One of the most influential principles to emerge in functional medicine and nutrition in recent years is the concept of biochemical individuality. From polymorphisms in methylation to variance in amylase gene copy frequency and differing capacity to convert beta-carotene to true vitamin A there are a multitude of examples that indicate that a ‘one size fits all’ approach does not exist when it comes to optimal diets. We have already seen that the blanket recommendation for all individuals to consume a high-carbohydrate low-fat grain-based diet has proven to be disastrous for many people.

There are genetic and epigenetic factors that contribute to the nuances of an optimal diet for any one individual. But even beyond that to some extent the composition of someone’s diet largely determines the requirements of said diet.

For example people consuming high-carbohydrate diets and deriving more of their energy from glycolysis may require more magnesium than those primarily fueling their bodies with fats such as on a lower-carbohydrate diet. The reactions of glycolysis require ten magnesium molecules in order to convert one molecule of glucose to pyruvate. Not surprisingly then magnesium deficiency has been implicated as a potential contributor to conditions related to carbohydrate intolerance including obesity insulin resistance and type 2 diabetes. Of course even low-carb dieters still require plenty of magnesium as glycolysis is an essential function regardless of one’s diet and magnesium is a cofactor for a multitude of enzymes beyond glycolysis as well as contributing to the physical structure of bone. This is merely one example of how the preponderance of various biochemical processes influenced by diet can alter the requirements of that diet.

High-carbohydrate intakes might also increase the requirement for vitamin C. Glucose and ascorbic acid compete for intracellular transport with elevated blood glucose levels having a concentration-dependent inhibition on uptake of ascorbate. In fact for some time now the competition between vitamin C and glucose is thought to underlie some of the complications resulting from the hyperglycemia attendant with poorly controlled diabetes such as dysfunction of vascular endothelial tissue due to insufficient ascorbic acid. 

As with magnesium vitamin C has a myriad of roles in the body but one of them is to provide hydroxyl groups for the hydroxylation of proline and lysine in order to form collagen. This of course is why vitamin C deficiency underlies scurvy with bleeding gums and easy bruising being the most severe manifestations of malformed connective tissue. High-carb diets—particularly ones that are low in animal protein—may necessitate increased vitamin C intake. Beyond the issue of glucose inhibiting ascorbate uptake individuals consuming gelatinous cuts of meat or who consume broth made from bones and cartilaginous joints will consume pre-formed gelatin with its full complement of collagen-building amino acids. Vegetarians and vegans whose diets exclude these items may need supplemental sources of these nutrients—or increased vitamin C—as a baseline and the need might be exacerbated further by a high carbohydrate intake.

Another issue that may influence the need for dietary tailoring to meet individual nutritional needs is the source of dietary iron. Animal foods provide iron in the heme form which is better absorbed than iron from plant foods which occurs in the non-heme form. So even when people consume foods that are considered good sources of iron such as beans the amount actually available to the body may not be as high as would be assumed.

Individuals on low-carbohydrate diets derive much of their energy from the oxidation of fatty acids. Long-chain fatty acids require carnitine in order to be transported into mitochondria. Carnitine is synthesized endogenously but those whose bodies are fueled primarily by fat may require higher amounts than are typically generated in the body. The richest sources of carnitine are animal proteins so most low-carb dieters likely get sufficient amounts but those who follow mostly plant-based diets but would still like to get the metabolic benefits of reduced carbohydrate intake might benefit from supplemental carnitine.

Issues like these are important when helping patients to create optimal diets and supplement regimens. Also nutritional needs change throughout the life cycle as well as during periods of increased stress or recovery from illness and injury so what’s ideal for someone at one point in time will most likely need to be reevaluated and adjusted as circumstances change.