From an awesome new study
measuring gene expression differences in a crossover design (directly changing each individual’s diet and taking blood to measure the impact), using powdered food for reproducibility, we learn that moderate-carb diets (less than 40% calories from carbs, with no single-meal high-carb spikes at all) are *extremely* healthier than conventional (insanely wrong) dietary recommendations (2/3 calories from carbs, and only 10% fat by mass!). Extremely low carb diets weren’t compared. Each (overweight) participant tried both traditional (high-carb) and moderate-carb diets for about a week.
One of the study authors emphasizes macronutrient balance in every meal. I think this is likely nonsense, except that you should avoid large snacks or meals that are too high in carbs (this is reasonable to believe even though they didn’t test it, because insulin is implicated as the mechanism for harm in a high-carb diet, and any large burst of fast-digesting carbs is suspect). But perhaps it’s fine to have a 50% carbs meal at lunch and a 30% carbs meal at night. They didn’t measure that.
A study author also repeats conventional wisdom which should be considered suspect due to the success (mostly anecdotal) of paleo-diet advocates. For example, paleo usually recommends for root vegetables like sweet potato, against whole grain (because grain hulls contain phytic acid, which impairs some nutrient absorption), and is tolerant of white rice in moderation. The study author advocates (without evidence) exactly the opposite of that.
Diet #1: Current Dietary Recommendations (USDA)
65 % Carbs
Diet #2: Moderate Carb Diet
Important: these are percentages by calories. Fat is twice as calorie-dense as the others.
Everyone ate the same amount, at the same times, in the same portions. Their diets were adjusted so they would maintain body weight.
Blood tests were taken before and after each dietary intervention. Each person’s gene expression was compared to their own previous results – not the group average.
The group that ate a “healthy” amount of carbohydrates (according to USDA guidelines) expressed genes that are directly involved in some of the worst modern diseases such as type 2 diabetes, cardiovascular disease, Alzheimer’s, and cancer.
“This affects not only the genes that cause inflammation in the body, which was what we originally wanted to study, but also genes associated with development of cardiovascular disease, some cancers, dementia, and type 2 diabetes – all the major lifestyle-related diseases,” says Berit Johansen, the lead researcher behind the study.
The moderate carb group activated genes that stop inflammation and cardiovascular disease. A moderate carb diet also activated a gene that is commonly called the “fountain of youth gene.” This gene (FoxMB1) can renew stem cells and generate new tissue.
“It was interesting to see the reduction in genetic activity, but we were really happy to see which genes were involved. One set of genes is linked to cardiovascular disease. They were down-regulated in response to a balanced diet, as opposed to a carbohydrate-rich diet.”
There’s been a lot of talk in the blogosphere about problems with the carbohydrate hypothesis. While the idea that “carbs make you fat” is incomplete, there are still good reasons to minimize carb intake. All high-carb diets turn on the genes associated with disease, regardless of the type of carbohydrate. As this study showed, it’s directly tied to insulin levels.
“Genes respond immediately to what they have to work with. It is likely that insulin controls this arms race,” Johansen says. “But it’s not as simple as the regulation of blood sugar, as many believe. The key lies in insulin’s secondary role in a number of other mechanisms. A healthy diet is about eating specific kinds of foods so that that we minimize the body’s need to secrete insulin. The secretion of insulin is a defense mechanism in response to too much glucose in the blood, and whether that glucose comes from sugar or from non-sweet carbohydrates such as starches (potatoes, white bread, rice, etc.), doesn’t really matter.”
Caveat: you have to believe that the short-term markers that are known to be statistically linked to death and disability, in fact cause them (or at least that the true cause of the change in markers will also harm health) - something that turned out not to be true for blood cholesterol or the statins prescribed to treat them. The reason we have to trust in these short-term measurements for now is that long-term controlled-diet studies are infeasible (and would take years to complete).
Another caveat: perhaps they used a good blend of fats which you may have trouble reproducing (but you can still do well by avoiding high-carb spikes). Opinions differ about the best blend of dietary fats. Everyone knows you need some Omega-3 and Omega-6 (I think there’s an optimal ratio, and Omega-3 are harder to come by), but USDA and friends recommend against animal saturated fats, even though there’s plenty of support for benefits from high-quality saturated animal fat (e.g. grass-fed eggs/butter/beef/lamb), at least to the brain (and what’s good for brain is likely good overall). You should probably avoid saturated animal fat when the animal’s feed was adulterated or environment contaminated, since some harmful substances are fat-soluble and accumulate over an animal’s life (same goes for high-in-foodchain seafood). You should also probably minimize vegetable oil intake (saturated coconut oil is better for you than corn/safflower/canola oil). High quality olive oil is ok. I drank flaxseed oil for a while (it seemed beneficial and I’ll grab some more when I get around to it, but as it’s polyunsaturated, it becomes rancid quickly - so get it fresh).