A new study just released has found that a small but powerful plant compound called lignans can protect against cardiovascular disease, and there is other evidence that shows lignans may even protect against breast and prostate cancer. Here's everything to know about lignans, where to find them, and how to work them into your diet.

Lignans are a type of polyphenol, which are plant chemicals that contain antioxidants and other compounds that offer wide-ranging health benefits once inside your body. Polyphenols can be flavonoids, stilbenes, phenolic acids, lignans, and other plant compounds – but this study focused on lignans, and specifically what happens to people who eat a diet rich in them. Or what doesn't happen: They don't get heart disease.

"Lignans are polyphenols converted by gut bacteria into enzymes that appear to lower risk of heart disease," explains Dr. Joel Kahn, cardiologist and plant-based advocate, who now tells all of his patients to load up on lignans. "I used to tell them to eat more fiber and omega-3s. My patients who are vegan and who are not vegan lack for both, but now I tell them to eat lignans," Dr. Kahn said in a recent interview.

(Confusion alert: Lignans are not to be mistaken for lignins, which are the structural materials in the support tissues of most plants, and are also present in fruits and vegetables.)

What are lignans and why should we eat more of them?

"Lignans are a top-secret nutritional hero," explains Dr. Kahn, who is the founder of the Kahn Center for Cardiac Longevity and a professor of medicine at Wayne State University School of Medicine. "You hear about lectins and everyone is scared of eating a lentil, and you hear about fiber. But lignans are a chemical class of polyphenols. Lignans are a group of foods that have incredible science for optimizing our health, particularly heart health."

"What is really exciting -- and this is why I am excited – is that in the past ten days, the Journal of American Cardiology published this study that looked at more than 214,000 men and women who they followed for years and years of epidemiology nutrition studies.

"What source of food was associated with fewer heart attacks, longer lifespan, fewer bypasses, and fewer stents? Lignans! The more lignans in your diet, the lower chance of the number one killer of Americans and that is heart disease," says Dr. Kahn. The inverse was also true: The fewer lignans people ate, the higher their risk of heart disease.

The study found "a strong association with dietary total lignan intake and Cardiovascular Heart Disease (CDH) events" across a wide population, studied over years of collecting data, that looked at what they ate and found that those who ate lignans had lower incidents of heart attack, stroke, high blood pressure and all the usual symptoms of heart disease.

"Now to be fair, there is also fiber in lignan-rich foods, so it's not just the lignans in most plant-based foods, but also the fiber that can benefit heart health," Dr. Kahn points out. "So it's a one-two winning punch. But the study found that specifically, it was lignans, a polyphenolic rich fiber, that helps fight heart disease and add to longevity."

What foods contain lignans: Flaxseeds are at the top of the list

Lignans are found in various vegetables and fruits, legumes, whole grain cereals, and oilseeds but they are most bountiful in flaxseeds and can also be found in sesame seeds and other plant-based foods. Dr. Kahn now goes so far as to hand patients small packs of flaxseeds which are packed with lignans, fiber, and have heart-healthy omega-3 fatty acids, "so it's a win-win-win," he adds.

Dr. Joel Kahn says in light of the recent study findings, it would be wise to start adding flax seeds to our smoothies, salads, oatmeal, sprinkle them on avocado toast, and more. The study in the Journal of American College of Cardiology found that "increased long-term intake of lignans was associated with a significantly lower risk of total Cardiovascular Heart Disease in both men and women."

The top 2 foods rich in lignans everyone should put in their diet

  • Flaxseeds contain 85 milligrams of lignans per ounce, making flax seeds the winner by far. Flaxseed contains 75 to 800 times more lignans than other plant foods, according to sources.

"If they gave an academy award of lignans, it would be given to ground flax seeds," says Dr. Kahn. "Ground flax seeds have so many health benefits – from lowering cholesterol to helping fight heart disease, to helping reduce the risk of cancer."

"These are the unsung hero of a heart-healthy diet," Dr. Kahn asserts. "So every time you put a couple of tablespoons of flax seeds on your oatmeal or your smoothies or your salad, you are adding 85 milligrams of lignans to your diet," Dr. Kahn points out. That's why he gives flax seeds to his patients. "I would recommend that people avoid flax oil and just go for the fiber-rich ground flax seeds," he adds.

  • Sesame seeds contain 11 milligrams of lignans per ounce, the second richest lignan food. "I have gotten in the habit of keeping sesame seeds in my office for my lunch," Dr. Kahn explains.

"The second most lignan-rich food is sesame seeds. It has 11 milligrams of lignans in an ounce – not 85 so not as much – but it's number two in lignans. Sesame seeds also lower cholesterol and have plant sterol and they are the unsung hero of plant-based foods

Other lignan rich foods

Kale, broccoli, apricots, strawberries, apples, and bananas all have small amounts of lignans – but under 1 milligram per serving. Lignans are also in pumpkin seeds and legumes, nuts, whole grains, and fruit and vegetables, all of which have lignans as well as fiber and have been shown to be protective in reducing the risk of cardiovascular disease.

According to the Linus Pauling Institute at Oregon State University: "Diets rich in foods containing plant lignans (whole grains, nuts and seeds, legumes, and fruit and vegetables) have been consistently associated with reductions in risk of cardiovascular disease. However, it is likely that numerous nutrients and phytochemicals found in these foods contribute to their cardioprotection." All these foods are good for you," Kahn explains, "but you can't beat getting 85 milligrams in one ounce of flax seeds and 11 milligrams in one ounce of sesame seeds."

Dr. Kahn adds that as a plant-based advocate it's important to point out that only plant foods contain lignans, not meat or dairy or poultry: "How much lignans are in meat?" he asks rhetorically. "Big zero! Goose egg!"

He says he keeps a big mason jar of ground flax seeds on the counter in his kitchen and continually adds flax seeds to his meals and snacks throughout the day. But in his office, he keeps handy small sleeves that contain flax seeds to hand out to patients.

"When I send my patients home with these [flax seeds] I tell them they need these for omega-3s. I always check their blood for omega-3s, and all my patients, vegan or meat eaters – are deficient in omega 3s. So now there is  yet another reason to be flax seed crazy."

Lignans have plant estrogen and antioxidant qualities. Does that make them unhealthy?

Lignans are phytoestrogens, but since they look like estrogen but don't act like estrogen they may be thought of as "blockers" that will bind to estrogen receptors in the body and reduce the amount of estrogen your body has circulating.

Dr. Kahn explains that these plant-estrogens, like lignans, "can provide some protection in terms of breast health, since according to the research by Dr. Kristy Funk [breast cancer doctor, researcher, author, and speaker], at a cellular level, phytoestrogens act more like an estrogen blocker, even though we call them "plant estrogens."

The contrast, according to Dr. Kahn and others, is that when you eat animal products such as chicken and beef or ham from a female animal, you are getting real estrogen in the meat products. And these estrogens can interact with the estrogen receptors in your body. So when you are eating those animal foods – as well as real dairy – you are getting real estrogen in the body, Dr. Kahn explains.

But soy estrogen is actually not estrogen, Dr, Kahn adds. The plant-estrogens can mimic estrogen and they actually block estrogen. When you get estrogen from soy protein, he adds, your own circulating estrogen can not interact with the estrogen because it gets blocked. The data is that when you eat plant-based estrogens, you reduce your risk of breast cancer.

Bottom Line: Eat flax seeds daily to get lignans into your diet to protect against heart disease.

The more people ate lignans the lower their risk of heart attack, stroke, high blood pressure, and stents, according to a new study published in theJournal of American College of Cardiology. Flaxseeds also contain omega-3 fatty acids, which are heart-healthy, and fiber, which is beneficial to gut health. Flax seeds are a win, win, win, according to Dr. Kahn.

For more great health and nutrition content check out The 20 Best Sources of Fiber, Your Diet's Unsung Hero, and The 6 Seeds With the Most Protein.

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