It’s clearly diet/lifestyle. The children of affluent Chinese in China, who have more access to food from a young age, also grow much taller.
But you’re talking about countries that have emerged (Japan) or are recently emerging (China) economies, and who have also had periods of serious deprivation in living memory. Those who were born in and grew up under those conditions will be smaller in stature.
Look also at the differences between the North Koreans and South Koreans; these are the same people, culturally and genetically, yet the South Koreans are, on average, two to three inches taller.
These differences are definitely a function of inadequate nutrition versus ample nutrition. In a circumstance of inadequate nutrition, it’s very possible that certain specific things might help. For example, if you’re not able to get fish to eat, and are low on all oils, including essential oils, perhaps using some less expensive fish oil would be good for your skin, as it directly provides essential oils (EPA/DHA).
If you’re eating enough essentail oils, adding fish oil wouldn’t provide that benefit.
Likewise, turmeric has been found to contain antibacterial and antifungal compounds. This means it may be useful as a medicinal. But, if you’re not ill, using it wouldn’t necessarily provide a benefit.
And there’s also the counter-example to consider - what plant compounds are we avoiding which are bad for us? Most plants produce compounds toxic to animals; this prevents them from being consumed to extinction. Over time, we’ve identified (or bred) varieties which are edible, but they may also contain traces of unhealthy compounds. For example, common apples contain a little cyanide. Fortunately, most of the cyanide is in the seeds, so we avoid it by not eating the seeds - but farmers have to be careful to keep their horses and cattle from eating too many apples that fall on the ground, or they’ll become sick.
Most foods are a mix of compounds that promote health, and compounds that promote problems, including cancer. Eating a simple diet of a few healthy foodstuffs avoids both.
Now, are we Soylenteers basing the diet on the right foodstuffs? Are they the most healthful options available? That’s a matter for a lot of continued research!