Wheat Germ

Polenta rounds out the first dozen. The high spermidine content in corn has even led some to speculate that it might explain why the Parkinson’s death rate is so much lower in some corn-growing regions of Japan. Parkinson’s is caused by misfolded proteins deposited in the brain, which can be broken down when spermidine triggers autophagy.

Whether vegetables are grown organically or conventionally doesn’t make much difference. When cooking, some of the spermidine can leach out of vegetables into the cooking water, but only cooking methods that use high, dry heat seem to destroy it. The same applies to meat. For example, roasting and grilling chicken destroys about half the spermidine, whereas boiling or braising causes only a loss of about 15 percent. Either way, chicken’s contribution is minimal.

While unprocessed plant foods make up only about 10 percent of the American diet, in Western countries plants supply over 80 percent of spermidine. Eggs contain none at all, most dairy products only a little, and few people eat organ meats, whose spermidine content is higher. Spermidine in muscle meat is relatively low, averaging 0.4 milligrams per serving (about 85 g), and in fish only 0.2 milligrams. The meat with the highest content is mussel muscle. Scallops and other shellfish don’t seem to contain as much, but oysters and mussels make it onto the table.

If you wanted to extend the list downward to 1.5 milligrams per serving, the next entries would be 1.9 for a potato (170 g), 1.8 in rabbit liver (about 30 g), 1.8 for pine nuts (about 30 g), 1.7 for asparagus, 1.6 for peanuts (about 30 g), 1.6 for cucumbers, 1.5 for rabbit spleen (about 30 g), 1.5 for pork lung (about 30 g), and 1.5 for black-eyed peas. Some individual components may not deliver the needed performance, but together—such as in a peanut butter and jelly sandwich—it could be enough, given its 1.6 milligrams in 30 grams of peanuts (about two tablespoons) and the 1.3 milligrams in two slices of whole wheat bread. That’s in the range of a quarter can of chickpeas. A hummus sandwich could be even higher.

Hard to swallow

I had to look twice at this line in a medical journal: "Spermidine is also found in fruit, such as mango, in semen, and especially in red wine." That’s a bold cocktail! Mangoes do great, but wine actually doesn’t contain much at all. And semen?

You can imagine how excited headline writers were at the news that spermidine promotes a long life. Cosmopolitan published a column about it. One of the provocative headlines was: "Swallowing Semen Could Extend Your Life."

Since a teaspoon of semen contains only about one calorie, it can’t even compete with lentil soup in terms of spermidine per calorie. But according to an average of five dozen men, a "serving" contains only 0.1 milligrams, so: no. Semen doesn’t make the list.

Wheat Germ

The spermidine in seminal fluid bears witness (from "testimony," not "conception") to its DNA-protective properties. The same is true for wheat germ, the tiny plant embryos in the unrefined wheat kernel. Although they rank fairly far down the spermidine scale by serving, you’ll notice they have the smallest serving size, namely just one tablespoon, or 7 grams. In terms of the ratio between volume and weight, wheat germ definitely wins the race.

They are also the cheapest spermidine source, because they cost only 2 cents per milligram. Wheat germ is a byproduct of white flour production and is usually simply discarded, which is presumably the reason for the low price. You can tell it’s a bargain because, in nutrients per dollar, it even beats dried beans.

Taking spermidine as a supplement?

I was astonished to read that spermidine isn’t sold commercially as a dietary supplement. That couldn’t be true. I searched online, and bam!—there it was, a bottle with SPERMIDINE printed in big letters. But when you read the label, you find it’s just wheat germ stuffed into capsules. Not even an extract. Literally just wheat germ.

On the one hand, it’s nice to see that supplement manufacturers aren’t trying to dream up some formula they can then lay claim to. I often take turmeric in capsules, for example, to reach the required amount in my Daily Dozen (see How Not to Die), because I don’t want to season all my meals with curry. It may be harder to find pure turmeric in capsules rather than a patented extract, but if you do, the markup for the convenience is considerable.

In contrast to turmeric, wheat germ has a pretty neutral taste, and I’ve found that I can simply sprinkle it on food. (I mix it with ground flaxseed, which is also part of my Daily Dozen.) Wheat germ comes in bulk packages for only $3 per pound. As capsules, wheat germ runs to over $200 per pound, which comes out to at least a dollar per teaspoon instead of a penny or 2 cents.

Our little helpers

At sufficient doses, wheat germ also improves cholesterol, triglycerides, diabetics’ blood sugar, as well as pain, exhaustion, headaches, and mood swings during painful menstrual bleeding (for details, see see.nf/wheatgerm). They can also support bifidobacteria in the gut. Bifidobacteria are a common component of commercial probiotics, are regarded as one of the indicators of the proper balance of good bacteria in general, and may even have the side effect of introducing additional spermidine into the system.

Our good gut flora produces spermidine, which enters the blood from the large intestine and circulates throughout the body. Eating tempeh or sprinkling wheat germ on dishes can provide regular increases in levels at meals, but it’s even better if your gut bacteria make it around the clock. The fact is that the good gut flora in most of us releases more spermidine than we eat. So it may be that we absorb less spermidine from above than from below, although that could change with age.

As we get older, spermidine levels fall not only in the blood but also in the stool. In the excrement of 30-year-olds, you can find a more than twice as high spermidine concentration as in that of 80-year-olds, and this decline is associated with changes in the microbiome.