Before World War II, the Inuit people of the Arctic Circle never or rarely got cancer. It was largely non-existent as a disease before the economy opened up and brought new foods to this population. Their traditional diet was high in protein and fat but low in carbohydrates. After the 1950s their diet shifted as more imported foods of refined grains and sugars made their way up to the north and the Inuit lifestyle shifted. The rate of cancer more than doubled in ten years. The genetic makeup of the population was unchanged, but diet changed dramatically. It was just one example of how the addition of sugar, processed foods, and simple carbs can drive up cancer.

In his excellent book, The Cancer Code, Dr. Jason Fung creates a complex and complete picture of cancer: How it works, what we know about its growth, prevention, and treatment, and what we thought we knew that is now debunked, having been based on false assumptions. Cancer exists in the body at all times, but your immune system helps keep it in check, and this equilibrium is a delicate dance that is constantly happening, so anything we can do to promote our immune system and suppress cancer is worth considering.


“Imagine if we could change our diets by eating natural foods and reduce our risk of certain cancer so that, like the indigenous peoples of the Far North, we too were considered ‘immune’ to cancer," Dr. Fung writes. It turns out there are things we can do to lower our risk.

Dr. Fung is a Canadian nephrologist and world-leading expert on intermittent fasting and low-carb diets, especially for treating people with type 2 diabetes. He has written  including The Obesity Code.

Cancer in the US is actually on the retreat, if you look at the cancer statistics in their entirety, due to smoking cessation initiatives, and the decrease in lung cancer deaths. But other cancers are rising, especially those connected to diet and obesity, which has a direct link to cancer risk, especially those cancers related to type 2 diabetes. The CDC says 40 percent of all cancers are now attributable to obesity, including increased risk of 13 types of cancer, including colorectal, breast, and pancreatic, liver, and kidney cancers, according to the NIH.

National Institutes of Health
National Institutes of Health

To lower cancer risk, lower the levels of insulin, a growth hormone

The role that diet plays in cancer is undeniable, according to the statistics Dr. Fung cites, including the fact that people who have type 2 diabetes or are obese are at an increased risk for 13 types of cancer, and the key link appears to be insulin. Insulin is a growth hormone, he explains, closely tied to IGF-1 (Insulin Growth Factor), and when cells get the signal that nutrients are available, they grow.

When cancer gets started growing, multiplying, and circulating in the bloodstream, your immune system has the ability to find it, kill it, and knock it out. This constant interplay between growing cancer cells that travel through the bloodstream looking for a new safe harbor, and the natural killer cells of your immune system, which are constantly searching and destroying “foreign” cells, including these cancer cells, is at play every day in our bodies. The equilibrium stays under control, most of the time, Dr. Fung explains, except if the boy is bombarded with chronic cancer-promoters, or compromised. When your insulin levels are routinely locked in overdrive, such as on a diet high in carbs and sugar, or when the immune system gets compromised or overstressed, then cancer has the chance to take hold.

Cancer is always trying to grow and spread, and your best defense is diet

Dr. Fung explains that we have fought cancer on its own terms: By fighting the growth of the cells with chemotherapy, radiation, and surgery that is designed to halt its march. Instead, he says, we should play to our own innate strengths, and find cancer’s weakness. Two ways of doing this are by strengthening the immune system and through our diet.

1. Stay away from sugar and simple carbs, which cancer cells are hungry for

“It is reasonable to hypothesize that diets targeted to reduce insulin effect may be beneficial for cancer,” Dr. Fung writes, but more studies need to be done. Cancer uses glucose to fuel its growth, so sugar and diets high in simple carbs stoke the flames. Meanwhile when we eat a high-sugar diet, insulin spikes. So the first line of defense against cancer is to lower our sugar intake and stay away from simple carbs that easily turn into glucose and raise our blood sugar, causing insulin to surge in the body.

2. Maintain a healthy weight and choose high-nutrient foods to boost immunity

Approximately 20 percent of all cancer cases in Europe and North America are attributable to obesity, Dr. Fung writes, and intentional, dramatic weight loss can reduce the risk of cancer death by 40 to 50 percent. In a lab, mice with cancer that were given just enough food to survive, and their cancer showed no growth, whereas cancer in mice allowed to eat as much as they wanted, grew the fastest.

Calorie restriction is hard, though, so Dr. Fung suggests eating a whole food diet of nutrient-rich foods combined with intermittent fasting, which encourages autophagy in the body, allowing it time to self-cleanse, and dispose of cells that are compromised before cancer can develop.

Choosing foods that are nutrient-dense is another way to play to our body’s strength, since antioxidants, vitamins, and phytochemicals–vegetables, fruit, whole grains, legumes, nuts, and seeds–help bolster the immune system and undermine cancer. Unlike your body’s healthy cells, cancer cells don’t need nutrients to grow. They respond to glucose, and when glucose is not present they will grab at any fuel they can and turn it into growth. But eating a diet rich in vegetables, fruit, herbs and whole foods helps your immune system arm itself in the fight against invaders, including cancer.

3. What to Add: Green tea, with powerful catechins that deprive cancer of growth

Green tea is especially high in a polyphenol called epigallocatechin gallate, (or EGCG), which has been shown to slow cancer growth, in several recent studies have revealed. EGCG is considered a "chemopreventive polyphenol,"  which fights cancer in several ways. One is that it activates natural cell death, or "apoptosis" which is the orderly and healthy cell demise that takes place in the body when cells are ready to be replaced with new healthy cells. When apoptosis happens in a controlled and orderly way, cancer can not take advantage of vulnerable cells. This is no small feat since the body replaces about 330 billion cells a day, or about 1 percent of your cells get carried off and replaced by design every day. When this happens in a healthy, orderly fashion, it prevents cancer from taking hold in those cells that are ready to get recycled.

EGCG also signals to a nutrient pathway called AMPK that energy is low, so it doesn't promote cell growth. AMPK acts like the body’s fuel gauge. When AMPK senses that nutrients are low it signals to the cells that they should not try to grow, since there is not enough energy present. AMPK also activates autophagy, the process your body uses to self-clean, so it can accomplish the important job of carting waste off to be disposed of safely.

The nutrient sensors in the body, insulin (which responds to carbs) mTOR (which is protein sensitive), and AMPK (which gauges the overall fuel supply to the cells) all signal to the cells to grow. But EGCG appears to tell the cells: Don't grow, and actually, burn fat instead.

Studies have shown that taking green tea extract (as opposed to simply drinking it) helps with weight loss, promoting fat burning, and helping burn belly fat. EGCG also lowers cancer risk, which is a rare natural food that can have such a powerful effect. If you add one thing to your healthy whole food diet, to lower cancer risk, it should be a daily cup (or more) of green tea or taking green tea extract, Dr. Fung writes.

Green tea, which is higher in EGCG than black tea, can help reduce some of the risk factors of cancer, such as promoting weight loss, lowering insulin resistance, fighting inflammation, and helping to prevent type 2 diabetes, according to Dr. Fung. A study of women in Japan found that high consump[tion of green tea delayed breast cancer onset by over 7 years, and reduced breast cancer recurrence in those who had it once. Green tea is ‘one of the few chemopreventive tools that is a low-cost, natural food with no negative side effects.’

Bottom Line: According to Dr. Fung,  If you are overweight, lose weight. Do whatever you can to avoid or reverse type 2 diabetes. If you have type 2 diabetes consider taking metformin, which can help reduce the risks of insulin. And drink more green tea.

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