David Khayat, MD, PhD, head of medical oncology at the Pitié-Salpêtrière Hospital in Paris, has been treating cancer patients for 35 years. In that time, he says, many of them have asked for advice about changing their diets. “I didn’t have any to give,” he says, “so I decided to look into nutrigenomics, the study of the effects food and food materials have on our genes. What I found was a ton of myths and misinformation.”

This was Khayat’s inspiration for writing “The Anticancer Diet: Reduce Cancer Risk Through the Foods You Eat.” Here’s what he told SafeBee about the many ways in which what we eat — and don’t eat — can affect our risk of cancer.

What's the connection between food and cancer?

Diet accounts for about 20 percent of all cancers in developed countries. Most others result from tobacco and hormones.

Here’s how it works: The human body is made up of trillions of cells. Millions of them die every day and need to be replaced. What do you think we use to produce new cells? What we eat —proteins, carbohydrates, fats, minerals and vitamins. The quality of the cells we make depends greatly on the quality of our diet.

Related: Why Are Many of Us Failing to Get Routine Cancer Screenings?

Do some foods help prevent cancer directly?

Yes — foods with antioxidants. When cells “breathe,” they turn oxygen molecules into free radicals that damage cells, occasionally causing DNA mutations that lead cells to become cancerous. Antioxidants — such as vitamins C and E and carotenoids — seek out and destroy free radicals, protecting our genes from mutation. Plant-based foods, including fruits, vegetables, whole grains, nuts, seeds, herbs and spices and even chocolate — are the best dietary sources of antioxidants.

If you could add only five foods to your diet, what would they be?

There’s no such thing as a universal anti-cancer diet because we’re all genetically different. Each of us digests and processes food differently.

That said, there are foods that should be good for everybody. I call them my Top Seven: pomegranate, turmeric, green tea, broccoli, foods with selenium such as Brazil nuts and oysters, foods with quercetin, such as capers and onions, and garlic. Studies show these foods can lower or at least never increase the risk of any cancer.

Related: Want to Cut Your Risk of 5 Major Killers? Eat Berries

Are there foods everyone should avoid?

That varies by gender and other factors, both genetic and lifestyle. Dairy products seem to decrease the risk of colon cancer by 30 percent in women. In large quantities, however, dairy raises the risk of prostate cancer in men.

Vitamin E seems fine for women but taking it daily can significantly increase the risk of prostate cancer in men. Vitamin A or its related compounds, such as retinoids and beta-carotene, increase the risk of lung cancer in smokers but don’t harm non-smokers. Some studies have linked eating red meat to colon cancer in both sexes, but you can lower your risk significantly by consuming small portions of high-quality lean cuts.

Related: The Okinawa Diet: Add These 7 Foods to Live Longer

Do we need to cut out sugar for cancer prevention?

All cells, both cancerous and non-cancerous, feed on sugar — both sugar you eat and sugar your body makes from fat and proteins, so there’s no point in cutting out sugar entirely (or artificial sweeteners for that matter). Following the USRDA guidelines on sugar consumption is a sensible approach.

How about fat?

No more than 30 to 35 percent of your daily calories should come from fat, even healthy ones. Fat has more than double the amount of calories per gram as sugar and protein. Excess calories and being overweight increases the risk of most common cancers.

Should we stick to unsaturated fats if possible?

All oils, whether high in unsaturated fatty acids or not, are likely to make you put on weight, which is a huge risk factor for cancer. What’s more, many vegetable oils contain as much saturated fat as meat and dairy products. Do avoid oils that are high in polyunsaturated fatty acids — specifically rapeseed, perilla and hempseed oils. As far cancer risk is concerned, they’re potentially dangerous, especially at very high temperatures.

What about alcohol?

Alcohol is a negative factor for many cancers, including mouth, esophageal, gastric and liver cancers. However, this is not the case for wine, as long as it's consumed in moderation — one drink per day for women, one to two drinks per day for men.

Should we eat only organic or is it not that important?

Well, nobody can say that it’s good to eat pesticides! But there’s no scientific evidence linking the amount we get in our daily diet to cancer. If you’re worried, rinse your vegetables with a bit of soap in water (because they won’t dissolve in water alone) and then rinse again with plain water to remove the soap.

Does it matter how we cook our food?

It can. Barbecuing is problematic because flames hovering above 464 degrees F touch the food, creating byproducts called polycyclic aromatic hydrocarbons and heterocyclic amines that can be cancerous.

A wok does the same thing by scorching food at high temperatures, above 450 degrees F. That may be why Chinese women living in Hong Kong have one of the highest rates of lung cancer anywhere in the world.

It’s not that you should never eat Chinese food or use the grill, but try not to do it too often. It also helps to cook at lower temperatures in general — whether you’re baking, boiling or simmering — since high heat can cause the formation of acrylamides, a cancer-causing chemical compounds, in certain foods.

If you could adopt one eating habit to help prevent cancer, what would it be?

Mix up your menu. That means not eating the same things every day and not always cooking the same way. One way to diversify your menu is to follow the seasons with your foods. Diversity is the key until we know more about the links between food and cancer. Lastly, don’t get overweight, exercise and try to be happy!