Aspirin: The Pro-Metabolic Case, How I Take It, and the Real Risks

Aspirin is not a blood thinner brand.

It stops platelets from dumping thromboxane, lowers free fatty acids so glucose can get into the cell, works against estrogen and serotonin, and blocks the inflammatory molecules made from omega-6 fats. I take it almost daily, and I think it is the most useful anti-inflammatory there is.

It is also a real drug with real risks. In a large trial in healthy older adults it increased major bleeding. So this article has two halves: why I use it, and who should stay away from it. Read both.

A very old medicine

People have used willow bark, which contains a relative of salicylic acid, for thousands of years. A historical review traces it back to the Sumerians and Egyptians. Aspirin itself, acetylsalicylic acid, has been sold since 1899.

In the body aspirin quickly splits into acetic acid and salicylic acid. Salicylic acid is found in many fruits, and it does a lot of the work.

How aspirin works

It blocks the prostaglandin enzymes

Prostaglandins, leukotrienes and thromboxanes are inflammatory mediators made from omega-6 fats. Aspirin blocks the COX enzyme that produces prostaglandins. This is the textbook mechanism, and it is real. Prostaglandins also switch on aromatase, the enzyme that makes estrogen, so less of them means less estrogen.

It lowers free fatty acids

This is the part most people miss. High free fatty acids in the blood block the burning of glucose. In insulin-dependent diabetics given a drug that triggers fat release, a form of aspirin cut the rise in free fatty acids by half.

In obese rodents, high doses of salicylates reversed high blood sugar, high insulin and abnormal blood fats by making insulin signaling work again. That study, published in Science, tied insulin resistance to inflammation.

Niacinamide, vitamin E and thiamine lower free fatty acids too. Together with aspirin and B vitamins, they are the biggest lever I know for raising metabolism.

It protects cell energy

In brain cells deprived of oxygen and glucose, aspirin protected the cells by restoring ATP levels, at concentrations in the normal pain-relief range. The authors also saw it in isolated brain mitochondria.

It lowers serotonin

In platelets, aspirin significantly inhibited the release of serotonin. In rats with pulmonary hypertension, aspirin reduced plasma serotonin, and the improvement tracked the size of that reduction. More on why that matters in How to lower serotonin.

It works better with vitamin E

In immune cells, vitamin E made the COX-2 enzyme more sensitive to aspirin. The authors concluded that anti-inflammatory therapy might work with lower aspirin doses when combined with vitamin E. That matches how I use them.

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Aspirin and the stomach

This is the main objection, so let us be exact.

Standard medicine says aspirin irritates the stomach lining and can cause ulcers and bleeding. That risk is real and it goes up with dose, age, alcohol and other painkillers.

The research is more interesting than the warning, though. In rats, most anti-inflammatory drugs damaged the small intestine, and aspirin did not. Aspirin even prevented the intestinal lesions caused by indomethacin. The authors traced the protection to salicylic acid, the part of aspirin that is left after it splits.

An older study found that salicylic acid reduced the stomach lesions caused by indomethacin in rats.

My view is that inflammation is the main thing that damages the gut barrier, and aspirin is a strong anti-inflammatory. I have not seen data showing that it destroys the microbiome. But these are animal studies, and human stomachs do bleed on aspirin. I dissolve it, I buffer it, and I do not take it on top of alcohol or other painkillers.

Stress hormones and exercise

Twelve male athletes took aspirin or placebo for three days before a 30-minute treadmill test. Aspirin significantly blunted the rise of ACTH, cortisol and growth hormone before exercise, lowered cortisol after it, and reduced the prolactin response.

A second study in 19 students found lower aldosterone with aspirin but similar cortisol after intense cycling. So the cortisol effect is not guaranteed.

My own test has run for more than a year. Every Saturday I grapple. Without aspirin I do 5 to 6 rounds. With aspirin and baking soda 30 minutes before, I do 8 to 9.

What I take before training:

• Two hours before: coffee with 60 g of sugar, 20 g of beef gelatin, 5 g of taurine, and half a liter of Coke.
• 30 minutes before: 500 mg of aspirin with 5 g of baking soda and 200 mg of niacinamide.
• During: Coke and salted water.

The baking soda is there to buffer lactate. Lactate lowers carbon dioxide and tightens blood vessels.

Aspirin for erections

In a randomized, placebo-controlled trial, 336 men with vascular erectile dysfunction were split into four groups for six weeks: aspirin 100 mg a day, tadalafil 5 mg a day, both, or placebo.

The improvement in erectile function score:

• Aspirin: +7.2
• Tadalafil: +7.3
• Aspirin + tadalafil: +7.5
• Placebo: +2.0

Aspirin alone did as well as the standard drug. The combination had the fewest side effects, while tadalafil alone had the most.

It makes sense to me. Erections depend on blood flow and on the ability of the tissue to burn glucose. Lower inflammation, better flow, more carbon dioxide. If you have erectile problems: aspirin, sugar and sunlight are where I would start, after a doctor has checked your heart.

Bones, brain and eyes

• Bones. In rats with osteoporosis after removal of the ovaries, aspirin increased bone density and bone strength by stimulating bone formation.
• Eyes. In an older human study, cataract formation was delayed in patients who took aspirin, by about ten years in a group with osteoarthritis.
• Brain. Ray Peat pointed to the lower rate of Alzheimer's disease in people who take anti-inflammatory drugs for arthritis.

Aspirin on the skin and scalp

Women pay a lot for salicylic acid serum. You can dissolve an aspirin tablet in a cup of water and rinse your face with it, for cents.

For hair, I see hair loss as a metabolic problem with inflammation at the scalp. Balding scalps have high levels of prostaglandins, and aspirin blocks the enzyme that makes them. I have used it topically along with niacinamide and caffeine. Use plain aspirin for this, not the coated kind.

Aspirin and unsaturated fat

Aspirin blocks the release of stored unsaturated fats and the inflammatory products made from them. If you are clearing PUFA from your tissues, this is my list:

• High carb, low fat
• Coconut oil
• Vitamin E
• Aspirin

I used to burn in the sun within an hour and blamed my genes. Since I stopped eating PUFA I do not burn, and aspirin before sun exposure helps further.

Aspirin vs ibuprofen and acetaminophen

They are not interchangeable. In a study of young men, ibuprofen produced a state of compensated hypogonadism: the testes needed more stimulation to make the same testosterone, and in lab tests ibuprofen suppressed testosterone production by testicular cells.

Aspirin was pushed aside in the 1980s over Reye syndrome in children. Ray Peat cited an Australian study in which far more of the affected children had used acetaminophen than aspirin. The official advice has not changed, and I am not telling anyone to give aspirin to a child.

How I take it

• Plain, uncoated aspirin. The coating is there to get it past the stomach. I want it dissolved.
• Dissolved in hot water with baking soda. It buffers the acid and lowers irritation.
• 500 mg, most days. That is my dose, not a recommendation.
• Vitamin K2 alongside. Aspirin may lower vitamin K, so I take K2 with it.
• Gelatin or glycine first. 5 to 15 g with some sugar, then the aspirin.
• Not with a large meal when I use baking soda, because it lowers stomach acid for a while.
• With vitamin E in my routine, for the reasons above.

The risks, and who should not take aspirin

Do not skip this part.

The largest modern trial in healthy people is ASPREE. More than 19,000 adults aged 70 and over took 100 mg of aspirin or placebo for several years. Aspirin did not lower cardiovascular disease and raised major bleeding by 38%. Deaths from any cause were slightly higher in the aspirin group, mainly from cancer, a result the authors called unexpected.

Because of results like these, guidelines no longer recommend routine daily aspirin for healthy older adults.

Talk to a doctor before taking aspirin, and do not take it on your own, if any of these apply:

• A history of stomach ulcers or bleeding in the gut
• A bleeding disorder, or blood thinners such as warfarin or the newer anticoagulants
• Other painkillers of the NSAID family, or steroids
• Heavy drinking
• Asthma or allergy triggered by aspirin
• Kidney disease
• Pregnancy
• Surgery or dental work coming up
• Age under 18, because of Reye syndrome
• Age over 70

Black or bloody stool, vomiting blood, ringing in the ears or unusual bruising mean stop and get medical help.

What Ray Peat wrote about aspirin

My interest started with his article Aspirin, brain and cancer. He argued that the fear of aspirin was built by companies selling its competitors, that salicylic acid protects the stomach, and that aspirin's benefits go far beyond prostaglandins. I summarized it, with the 66 studies he cited, here: Ray Peat on aspirin.

The honest part

I am a fan of aspirin and I use it. But my experience is one person's, and much of the mechanistic evidence is from animals and cells. The best human trial data we have, in older adults, shows more bleeding and no benefit for the heart.

The people in those trials were not eating the way I eat, taking vitamin K or using it the way I do, and I think that matters. I cannot prove it.

So treat this as a description of what I do and why, not as advice to start a drug. Own your health, and include your doctor in it.

Quick answers

What does aspirin do besides thin the blood?

It blocks the enzymes that make inflammatory prostaglandins, lowers free fatty acids, reduces the release of serotonin from platelets, and in studies it has affected insulin signaling, stress hormones and cell energy.

Is aspirin as good as tadalafil for erectile dysfunction?

In one randomized trial of 336 men with vascular erectile dysfunction, 100 mg of aspirin a day improved erectile function scores by 7.2 points, compared with 7.3 for tadalafil and 2.0 for placebo.

Why take aspirin with baking soda?

Dissolving aspirin in water with baking soda buffers the acid and is meant to reduce stomach irritation. Before exercise, baking soda also buffers lactate.

Is daily aspirin safe?

Not for everyone. In the ASPREE trial of healthy adults over 70, daily low-dose aspirin raised major bleeding by 38% and did not lower cardiovascular disease. People with ulcers, bleeding problems or on blood thinners should not take it without a doctor.

Why take vitamin K with aspirin?

Aspirin may lower vitamin K, which the body needs for normal clotting and for directing calcium into bone. That is why I take vitamin K2 with it.