Ross Grant and colleagues at the University of New South Wales in Sydney––a mecca for the barbecued steak and kangaroo burger––have published in this issue of PLoS that people who eat a lot of protein have lower NAD levels, which means that those "healthy" high protein diets might not be so healthy after all.
In our bodies there are two important aging defense pathways––mTOR and the sirtuins––which sense when we are not eating enough amino acids or energy sources, and go to work putting our bodies in a state of defense. This is a good thing: It is likely why eating fewer calories, without being malnourished, is so good for you and your longevity.
High-protein diets are popular and can be effective for some purposes. These diets can stimulate muscle growth and put the body into ketosis, a metabolic state that uses amino acids for fuel, helping burn fat. But let's pause to look at some old and some new data.
Not only do some animal protein sources carry suspected carcinogens, especially over-cooked and preserved meats, but high levels of amino acids will keep the mTOR protein active in your body. That's a bad thing in the long-run––it will turn off your natural defenses against aging and disease.
NAD is a small molecule you should know about. Not only because it is essential for life–– you'd be dead in 30 seconds without it—but because it is essential for your long-term health, too. The more NAD you have the more active your sirtuins are. This family of seven cell defense enzymes (SIRT1-7) works with mTOR to control most of our body's cellular mechanisms, and ostensibly keeps us healthy into old age––growing blood vessels, reducing inflammation, among dozens of other likely benefits.
Mice engineered with extra copies of sirtuin genes are healthier into old age and, in the case of SIRT1 and SIRT6, live longer. Same too for mice fed so-called "sirtuin activators," also known as STACs, such as resveratrol and SRT2104, and NAD-boosting molecules such as NMN and NR.
I'm helping teams working to make even more potent and stable NAD boosters that could be next-gen drugs to delay aging and treat age-related diseases. In Boston, clinical trials are in progress. These are exciting times.
To test if protein intake affect NAD levels in the blood, the research team asked 100 test subjects what they were eating using a validated questionnaire. They then tested fasting blood levels of urea, NAD, and inflammatory biomarkers. Plasma levels of NAD were significantly higher people with lower protein intake, an association that was even stronger when plasma levels of the protein breakdown product urea were taken into account.
The lower the protein, the lower the urea, the higher NAD.
This could have implication for elderly people with kidney issues, because urea can accumulate, which could reduce the activity of sirtuin defenses and make them even more susceptible to other diseases.
This is good news for our family dog, Caidy, who has a congenital kidney defect. She drinks a lot, pees a lot, and has high blood urea levels. She is expected to live only five years. She is two years old now, and on a strict low-protein diet and 250 mg a day of NMN in a pill pocket. Perhaps we can get her past five years. We'll see. My wife, Sandra, gives her lots of love and the best of care. We will report back here as things continue.
In the meantime, I'm sticking as best I can to a low protein diet.
Except when I have a chance to eat kangaroo, that is. They do taste good.
---
While you're here, hop over to Twitter—I'm @davidasinclair—and ask me a question. I can't respond to everything, but as often as possible I'll write a lengthy response here.
