Category: Breeding

Gary Taubes has been making a pretty decent living of late pushing the line that sugar is a poison. His argument was recently summarized in The American Conservative, which should perhaps give pause for thought, but let that slide:

…to science journalist Gary Taubes the idea that successful weight loss depends on eating less and exercising more is a dangerous myth. In Why We Get Fat he argues that obesity is the result not of sloth, gluttony, or diets overly rich in calories and animal fats but comes instead from consuming too many carbohydrates, particularly from wheat flour and sugar.

You can also hear an interview with him on Skepticality. I’m not really able to judge the merits of his claim of sugar toxixity. Some of the things he says seem plausible to me, but I’m always suspicious of analyses of problems as complicated as the epidemic of obesity, heart disease and diabetes which miraculously find a single culprit. But that’s not really what I wanted to talk about here, though you are of course welcome to comment on that topic if you like. What I wanted to reflect on is the claim by Taubes in that interview I linked to above that modern plant breeders have consciously aimed at producing, and have been successful in developing, fruit that is ever-higher in sugar. Certainly provocative. But is it true?

So I put the question on the GIPB mailing list, and I got a number of interesting replies. Kicking off the discussion, Pat Heslop-Harrison said:

If you count tomato as a fruit, then Dani Zamir has some good data with Brix-number and has certainly been able to increase it (and solids).

But it hasn’t always been easy, apparently. Ron Clayman came back with this:

I had a tomato with 24brix. unfortunately it didn’t breed true. back to square one. I think it has something to do with the genetic pathway that produces ascorbic acid as it and fructose are similar molecules.

Aside for those among us who don’t obsess about sugar: “one degree Brix is 1 gram of sucrose in 100 grams of solution.” Moving on, Mark Hart of Mt. Ashwabay Vineyard & Orchard, Bayfield, WI, USA had this to say:

I am skeptical that sugar in fruit and produce has played any significant role in the increase in obesity. I think that is the opposite is true, that a switch from fruit consumption to artificially sweetened processed foods as been the driver behind obesity on the diet side (the activity side is equally important).

I breed grapes, and the sugar level in modern wine grapes is very similar to that found in wild Vitis vinifera (sylvestris) 20-24 brix. The range in other wild Vitis is wider, 15-30%, but the target for wine is driven by alcohol levels. In table grapes fruit firmness and sugar/acid balance is more important than absolute sugar level. The sugar level of grapes consumed has actually dropped as the fruit is increasingly transported and the need for firmness increased. People used to eat locally produced grapes that were actually ripe and at a high sugar content because they were not harvested 2 weeks and 2000 km from consumption.

A statement that supports the high sugar view can be found in this recent popular press article. A breeder of specialty tree fruit in California said: “We want real sugar fruit. We want you to have to go to the dentist.” Probably true, but I don’t know if it is effective PR.

Which elicited this from Harvey K. Hall in New Zealand:

It is interesting to read the comments of Mark Hart. Certainly I think that selection in a lot of small fruits is for higher sugar content but from my experience I would say that the cultivated varieties are not yet as high in Brix as some wild accessions that I have looked at, including red raspberries at a Brix of 16, blackberries with a similar Brix and a similar story with Ribes cultivars. The challenge for a breeder is to keep the Brix up while achieving higher yields, in other words getting the new cultivar to fix more sugars to accompany increased fruit production. In raspberries in particular it took a lot of work to get the Brix up with early breeding at East Malling. Tulameen also became popular because of its low acid and moderately high Brix.

There is plenty of room for improvement in fruit quality and a balanced sugar/acid ratio is a key to high fruit quality and customer appeal. Fortunately we do not have the issue of high carbs content that is found with cereals and especially added-sugar bakery products. Fruit is a good
relatively low carb dietary component that does not give a high glycemic spike in the morning and have us craving more carbs all day.

So from this very limited sample it does seem that high sugar content has indeed been a breeding objective in some fruits, but that it has not always been achieved, and that other characteristics have in fact taken precedence. Perhaps other fruit breeders out there — and fruit consumers for that matter — will add to the discussion.

That last point from Harvey about cereals reminded me that Professor Harriet Kuhnlein, a nutritionist at McGill University in Canada, had recently put a very similar request to my own for information about the results of modern plant breeding on a different mailing list, one populated by nutritionists this time, rather than breeders. She points to a Chicago Tribune article on William Davis’ recent book “Wheat Belly,” which suggest, among other things, that breeding semi-dwarf wheat has had some, ahem, unforeseen consequences:

His book, which has spent time this fall on The New York Times best-seller list for advice books, posits that when traditional wheat was genetically altered to become semi-dwarf wheat in the last century, it was assumed, without any testing, that the modifications would not change the way it affected those who ate it.

But Davis theorizes that those genetic changes could be responsible for the rise in celiac disease and gluten sensitivity we are seeing today. He further pinpoints unique compounds in wheat such as gliadin, amylopectin A and others as triggers of hunger, sharper blood sugar spikes, behavioral disorders and destructive inflammation.

Prof. Kuhnlein asked her nutritionist colleagues for help, but didn’t get very far:

I am getting questions from friends and I don’t know how to give an informed response. Does anyone in the network know whether or not “recent” wheat breeding has resulted in new risks for obesity? I have also seen something in the pop literature about pesticide resistance being inserted GM into wheat, that may also result in “allergies” and obesity. Who’s the wheat expert in the biodiversity and nutrition network? We need some authoritative responses in the media that are beyond the obvious — that too much wheat=obesity!

So, dear reader, whether you’re a wheat breeder or not: can you give Prof. Kuhnlein a helping hand?