Beware the Killer Asparagus: Headlines, Hype and Hope for Food Science

It is clear as day that the acceptance of a diet partly or completely based in plant foods, often characterized as a vegan diet, is catching on at breakneck speed. For example, a week-long series in the English papers this week is featuring Michael Greger, MD of Nutritionfacts.org and has generated much attention. Not all are celebrating the rise of plant diets and it seems like the media and meat frenzied bloggers are ready to pounce on any shred of inconsistency that plants heal.

This week a member of the plant kingdom was mentioned in dozens of headlines based on a study in mice suggesting that an amino acid we all make, asparagine, and the enzyme that forms it, might be a target to prevent breast cancer metastases, at least in mice. The fact that this pathway is already known to be active in acute leukemia and is a path for therapy was rarely mentioned so the news may not be all that shocking, but shock sells. A review of some of the headlines blasted across laptops and smart phones included:

1) A new study linking asparagus to cancer is freaking people out — here’s how concerned you should be (Business Insider)

2) Amino acid in asparagus could cause the spread of cancer, study says (Atlanta Journal Constitution)

3) Laying off asparagus may help beat cancer (The Times U.K.)

4) Asparagus Could Kill Me? (CureToday.com)

5) Amino acid in asparagus may cause breast cancer (TechnoChops.com)

Most health-conscious individuals reading banners like these might just swear off those green stalks. But how dangerous could asparagus, known for producing fragrant urine, possibly be? After all, vegetables in general are associated with a reduction in the risk of heart diseases. Asparagus in particular has been associated with a reduction in hypertension in mice. A few headlines read a bit deeper into the research study and identified more likely culprits associated with cancer in general and the spread of cancer specifically. How different are these banners:

Eating Meat and Potatoes Linked to Spread of Cancer in Mice (Newsweek)

Eating meat and fish ‘adds more fire’ to breast cancer (Amore.Ng)

Diet rich in fruits and veggies may help halt spread of breast cancer (The Kashmir Monitor)

Finally, you cannot blame the asparagus growers for standing up for their crop in headlines like these:

Farmers Quick To Question Study Linking Asparagus To Breast Cancer (CBS Sacramento)

What did the “killer asparagus” study actually report? In abstract form their findings were:

Here we show that asparagine bioavailability strongly influences metastatic potential. Limiting asparagine by knockdown of asparagine synthetase, treatment with L-asparaginase, or dietary asparagine restriction reduces metastasis without affecting growth of the primary tumour, whereas increased dietary asparagine or enforced asparagine synthetase expression promotes metastatic progression. Altering asparagine availability in vitro strongly influences invasive potential, which is correlated with an effect on proteins that promote the epithelial-to-mesenchymal transition. This provides at least one potential mechanism for how the bioavailability of a single amino acid could regulate metastatic progression.

For now, is there any practical importance to the headlines and the study? Should you stop eating asparagus? I would advise you to keep on buying and eating asparagus and I treated myself to a large plate of lightly steamed green stalks last night. One balanced review on this study indicated that one cup of asparagus has 616 mg of asparagine. This means that even if you literally only ate asparagus you would not get enough asparagine in your diet to match the levels in the study.

However, there is a connection between the amino acid asparagine, which all humans manufacture, and its transformation under heat into a potentially cancer causing toxin family called acrylamides. The toxins can form much more readily from asparagine than other dietary amino acids. Potatoes also have asparagine in them, hence the headline about meat and potatoes. But the real action occurs when you fry potatoes into potato chips. The chemical reactions creates a phenomenal amount of acrylamides compared to other foods and reason would be to skip the potato chips and eat the raw or steamed asparagus.

Headlines sell papers and ad views but they also influence a public that rarely reads an entire article and even less likely reads the original science. To reassure you, I can confidently state that:

1) Asparagus do not cause cancer

2) Whether you have breast cancer or not, it would be wise to avoid meat, eggs, dairy and potato chips

3) Eating more fruits and vegetables will reduce your risk of heart disease, cancer, type 2 diabetes, dementia and a dozen other chronic disease.

4) “Where do you get your protein?” is a nearly worthless question. Individual amino acids activate different nutrient sensing pathways that may promote health or disease. And, keep calm, plants have amino acids too packaged with fiber, phytonutrients, vitamins, and minerals.

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