“The woman who once marched up to the French chef Jean-Louis Paladin and told him a dish didn’t have enough salt can no longer taste the difference between a walnut and a pecan, or smell whether the mushrooms are burning. The list of eight languages she once understood has been reduced to English. Maybe 40 percent of the words she knew have evaporated.”
This description, in the New York Times, is of Paula Wolfert, an American culinary treasure, the woman who some claim introduced us to Mediterranean food. Now 78, she suffers from dementia and in the words of the Times,
“Thus, the so-called bulletproof coffee she makes every morning and the squares of dark chocolate she eats after lunch, in the belief they will bolster her brainpower. In between, she eats a carbohydrate-free diet built on salmon, berries, and greens, along with extracts of turmeric, cinnamon, and eggplant.
The diet draws on an amalgam of theories she has culled from deep internet research, her doctors, the other dementia patients she meets with every week and long conversations with friends and experts…”
Wolfert is a member of an ever-growing American community that lives to eat as much as they eat to live. Our culinary history includes many such food evangelists, from Sylvester Graham of cracker fame and John Kellogg, brother to the cereal to name just two. They all share a common search for a therapeutic diet.
A therapeutic diet is a regular menu except modified “to fit the nutritional needs of a particular person.” Therapeutic diets have a medical meaning, they are diets prescribed by physicians (and increasingly by dieticians) for a patient with specific chronic medical conditions. These diets modify nutrients contained in our diet.  attempting
• To maintain/restore nutritional status
• To alter calories for weight control or gain
• To balance amounts of carbohydrates, fat, and protein for control of diabetes
• To adjust quantities of a nutrient such as protein or sodium
Though once the province of doctors and hospitals, the internet now offers them everywhere. People who won't trust Wikipedia because it isn't written by experts will embrace web-based diets from Blue Apron or Purple Carrot or Green Chef come to mind.  Yet they are simply logistical services, making it easy to eat ‘nutritious’ meals conveniently. Blue Apron’s vision statement captures the idea
Our food system—the way in which food is grown and distributed—is complicated, and making healthy choices for your family can be difficult. We are changing that: By partnering with farmers to raise the highest-quality ingredients, by creating a distribution system that delivers ingredients at a better value and by investing in the things that matter most—our environment and our communities.
Some of these websites offer meals developed by Weight Watchers, or the American Diabetes Association (the standard for diets for individuals with diabetes), or meals based on New York Times recipes, Paleo meals, vegetarian meals, organic meals. There is even a site offering the Tom Brady TB12 diet  that mimics the food principles that Tom Brady applies to his diet.
I mention these dietary regimina because it speaks to an underlying problem that is ignored by dieticians and exploited by companies - there is no one-size-fits-all solution. Yes, there are basic nutritional principles (though we all know they are in flux based on the wide variation on what is reported as nutritious in any given year or decade) but what works for an NFL quarterback may not function as well for me, an old guy.
However, if you want to try it, there are at least two of these web-based programs that are worth examining. The first is Boston’s Community Servings, a non-profit that provides “medically tailored meals for nearly three decades to individuals with chronic diseases who have trouble shopping and preparing food.” What a great idea. The program’s dieticians design meal plans appropriate to each patient’s medical concerns using “elements of 17 medical diets [those previously mentioned therapeutic diets] tailored to clients with issues ranging from lactose intolerance to potassium management.”
Unlike Meals on Wheels, Community Serving’s target are specifically individuals with chronic diseases or undergoing chemotherapy. Services like this may be very impactful to one’s health; they may even be a valid medical service. Massachusetts General Hospital is currently conducting studies on Community Servings health benefit. Yet while the dietician's recommendations are more tailored than those of Blue Apron, they remain pretty much one size fits all.
The second is a company called Habit. They take personalization of diet in another direction entirely. They base their recommendations on your metabolic profile – how your body manages carbohydrates, fats and proteins. And they based that profile on a “metabolic challenge beverage that is nutritionally equivalent to a large American breakfast.”
Is there any science to Habit? That needs to be an article unto itself.
 A medically defined therapeutic diet can also manipulate texture, to take into account conditions affecting an individual's ability to swallow and diets that avoid allergies and sensitivities.
 An overview of these sites is available in the Forbes blogging section.
 “The quarterback eats 80 percent vegetables and whole grains, and 20 percent fish and lean meats, such as certain cuts of steak and duck. He doesn’t touch sugar, white flour or nightshade fruits and vegetables, which include tomatoes, peppers, eggplant, tomatillos, potatoes and certain berries. Fat comes from extra virgin olive oil on raw foods, and coconut oil on cooked foods.” And “80 percent alkaline and 20 percent acidic, which, he says, “maintain[s] balance and harmony through [his] metabolic system.” This last concept is without any scientific basis.