How to Boost DNA Repair with Produce

“In the light of strikingly consistent observations from many epidemiological [population-based] studies, there can be little doubt that the habitual consumption of diets high in fruits and vegetables helps to reduce the risk of development of degenerative diseases, including many types of cancers.” Not satisfied with merely telling people to eat their fruits and veggies, scientists want to know the mechanism. I discuss this topic in my Which Fruits and Vegetables Boost DNA Repair? video.

Not just vehicles for antioxidants, fruits and vegetables contain innumerable phytonutrients that can boost our detoxification enzymes, modulate gene expression, and even modulate DNA repair pathways. “Until fairly recently…it was generally assumed that functions as important as DNA repair were unlikely to be readily affected by nutrition,” but, if you compare identical twins to fraternal twins, only about half to three quarters of DNA repair function is genetically determined. We may be able to control the rest.

“It is estimated that, on average, there are 800 incidents of DNA damage [in our bodies] per hour,” which is about 19,000 hits to our DNA every day. What’s more, “that DNA damage can cause mutations and give rise to cancer, if not repaired.” Thankfully, “the regulation of [DNA] repair can be added to the list of biological processes that are influenced by what we eat—and, specifically, that this might constitute part of the explanation for the cancer-preventive effects of many plant-based foods.”

Any plants in particular? Nine fruits and vegetables were tested to find out which ones were better able to boost DNA repair: lemons, persimmons, strawberries, oranges, choy sum (which is like skinny bok choy), broccoli, celery, lettuce, and apples. Which ones made the cut? Lemons, persimmons, strawberries, broccoli, celery, and apples all conferred DNA protection at very low doses.

Lemons, for example, were found to cut DNA damage by about a third. Was it the vitamin C? No. Removing the vitamin C from the lemon extract did not remove the protective effect. However, if you first boiled the lemon for 30 minutes, the protective effect was lost.


If it’s not the vitamin C, what might it be? That’s the subject of my video Citrus Peels and Cancer: Zest for Life?

Surprised that the lemon benefit was abolished by cooking? Find out which vegetables it may be best to eat raw in Best Cooking Method.

What about cooked versus raw garlic? See my video Inhibiting Platelet Activation with Garlic and Onions.

For more on DNA protection and repair, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Healthier Salt Substitutes

As I discuss in my video Shaking the Salt Habit, the two most prominent dietary risks for death and disability in the world are not eating enough fruit and eating too much salt. Eating too little fruit kills nearly five million people every year, and eating too much salt kills four million.

There are three things we can do to lower our salt intake. First, don’t add salt at the table. One third of us add salt to our food before even tasting it! Second, stop adding salt while you’re cooking. At first, the food may taste bland, but within two to four weeks, “as the sensitivity of the salt taste receptors in the mouth become more sensitive to the taste of salt in the usual concentrations”—believe it or not—you may actually prefer the taste of food with less salt. Some of the flavorings you can use in the meanwhile instead of salt include “pepper, onion, garlic, tomato, sweet pepper, basil, parsley, thyme, celery, lime, chilli, nettle, rosemary, smoke flavoring, curry, coriander and lemon.” Even if you did add salt while cooking, though, it’s probably better than eating out, where even at non-fast food restaurants, they tend to pile it on. And, finally, avoid processed foods that have salt added.

In most countries, only about half of sodium intake comes from processed foods, so there’s more personal responsibility. In the United States, however, even if we completely stopped adding salt in the kitchen and dining room, it would only bring down salt intake a small fraction. This has led public health commentators to note how challenging it is for everyone to reduce their salt intake, since so much of our sodium intake is out of our control. But is it? We don’t have to buy all those processed foods. We can choose not to turn over our family’s health to food corporations that may not have our best interests at heart.

If we do buy processed foods, there are two tricks we can use. First, try to only buy foods with fewer milligrams of sodium listed on the label than there are grams in the serving size. So, if it’s a 100-gram serving size, it should have less than 100 mg of sodium. Or, second, shoot for fewer milligrams of sodium than there are calories. For example, if the sodium is listed as 720 and calories are 260, since 720 is greater than 260, the product has too much sodium.

That’s a trick I learned from Jeff Novick, one of my favorite dieticians of all time. The reason it works is that most people get about 2,200 calories a day. So, if everything you ate had more calories than sodium, you’d at least get under 2,300 milligrams of sodium, which is the upper limit for healthy people under age 50. Of course, the healthiest foods have no labels at all. We should try to buy as much fresh food as possible because it is almost impossible to come up with a diet consisting of unprocessed natural foodstuffs that exceeds the strict American Heart Association guidelines for sodium reduction.


Not eating enough fruit as a leading killer? For more, see my video Inhibiting Platelet Aggregation with Berries.

In my latest sodium series, I lay out the evidence and dive into the manufactured controversy to expose salt industry shenanigans. See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Foods with Negative Calories

What are some dietary strategies for the prevention and treatment of obesity? Large portion sizes are often targeted, so restriction of portion size is an important element of many diet programs. But it’s hard to get people to eat less food. A more effective approach may be to shift the emphasis from the quantity of food eaten to the quality of food eaten. By choosing foods with lower calorie density, we can eat the same amount or even more food and still lose weight.

My video Are There Foods with Negative Calories? explores whether there are foods that take more energy to digest than they provide. Does eating celery, for example, result in a negative energy balance? “Celery is a readily available whole-food that has the ability to add bulk and flavour to a meal, without adding excess calories. Celery is also subject to a renowned health myth, that when consuming celery there is a ‘negative’ intake of calories and therefore the energy required for its digestion, assimilation and nutrient storage is assumed to be greater than the energy it contains.”

So researchers put it to the test. A cup of celery, which is about two stalks, has 16 calories. Digesting that much celery takes about 14 calories. So, no, consumption of celery does not induce a negative energy balance, but you are only left with 2 calories. “This fact combined with the high fibre and water content of celery does make it a good snack for inclusion in a diet for weight loss or management.”

Maybe negative calorie foods are not a myth after all, though. Researchers at Penn State offered people a meal of pasta and instructed them to eat as much as they wanted. What do you think happened when they gave people a small salad in addition to the all-you-can-eat pasta? The subjects consumed about 50 calories of salad. Were those 50 extra salad calories in addition to the pasta calories? No. Subjects ended up eating less pasta overall, and not just 50 calories less. They consumed 65 fewer calories of pasta.

When researchers added an even bigger salad, the subjects ended up eating 100 fewer calories of pasta. So, effectively, the salad did provide “negative calories” in that the subjects ate more food than had they only eaten pasta but ended up with fewer calories in their system because the salad bulked up their stomachs so much. Of course, it depends what kind of salad. We’re not talking about the typically available salads with ranch dressing and cheese. With those types of salads, you may end up eating less pasta, but there are so many calories in conventional salads you end up worse off calorie-wise in the end. But, healthy salads worked. The study concluded, “‘Eat less’ is not always the best advice. For foods very low in energy density, such as water-rich vegetables, larger portions increase satiety [the feeling of fullness] and reduce meal energy [calorie] intake.”


It’s not surprising that filling up on healthy food right before a meal cuts down on overall caloric intake, but what if, instead, we snack on healthy foods between meals? Would we get the same weight-reducing effect? Find out in my video Eating More to Weigh Less.

Other videos related to this topic you may find fascinating:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

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