike the more common Omega-6 PUFAs, Omega-3s are actually anti-inflammatory. The ideal diet would contain a small amount of overall PUFA with a ratio of Omega-6 to Omega-3 lower than 4:1. The modern American diet contains far too much PUFA overall, especially too much Omega-6 and not nearly enough Omega-3.

As well as all kinds of inflammatory diseases, a deficiency of Omega-3 fatty acids has been linked to depression. And fish are one of the very few foods that have more Omega-3s than Omega-6s, making them ideal for balancing out a skewed ratio. Unsurprisingly, fish consumption has been correlated with lower rates of depression worldwide, and Omega-3 deficiency tends to correlate with an increased risk of all kinds of psychiatric disorders.

In clinical trials, Omega-3 supplements have shown promise for depression, social anxiety, and other mood disorders as different as anorexia, PMS, bipolar disorder, and borderline personality disorder. While they haven’t been linked specifically to seasonal depression, the strong correlation with depression and mood disorders in general is promising. And like increasing the Vitamin D in your diet, eating more Omega-3 fats has almost no risk of negative effects and the potential to do more than just treat depression.

The minimum recommended intake of Omega-3 fats is 650mg per day. Any kind of fish will contain significant amounts of Omega-3 fats, but some special Omega-3 superstars (per 6 ounces, which is about how much you’d eat at a Paleo meal) are:

Since you can easily get enough Omega-3 fats from seafood alone, it’s healthiest to get them from real foods, and not rely on supplements: Omega-3s, like all PUFA, are fragile, and fish oil supplements go rancid very easily. A rancid supplement does more harm than good, so stick with whole foods and avoid the problem altogether.


The specific kinds of fish and seafood included in traditional high-latitude diets also contain high levels of the amino acid tryptophan. Specifically, tryptophan is abundant in traditional Alaska Native foods like sea lion meat, dried beluga whale meat, caribou, and halibut. And if anyone knows how to survive a long winter, it’s the natives of Alaska!

The reason why tryptophan might be important for SAD is that it’s a precursor (a kind of building block) for the neurotransmitter serotonin. Remember that the short period of sunlight exposure in the wintertime decreases production of serotonin, which can affect your mood and sleep regulation. Some foods contain serotonin itself, but just getting it through diet doesn’t actually work, because serotonin in foods can’t cross the blood-brain barrier (an otherwise very useful boundary that stops any old thing you eat from making its way into your brain).

Tryptophan, on the other hand, can easily pass through the blood-brain barrier. So a diet rich in tryptophan and Vitamin B6 (which helps convert the tryptophan into serotonin) may help alleviate symptoms of depression by increasing serotonin levels.

This is backed up by quite a large base of research into tryptophan and depression. Tryptophan supplements are a fairly effective treatment for SAD, and on the other hand, in formerly depressed patients, tryptophan depletion can set off a reappearance of depressive symptoms.

A sign that you might benefit from tryptophan supplementation is a constant craving for carbohydrates. A high-carb meal increases the ratio of tryptophan to other amino acids in your blood, temporarily increasing the production of serotonin. So carbohydrate-rich foods are a kind of temporary self-medication for tryptophan depletion (unfortunately, this effect doesn’t last, so it’s just a band-aid, not a solution).

If you can’t get hold of some fresh sea lion, almost any other protein-containing food provides at least some tryptophan as well – even spinach has some. Per cooked 6-ounce portion (roughly the size of a Paleo meal), foods high in tryptophan include:

Tryoptophan is also available as a prescription supplement, but the doses used in most studies (1-2g) are reasonably obtainable from foods, so just making the effort to include more tryptophan-rich foods in your diet is probably enough.

Other Therapies For SAD

Traditional diets give us a lot of clues about eating to keep the winter blues away, but there are also several safe, effective, and relatively simple ways to supplement a good diet with some appropriate lifestyle therapies.


One route is to give your hormone regulation a bit of a boost, usually by supplementing with melatonin. Remember that the longer periods of darkness during the winter can increase production of melatonin to unhealthy levels. It seems a little counterintuitive to take more melatonin to solve this problem, but it does actually seem to work or some people: in one study, taking melatonin in the afternoon improved symptoms.

Light Therapy

Even less invasive than melatonin, light therapy (also called phototherapy or bright light therapy) is a very promising option, and the best-studied of all treatments for SAD. This is pretty much what it sounds like: a special lamp, much brighter than a regular light, that imitates the wavelength of the sun. This artificially extends your body’s experience of “daylight,” either by imitating “dawn” before the sun is actually up, or by extending your exposure to “sunlight” even after the actual sun has set.

With the longer period of light exposure, melatonin production is suppressed back to normal (summertime) levels. Bright light therapy can also help compensate for tryptophan depletion, suggesting that it may help induce the synthesis of serotonin. In a nutshell, it helps re-regulate the hormonal and neurological rhythms that get thrown out of balance during the winter, thus reducing the symptoms of SAD.

The effects of this can be quite dramatic: in one study, just two hours of light exposure in the morning (6-8am) improved the timing of melatonin production and decreased depression scores. It doesn’t actually have to be early in the morning, either: early-morning exposure is better, but in this study, evening exposure still helped.

An even better alternative is a “dawn simulation:” a light that gradually increases in intensity early in the morning. In one study, this improved symptoms even more than bright light therapy. And combining light therapy with tryptophan helped a group of patients who didn’t respond to either alone.

Bright light therapy doesn’t work for everyone (about 50% of people see benefits from a non-individualized routine, and that number rises to 80% with a schedule customized to their individual case). This suggests that the causes of SAD might be different among individuals. But like dietary intervention, it’s completely harmless even if it doesn’t work, so there’s no real reason not to give it a try. The only drawback is that it’s hard to make the time commitment to looking at a light box every day, but if the alternative is spending 24 hours in nonfunctional depression, 2 hours spent on phototherapy might seem like a great trade-off. You can buy a light therapy light yourself without a prescription, although insurance rarely covers it.

Negative Air Ionization Therapy

It sounds like something out of Star Trek, but apparently the future is here, because this really is a legitimate therapy. One doctor effectively treated SAD patients with an air ionizer, a noiseless device that sat beside the patients’ beds and changed the charges of air particles in their bedroom. At low levels, this had no effect, but at high levels it was almost comparable to light therapy: 48% of the ion patients improved, compared to 57% of bright light patients and 50% of dawn simulation.

The main researcher involve speculated that it might help because the air in the summertime is generally more negatively charged, so the ionizers help replicate summertime conditions. This treatment is still extremely experimental, and there hasn’t been a lot of research on it yet, but like light therapy there’s really no plausible way that it could hurt you if you want to give it a try.


If the approach of winter has you curled up under the blankets dreading the approach of every new day, you really owe it to yourself to look into some of your options for treating SAD. It’s not just being overdramatic or wimpy: it’s a real problem. And while nothing has shown to completely eliminate symptoms, eating a lot of wild-caught fatty fish and possibly investing in a bright light generator might make all the difference between a winter that’s miserable and one that’s at least livable. Just think of it as winterizing your diet, the same way you’d winterize your car. You might just need a little extra nutrition when the sun isn’t out – and now you know how to get it.

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Hi I’m Ashley, I’m an ADAPT Certified Functional Health Coach

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