Wednesday, August 4, 2010

The baffling rise in seasonal allergies: Global warming or obesity?

The July 26, 2010 issue of Fortune has an interesting set of graphs on page 14. It shows the rise of allergies in the USA, together with figures on lost productivity, doctor visits, and medical expenditures. (What would you expect? This is Fortune, and money matters.) It also shows some cool maps with allergen concentrations, and how they are likely to increase with global warming. (See below; click on it to enlarge; use the "CRTL" and "+" keys to zoom in, and CRTL" and "-" to zoom out.)

The implication: A rise in global temperatures is causing an increase in allergy cases. Supposedly the spring season starts earlier, with more pollen being produced overall, and thus more allergy cases.


I checked their numbers against population growth, because as the population of a country increases, so will the absolute number of allergy cases (as well as cancer cases, and cases of almost any disease). What is important is whether there has been an increase in allergy rates, or the percentage of the population suffering from allergies. Well, indeed, allergy rates have been increasing.

Now, I don’t know about your neck of the woods, but temperatures have been unusually low this year in South Texas. Global warming may be happening, but given recent fluctuations in temperature, I am not sure global warming explains the increases in allergy rates. Particularly the spike in allergy rates in 2010; this seems to be very unlikely to be caused by global warming.

And I have my own experience of going from looking like a seal to looking more like a human being. When I was a seal (i.e., looked like one), I used to have horrible seasonal pollen allergies. Then I lost 60 lbs, and my allergies diminished dramatically. Why? Body fat secretes a number of pro-inflammatory hormones (see, e.g., this post, and also this one), and allergies are essentially exaggerated inflammatory responses.

So I added obesity rates to the mix, and came up with the table and graph below (click on it to enlarge).

Obesity rates and allergies do seem to go hand in hand, don’t you think? The correlation between obesity and allergy rates is a high 0.87!

Assuming that this correlation reflects reasonably well the relationship between obesity and allergy rates (something that is not entirely clear given the small sample), obesity would still explain only 75.7 percent of the variance in allergy rates (this number is the correlation squared). That is, about 24.3 percent of the variance in allergy rates would be due to other missing factors.

A strong candidate for missing factor is something that makes people obese in the first place, namely consumption of foods rich in refined grains, seeds, and sugars. Again, in my experience, removing these foods from my diet reduced the intensity of allergic reactions, but not as much as losing a significant amount of body fat. We are talking about things like cereals, white bread, doughnuts, pasta, pancakes covered with syrup, regular sodas, and fruit juices. Why? These foods also seem to increase serum concentrations of pro-inflammatory hormones within hours of their consumption.

Other candidates are vitamin D levels, and lack of exposure to natural environments during childhood, just to name a few. People seem to avoid the sun like the plague these days, which can lower their vitamin D levels. This is a problem because vitamin D modulates immune responses; so it is important in the spring, as well as in the winter. The lack of exposure to natural environments during childhood may make people more sensitive to natural allergens, like pollen.


Aaron Blaisdell said...

Very nice analysis. My theory is that a major contributor to the rise in allergy rates, along with those you mention, is the increase in omega6/rancid oils in our diet. McDonalds switched from beef tallow to "vegetable" oils in 1990 for all their frying needs. Billions were then served rancid, oxidized oils. If I were a bettin man, that's where I'd lay down my money. Or at least the one-two punch of that plus the spike in HFCS consumption that accompanied it.

Michael Barker said...

Ned, if there was a Vit D connection wouldn't you be able to see a rise in allergies as the population ages since it's known that Vit D creation tends to be less effective as one gets older?

Pål Jåbekk said...

My first encounter with carbohydrate restriction was when my wife tried Atkins and for the first time in many years didn't have to take her allergy meds during pollen season. It was an eye opener. Since then, reductions in inflammation derived symptoms are one of most striking results I see in people cutting carbs. It is also interesting to see that the symptoms often return if people return to their old diets.

Ned Kock said...

Hi Aaron.

Indeed, omega 6 fats tend to be pro-inflammatory. Particularly our friend arachidonic acid, whose name reminds me arachnids!

Ned Kock said...

Hi Michael.

Among the elderly (i.e., those aged 65 or above) pre-sunburn full-body exposure to sunlight is equivalent to an oral vitamin D intake of 218 µg (8,700 IU). That is close to 90 percent of what a 20-year-old would produce:

Ned Kock said...

Hi Pål.

Another one that tends to disappear, or reduce a lot, when refined carbs are removed is acne.

Gretchen said...

I've had hay fever since I was a child. I remember walking home from school with my eyes running and itching.

In college I was tested and found to be allergic to tree pollen and mold.

As an adult, I used to wake up at 4 a.m. with nonstop sneezing and dripping eyes. I'd take an antihistamine and eat something and I'd be better in about 30 minutes.

After I was Dx'd with type 2 diabetes in 1996, my allergies disappeared. I lost weight, but not on a LC diet. But I kept reducing carbs until I was pretty LC after a year or so.

This summer I've had terrible allergies again. I haven't gained weight. I'm not eating carbs.

So I think there's more to this than LC diets and losing weight. Maybe the hot, humid weather has allowed more mold to grow.

Ned Kock said...

Hi Gretchen.

Yes, there must be other factors as well. One interesting thing about your experience is that the allergies disappeared after the T2D diagnosis.

Both cortisone and cortisol suppress the immune system. This may sound odd, but the stress caused by the diagnosis could have led to a period of chronically and highly elevated cortisol levels.

Those high levels have a number of negative health effects, but they will suppress the immune system and thus should alleviate allergy symptoms.

Cortisone has long been know to suppress allergies (more in some people than in others), but it also has many negative side effects.

Amber said...

So what you are saying is that obesity is caused by global warming?

Berny3 said...

I read a year or two ago that, at least in urban and suburban areas, there is more pollen out there than there used to be. The reason is that when professional landscapers are hired to plant trees in industrial parks, median strips and other public places, they try to avoid planting female trees, which are considered "messy" because they drop seeds and/or fruit. So, assuming a tree can be identified as male or female, males are chosen, which of course contain pollen.

Ned Kock said...

Hi Amber.

No, I didn't mean to imply that.

There are people who think that warm climates cause an increase in obesity.

I don't, because hunter-gatherers in regions near the Equator tend to have low body fat.

Ned Kock said...

Hi Berny3.

Very interesting, and makes sense. Thanks.

We smart humans can't help messing things up eh?

Aaron Blaisdell said...

"We smart humans can't help messing things up, eh?" That's an astute comment. I've been thinking for a few months now that politicians, policy makers, and administrators of any kind and persuasion really need their version of a Hippocratic oath "do no harm". If one is not sure whether an act--though meant for good--may have unintended and unexpected negative consequences, then don't act! Do no harm. I feel like society is a wobbling bicycle going at top speed. Every action a politician or law maker takes to try to correct the bicycles course only sends it wobbling off in the opposite direction. We need to stop the bike, take a deep breath, and get back on at a slow and steady pace.

Take the "statins in the public water supply" example. Who knows what the unintended consequences may be? Look at what fluoridation of our water supplies may have done (so we can keep munching our sweets, presumably). Public policies should not be allowed to go forward when we are blind to the consequences (which is just about always). Okay, enough of my libertarian rant.

Ned Kock said...

The fluoridation of water is supposed to prevent tooth decay. The Centers for Disease Control and Prevention calls it "one of 10 great public health achievements of the 20th century".

Still, we have plenty of tooth decay. I am reading Humboldt's "Personal narrative of a journey to the equinoctial regions of the new continent". On page 121 he says that:

"It could be said that Indians do not know toothache, and Spaniards who live in the Tropics do not suffer from this pain either."

Humboldt is generally reliable. These folks ate plenty of carbs, in the form fruits and starches. Fruits have sugar. And I don't think fluoridation of water was a priority for them.

I like the wobbling bicycle analogy Aaron!

Anonymous said...

"This is a problem because vitamin D modulates immune responses"

Does it? Vitamin D and host resistance to infection? Putting the cart in front of the horse

Ned Kock said...

Certainly the interactions are complex, as in any multifactorial health-related issue.

D levels today are in those who avoid the sun are likely vastly lower than among our ancestors, and the D is clearly involved in a number of metabolic processes that are adaptive.

Getting 400 IU of D per day, when our ancestors likely got 10,000 IU, is not natural. Not always what is natural is good for us (our ancestors had no antibiotics either), but often that is the case.

Ned Kock said...

Just an addendum to my comment above, regarding interactions. There is evidence of an interaction effect between vitamin D and calcium, as far as immunity is concerned:

Anonymous said...

Guess again. Genetically engineered food products have been introduced into the food chain since the first commercial planting in 1996. According to Monsanto (2011) "Since then, more than two trillion meals containing ingredients from biotech crops have been safely consumed." Safely consumed? By what definition?