For today’s edition of Dear Mark , I’m answering one reader question. It’s an important one from last week’s post on insulin and illness . Given the potential effects of excess insulin on cancer development and growth, should we be worrying about the insulinogenic effects of a food like whey protein—which is one of the most insulinogenic foods of all? I sell the stuff , so I’d better know what I’m doing. Do I?
Let’s find out.
Rob H. asked:
Great post Mark, very thought-provoking. However it throws up a big question for me: you wrote that “colon cancer patients who eat the most insulinogenic foods have poorer outcomes” and from clicking through to the study it appears this was based on the insulin index of foods. Now, as I understand it, whey protein is one of the most insulinogenic of foods (higher even than white bread), so is this something we should be avoiding? I take 40g of your ‘Primal Whey Protein’ every morning before breakfast, but is that going to cause me problems down the line? From your 2011 article on dairy you wrote: “It comes down to the amino acid composition of dairy proteins, specifically the amino acids leucine, valine, lysine, and isoleucine. These are the truly insulinogenic proteins, and they’re highest in whey (which is probably why whey protein elicits the biggest insulin response).” Does this mean we should be avoiding whey protein if the insulin response it produces fuels pre-cancerous growth (often very commonplace) into full-blown tumours?
Nice catch and great question.
I don’t think you should worry about whey protein and cancer. Here’s why:
We Primal people exist in a strange (but growing) bubble. The foods we eat that provoke insulin are way different from the foods most others are eating. Most other people by and large probably aren’t chowing down on grass-fed lamb  leg, roast chicken, sockeye salmon , canned sardines, and whey protein shakes. The bulk of the insulinogenic foods the colon cancer folks ate were carbs, not animals. We can’t extrapolate from french fries and soda to whey shakes and steak .
Even if you ignore the differences in micronutrient content between animal protein and carbs, you can’t ignore their disparate effects on glucagon. Protein like whey provokes insulin release, but it also releases glucagon, a hormone that counters some of the effects of insulin and has potential inhibitory effects on tumor growth . Carbohydrate consumption does not lead to glucagon secretion.
The available evidence suggests to me that whey  isn’t harmful in the contest of cancer and may even be protective, even when the cancer is already established (and presumably highly responsive to insulinogenic foods).
For one, many oncologists are actually recommending their patients take whey protein or similar protein sources to deal with muscle wasting, a terrible affliction that can really increase mortality and worsen outcomes. In one study, taking essential amino acids—of which whey is a great source—helped  people with advanced lung cancer retain muscle mass without affecting disease trajectory.
You might be surprised to learn that whey supplements are an accepted part of pre-op preparation and post-op recovery for cancer patients.
Among colon cancer patients awaiting surgery , those who partake in a multimodal prehabilitation program that includes whey protein, exercise, nutritional assessments, and anxiety coping techniques have better outcomes.
Colon cancer surgery patients who take whey  are able to walk farther than patients who don’t take whey.
Helping preserve muscle and functional capacity is to be expected. That’s not affecting the cancer itself, though. What about that?
Well, whey promotes glutathione production . Glutathione is the body’s premier endogenous antioxidant. It lowers oxidative stress  and inflammation and helps detoxify various toxins—real ones, like ethanol and heavy metals—which can trigger carcinogenesis. That said, glutathione may also reduce the effect of chemotherapy . By and large, glutathione is probably better to have than not if you’re worried about cancer prevention.
Culture studies where they bathe isolated cells in whey have mixed results. Usually it helps, increasing cellular resistance to cancer. Sometimes  it seems to cause certain types (prostate) of cancer cells to proliferate while reducing proliferation in others (breast). Whatever the result of these studies, in reality, eating a whey shake doesn’t “bathe” your prostate in whey protein. That’s not how food works. If anything, it seems protective against prostate cancer .
In animal studies , whey protein shines, outclassing most other proteins in the suppression of tumor growth. There are also human case studies  where whey protein consumption coincides with the suppression of urogenital tumors. I’m optimistic.
Finally, insulin isn’t bad in and of itself, as I’ve said time and time again . Insulin spikes are a normal part of eating. Without insulin, we’d have a hell of a time trying to build muscle or move glycogen  into muscle stores. The whole premise of the post from last week was that insulin becomes problematic in the context of insulin resistance and hyperinsulinemia. That’s it. Spikes, normal. Perpetual elevation, not normal. How does whey affect that?
In overweight and obese folks, whey protein reduces fasting insulin levels .
I’m open to having my mind changed, but I think the evidence stands for itself. Whey is probably safe and may even be one of the best weapons we have in the fight against cancer—on several fronts.
Thanks for reading, everyone. Take care, be well, and lend your input down below!