Was It the Food or the Exercise?

Was it the food or the exercise?

To answer the decisive question of the Ornish study—Was it the plant-based diet, the exercise, or the weight loss?—a study would ideally need to randomize people into at least three groups: a control group that does nothing (inactive lifestyle with the usual diet), a group that only exercises, and one that loses weight with the usual diet but smaller portions. And that is exactly the kind of study a group of American and Canadian scientists published.

About 400 postmenopausal women were randomly assigned for one year to one of four groups: a control group, an exercise group, a group that ate smaller portions, or one that exercised and ate less. As expected, there was little change in the control group, which did nothing for twelve months. What did a year of exercise look like? These participants didn’t fare any better either, and the exercise group in this study had done more than just take a half-hour walk like those in the Ornish study: Participants were supposed to do 45 minutes of moderate to vigorous exercise, for example jogging. And the smaller-portion group? The weight loss showed no effect, and the group that combined exercise and weight loss also showed no significant change in telomere length. That matches the inconsistent results from interventions that attempted to restore telomere integrity through weight loss.

So as long as we eat the same way we always have, it doesn’t matter how small the portions are, how much weight we lose, or how often we exercise. After one year, there was no benefit for the participants. In contrast, the participants in the Ornish study achieved fairly significant telomere protection with a whole-food, plant-based diet, while getting only half as much exercise and having lost the same amount of weight after only three months. In other words: Neither weight loss nor exercise reversed cellular aging by rebuilding telomeres. It was the food—and it wasn’t just any diet. A similar and similarly long study—four and a half years of moderate dietary counseling, for example eating low-fat dairy products or skinless chicken breast, plus more fruits, vegetables, and whole grains—did not meaningfully affect telomere length.

Foods to avoid

Not all plant foods are good for you. For example, eating French fries is associated with shorter telomeres. Yes, vegetable consumption goes hand in hand with longer telomeres, but a deep fryer can cancel it out. Refined carbohydrates like cookies and crackers can also gnaw at your telomeres. Cutting out junk food is one of the benefits of building your diet around whole plant foods. Those who consume ultra-processed foods have nearly double the risk of shorter telomeres—not to mention a high risk of obesity, depression, heart disease, stroke, and premature death overall.

Alcohol is another processed plant product. Researchers followed a cohort of businesspeople from Helsinki for nearly 30 years and found that the telomeres of those who drank the most aged an extra decade. They also found that even light alcohol consumption in midlife results in shortened telomeres, but a 2021 systematic review concluded that alcohol negatively affects telomeres only in heavier, dependent drinkers.

Participants in the Ornish study were supposed to avoid not only alcohol but also processed meat. Consumption of bacon, ham, hot dogs, breakfast meats, sausage, and the like is associated with both cancer and shorter telomeres, although unprocessed red meat— a steak, for example—does not appear to be related to telomere length. Some studies found an association with meat including game, poultry, and fish, but overall the problem seems more to lie with processed meat.

Long-chain omega-3 fats in fish and fish oil were thought to benefit telomeres, since in the Dietary Inflammatory Index they are listed as anti-inflammatory. In 2010, in a five-year population study, higher blood levels of omega-3 fatty acids correlated with less telomere shortening, which triggered a series of randomized controlled trials. Although the second analysis of a clinical trial in people with schizophrenia found an increase in telomerase activity, unfortunately not a single one of the randomized controlled trials that examined fish oil supplementation was able to show a significant effect on telomere length.

The most strongly proinflammatory dietary component is saturated fat. Believing it is never too early to eat more healthfully, researchers randomly assigned more than 1000 toddlers either to a group that was to eat low saturated fat for 20 years or to a control group. This remarkable Finnish study then found that the control-group participants lost twice as many telomeres each year as the healthy-diet group. However, more than just reducing saturated fat may have been responsible. That was the main focus of the study, but participants in the intervention group were also encouraged to eat less salt and more fruits, vegetables, and whole grains, making it impossible to determine the decisive factor precisely.

At the other end of the research spectrum is a series of randomized controlled dietary studies that lasted only four weeks but were innovatively designed. Cells from umbilical cords (a convenient source of human tissue) were cultured in the blood of older participants after they had spent a month either consuming a lot of butter or, with an otherwise similar diet, a lot of olive oil. Of the cells that had bathed in the buttery blood, a higher percentage had shortened telomeres. So a Mediterranean diet, which typically includes more olive oil and fewer dairy products, isn’t enough either. Although cross-sectional studies found that more Mediterranean-style diets correlated with longer telomeres, the only controlled long-term studies found that telomeres were the same length or even shorter.

The harmful effect of saturated butterfat may also explain the link between accelerated biological aging and the consumption of high-fat milk from a nationwide survey of thousands of Americans. Just drinking milk that was 1 percent higher in fat—for example, switching from low-fat milk with 1 percent fat to 2-percent milk—correlated with a telomere loss equivalent to more than four years, presumably the result of the inflammatory response and oxidative stress triggered by the saturated fat.

Telomere-protective foods

The most strongly anti-inflammatory dietary components are fiber. The same representative sample of thousands of adult Americans found that the more fiber they ate, the longer their telomeres were. Since the increase appeared to be linear, the scientists were able to calculate it. It seems that 10 grams more fiber per 1000 calories means four years less telomere aging. In the opposite direction, that corresponds roughly to consuming processed meat (plus 4.0 years), more than half a liter of soda per day (plus 4.6 years), or smoking (plus 4.6 years).