 Telomere length is considered a biomarker of aging. Shorter telomeres are associated with decreased life expectancy and increased rates of age-related chronic diseases. Telomere shortening has been shown to be accelerated by oxidative stress and inflammation, so since plant foods contain plenty of compounds with antioxidants and anti-inflammatory properties, it's plausible that their sustained consumption might help counteract telomere attrition. And indeed, if you pull all the best studies on the impact of nutrition on telomere length, the consumption of vegetables, fruits, beans, and nuts has been associated with positive effects on markers of inflammation and oxidative stress in parallel with longer telomeres. By contrast, processed meats, alcoholic and sugar-sweetened beverages, and other foods rich in saturated fats, alcohol, and sugar are linked to an increase in inflammation and oxidative stress in parallel with shorter telomeres. In my last video on telomeres, I featured a randomized controlled trial showing a whole-food plant-based diet and lifestyle program could actually lengthen telomeres. Is it just because they cut out the junk? Those eating the most ultra-processed foods have been found to have almost twice the odds of having short telomeres. Maybe it's because they cut out the processed meat, like bacon, ham, hot dogs, lunch meat, sausage, which have been associated with not only cancer and diabetes risk, but shorter telomeres as well, meaning accelerated cellular aging, though just having something like a steak was not similarly associated with telomere length. Processed meat, but not unprocessed red meat, is associated with shorter telomere length. This is perhaps due to the particularly high concentrations of glycotoxins, the advanced glycation end products, as well as carcinogenic nitrosamines in the processed meat that may promote inflammation and oxidative stress. The only unprocessed meat associated with shorter telomeres was poultry. For dairy, it appears to be the milk fat. A national survey of thousands of Americans found an association between increased biological aging and the consumption of high-fat milk. Even people just going up like 1% milk fat from like 1% milk to 2% milk, low-fat milk to reduced fat milk, appeared to have more than four years of additional biological aging. We think it's because of the saturated fat, given that saturated fats trigger an inflammatory response. Not all plant foods are good for you, though. Orange fries and potato chip consumption is associated with shorter telomeres. Yes, fiber intake goes hand-in-hand with longer telomeres as does higher vegetable and fruit consumption, but that may be trumped by a deep fryer. What about the consumption of a high-fat whole plant food, like nuts? We know higher telomere-building enzyme activities associated with a higher dietary antioxidant score, and botanically, seeds are packed with antioxidants. Even by seeds, they mean any food you can put in the ground and sprout a whole plant, like whole grains, beans, chickpeas, lentils, nuts. They are naturally enriched in antioxidant compounds that protect the seed DNA from damage. Four weeks of navy beans didn't seem to affect telomere length, though. What about nuts? Well, based on how much your telomere shorten every year, you can estimate the rate of aging. In other words, two people can have the same chronological age, same calendar age, but suffer more or less effective cellular aging. So, for example, if you smoke a pack a day for a decade, your cells may age about three years faster. Or if you drink soda every day, it's like almost two years of additional aging. So what about nuts? US adults of the same age would experience almost two years less biologic aging per ounce of nuts and seeds consumed per day, the amount I recommend in my free Daily Dozen app. The estimated biologic aging advantage would be nearly one year for each hundred calories of nuts and seeds consumed every day. The researchers conclude that clearly consumption of nuts and seeds accounts for meaningful lower levels of biologic aging in US men and women, but that's just an association. You don't know if nuts can slow telomere shortening until you put it to the test. A randomized controlled trial investigating whether the inclusion of one or two ounces of walnuts a day for two years would help maintain telomere length, which normally shortens with age. In the control group, their telomeres shortened as expected over those two years, whereas the walnut group telomeres maintained their length, though the difference didn't reach statistical significance. Now that was measuring average telomere length, and it's probably more telling to look at how long the shortest telomeres are rather than the average. And if you do that, look at the percentage of telomeres that are particularly short, the walnut group does edge out over the control group. As well as the length of the shortest telomeres, the key biomarker in the onset of senescence, the researchers conclude that the inclusion of walnuts in the regular diet for two years tends to delay leukocyte telomere shortening in older individuals. A study on pistachio consumption two ounces a day for four months reduced signs of DNA damage, but did not significantly slow the rate of telomere shortening. And this study, which randomized people to eat more mixed in nuts, found a higher risk of telomere shortening in the nut group, or which the researchers could offer no explanation, so it's not clear whether nuts help with telomeres or not. Most supplement intervention studies observed no effects on telomere length as well, with the exception of green tea. Thirty-six elderly women were randomly divided into two groups, exercise alone or exercise with green tea consumption for five months, and a significant boost in telomere length in the green tea group with no change from the placebo. Green tea is essentially a green leafy vegetable we dip in hot water. How about eating green leafy vegetables? In fact, the healthiest kind cruciferous vegetables like broccoli, cabbage, collards, and kale, they pitted a raw versus cooked and found that cooked was better than raw for reducing DNA damage from a carcinogen, but raw was more anti-inflammatory. Consequently, to fully exploit the complexity of the health-promoting potential of Ethiopian kale, and by extension maybe other cruciferous, a mix of both raw and cooked vegetables should be part of the diet. OK, but what about for boosting the telomere-lengthening age-reversal enzyme? Raw or cooked? Which do you think? A short-term dietary intervention showed that cooked, but not raw, boosted telomerase activity in as short as five days, eating one and a quarter cups of this kale a day. It was thought that you'd need like four months of a change to affect telomeres, but this study provides for the first time evidence that telomerase activity can respond in a matter of days to a food intervention, but not just any food, but the healthiest food out there, cruciferous dark green leafy vegetables.