High doses of vitamin C can be useful in decreasing glucose in diabetics. In one study, 1000mg of vitamin C caused a significant reduction in fasting glucose and HbA1c– a measure for long-term glucose handling. Notably, the other group receiving 500mg of vitamin C did not share these favorable changes. (57) In normal subjects, vitamin C also affects glucose homeostasis. Along with diabetics, vitamin C enhanced whole body glucose disposal by positively affecting non-oxidative glucose metabolism. (58)
Unless it is in liposomal form, high concentrations of vitamin C cannot be attained all at once. Vitamin C is best absorbed taken in doses no more than 200mg at a time (148) throughout the day depending on individual needs. Ascorbic acid is the most common form and can be absorbed without a meal, but if ingestion occurs, less acidic variants (e.g., sodium ascorbate) are available. Smokers and those under stress will require more.
The sunshine vitamin plays an integral part in a multitude of areas concerning health, and apparently this extends to maintaining insulin sensitivity. Those who already have developed type II diabetes with vitamin D deficiency ( ≤ 20 ng/ml) or even with suboptimal vitamin D levels (<50 ng/ml) have been shown to improve their diabetic condition in various markers such as plasma fasting glucose, insulin, and in measures of insulin resistance and beta cell function. (20) The lower the initial vitamin D level, the higher the benefits are from vitamin D on blood sugar and insulin sensitivity. For example, vitamin D replenishment led to 60% amelioration in insulin sensitivity from 10ng/ml to 30ng/ml, whereas metformin and troglitazone delivered improvements of 13% and 54% respectively. In critically low states, vitamin D supplementation is even more helpful than conventional drugs. (21)
Why vitamin D modifies a broad range of areas affecting blood sugar is no mystery. The vitamin D receptor is present on pancreatic beta cells, the insulin gene, and in skeletal muscle. (22-24) Moreover, vitamin D regulates the renin system, mitigating oxidative stress and dysfunctional insulin signaling. (25-26)
To achieve optimal levels of vitamin D, 2000-5000IU is recommended in the form of D3, which is the active form in animals, as opposed to D2, or the plant-derived form of vitamin D.
Diets high in lipid hydroperoxide as a result of a vitamin E deficiency are burdened by insulin resistance and faulty insulin secretion in animals. (59) High doses of natural vitamin E (900mg daily) in the form of d-alpha-tocopherol lowered plasma glucose and HbA1c levels in elderly type II diabetic patients. (60)
Intriguingly, the neglected types of natural vitamin E – tocotrienols – also combat high blood sugar. Apparently, vitamin E tocotrienols improve insulin sensitivity by activating PPARs (peroxisome proliferator-activated receptor). (61) In particular, alpha- and gamma-tocotrienol activated PPARalpha, whereas delta-tocotrienol activated PPARalpha, PPARgamma, and PPARdelta. This is very important to note as synthetic PPAR agonists are already used to manage diabetes with success. It is likewise worthy to note that tocotrienols seem to possess 40 to 60x greater antioxidant activity against lipid peroxidation than tocopherols. (62) Lipid peroxidation precedes poor glucose control that arises from a defective insulin response. (63) Lipid peroxidation is a damaging reaction that leads to high glucose and eventual diabetes by destroying the integrity of the pancreatic beta cells that are relied upon for the insulin response. Vitamin E can protect against this form of oxidative stress.
Vitamin K exists in nature as phylloquinone (vitamin K1) and as menaquinone (vitamin K2). The former is found in many leafy greens whereas the latter in found in primarily in natto, curd, cheese, and sauerkraut (fermented foods), but is also present in meats, eggs, poultry, liver, and grass-fed butter, in moderate concentrations. Both forms of the vitamin are associated with better glucose control and a decreased risk of diabetes. (82)
It is known that vitamin K carboxylates osteocalcin, meaning carboxyl groups are added to a marker of bone formation. In simpler terms, vitamin K aids in bone building-process. This relates to insulin sensitivity as osteocalcin regulates glucose metabolism. Upon supplementing healthy male subjects with 30mg of vitamin K2 daily, insulin sensitivity improved in relation to increased levels of carboxylated osteocalcin. (83) In a different study, elevated levels of carboxylated osteocalcin were linked with lower insulin resistance. (84) Vitamin K’s anti-inflammatory effects (85), especially K2, may also explain its protection of insulin sensitivity.
Due to the difficulty of attaining sufficient concentrations of K2 from diet alone, supplementation is usually required.
Given that zinc behaves like insulin to promote glucose transport, it is a vital mineral for maintaining healthy glucose levels. (68) In addition to affecting insulin signaling and glucose transport, zinc reduces the production of proinflammatory cytokines, protecting the coveted beta cells from cytokine-induced death. (69) A zinc deficiency is correlated with increased insulin resistance (70), and to no surprise, most diabetics suffer from hyperzincuria (high zinc loss through the urine) and depressed serum zinc levels. (71)
Zinc occurs in small amounts in various foods, with the most being in meats. Vegetarians who do not supplement with zinc are more often deficient in the mineral, but even moderate to low meat consumption may beget zinc insufficiency. What most do not know is factors other than a lack of dietary zinc can lead to a deficiency through both decreased absorption and increased excretion. Some examples that can reduce total zinc and raise the normal zinc requirement are high calcium diets, alcoholism, chronic stress and anxiety, high-intensity exercise, frequent ejaculation, antacids/low stomach acid, diuretics, gastrointestinal disorders, liver diseases, and renal disorders.
Many studies demonstrate a clear benefit from zinc supplementation in diabetics. (72-73) High doses of zinc (20-30mg) have resulted in significant improvement in multiple measures pertaining to blood sugar management such as fasting blood glucose, 2 hour postprandial (post-meal), and HbA1c (extended blood sugar average). Other studies have generated very positive effects with much higher doses of zinc (74), but these studies were short-term and needed to correct sufficiently decreased zinc levels, so long term toxicity was not considered. Supplementary zinc over 50mg per day decreases healthy cholesterol (HDL), at least in healthy men, while higher levels supplemented for a prolonged period of time after zinc repletion can led to thrombogenesis. (75)
For the possibly of eventual overdose, it is advised to supplement with no more than 30mg of zinc daily if done unmonitored.
(References in last section)