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Comment by overgard | Hacker News Reader

I think common sense here can be a guide though. You don't need sugar at all, excluding high levels of anaerobic exercise. Your liver can produce the glucose your body actually needs from other sources (gluconeogenesis) and a lot of your tissues that use glucose also can use fatty acids or ketones. Fructose isn't needed at all. ("low blood sugar" isn't a symptom of not consuming enough sugar, it's a symptom of a disregulated metabolism -- ie insulin resistance or other conditions)

Saturated fats have all sorts of uses biologically.

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That has nothing to do with whether excesses of those nutrients cause cardiovascular disease, though. The general consensus is that the healthiest diet is one with 5-10% of total calories from saturated fat. For most people, it's necessary to restrict saturated fat to land in that range. We also need to distinguish between sugar and carbohydrates. Again, the general consensus is that intake of sugar and refined carbohydrates should be minimized, while 50-75% of total calories should come from sources of complex carbohydrates like vegetables, beans, and whole grains.

Funny you should say that after today's FDA announcement. (Not taking any side here just interested in how we determine what is a consensus these days)

It's hard, because when an issue becomes politicized everyone has their own preferred "consensus". I would say it should come from the scientific community, not government agencies. Sometimes government agencies agree with the scientific consensus, but not always.

My go-to source for nutrition information is Understanding Nutrition by Whitney and Rolfes.

> everyone has their own preferred "consensus"

For some people choice of diet really does seem core to their identity. It’s literally all the OP ever posts about.

There is a third option: looking at the diets of your closest ancestors with the best longevity.

There may be a misconception that there is one single best diet for everyone, when in reality we people (over generations) evolve with our diets, and your best diet and my best diet may be completely different.

The problem with using science as a guide is that there are just too many variables and not enough time, data and money to isolate them all sufficiently.

However that is distinct from the idea that too much of something like refined sugar might be unhealthy for just about everyone. So science does have an important role to play, I just don't think it's advanced far enough to fully answer the question for everyone.

Carbohydrates are sugars (from the first sentence on wikipedia): "A carbohydrate (/ˌkɑːrboʊˈhaɪdreɪt/) is a sugar (saccharide) or a sugar derivative." Saying you need "50-75% of your energy from [sugar]" illustrates why that is a somewhat odd statement. Yes, glucose is much better than fructose, but eating a ton of glucose will still lead to high insulin spikes and inflammatory diseases. Complex carbohydrates are better in that they take longer to digest, not because they're magically different. Vegetables are good for nutrients not because you need their carbs.

GP was talking specifically about calories, not other nutrients. My impression is when a vegetable provides significant calorie content it tends to be in the form of carbohydrates.

You have to get your calories (ie raw energy) from somewhere. If you limit saturated fat to 10% then what's left for the other 90% is (roughly speaking) unsaturated fat, simple sugars, carbohydrates (ie complex sugars), and protein. In terms of long term habits converting protein to calories is probably not a great choice for your health. If you decide to go for complex carbohydrates over various oils then vegetables that provide those are a good option.

People are on ketogenic diets for years and even decades with no adverse affects. There's nothing wrong with getting energy from other sources, your body can manage it fine.

Ketogenic diets are high fat. I suggested that a diet where the bulk of your calories comes from protein (not lipids, carbohydrates, or simple sugars) was probably not great for your health.

Your body can certainly "manage" on a high protein low fat low carb diet but I don't understand it to be good for you.

I would caution that just because your body can make something doesn't mean it will have optimal performance when doing so. People in ketosis do have worse peak performance in sports than those that eat more carbs/sugar.

True, but also what performance are we optimizing? Do I want to be able to run faster, hit harder, lift more, etc..?

Or do I want to live longer?

They aren't necessarily mutually exclusive, but different actions could result in different outcomes for each.

This is true, but I don't think our understanding of nutrition is good enough to really pick and choose what we want to optimize for. Eg we still don't have a recommendation on whether we should costume external vitamin K2 or not. The same goes for many amino acids. Some of the non-essential ones can have interesting effects when taken alone, eg glutamine - seems to help the gut lining. (We also don't know whether that's perfectly safe due to cancer risks, because some cancers eat glutamine.)

> worse peak performance in sports

For nearly everyone, this isn't impactful to their life. Only their vanity

Your mind and health are impacted by your physical body. If eating a certain way impacts your physical performance then it might also have effects on your health (and mind) in unexpected ways.

I'm not saying that ketosis has this kind of an effect, but rather that eating or not eating some other things might. Eg vitamin K2. The body is be able to make vitamin K2, but we might have stronger bones and teeth, and a healthier cardiovascular system, if we get extra K2 from an external source.

Looks like it's true that low-carb adapted athletes rely more on fat oxidation during exercise but performance suffers nonetheless because of increased oxygen demands that basically cannot be met.

Your entire argument here applies in the other direction as well. You do not need dietary saturated fats, and sugar has all sorts of uses biologically.

That is only partly true: you don't need dietary saturated fats, but you do need essential fats (omega-3 and omega-6), which are polyunsaturated. However, sugar does not have all sorts of uses biologically; it has only one: as one (but not the only one) source of energy.

It isn't just a source, it is also a storage mechanism, both in the liver and in muscle tissue.

That sugar however is produced by the body itself.

Technically speaking, dietary requirement for sugar is 0. This doesn't mean it isn't useful to have some, but it definitely shouldn't be the basis of the food pyramid.

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